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    INTERNATIONAL PROGRAMME ON CHEMICAL SAFETY



    ENVIRONMENTAL HEALTH CRITERIA 169





    LINEAR ALKYLBENZENE SULFONATES
    AND RELATED COMPOUNDS











    This report contains the collective views of an international group
    of experts and does not necessarily represent the decisions or the
    stated policy of the United Nations Environment Programme, the
    International Labour Organisation, or the World Health Organization.


    First draft prepared at the National Institute of Health Sciences,
    Tokyo, Japan, and the Institute of Terrestrial Ecology, Monk's Wood,
    United Kingdom


    Published under the joint sponsorship of the United Nations
    Environment Programme, the International Labour Organisation, and
    the World Health Organization


    World Health Organization
    Geneva, 1996

        The International Programme on Chemical Safety (IPCS) is a joint
    venture of the United Nations Environment Programme, the
    International Labour Organisation, and the World Health
    Organization. The main objective of the IPCS is to carry out and
    disseminate evaluations of the effects of chemicals on human health
    and the quality of the environment. Supporting activities include
    the development of epidemiological, experimental laboratory, and
    risk-assessment methods that could produce internationally
    comparable results, and the development of manpower in the field of
    toxicology. Other activities carried out by the IPCS include the
    development of know-how for coping with chemical accidents,
    coordination of laboratory testing and epidemiological studies, and
    promotion of research on the mechanisms of the biological action of
    chemicals.

    WHO Library Cataloguing in Publication Data

    Linear Alkylbenzene Sulfonates and Related Compounds.

    (Environmental health criteria ; 169)
    1.Alkane sulfonates - adverse effects  2.Environmental exposure 
    3.Guidelines I.Series

    ISBN 92 4 157169 1                      (NLM Classification: QU 98)
    ISSN 0250-863X

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    cWorld Health Organization 1996

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    CONTENTS

    WHO TASK GROUP ON ENVIRONMENTAL HEALTH CRITERIA FOR LINEAR
    ALKYLBENZENE SULFONATES AND RELATED COMPOUNDS

    NOTE TO READERS OF THE CRITERIA MONOGRAPHS

    ENVIRONMENTAL HEALTH CRITERIA FOR LINEAR ALKYLBENZENE SULFONATES AND
    RELATED COMPOUNDS

    1. OVERALL SUMMARY, EVALUATION, AND RECOMMENDATIONS

         1.1. Identity and analytical methods
         1.2. Sources of human and environmental exposure
         1.3. Environmental concentrations
               1.3.1. Linear alklylbenzene sulfonates
               1.3.2. alpha-Olefin sulfonates and alkyl sulfates
         1.4. Environmental transport, distribution, and transformation
               1.4.1. Linear alklylbenzene sulfonates
               1.4.2. alpha-Olefin sulfonates
               1.4.3. Alkyl sulfates
         1.5. Kinetics
         1.6. Effects on experimental animals and  in vitro
               test systems
         1.7. Effects on humans
         1.8. Environmental effects
               1.8.1. Linear alklylbenzene sulfonates
                       1.8.1.1   Aquatic environment
                       1.8.1.2   Terrestrial environment
                       1.8.1.3   Birds
               1.8.2. alpha-Olefin sulfonates
                       1.8.2.1   Aquatic environment
                       1.8.2.2   Terrestrial environment
               1.8.3. Alkyl sulfates
                       1.8.3.1   Aquatic environment
                       1.8.3.2   Terrestrial environment
         1.9. Human health risk evaluation
         1.10. Evaluation of effects on the environment
         1.11. Recommendations for protection of human health
               and the  environment
         1.12. Recommendations for further research

    A.  Linear alkylbenzene sulfonates and their salts.

    A1.  SUMMARY

    A2.  IDENTITY, PHYSICAL AND CHEMICAL PROPERTIES, AND
         ANALYTICAL METHODS

         A2.1  Identity (sodium salt)
         A2.2  Physical and chemical properties
         A2.3  Analysis
               A2.3.1  Isolation
               A2.3.2  Analytical methods
                       A2.3.2.1  Nonspecific methods
                       A2.3.2.2  Specific methods

    A3.  SOURCES OF HUMAN AND ENVIRONMENTAL EXPOSURE

         A3.1  Natural occurrence
         A3.2  Anthropogenic sources
               A3.2.1  Production levels and processes
               A3.2.2  Uses

    A4.  ENVIRONMENTAL TRANSPORT, DISTRIBUTION, AND TRANSFORMATION

         Section summary

         A4.1  Transport and distribution between media
               A4.1.1  Wastewater treatment
               A4.1.2  Surface waters, sediments, and soils
               A4.1.3  Fate models
         A4.2  Environmental transformation
               A4.2.1  Biodegradation
                       A4.2.1.1  Aerobic degradation
                       A4.2.1.2  Anaerobic degradation
               A4.2.2  Abiotic degradation
                       A4.2.2.1  Photodegradation
                       A4.2.2.2  Cobalt-60 irradiation
               A4.2.3  Bioaccumulation and biomagnification
                       A4.2.3.1  Aquatic organisms
                       A4.2.3.2  Terrestrial plants

    A5.  ENVIRONMENTAL LEVELS AND HUMAN EXPOSURE

         Section summary

         A5.1  Environmental levels
               A5.1.1  Wastewater, sewage effluent, and sludge
               A5.1.2  Sediment
               A5.1.3  Surface water
               A5.1.4  Soil and groundwater
               A5.1.5  Drinking-water
               A5.1.6  Biota

         A5.2  Environmental processes that influence concentrations
               of linear alkylbenzene sulfonates
               A5.2.1  Changes in chain length distribution during
                       environmental removal of linear alkylbenzene
                       sulfonates
               A5.2.2  Specification of linear alkylbenzene sulfonates
                       in surface waters
         A5.3  Estimation of human intake

    A6.  KINETICS

         Section summary

         A6.1  Absorption, distribution, and excretion
         A6.2  Biotransformation

    A7.  EFFECTS ON LABORATORY MAMMALS AND  IN VITRO TEST SYSTEMS

         Section summary

         A7.1  Single exposures
         A7.2  Short-term exposure
               A7.2.1  Mouse
               A7.2.2  Rat
                       A7.2.2.1  Administration in the diet
                       A7.2.2.2  Administration by gavage
                       A7.2.2.3  Dermal application
                       A7.2.2.4  Subcutaneous injection
               A7.2.3  Guinea-pig
               A7.2.4  Monkey
         A7.3  Long-term exposure; carcinogenicity
               A7.3.1  Mouse
                       A7.3.1.1  Administration in the diet
                       A7.3.1.2  Administration in the drinking-water.
               A7.3.2  Rat
                       A7.3.2.1  Administration in the diet
                       A7.3.2.2  Administration in the drinking-water.
                       A7.3.2.3  Administration by gavage
                       A7.3.2.4  Dermal application
         A7.4  Skin and eye irritation; sensitization
               A7.4.1  Studies of skin
               A7.4.2  Studies of the eye
         A7.5  Reproductive toxicity, embryotoxicity, and teratogenicity
         A7.6  Mutagenicity and related end-points
               A7.6.1  Studies  in vitro
               A7.6.2  Studies  in vivo
         A7.7  Special studies
               A7.7.1  Studies  in vitro
               A7.7.2  Biochemical effects

    A8.  EFFECTS ON HUMANS

         Section summary

         A8.1  Exposure of the general population
         A8.2  Clinical studies
               A8.2.1  Skin irritation and sensitization
               A8.2.2  Effects on the epidermis
               A8.2.3  Hand eczema
               A8.2.4  Occupational exposure
               A8.2.5  Accidental or suicidal ingestion

    A9.  EFFECTS ON OTHER ORGANISMS IN THE LABORATORY AND THE FIELD

         Section summary

         A9.1  Effect of chain length on the toxicity of linear
               alkylbenzene sulfonates
         A9.2  Microorganisms
         A9.3  Aquatic organisms
               A9.3.1  Aquatic plants
                       A9.3.1.1  Freshwater algae and cyanobacteria
                       A9.3.1.2  Marine algae
                       A9.3.1.3  Macrophytes
               A9.3.2  Aquatic invertebrates
                       A9.3.2.1  Acute toxicity
                       A9.3.2.2  Short-term and long-term toxicity
                       A9.3.2.3  Biochemical and physiological effects
               A9.3.3  Fish
                       A9.3.3.1  Acute toxicity
                       A9.3.3.2  Chronic toxicity
                       A9.3.3.3  Biochemical and physiological effects
                       A9.3.3.4  Behavioural effects
                       A9.3.3.5  Interactive effects with other
                                 chemicals
               A9.3.4  Amphibia
               A9.3.5  Studies of the mesocosm and communities
               A9.3.6  Field studies
               A9.3.7  Toxicity of biodegradation intermediates and
                       impurities of linear alkylbenzene sulfonates
                       A9.3.7.1  Individual compounds
                       A9.3.7.2  Effluents
         A9.4  Terrestrial organisms
               A9.4.1  Terrestrial plants
               A9.4.2  Terrestrial invertebrates
               A9.4.3  Birds

    B.  alpha-Olefin sulfonates

    B1.  SUMMARY

    B2.  IDENTITY, PHYSICAL AND CHEMICAL PROPERTIES, AND
         ANALYTICAL METHODS

         B2.1  Identity
         B2.2  Physical and chemical properties
         B2.3  Analytical methods

    B3.  SOURCES OF HUMAN AND ENVIRONMENTAL EXPOSURE

         B3.1  Natural occurrence
         B3.2  Anthropogenic sources
               B3.2.1  Production levels and processes
               B3.2.2  Uses

    B4.  ENVIRONMENTAL TRANSPORT, DISTRIBUTION, AND TRANSFORMATION

         Section summary

         B4.1  Transport and distribution between media
         B4.2  Biotransformation
               B4.2.1  Biodegradation
                       B4.2.1.1  Aerobic biodegradation
                       B4.2.1.2  Anaerobic degradation
               B4.2.2  Abiotic degradation
               B4.2.3  Bioaccumulation and biomagnification
         B4.3  Interaction with other physical, chemical, and
               biological factors

    B5.  ENVIRONMENTAL LEVELS AND HUMAN EXPOSURE

    B6.  KINETICS

         Section summary

         B6.1  Absorption, distribution, and excretion
         B6.2  Biotransformation

    B7.  EFFECTS ON LABORATORY MAMMALS AND  IN VITRO TEST SYSTEMS

         Section summary

         B7.1  Single exposures
         B7.2  Short-term exposure
         B7.3  Long-term exposure; carcinogenicity
               B7.3.1  Mouse
               B7.3.2  Rat
         B7.4  Skin and eye irritation; sensitization
         B7.5  Reproductive toxicity, embryotoxicity, and teratogenicity
         B7.6  Mutagenicity and related end-points
         B7.7  Special studies

    B8.  EFFECTS ON HUMANS

         Section summary

         B8.1  Exposure of the general population
         B8.2  Clinical studies
               B8.2.1  Skin irritation and sensitization
               B8.2.2  Effect on the epidermis
               B8.2.3  Hand eczema
               B8.2.4  Accidental or suicidal ingestion

    B9.  EFFECTS ON OTHER ORGANISMS IN THE LABORATORY AND THE FIELD

         Section summary

         B9.1  Microorganisms
         B9.2  Aquatic organisms
               B9.2.1  Aquatic plants
               B9.2.2  Aquatic invertebrates
               B9.2.3  Fish
         B9.3  Terrestrial organisms
               B9.3.1  Terrestrial plants
               B9.3.2  Terrestrial invertebrates
               B9.3.3  Birds

    C.  Alkyl sulfates

    C1.  SUMMARY

    C2.  IDENTITY, PHYSICAL AND CHEMICAL PROPERTIES, AND
         ANALYTICAL METHODS

         C2.1  Identity
         C2.2  Physical and chemical properties
         C2.3  Analysis
               C2.3.1  Isolation
               C2.3.2  Analytical methods

    C3.  SOURCES OF HUMAN AND ENVIRONMENTAL EXPOSURE

         Section summary

         C3.1  Natural occurrence
         C3.2  Anthropogenic sources
               C3.2.1  Production levels and processes
               C3.2.2  Uses

    C4.  ENVIRONMENTAL TRANSPORT, DISTRIBUTION, AND TRANSFORMATION

         Section summary

         C4.1  Transport and distribution between media
         C4.2  Biotransformation
               C4.2.1  Biodegradation
                       C4.2.1.1  Biodegradation pathway; mechanism
                       C4.2.1.2  Biodegradation in the environment
                       C4.2.1.3  Anaerobic degradation
               C4.2.2  Abiotic degradation
               C4.2.3  Bioaccumulation and biomagnification
         C4.3  Interaction with other physical, chemical,
               and biological factors
         C4.4  Ultimate fate following use

    C5.  ENVIRONMENTAL LEVELS AND HUMAN EXPOSURE

         Section summary
         Environmental levels

    C6.  KINETICS

         Section summary
         C6.1  Absorption, distribution, and excretion
         C6.2  Biotransformation

    C7.  EFFECTS ON LABORATORY MAMMALS AND  IN VITRO TEST SYSTEMS

         Section summary

         C7.1  Single exposures
         C7.2  Short-term exposure
               C7.2.1  Rat
                       C7.2.1.1  Administration in the diet
                       C7.2.1.2  Administration in the drinking-water
                       C7.2.1.3  Dermal application
               C7.2.2  Rabbit

         C7.3  Long-term exposure; carcinogenicity
               C7.3.1  Mouse
               C7.3.2  Rat
                       C7.3.2.1  Administration in the diet
                       C7.3.2.2  Administration in the drinking-water
         C7.4  Skin and eye irritation; sensitization
               C7.4.1  Local irritation
                       C7.4.1.1  Skin
                       C7.4.1.2  Eye
               C7.4.2  Skin sensitization
         C7.5  Reproductive toxicity, embryotoxicity, and teratogenicity
         C7.6  Mutagenicity and related end-points
         C7.7  Special studies

    C8.  EFFECTS ON HUMANS

         Section summary

         C8.1  Exposure of the general population
         C8.2  Clinical studies
               C8.2.1  Skin irritation and sensitization
               C8.2.2  Effects on the epidermis
               C8.2.3  Hand eczema
               C8.2.4  Accidental or suicidal ingestion

    C9.  EFFECTS ON OTHER ORGANISMS IN THE LABORATORY AND THE FIELD

         Section summary

         C9.1  Microorganisms
         C9.2  Aquatic organisms
               C9.2.1  Aquatic plants
                       C9.2.1.1  Freshwater algae
                       C9.2.1.2  Macrophytes
               C9.2.2  Aquatic invertebrates
               C9.2.3  Fish
               C9.2.4  Tests in biocenoses
         C9.3  Terrestrial organisms

    APPENDIX I

    REFERENCES

    RESUME

    RESUMEN
    

    WHO TASK GROUP ON ENVIRONMENTAL HEALTH CRITERIA FOR LINEAR
    ALKYLBENZENE SULFONATES AND RELATED COMPOUNDS

     Members

    Dr R.S. Chhabra, National Institutes of Health, Institute of
        Environmental Health Sciences, Research Triangle Park, North
        Carolina, USA

    Dr A. Granmo, University of Göteborg, Marine Research Station at
        Kristineberg, Fiskebackskil, Sweden

    Ms K. Hughes, Priority Substances Section, Health and Welfare
        Canada, Ottawa, Ontario, Canada

    Mr H. Malcolm, Institute of Terrestrial Ecology, Huntingdon, United
        Kingdom

    Dr E. van der Plassche, Toxicology Advisory Centre, National
        Institute of Public Health and Environmental Protection,
        Bilthoven, Netherlands

    Dr J. Sekizawa, Division of Information on Chemical Safety, National
        Institute of Hygienic Sciences, Tokyo, Japan

    Ms R. Takei, Research Planning and Administration Department, Lion
        Corporation, Tokyo, Japan

    Dr D.G. Van Ormer, Health Effects Division, Office of Pesticides
        Programs, Environmental Protection Agency, Washington DC, USA

    Professor P.N. Viswanathan, Industrial Toxicology Research Centre,
        Lucknow, India

     Representatives/Observers

    IUTOX

    Dr P. Montuschi, Department of Pharmacology, Catholic University of
        the Sacred Heart, Rome, Italy

    CEFIC

    Dr J.L. Berna, Petresa, Madrid, Spain (20-21 October)

    Dr L. Cavalli, Enichem Augusta Industriale Srl, Milan, Italy
        (18-19 October)

    IASD

    Dr G. Holland, UNILEVER Ltd, Environmental Safety Laboratory,
        Sharnbrook, United Kingdom

    Dr M. Stalmans, Procter & Gamble ETC, 100 Temselaan,
        Strombeek-Bever, Belgium

     Secretariat

    Dr H.-J. Poremski, Umweltbundesamt, Berlin, Germany (21 October)

    Dr E. Smith, International Programme on Chemical Safety, World
        Health Organization, Geneva, Switzerland  (Secretary)

    Dr B. Wittann, Umweltbundesamt, Berlin, Germany (18-20 October)

    NOTE TO READERS OF THE CRITERIA MONOGRAPHS

        Every effort has been made to present information in the
    criteria monographs as accurately as possible without unduly
    delaying their publication. In the interest of all users of the
    environmental health criteria monographs, readers are requested to
    communicate any errors that may have occurred to the Director of the
    International Programme on Chemical Safety, World Health
    Organization, Geneva, Switzerland, in order that they may be
    included in corrigenda, which will appear in subsequent volumes.

                                   *  *  *

        A detailed data profile and a legal file can be obtained from
    the International Register of Potentially Toxic Chemicals, Case
    Postale 356, 1219 Châtelaine, Geneva, Switzerland (Telephone no.
    979 9111).

                                   *  *  *

        This publication was made possible by financial support from the
    US Environmental Protection Agency, USA, and from the European
    Commission.

    ENVIRONMENTAL HEALTH CRITERIA FOR LINEAR ALKYLBENZENE SULFONATES AND
    RELATED COMPOUNDS

        A WHO Task Group on Environmental Health Criteria for Linear
    Alkylbenzene Sulfonates and Related Compounds met at the World
    Health Organization, Geneva, on 18-22 October 1993. Dr E. Smith,
    IPCS, welcomed the participants on behalf of Dr M. Mercier, Director
    of IPCS, and of the three IPCS cooperating organizations (UNEP, ILO,
    and WHO).  The Group reviewed and revised a draft document and
    evaluated the risks for human health and the environment of exposure
    to linear alkylbenzene sulfonates, a-olefin sulfonates, and alkyl
    sulfonates.

        The sections of the first draft on toxicology and human health
    were prepared at the National Institute of Health Sciences (NIHS),
    Tokyo, Japan, and the sections on the environment at the Institute
    of Terrestrial Ecology (ITE), Monks Wood, United Kingdom.

        Dr E. Smith of the IPCS Central Unit was responsible for
    the scientific content of the monograph and Mrs E. Heseltine,
    St Léon-sur-Vézère, France, for the editing.

        The authors who contributed to the first draft were:
    Dr S. Dobson, ITE, Monks Wood, United Kingdom
    Dr R. Hasegawa, NIHS, Tokyo, Japan
    Dr Y. Hayashi, NIHS, Tokyo, Japan
    Dr K. Hiraga, Public Health Research Laboratory, Tokyo, Japan
    Dr P. Howe, ITE, Monks Wood, United Kingdom
    Dr Y. Ikeda, NIHS, Tokyo, Japan
    Dr Y. Kurokawa, NIHS, Tokyo, Japan
    Dr H. Malcolm, ITE, Monks Wood, United Kingdom
    Dr A. Matsuoka, NIHS, Tokyo, Japan
    Dr K. Morimoto, NIHS, Tokyo, Japan
    Dr M. Nakadate, NIHS, Tokyo, Japan
    Dr K. Oba, Lion Chemical Corporation, Tokyo, Japan
    Dr J. Sekizawa, NIHS, Tokyo, Japan
    Dr T. Sohuni, NIHS, Tokyo, Japan
    Dr M. Takahashi, NIHS, Tokyo, Japan
    Dr R. Takei, Lion Chemical Corporation, Tokyo, Japan
    Dr S. Tanaka, NIHS, Tokyo, Japan
    Dr S. Tomiyama, Lion Chemical Corporation, Tokyo, Japan
    Dr T. Yamaha, NIHS, Tokyo, Japan
    Dr S. Yoshikawa, Environmental Research Institute, Kawasaki, Japan 
    Dr M. Wakabayashi, Water Quality Management Centre, Tokyo, Japan
    Dr Y. Watanabe, Central Railway Hospital, Tokyo, Japan

        Dr P. Howe, Dr H. Malcolm, and Dr J Sekizawa also contributed to
    the second draft.

        The efforts of all who helped in the preparation and
    finalization of the monograph are gratefully acknowledged.

    1.  OVERALL SUMMARY, EVALUATION, AND RECOMMENDATIONS

    1.1  Identity and analytical methods

        Linear alkylbenzene sulfonates (LAS), alpha-olefin sulfonates
    (AOS), and alkyl sulfates (AS) are anionic surfactants with
    molecules characterized by a hydrophobic and a hydrophilic (polar)
    group. Commercial mixtures consist of isomers and homologues of
    related compounds, which differ in physicochemical properties,
    resulting in formulations for various applications.

        LAS, AOS, and AS can be analysed by nonspecific methods. The
    assay usually used is one for substances that react with methylene
    blue, which responds to any compound containing an anionic and
    hydrophobic group. It thus suffers from analytical interference if
    used for environmental samples; furthermore, the sensitivity of this
    method is about 0.02 mg/litre. Although nonspecific alternatives to
    this method have been developed, they are not commonly used.
    Specific methods for environmental analysis are available only for
    LAS and AS. An improved method based on methylene blue reactivity
    and high-performance liquid chromatography (HPLC) is available for
    analysis of AOS.

        LAS are nonvolatile compounds produced by sulfonation of linear
    alkylbenzene. Commercial products are always mixtures of homologues
    of different alkyl chain lengths (C10-C13 or C14) and isomers
    differing in the phenyl ring positions (2 to 5 phenyl). All of the
    homologues and isomers of LAS can be determined in environmental
    samples and other matrices by specific analytical methods such as
    HPLC, gas chromatography, and gas chromatography-mass spectrometry.

        AOS are nonvolatile compounds produced by sulfonation of
    alpha-olefins. They are mixtures of two compounds, sodium alkene
    sulfonate and hydroxyalkane sulfonate, with alkyl chain lengths of
    C14-C18.

        AS are nonvolatile compounds produced by sulfation of
    oleochemical or petrochemical alcohols. They are mixtures of
    homologues with alkyl chain lengths of C10-C18. Specific
    analytical methods are being developed for environmental monitoring.

    1.2  Sources of human and environmental exposure

        LAS, AOS, and AS are used as active ingredients in household and
    personal care products and in specialized applications. After use,
    such detergent compounds are discharged into the environment in
    wastewater.

        There is occupational exposure to these compounds. The exposure
    of the general human population and of environmental organisms
    depends on the application of LAS, AOS, and AS (and other

    surfactants), on local sewage treatment practices, and on the
    characteristics of the receiving environment.

        In 1990, worldwide consumption figures were about 2 million
    tonnes of LAS, 86 000 tonnes of AOS, and 289 000 tonnes of AS.

    1.3  Environmental concentrations

    1.3.1  Linear alkylbenzene sulfonates

        Concentrations of LAS have been quantified by means of a
    specific, sensitive analytical method in almost every environmental
    compartment in which they might be present. The concentrations
    decrease progressively in the order wastewater > treated effluent
    > surface waters > the sea.

        In areas where LAS are the predominant surfactants used, the
    concentrations are usually 1-10 mg/litre in wastewater,
    0.05-0.1 mg/litre in effluents treated biologically,
    0.05-0.6 mg/litre in effluents treated with a percolating filter,
    0.005-0.05 mg/litre in surface waters below sewage outfalls (with
    concentrations decreasing rapidly to 0.01 mg/litre downstream of the
    outfall), < 1-10 mg/kg in river sediments (< 100 mg/kg in highly
    polluted sediments near discharge zones), 1-10 g/kg in sewage
    sludge, and < 1-5 mg/kg in sludge-amended soils (initially
    5-10 mg/kg; - 50 mg/kg have been reported after atypically high
    applications of sludge). The concentrations of LAS in estuarine
    waters are 0.001-0.01 mg/litre, although higher levels occur where
    wastewater is discharged directly. The concentrations in offshore
    marine waters are < 0.001-0.002 mg/litre.

        It should be noted that the environmental concentrations of LAS
    vary widely. This variation is due to differences in analytical
    methods, in the characteristics of sampling sites (ranging from
    highly polluted areas with inadequate sewage treatment to areas
    where sewage undergoes extensive treatment), in season (which can
    account for a difference of twofold), and in consumption of LAS.

        Environmental monitoring shows that there has been no
    accumulation of LAS in environmental compartments over time. The
    concentrations in soil do not increase with time but decrease owing
    to mineralization. As LAS do not degrade under strictly anaerobic
    conditions (to generate methane), it cannot be concluded that they
    are mineralized in anaerobic sediments. With current use, the rate
    of assimilation of LAS in all receiving environmental compartments
    is equal to the rate of input, implying a steady state.

    1.3.2  alpha-Olefin sulfonates and alkyl sulfates

        Limited data are available on the concentrations of AOS in the
    environment owing to the difficulty of analysing them in
    environmental samples. Nonspecific colorimetric methods (such as
    that based on methylene blue) allow detection of anionic surfactants
    in general, but they suffer from analytical interferences and are
    not suitable for determining specific concentrations of AOS. A
    specific method is being developed for measuring AS in environmental
    samples.

        Studies conducted in the laboratory indicate that AOS and AS are
    mineralized rapidly in all environmental compartments and are
    virtually entirely removed from sewage during treatment. The
    concentrations in surface water, sediments, soil, estuarine water,
    and the marine environment are probably low. The levels of AOS in
    river water have been found to be low.

    1.4  Environmental transport, distribution, and transformation

        At te  mperatures below 5-10°C, the biodegradation kinetics of
    LAS, AOS, and AS is reduced because of a reduction in microbial
    activity.

    1.4.1  Linear alkylbenzene sulfonates

        The routes by which LAS enter the environment vary among
    countries, but the main route is via discharge from sewage treatment
    works. When wastewater treatment facilities are absent or
    inadequate, sewage may be discharged directly into rivers, lakes,
    and the sea. Another route of entry of LAS to the environment is by
    the spreading of sewage sludge on agricultural land.

        Throughout their passage into the environment, LAS are removed
    by a combination of adsorption and primary and ultimate
    bio-degradation. LAS are adsorbed onto colloidal surfaces and onto
    suspended particles, with measured adsorption coefficients of
    40-5200 litres/kg depending on the media and the structure of the
    LAS. They biodegrade in surface water (half-life, 1-2 days), aerobic
    sediments (1-3 days), and marine and estuarine systems (5-10 days).

        During primary sewage treatment, about 25% of LAS (range,
    10-40%) are adsorbed onto and removed with waste sludge. They are
    not removed during anaerobic sludge digestion but are removed during
    aerobic treatment of sludge, with a half-life of about 10 days.
    After application of sludge to soil, 90% of LAS are generally
    degraded within three months, with a half-life of 5-30 days.

        The whole-body concentration factors for LAS range from 100 to
    300, for the sum of 14C-LAS and 14C metabolites. Uptake by fish
    occurs mainly through the gills, with subsequent distribution to the

    liver and gall-bladder after biotransformation. LAS are excreted
    rapidly, and there is therefore no evidence that they undergo
    biomagnification.

    1.4.2  alpha-Olefin sulfonates

        Fewer data are available on the environmental transport,
    distribution, and transformation of AOS than for LAS.  It can be
    inferred that AOS are transported into the environment in a manner
    similar to that established for LAS, AS and other detergent
    surfactants, and the environmental fate of AOS is similar to that of
    LAS and AS. It is readily biodegraded under aerobic conditions, and
    primary biodegradation is complete within 2-10 days, depending on
    the temperature.  Limited data are available on the bioaccumulation
    of AOS; no bioaccumulation was observed in fish. There are no data
    on abiotic degradation.

    1.4.3  Alkyl sulfates

        AS are transported into the environment by mechanisms similar to
    those that operate for LAS and AOS. They are readily biodegradable
    under aerobic and anaerobic conditions in the laboratory and under
    environmental conditions; primary biodegradation is complete within
    2-5 days. The whole-body bioconcentration factor ranges from 2 to 73
    and varies with the chain length of alkyl sulfate homologues. AS are
    taken up, distributed, biotransformed, and excreted by fish in the
    same way as LAS and are not bioconcentrated in aquatic organisms.

    1.5  Kinetics

        LAS, AOS, and AS are readily absorbed by the gastrointestinal
    tract, widely distributed throughout the body, and extensively
    metabolized. LAS undergo omega- and ß-oxidation. The parent
    compounds and metabolites are excreted mainly through the kidney,
    although a proportion of an absorbed dose may be excreted as
    metabolites in the faeces by biliary excretion. Only minimal amounts
    of LAS, AOS, and AS appear to be absorbed through intact skin,
    although prolonged contact may compromise the integrity of the
    epidermal barrier, thereby permitting greater absorption; high
    concentrations may reduce the time required for penetration.

    1.6  Effects on experimental animals and  in vitro test systems

        The oral LD50 values for sodium salts of LAS were 404-1470
    mg/kg body weight in rats and 1259-2300 mg/kg body weight in mice,
    suggesting that rats are more sensitive than mice to the toxicity of
    LAS. An oral LD50 of 3000 mg/kg body weight was measured for a
    sodium salt of AOS in mice. The oral LD50 values of AS in rats
    were 1000-4120 mg/kg body weight. LAS, AOS, and AS irritate the skin
    and eye.

        Minimal effects, including biochemical alterations and
    histo-pathological changes in the liver, have been reported in
    subchronic studies in which rats were administered LAS in the diet
    or drinking-water at concentrations equivalent to doses greater than
    120 mg/kg body weight per day. Although ultrastructural changes were
    observed in liver cells at lower doses in one study, the changes
    appeared to be reversible. Effects were not seen at similar doses in
    other studies, but the organs may have been examined more closely in
    the initial study. Reproductive effects, including decreased
    pregnancy rate and litter loss, have been reported in animals
    administered doses > 300 mg/kg per day. Histopathological and
    biochemical changes were observed after long-term dermal application
    to rats of solutions of > 5% LAS, and after 30 days' application to
    the skin of guinea-pigs of 60 mg/kg body weight. Repeated dermal
    application of > 0.3% solutions of LAS induced fetotoxic and
    reproductive effects, but also induced maternal toxicity. Few data
    are available from studies in experimental animals that allow
    evaluation of the potential effects of AOS in humans. No effects
    were observed in rats administered oral doses of 250 mg/kg body
    weight per day chronically, but fetotoxicity was seen in rabbits
    administered a maternally toxic dose of 300 mg/kg body weight per
    day. Application of AOS to the skin and eyes of experimental animals
    induced local effects.

        Although the effects of short- and long-term exposure of animals
    to AS have been investigated in several studies, most suffered from
    inadequate histopathological examination or small group sizes;
    furthermore, the highest doses used in the long-term studies did not
    produce any toxic effects, so that an NOAEL could not be
    established. Effects have, however, been reported consistently in
    rats administered AS in the diet or drinking-water at concentrations
    equivalent to 200 mg/kg body weight per day or more. Local effects
    have been observed on the skin and eyes after topical application of
    concentrations of about 0.5% AS or more. Maternally toxic and
    fetotoxic effects have been observed at higher concentrations.

        Most of the long-term studies are inadequate to evaluate the
    carcinogenic potential of LAS, AOS, and AS in experimental animals,
    owing to factors such as small numbers of animals, limited numbers
    of doses, absence of a maximal tolerated dose, and limited
    histo-pathological examination in the majority of studies. In those
    studies in which the pathological findings were adequately reported,
    maximal tolerated doses were not used, and the doses did not produce
    toxic effects. Subject to these limitations, however, the studies in
    which animals were administered LAS, AOS, or AS orally gave no
    evidence of carcinogenicity; long-term studies in which AOS was
    applied by skin painting studies also showed no effect.

        On the basis of limited data, these compounds do not appear to
    be genotoxic  in vivo or  in vitro.

    1.7 Effects on humans

        The results of patch tests show that human skin can tolerate
    contact with solutions containing up to 1% LAS, AOS, or AS for 24 h
    with only mild irritation reactions. These surfactants caused
    delipidation of the skin surface, elution of natural moisturizing
    factor, denaturation of the proteins of the outer epidermal layer,
    and increased permeability and swelling of the outer layer. Neither
    LAS, AOS, nor AS induced skin sensitization in volunteers, and there
    is no conclusive evidence that they induce eczema. No serious
    injuries or fatalities have been reported following accidental
    ingestion of these surfactant by humans.

    1.8 Environmental effects

    1.8.1  Linear alkylbenzene sulfonates

    1.8.1.1  Aquatic environment

        LAS have been studied extensively both in the laboratory (short-
    and long-term studies) and under more realistic conditions (micro-
    and mesocosm and field studies). In general, a decrease in alkyl
    chain length or greater internalization of the phenyl group is
    accompanied by a decrease in toxicity. Observations in fish and
     Daphnia indicate that a decrease in chain length of one unit (e.g.
    C12 to C11) results in an approximately twofold decrease in
    toxicity.

        The results of laboratory tests are as follows:

        --  Microorganisms: The results are highly variable owing to
    the use of a variety of test systems (e.g. inhibition of activated
    sludge; mixed cultures and individual species). The EC50 values
    range from 0.5 mg/litre (single species) to > 1000 mg/litre. For
    microorganisms, there is no linear relationship between chain length
    and toxicity.

        --  Aquatic plants: The results are highly species dependent.
    For freshwater organisms, the EC50 values are 10-235 mg/litre
    (C10-C14) in green algae, 5-56 mg/litre (C11.1-C13) in blue
    algae, 1.4-50 mg/litre (C11.6-C13) in diatoms, and
    2.7-4.9 mg/litre (C11.8) in macrophytes; marine algae appear to be
    even more sensitive. In algae, there is probably no linear
    relationship between chain length and toxicity.

        --  Invertebrates: The acute L(E)C50 values for at least 22
    freshwater species are 4.6-200 mg/litre (chain length not specified;
    C13) for molluscs; 0.12-27 mg/litre (not specified; C11.2-C18)
    for crustaceans; 1.7-16 mg/litre (not specified; C11.8) for worms,
    and 1.4-270 mg/litre (C10-C15) for insects. The chronic L(E)C50
    values are 2.2 mg/litre (C11.8) for insects and 1.1-2.3 mg/litre

    (C11.8-C13) for crustaceans. The chronic no-observed-effect
    concentration (NOEC; based on lethality or reproductive effects) is
    0.2-10 mg/litre (not specified; C11.8) for crusta-ceans. Marine
    invertebrates appear to be more sensitive, with LC50 values of 1
    to >100 mg/litre (almost all C12) for 13 species, and NOECs of
    0.025-0.4 mg/litre (not specified for all tests) for seven species
    tested.

        --  Fish: The acute LC50 values are 0.1-125 mg/litre
    (C8-C15) for 21 freshwater species; the chronic L(E)C50 values
    are 2.4 and 11 mg/litre (not specified; C11.7) for two species;
    and the NOECs are 0.11-8.4 to 1.8 mg/litre (not specified;
    C11.2-C13) for two species. Again, marine fish appear to be more
    sensitive, with acute LC50 values of 0.05-7 mg/litre (not
    specified; C11.7) for six species and chronic LC50 values of
    0.01-1 mg/litre (not specified) for two species. In most of the
    reports, the chain length was not reported. An NOEC of <
    0.02 mg/litre (C12) was reported for marine species.

        The average chain length of products commonly used commercially
    is C12. Compounds of many different chain lengths have been tested
    in  Daphnia magna and fish, but the length tested in other
    freshwater organisms has usually been C11.8. The typical acute
    L(E)C50 values for C12 LAS are 3-6 mg/litre in  Daphnia magna
    and 2-15 mg/litre in freshwater fish, and the typical chronic NOECs
    are 1.2-3.2 mg/litre for Daphnia and 0.48-0.9 mg/litre for
    freshwater fish. The typical acute LC50 values for LAS of this
    chain length in marine fish are < 1-6.7 mg/litre.

        Saltwater organisms, especially invertebrates, appear to be more
    sensitive to LAS than freshwater organisms. In invertebrates, the
    sequestering action of LAS on calcium may affect the availability of
    this ion for morphogenesis. LAS have a general effect on ion
    transport. Biodegradation products and by-products of LAS are 10-100
    times less toxic than the parent compounds.

        The results obtained under more realistic conditions are as
    follows: LAS have been tested in all freshwater tests at several
    trophic levels, including enclosures in lakes (lower organisms),
    model ecosystems (sediment and water systems), rivers below and
    above the outfall of wastewater treatment plants, and in
    experimental streams. C12 LAS were used in almost all cases. Algae
    appear to be more sensitive in summer than in winter, as the 3-h
    EC50 values were 0.2-8.1 mg/litre after photosynthesis, whereas in
    model ecosystems no effects were seen on the relative abundance of
    algal communities at 0.35 mg/litre. The no-effect levels in these
    studies were 0.24-5 mg/litre, depending on the organism and
    parameter tested. These results agree fairly well with those of
    laboratory tests.

    1.8.1.2  Terrestrial environment

        Information is available for plants and earthworms. The
    NOECs for seven plant species tested in nutrient solutions are
    < 10-20 mg/litre; that for three species tested in soils, based
    on growth, was 100 mg/kg (C10-C13). The 14-day LC50 for earthworms
    was > 1000 mg/kg.

    1.8.1.3  Birds

        One study of chickens treated in the diet resulted in an NOEC
    (based on egg quality) of > 200 mg/kg.

    1.8.2  alpha-Olefin sulfonates

        There are limited data on the effects of AOS on aquatic and
    terrestrial organisms.

    1.8.2.1  Aquatic environment

        Only the results of laboratory tests are available:

        --  Algae: EC50 values of > 20-65 mg/litre (C16-C18)
    have been reported for green algae.

        --  Invertebrates: LC50 values of 19 and 26 mg/litre (C16-C18)
    have been reported for Daphnia.

        --  Fish: The acute LC50 values are 0.3-6.8 mg/litre (C12-C18)
    for nine species of fish. On the basis of short-term studies in
    brown trout  (Salmo trutta), golden orfe  (Idus melanotus), and
    harlequin fish  (Rasbora heteromorpha), it can be concluded that
    the toxicity of C14-C16 compounds is about five times lower than
    that of C16-C18, with LC50 values (all measured concentrations)
    of 0.5-3.1 (C16-C18) and 2.5-5.0 mg/litre  (C14-C16). Two
    long-term studies in rainbow trout showed that growth is the most
    sensitive parameter, resulting in an EC50 of 0.35 mg/litre. In a
    marine fish, the grey mullet (Mugal cephalus), the 96-h LC50 value
    was 0.70 mg/litre.

    1.8.2.2  Terrestrial environment

        One study of plants in nutrient solutions showed NOECs of
    32-56 mg/litre. In a study of chickens treated in the diet, an NOEC
    (based on egg quality) of > 200 mg/kg was reported.

    1.8.3  Alkyl sulfates

    1.8.3.1  Aquatic environment

        AS have been studied in short- and long-term studies and in one
    study under more realistic conditions. Their toxicity is again
    dependent on the alkyl chain length; no information was available on
    any difference in toxicity between linear and branched AS.

            The results of the laboratory tests are as follows:

        --  Microorganisms: The EC50 values in a marine community
    were 2.1-4.1 mg/litre (C12). The NOECs in Pseudomonas putida were
    35-550 mg/litre (C16-C18).

        --  Aquatic plants: The EC50 values were > 20-65 mg/litre
    (C12-C13) in green algae and 18-43 mg/litre (C12) in
    macrophytes. The NOECs were 14-26 mg/litre (C12-C16/C18) in
    green algae.

        --  Invertebrates: The LC50 and EC50 values were 4-140 mg/litre
    (C12/C15-C16/C18) in freshwater species and 1.7-56 mg/litre
    (all C12) in marine species. The chronic NOEC in Daphnia magna was
    16.5 mg/litre (C16/C18) and those in marine species were
    0.29-0.73 mg/litre (chain length not specified).

        --  Fish: The LC50 values were 0.5-5.1 mg/litre (not
    specified; C12-C16) in freshwater species and 6.4-16 mg/litre
    (all C12) in marine species. No long-term studies were available.

        It should be noted that many of these studies were carried out
    under static conditions. As AS are readily biodegradable, their
    toxicity may have been underestimated. In a 48-h study with  Oryzias
     latipes, the LC50 values were 46, 2.5 and 0.61 mg/litre
    (measured concentrations) for C12, C14, and C16 compounds,
    respectively. This and other studies indicate that toxicity differs
    by a factor of five for two units of chain length. In a flow-through
    biocenosis study with compounds of C16-C18, an NOEC of
    0.55 mg/litre was observed.

    1.8.3.2  Terrestrial environment

        NOEC values of > 1000 mg/kg (C16-C18) were reported for
    earthworms and turnips.

    1.9  Human health risk evaluation

        LAS are the most widely used surfactants in detergents and    
    cleaning products; AOS and AS are also used in detergents and
    personal care products. The primary route of human exposure is,
    therefore, through dermal contact. Minor amounts of LAS, AOS, and AS

    may be ingested in drinking-water and as a result of residues on
    utensils and food. Although limited information is available, the
    daily intake of LAS via these media can be estimated to be about
    5 mg/person. Occupational exposure to LAS, AOS, and AS may occur
    during the formulation of various products, but no data are
    available on the effects in humans of chronic exposure to these
    compounds.

        LAS, AOS, and AS can irritate the skin after repeated or
    prolonged dermal contact with concentrations similar to those found
    in undiluted products. In guinea-pigs, AOS can induce skin
    sensitization when the level of gamma-unsaturated sultone exceeds
    about 10 ppm.

        The available long-term studies in experimental animals are
    inadequate to evaluate the carcinogenic potential of LAS, AOS, and
    AS, owing to factors such as study design, use of small numbers of
    animals, testing of insufficient doses, and limited
    histopathological examination. In the limited studies available in
    which animals were administered LAS, AOS, or AS orally, there was no
    evidence of carcinogenicity; the results of long-term studies in
    which AOS were administered by skin painting were also negative.
    These compounds do not appear to be genotoxic  in vivo or
     in vitro, although few studies have been reported.

        Minimal effects, including biochemical alterations and
    histopathological changes in the liver, have been reported in
    subchronic studies of rats administered LAS in the diet or
    drinking-water at concentrations equivalent to a dose of about
    120 mg/kg body weight per day, although no effects were observed in
    studies in which animals were exposed to higher doses for longer
    periods. Dermal application of LAS caused both systemic toxicity and
    local effects.

        The average daily intake of LAS by the general population, on
    the basis of limited estimates of exposure via drinking-water,
    utensils, and food, is probably much lower (about three orders of
    magnitude) than the levels shown to induce minor effects in
    experimental animals.

        The effects of AOS in humans observed in the few studies
    available are similar to those reported in animals exposed to LAS.
    As insufficient data are available to estimate the average daily
    intake of AOS by the general population and on the levels that
    induce effects in humans and animals, it is not possible to evaluate
    with confidence whether exposure to AOS in the environment  presents
    a risk to human health. The levels of AOS in media to which humans
    may be exposed are likely to be lower than those of LAS, however, as
    AOS are used less.

        Effects have been reported consistently in a few, limited
    studies in rats administered AS in the diet or drinking-water at
    concentrations equivalent to doses of 200 mg/kg body weight per day
    or more. Local effects on the skin and eyes have been observed after
    repeated or prolonged topical application. The available data are
    insufficient to estimate the average daily intake of AS by the
    general population. Since AS surfactants are not used as extensively
    as those containing LAS, however, intake of AS is likely to be at
    least three orders of magnitude lower than the doses shown to induce
    effects in animals.

    1.10  Evaluation of effects on the environment

        LAS, AS, and AOS are used in large quantities and are released
    into the environment via wastewater. Risk assessment requires
    comparison of exposure concentrations with concentrations that cause
    no adverse effects, and this can be done for several environmental
    compartments. For anionic surfactants in general, the most important
    compartments are sewage water treatment plants, surface waters,
    sediment- and sludge-amended soils, and estuarine and marine
    environments. Both biodegradation (primary and ultimate) and
    adsorption occur, resulting in decreased environmental
    concentrations and bioavailability. Reduction in chain length and
    loss of the parent structure both result in compounds that are less
    toxic than the parent compound. It is important that these
    considerations be taken into account when the results of laboratory
    tests are compared with potential effects on the environment.
    Furthermore, in assessing the risk associated with environmental
    exposure to these three anionic compounds, comparisons should be
    made with the results of tests for toxicity of compounds of the same
    chain length.

        The effects of LAS on aquatic organisms have been tested
    extensively. In laboratory tests in freshwater, fish appeared to be
    the most sensitive species; the NOEC for fathead minnow was about
    0.5 mg/litre (C12), and these results were confirmed in tests
    under more realistic conditions. Differences have been observed
    among phyto-plankton: in acute 3-h assays on phytoplankton, the
    EC50 values were 0.2-0.1 mg/litre (C12-C13), whereas no
    effects on relative abundance were found in other tests at
    0.24 mg/litre (C11.8). Marine species appeared to be slightly more
    sensitive than most other taxonomic groups.

        A broad range of concentrations of all three anionic compounds
    occurs in the environment, as shown by extensive measurements of
    LAS. Owing to this broad range, no generally applicable
    environmental risk assessment can be made for these compounds. A
    risk assessment must involve appropriate understanding of the
    exposure and effect concentrations in the ecosystem of interest.

        Accurate data on exposure to AS and AOS are needed before an
    environmental risk assessment can be made. Models are therefore
    being used to assess exposure concentrations in the receiving
    environmental compartments. Data on the toxicity of AS and AOS to
    aquatic organisms, especially after chronic exposure to stable
    concentrations, are relatively scarce. The available data show that
    the toxicity of AOS and AS is similar to that of other anionic
    surfactants.

        Saltwater organisms appear to be more sensitive than freshwater
    organisms to these compounds; however, their concentrations are
    lower in seawater, except near wastewater outlets. The fate and
    effects of these compounds in sewage in seawater have not been
    investigated in detail.

        For an evaluation of the environmental safety of surfactants
    such as LAS, AOS, and AS, actual environmental concentrations must
    be compared with no-effect concentrations. Research requirements are
    determined not only by the intrinsic properties of a chemical but
    also by its pattern or trend of consumption. As these can vary
    considerably among geographic areas, assessment and evaluation must
    be carried out regionally.

    1.11  Recommendations for protection of human health and
          the environment

    1.  As exposure to dusts may occur in the workplace (during
    processing and formulation), standard occupational hygiene practices
    should be used to ensure protection of workers' health.

    2.  The composition of formulations for consumer and industrial use
    should be designed to avoid hazard, particularly for formulations
    that are used for cleaning or laundering by hand.

    3.  Environmental exposure and effects should be appropriately
    monitored to provide early indications of any overloading of
    relevant environmental compartments.

    1.12  Recommendations for further research

     Human health

    1.  Since the skin is the primary route of human exposure to LAS,
    AOS, and AS and since no adequate long-term studies of dermal
    toxicity or carcinogenicity in experimental animals are available,
    it is recommended that suitably designed long-term studies in which
    these compounds are applied dermally be conducted.

    2.  In view of the lack of definitive data on the genotoxicity of
    AOS and AS, additional studies should be performed  in vivo and
     in vitro.

    3.  In view of the inadequacies of the available studies on
    reproductive and developmental toxicity, definitive studies should
    be carried out in laboratory animals to obtain data on the effects
    and on the effect and no-effect levels of LAS, AOS, and AS.

    4.  As exposure to LAS, AOS, and AS is not adequately defined, the
    exposure of the general population should be monitored, particularly
    when these surfactants are used for cleaning and laundering by hand.

    5.  Since LAS, AOS, and AS may enhance the transport of other
    chemicals in environmental media and modulate their bioavailability
    and toxicity in surface waters, river sediments, and soils to which
    humans may be exposed, interactions with other environmental
    chemicals and the consequences for humans should be investigated.

     Environmental safety

    6.  Additional studies should be carried out on the mechanisms of
    adsorption and desorption of AOS and AS. Studies should also be done
    on the partitioning of LAS, AOS, and AS between dissolved and
    suspended colloidal particles in water. Mathematical models of
    sorption coefficients should be developed and validated on the basis
    of physical-chemical parameters.

    7.  Studies of the biodegradation of AOS and AS in sludge-amended
    soils and river sediments should be carried out when exposure
    occurs. Studies in river sediments (aerobic and anaerobic zones)
    should be performed downstream of treated and untreated wastewater
    and sewage outfalls.

    8.  Environmental concentrations of LAS, AOS, and AS should be
    monitored regionally and nationally in order to obtain information
    on exposure. Analytical methods should be developed for detecting
    low levels of AOS and AS in relevant environmental compartments.

    9.  National databases should be developed on the concentrations of
    LAS, AOS, and AS in wastewater and rivers and on the types,
    efficiency, and location of wastewater treatment plants, in order to
    facilitate an assessment of the impact of discharges of these
    surfactants to the environment.

    10. Long-term studies of the toxicity of AOS and AS to fish
    (freshwater and marine) and aquatic invertebrates should be
    conducted in order to establish the relative sensitivity of these
    species.

    A.  Linear alkylbenzene sulfonates and their salts

    A1.  SUMMARY

        See Overall Summary, Evaluation, and Recommendations (pp. 7-21).

    A2.  IDENTITY, PHYSICAL AND CHEMICAL PROPERTIES, AND
         ANALYTICAL METHODS

    A2.1  Identity (sodium salt)

    Chemical formula:            CnH2n-1O3S Na ( n: 16-20) (for
                                 current commercial products)

    Chemical structure:          
                                 Chemical Structure

                                  j,k: integers ( j + k = 7-11)

    Common name:                 Sodium linear alkylbenzenesulfonate

    Common synonyms:             LAS, LAS sodium salt, linear
                                 alkylbenzene-sulfonic acid sodium salt,
                                 linear dodecyl-benzenesulfonic acid
                                 sodium salt, sodium straight chain
                                 alkylbenzenesulfonate

    CAS Registry number:         68411-30-3 (LAS sodium salt, C10-13
                                 alkyl)

    Common trade names:          Ablusol DBC, Agrilan WP, Alkasurf CA,
                                 Arylan, Atlas G-3300B, Atlox, Biosoft,
                                 Berol, Calsoft, Demelan CB-30, Elecut
                                 S-507, Elfan, Emulphor ECB, Emulsogen
                                 Brands, Gardilene, Hexaryl, Idet,
                                 Kllen, Lutopon SN, Manro, Marlopon,
                                 Marlon A, Nacconol 90 F, Nansa HS 80,
                                 Nansa Lutersit, Neopelex, Sandozin AM,
                                 Sipex, Sulfamin, Sulframin, Surfax 495,
                                 Teepol, Tersapol, Tersaryl, Ufaryl DL
                                 80P, Witconate (McCutcheon, 1993)

    Abbreviations:               LAS, LAS-Na

    Specification:               LAS are anionic surfactants which were
                                 introduced in the 1960s as more
                                 biodegradable replacements for highly
                                 branched alkyl-benzene sulfonates. LAS
                                 are produced by sulfonation of linear
                                 alkylbenzene (LAB) with sulfur trioxide
                                 (SO3), usually on a falling film
                                 reactor or with oleum in batch
                                 reactors. The corresponding sulfonic
                                 acid is subsequently neutralized with
                                 an alkali such as caustic soda. The
                                 hydrocarbon intermediate, LAB, is
                                 currently produced mainly by alkylation
                                 of benzene with  n-olefins or
                                  n-chloroparaffins using hydrogen
                                 fluoride (HF) or aluminium chloride
                                 (AlCl3) as a catalyst, and the LAS
                                 derivatives are thus generally referred
                                 to in that context (Cavalli et al.,
                                 1993a). Currently, 74% of world
                                 production of LAB is via HF and 26% via
                                 AlCl3 (Berna et al., 1993a).

        LAS are a mixture of homologues and phenyl positional isomers,
    each containing an aromatic ring sulfonated at the  para position
    and attached to a linear alkyl chain of C10-C14 (in Europe,
    predominantly C10-C13) at any position except the terminal one.
    The product is generally used in detergents in the form of the
    sodium salt.

        Some of the typical characteristics of LAS, including the
    distribution of alkyl chain lengths and the positions of the phenyl
    rings in the two types of LAS used in laundry detergents, are shown
    in the box below. The United States Toxic Substances Control Act
    inventory lists LAS homologues with chain lengths up to C18
    (Tables 1 and 2), but these products are not currently used for
    commercial purposes.

    A2.2  Physical and chemical properties

        The properties of LAS differ greatly depending on the alkyl
    chain length. Table 3 shows the Krafft points (temperature at which
    1 g of LAS dissolve in 100 ml of water) and the relative critical
    micelle concentrations of the single homologues.

                                                                                    

    Typical characteristics of linear alkylbenzene sulfonates used in laundry
    detergents:

    Appearance (commercial product):         White paste (containing water)
    Average length of alkyl carbon chain:    11.8
    Average relative molecular mass:         342
    Unsulfonated matter:                     1-2%
    Alkyl chain distribution:
                                 C10            10-15%
                                 C11            25-35%
                                 C12            25-35%
                                 C13            15-30%
                                 C14            0-5%

    Phenyl ring position             LAS (LAB-HFa)       LAS (LAB-AlCl3b)
    2-phenyl                         18                  28
    3-phenyl                         16                  19
    4-phenyl                         17                  17
    5-phenyl                         24                  18
    6-phenyl                         25                  18
                                                                                

    From Cavalli et al. (1993a)
    a Hydrofluoric acid-catalysed process
    b Aluminium chloride-catalysed process

    Table 1.  Mixtures of linear alkylbenzene sulfonates and their salts found in the
              United States Toxic Substances Control Act inventory

                                                                                      
    Generic benzene-            CAS number
    sulfonic acid groups                                                              
                                Acid             Salts
                                                                                      

    (C10-13)Alkyl-a                              68411-30-3  (sodium salt)
    (C10-16)Alkyl-              68584-22-5       68584-23-6  (calcium salt)
                                                 68584-26-9  (magnesium salt)
                                                 68584-27-0  (potassium salt)
    Mono (C6-12)alkyl-                           68608-87-7  (sodium salt)
    Mono(C7-17)alkyl-                            68953-91-3  (calcium salt)
                                                 68953-94-6  (potassium salt)
    Mono(C9-12)alkyl-                            68953-95-7  (sodium salt)
    Mono(C10-16)alkyl-                           68910-31-6  (ammonium salt)
                                                 68081-81-2  (sodium salt)
    Mono(C12-18)alkyl-                           68648-97-5  (potassium salt)
                                                                                      

    a There may be more than one alkyl substituent per benzene ring (United
      States Environmental Protection Agency, 1981).
    
        Table 2.  Individual linear alkylbenzene sulfonates (LAS) found in the United States Toxic Substances Control Act inventory
                                                                                                                                              

    Parent sulfonic acid      Empirical       CAS Registry number
    (abbreviation)            formula                                                                                                         
                                              Acids               Sodium salts          Other salts
                                                                                                                                              

    Dodecylbenzene            C16H26O3S       1322-98-1           1322-98-1
    (C10 LAS)                                 (140-60-3)a         (2627-06-7)a
    Undecylbenzene            C17H28O3S       50854-94-9          27636-75-5            NH4 salt, 61931-75-7
    (C11 LAS)
    Dodecylbenzene            C18H30O3S       27176-87-0          25155-30-0            Al salt, 29756-98-7; NH4 salt, 1331-61-9;
    (C12 LAS)                                                     (2211-98-5)a          Ca salt, 26264-06-2; K salt, 27177-77-1;
                                                                  (68628-60-4)b         also numerous salts with alkyl amines
                                                                  (18777-54-3)c
    Tridecylbenzene           C19H32O3S       25496-01-9          26248-24-8            Also salts with alkyl amines
    (C13 LAS)
    Tetradecylbenzene         C20H34O3S       30776-59-1          28348-61-0
    (C14 LAS)                                 (47377-10-2)a       (1797-33-7)a
    Pentadecylbenzene         C21H36O3S       61215-89-2                                K salt, 64716-02-5
    (C15 LAS)
    Hexadecylbenzene          C22H38O3S       (16722-32-0)a                             K salt, 64716-00-3
    (C16 LAS)
    Heptadecylbenzene         C23H40O3S       39735-13-2
    (C17 LAS)
                                                                                                                                              

    From United States Environmental Protection Agency (1981)
    a Specifies  para substitution
    b Specifies  para substitution at second position on alkyl chain
        Table 3.  Relationship between alkyl chain length, Krafft point,
              and critical micelle concentration (CMC) of linear
              alkylbenzene sulfonates

                                                                 

    Alkyl chain length   Krafft point (°C)    CMC × 10-3 (25°C)
                                                                 

    10                   -1                   5.8
    12                    3                   1.1
    14                    8                   0.24
    15                   -                    0.11
    16                   13                   -
                                                                 

    From Ohki & Tokiwa (1970)

        The solubility of surfactants in water, defined as the
    concentration of dissolved molecules in equilibrium with a
    crystalline surfactant phase, increases with rising temperature. For
    surfactants, a distinct, sharp bend (break point) is observed in the
    solubility/temperature curve. The steep rise in solubility above the
    sharp bend is caused by micelle formation. The point of intersection
    of the solubility and critical micelle curves plotted as a function
    of temperature is referred to as the Krafft point, which is a triple
    point at which surfactant molecules coexist as monomers, micelles,
    and hydrated solids. The temperature corresponding to the Krafft
    point is called the Krafft temperature. Above the Krafft temperature
    and critical micelle concentration, a micellar solution is formed
    and higher than aqueous solubility may be obtained.

        As commercial LAS are a mixture of homologues and phenyl-
    positional isomers, their properties may differ. Even some products
    with the same alkyl chain distribution (same average carbon number)
    have different properties, depending on the 2-phenyl isomer content.
    The solubility in water of commercial LAS used for detergents
    (average alkyl carbon length, 11.8), for example, which is important
    for liquid formulations, is typically about 25% at 25°C for LAS (LAB
    via HF) and about 38% at 25°C for LAS (LAB via AlCl3) (Cavalli et
    al., 1993a).

        As LAS are anionic surfactants, they lower the surface tension
    of water so that it can wet and penetrate fabrics more easily to
    loosen and remove soils and stains. Micelles, which are formed at
    low concentrations, solubilize oil and stains effectively (Ohki &
    Tokiwa, 1969). Other important properties of LAS are detergency,
    foaming, sensitivity to Ca and Mg ions, wetting, and surface
    tension, which reach their optimal values generally when the alkyl
    chain length is about C12 (Yamane et al., 1970).

        A physico-chemical property often used in environmental
    modelling is the octanol-water partition coefficient (Kow).
    Although it is impossible to measure the Kow for surface-active
    compounds like LAS, it can be calculated. Roberts (1989) modified
    the fragment method of Leo & Hansch (1979) in order to take the
    branching of position into account. He thus defined a function, log
    ( CP + 1), where  CP is found by pairing off carbon atoms along
    the two branches up to the terminus of the shorter branch. (In the
    case of LAS,  CP is the carbon number of the shorter of the
    integers  j and  k noted in section 2.1.) This gave the formula:

    log Kow =  ALK-1.44 log ( CP + 1),

    where  ALK is log Kow calculated without a branch factor.

        In order to calculate log Kow for multicomponent materials
    like LAS, the calculated Kow for each component is multiplied by
    the mole fraction of the corresponding component, the products are
    summed, and the logarithm is calculated to give log  WAK ( WA,
    weighted average).

    A2.3  Analysis

    A2.3.1  Isolation

        A number of analytical methods are available for the
    determination of LAS in water, but the primary method is assay as
    methylene blue-active substances (MBAS). The methylene blue reaction
    responds to any compound containing an anionic centre and a
    hydrophobic centre, because such compounds tend to form an
    extractable ion pair when they combine with cationic dyes such as
    methylene blue; as only the oxidized form is blue, many positive
    interferences may occur. Negative interference in MBAS analysis is
    seen in the presence of cationic substances such as proteins and
    amines (Swisher, 1970, 1987). Therefore, isolation of LAS from a
    sample is one of the most important aspects of their analysis. Most
    analytical methods include appropriate procedures for isolation.

    A2.3.2  Analytical methods

        The analytical methods available for determining LAS in water
    include nonspecific methods, involving colorimetric, fluorimetric,
    and atomic adsorption techniques, and specific methods involving
    techniques such as high-performance liquid chromatography (HPLC),
    gas chromatography (GC) and GC-mass spectrometry (MS).

    A2.3.2.1  Nonspecific methods

        The simplest procedure for the determination of LAS in aqueous
    solution is a two-phase titration method. LAS are titrated in a
    mixed aqueous chloroform medium with a standard solution of a
    cationic reagent, such as benzethonium chloride (Hyamine 1622), and
    a small amount of indicator, such as a mixture of dimidium bromide
    and acid blue. The end-point is determined by a change in the colour
    of the organic solvent (ISO 2271, 1972).

        The main nonspecific analytical method used is assay for MBAS,
    described above. Colorimetric techniques are routinely used to
    determine low concentrations of anionic surfactants, including LAS,
    in aqueous samples and have been used extensively in testing and
    environmental monitoring of these materials. The colorimetric
    methods have the same common analytical basis, that is, formation of
    solvent extractable compounds between the anionic surfactant and an
    intensely coloured cationic species. The most commonly used cationic
    reagent for this purpose is methylene blue (Swisher, 1970, 1987).
    The same principle has been used as the basis of many other
    procedures for the determination of anionic surfactants.

        It has been shown or predicted that organic sulfates,
    sulfonates, carboxylates, phenols, and even simple inorganic anions
    such as cyanide, nitrate, thiocyanate, and sulfate can be methylene
    blue-reactive (Swisher, 1970, 1987). The negative interferences that
    can occur as a result of direct competition of other 'cationic'
    materials are generally considered to be less important than
    positive interferences, and the entities detected by the analysis
    are correctly referred to as MBAS.

        The procedure developed by Longwell & Maniece (1955) and the
    improved version of Abbott (1962) are considered to be the best
    methods for the determination of MBAS in aqueous samples. The
    sensitivity of these procedures is such that levels of
    0.01-0.02 mg/litre MBAS can be determined.

        The MBAS response can be used as an acceptable overestimate of
    the synthetic anionics present in domestic wastewaters, but these
    materials may comprise only a small proportion of the total MBAS in
    surface waters (Waters & Garrigan, 1983; Matthijs & De Henau, 1987).
    Berna et al. (1991) found that LAS contributed 75% of the MBAS in
    integrated sewage and 50% in treated water. Direct methylene blue
    analysis of extracts derived from sludge, sediment, and soil
    invariably leads to highly inflated estimates of LAS (Matthijs & De
    Henau, 1987). Numerous attempts have been made to improve the
    specificity of methylene blue analysis, by using a variety of
    separation steps before the usual colorimetric estimation. Such
    indirect procedures are usually lengthy, difficult, and still
    susceptible to interference. A number of analytical methods for the
    determination of LAS involving extraction and methylene blue are
    summarized in Table 4.

        Table 4.  Analytical methods for anionic surfactants in environmental water using methylene
              blue and extraction

                                                                                                

    Method            Isolation method/            Limit of        Interference  Reference
                      procedure                    detection
                                                   (mg/litre)
                                                                                                

    Absorption        Extract LAS in water         50-300          Urea,         Jones (1945)
    photometry        into chloroform as                           thiocyanate,
                      ion-pair with MB; measure                    chloride
                      absorption of chloroform
                      solution at 650 nm

                      Extract from alkaline        10-100          As above      Longwell &
                      solution, wash with                                        Maniece
                      cidic MB                                                   (1955)

                      Remove impurities            0.1-1           As above      Abbot (1962)
                      from MBreagent by
                      chloroformextraction

                      Remove MBAS by TLC           0.1-1                         Oba & Yoshida
                                                                                 (1965)

                      Remove MBAS on                                             Takeshita &
                      polymer bead column                                        Yoshida
                                                                                 (1975)

                      Remove MBAS on ion           0.02                          Yasuda
                      exchange column                                            (1980)

    UV absorption     Re-extract LAS into          1                             Uchiyama
    photometry        water; measure UV                                          (1977)
                      absorption at 222 nm
                                                                                                

    Table 4 (contd)

                                                                                                

    Method            Isolation method/            Limit of        Interference  Reference
                      procedure                    detection
                                                   (mg/litre)
                                                                                                

    Infra-red         Use to reduce                1000                          Ambe &
    spectometry       interference from MBAS                                     Hanya
                                                                                 (1972)

    Gas               Convert into fluorine        0.02                          Tsukioka &
    chromatography    derivative; measure                                        Murakami
                      by ECD                                                     (1983)

    HPLC              Remove MB by cation          0.1                           Hashimoto et
                      exchange, HPLC                                             al. (1976)

                      Remove MB by anion           0.02                          Saito et al.
                      exchange, HPLC                                             (1982)
                                                                                                

    LAS, linear alkylbenzene sulfonates; MB, methylene blue; MBAS, methylene blue-active
    substances; TLC, thin-layer chromatography; UV, ultraviolet radiation; ECD, electron
    capture detection; HPLC, high-performance liquid chromatography
    
        Many other cationic dyes and metal chelates have been used as
    colorimetric (and fluorimetric) reagents for the determination of
    anionic surfactants, including LAS. Use of the cationic metal
    chelates has also led to the development of sensitive atomic
    absorption methods for indirect determination of anionic surfactants
    in fresh, estuarine, and marine waters. Although these alternative
    systems may offer some advantages over the methylene blue cation
    method, they cannot match the wide experience gained with methylene
    blue analysis. Some examples of analytical methods based on the use
    of alternative cationic reagents are shown in Table 5.

    A2.3.2.2  Specific methods

        Good progress has been made towards developing methods for the
    specific determination of the many homologues and phenyl-positional
    isomers of LAS in almost all laboratory and environmental matrices
    (liquid and solid) at concentrations down to micrograms per litre.
    High-resolution GC techniques have allowed determination of all the
    major components of LAS (homologues and phenyl-positional isomers)
    in environmental samples. Waters & Garrigan (1983) and Osburn (1986)
    reported improved microdesulfonation-GC procedures for the
    determination of LAS in both liquid and solid matrices.

        Derivatization techniques offer an alternative approach to
    desulfonation for increasing the volatility of LAS for GC (or GC-MS)
    analysis (Hon-nami & Hanya, 1980a; McEvoy & Giger, 1986; Trehy et
    al., 1990. The GC-MS technique was also applied, after ion-pair,
    supercritical fluid extraction and derivatization, to five sewage
    sludges, and the LAS were found to occur at 3.83-7.51 g/kg on a
    daily basis (Field et al., 1992). These GC procedures, however,
    involve extensive sample pre-treatment and depend on conversion of
    the isolated LAS into a suitably volatile form for GC determination;
    they are therefore time-consuming.

        HPLC offers a more convenient means for determining homologues
    of LAS in all types of environmental matrices routinely. Several
    researchers have reported HPLC procedures for LAS which involve
    trace enrichment of the surfactant as the first step (Kikuchi et
    al., 1986; Matthijs & De Henau, 1987; Castles et al., 1989; Di
    Corcia et al., 1991). Takita & Oba (1985) developed a modified
    analytical method based on MBAS-HPLC measurement. Further HPLC
    methods, some requiring no sample preparation, are listed in
    Table 6.

        Table 5.  Analytical methods involving reagents other than methylene blue

                                                                                                
    Method         Isolation method/              Limit of        Interference   Reference
                   procedure                      detection
                                                  (mg/litre)
                                                                                                

    Absorption     1-Methyl-4-(4-diethyl-         0.04            Fe[III]        Higuchi et al.
    photometry     aminophenylazo)pyridinium                                     (1982)
                   iodide; measure
                   chloroform solution at
                   564 nm

                   Bis[2-(5-chloro-2-             0.06                           Taguchi et al.
                   pyridylazo)-5-diethyl-                                        (1981);
                   aminophenolato]Co                                             Kobayashi
                   [III] chloride; measure                                       et al. (1986)
                   benzene solution at
                   560 nm

                   Ethylviolet; measure           0.01                           Motomizu et
                   benzene or toluene                                            al. (1982);
                   solution at 540 nm                                            Yamamoto &
                                                                                 Motomizu (1987)

    Atomic         Bis[2-(5-chloro-2-
    absorption     pyridylazo)-5-                 1 × 10-3        Hydro-         Adachi &
    spectrometry   diethylaminophenolato]                         chlorite       Kobayashi
                   Co [III] chloride; measure                     ion            (1982)
                   Co by atomic absorption
                   spectrometry

                   Potassium dibenzo-             0.05            Alkali,        Nakamura et al.
                   18-crown-6; measure K                          alkaline       (1983)
                                                                  earth
                                                                  metals
                                                                                                

    Table 5 (contd)

                                                                                                
    Method         Isolation method/              Limit of        Interference   Reference
                   procedure                      detection
                                                  (mg/litre)
                                                                                                

    Atomic         Cu[II] ethylenediamine         0.03 × 10-3                    Gagnon (1979);
    absorption     derivatives; measure Cu                                       Sawada et al.
    spectrometry                                                                 (1983)

    Absorption     Bis(ethylenediamine)Cu;        5 × 10-3                       Rama Bhat
    photometry     determine Cu after                                            et al. (1980)
                   addition of 1-(2-
                   pyridylazo)-2-naphthol
                   at 560 nm

    GC-MS          Extract solid phase on         1 × 10-3                       Trehy et al.
                   C8 column; derivatize                                         (1990)
                   LAS with sulfonyl
                   chloride for GC-MS
                                                                                                

    LAS, linear alkylbenzene sulfonates; GC-MS, gas chromatography-mass spectrometry
    
        Table 6.  Analytical methods for linear alkylbenzene sulfonates (LAS) by specific analysees
                                                                                                                                    

    Extraction method                    Analytical conditions                        Limit of detection       Reference
                                                                                      (mg/litre)
                                                                                                                                    

    Recover LAS on column                Column, silica gel, mobile phase             0.02-0.03                Takano et al. (1975)
    chromatograph packed                 hexane:ethanol containing
    with polymer beads                   sulfuric acid; UV at 225 nm

    Extract LAS with methylisobutyl      Column, ODS; mobile phase,                   0.05                     Matsueda et al.
    ketone                               ethanol:water; UV at 225 nm                                           (1982)

    Recover LAS by ionexchange           Column, cyanopropyl-modified silica;         0.04                     Saito et al.
    column                               mobile phase, ethanol:water;                                          (1982)
    chromatography                       UV at 225 nm

    Direct analysis                      Column, ODS; mobile phase, methanol:         0.1                      Nakae et al.
                                         water with sodium perchlorate;                                        (1980)
                                         fluorescence detector capable of
                                         determining alkyl homologue distribution

    Extract LAS using                    Column, ODS; mobile phase, acetonitrile:     0.1 × 10-3               Kikuchi et al.
    mini-column                          water with sodium perchlorate;                                        (1986)
                                         fluorescence detector

    Concentrate LAS using                Column, ODS; mobile phase, acetonitrile:     3 × 10-3                 Takami et al.
    mini-cartridge column                water with sodium perchlorate;                                        (1987)
    connected in sequence with           fluorescence detector
    HPLC system
                                                                                                                                    

    Table 6 (contd)
                                                                                                                                    
    Extraction method                    Analytical conditions                        Limit of detection       Reference
                                                                                      (mg/litre)
                                                                                                                                    

    Extract LAS with methylisobutyl      Column, ODS; mobile phase, acetonitrile:     NR                       Inaba & Amano
    ketone                               water (gradient elution to sharpen peak)                              (1988)
                                         with sodium perchlorate; UV at 222 nm

    Extract from solids with             Column, octyl-modified silica;               0.8                      Marcomini &
    methanol on Soxhlet                  mobile phase, 2-propanol:water:              (injected                Giger
                                         acetonitrile (gradient elution)              weight)                  (1987)
                                         with sodium perchlorate; fluorescence
                                         detector

    Two-step solid phase                 Column, C1 Sphesorb; mobile phase,           7 × 10-3                 Castles et al. (1989)
    extraction with C2 and               THF:water with sodium perchlorate;
    SAX cartridges                       fluorescence detector

    Extract LAS using                    Column, C8-DB (Supelco); mobile              0.8 × 10-3               Di Corcia et al.
    Carbopack B (graphitized             phase, methanol:water with sodium                                     (1991)
    carbon black) cartridge              perchlorate; fluorescence detector

    Concentrate LAS on                   Column, Wakosil 5C4; mobile phase,           10 × 10-3                Yokoyama & Sato
    anion-exchange pre-column            acetonitrile:water with sodium                                        (1991)
    connected to HPLC system             perchlorate; UV at 220 nm
                                                                                                                                    

    Table 6 (contd)
                                                                                                                                    

    Extraction method                    Analytical conditions                        Limit of detection       Reference
                                                                                      (mg/litre)
                                                                                                                                    

    Ion-pair extraction under            Column, capillary gas chromatography,        NR                       Field et al.
    SFE conditions using                 20 m; mass spectrometry with electron                                 (1992)
    tetralhyl-ammonium ion               impact ionization operating in
    pair reagents, coupled with          selected ion mode
    ion-pair derivatization

    Solid-phase extraction for           HPLC column, Bandapat C18                    10 × 10-3                Matthijs & De Henau
    purification and                     gradient elution water:acetonitrile          (water phase)            (1987)
    concentration                        and 0.15 mol/litre NaClOn                    0.1 (solid phase)
                                                                                                                                    

    UV, ultraviolet spectrometry; ODS, octadecyl silica; HPLC, high-performance liquid chromatography; NR, not reported;
    SFE, supercritical fluid extraction

        A3.  SOURCES OF HUMAN AND ENVIRONMENTAL EXPOSURE

    A3.1  Natural occurrence

        LAS do not occur naturally.

    A3.2  Anthropogenic sources

        LAS are synthetic surfactants that were introduced as prime
    components of almost all types of household surfactant products in
    the early 1960s to replace alkylbenzene sulfonates (ABS), which were
    then in widespread use. The change-over from ABS to LAS took place
    gradually, starting in the United Kingdom (1960) and then spreading
    to Germany (1961), the United States of America (1963), Japan (1965)
    and to other European countries (Brenner, 1968; Husmann, 1968;
    Waldmeyer, 1968; Tomiyama, 1972).

        After use, LAS are discharged into wastewater. As the surfactant
    components of the detergent products are soluble, they eventually
    reach raw sewage at concentrations of 1-7 mg/litre (Rapaport et al.,
    1987). Unlike ABS, which has a branched alkyl chain structure, LAS
    with a linear, straight alkyl chain structure are readily
    biodegradable. Their use has alleviated significant environmental
    hazards such as foaming and residual surfactant in water.

    A3.2.1   Production levels and processes

        Annual world production of surfactants, excluding soap, in 1990
    was estimated to be about 7 million tonnes (Colin A. Houston &
    Associates, Inc., 1990; Richtler & Knaut, 1991). World consumption
    of LAS in 1989 was about 2.43 million tonnes, 50% of which was used
    in North America, western Europe, and Japan (Hewin International
    Inc., 1992). Worldwide consumption of LAS in 1990 was about 2
    million tonnes, with the following geographical distribution:
    western Europe, 23%; North America, 19%, eastern Asia, 16%,
    South-east Asia, 12%; eastern Europe, 11%; western Asia, 7%; South
    America, 7%; and Africa, 5% (CEFIC, 1992).  Berna et al. (1993a)
    reported that, in 1990, 380 000 tonnes were used in western Europe,
    180 000 tonnes in eastern Europe, 110 000 in  Africa, 100 000 
    tonnes in western  Asia, 305 000 in eastern Asia, 180 000 in
    South-east Asia, 295 000 in North America, and 140 000 in Latin
    America. An additional demand of 650 000 tonnes is expected by the
    year 2000. The estimates for 1990 show an increase over 1987, when
    LAS production in the United States, Japan, and western Europe was
    about 1.4 million tonnes, on the basis of global demand for linear
    alkylbenzene (Painter & Zabel, 1988), and consumption of LAS was
    about 307 500 tonnes in the United States, 485 000 tonnes in western
    Europe, and 145 000 tonnes in Japan (Richtler & Knaut, 1988).

        LAS are complex mixtures of isomers and homologues in
    proportions dictated by the starting materials and reaction
    conditions. LAS are manufactured by reacting the parent
    alkylbenzenes with sulfuric acid or sulfur trioxide to give the
    corresponding sulfonic acid, which is then neutralized to the
    desired salt. This is usually the sodium salt but ammonium, calcium,
    potassium, and triethanolamine salts are also made. The reactions
    are smooth and the yields nearly quantitative.  Commercial LAS
    contain linear alkyl chains 10-14 carbons in length, with phenyl
    groups placed at various internal positions on the alkyl chain, with
    the exception of 1-phenyl (Painter & Zabel, 1988).

        LAS are manufactured in an enclosed process; under normal
    conditions, therefore, exposure can occur only at the stage of
    detergent formulation, by inhalation or dermally. Dermal exposure is
    generally short and accidental, whereas exposure by inhalation can
    occur continually.

        The concentration of surfactants in water from washing machines
    is 0.2-0.6%. LAS are estimated to represent 5-25% of the total
    surfactant mixture.

        In Germany in 1988, when annual consumption of LAS in the
    western states was about 85 000 tonnes, daily consumption was 3.8 g
    per inhabitant per day. As consumption of drinking-water was 190
    litres per inhabitant per day, the average LAS concentration in
    sewage was 20 mg/litre. Consumption of LAS per capita in other
    countries is shown in Table 7 (Huber, 1989).

    A3.2.2  Uses

        LAS are the most widely used surfactants in detergent and
    cleaning products, in both liquid and powder preparations and for
    household and industrial use. The amount of LAS in a product depends
    on several factors, including the type of application (washing-up
    products, light- and heavy-duty powders and liquids) and the
    formulation, but is usually 5-25%. Small amounts of LAS are used in
    non-detergent applications, but these represent less than 5% of
    total world consumption.

        Table 7.  Specific consumption of linear alkylbenzene sulfonates (LAS)
              in various countries

                                                                                     
    Country           Water usage          LAS usage       Reference
                      (litres per capita   (g per capita
                      per day)             per day)
                                                                                     

    Germany           -                    3.8             Huber (1989)
                      185                  2.2             Wagner (1978)

    United States     560                  2.6a, 2.1b      Rapaport et al.
                                                           (1987)

    United Kingdom    208                  3.5c, 2.7c      Standing Technical
                                                           Committee on
                                                           Synthetic Detergents
                                                           (1978, 1989)

    Spain             -                    5.6a, 2.6b      Berna et al. (1989)

    Japan             493                  2.7             Ministry of Health and
                                                           Welfare (1992);
                                                           Hewin International
                                                           Inc. (1992)
                                                                                     

    a Calculated from sales
    b Calculated by analysis
    c Methylene blue-active substances
    
    A4.  ENVIRONMENTAL TRANSPORT, DISTRIBUTION, AND TRANSFORMATION

     Section summary

        The way in which LAS enter the environment varies between
    countries, but the major route is via discharge from sewage
    treatment works. Direct discharge of sewage to rivers, lakes, and
    the sea occurs when wastewater treatment facilities are absent or
    inadequate. Another route of entry of LAS into the environment is
    via disposal of sewage sludge on agricultural land.

        Throughout their journey into the environment, LAS are removed
    by a combination of adsorption and primary or ultimate
    biodegradation. LAS adsorb onto colloidal surfaces and suspended
    particles, with measured adsorption coefficients of 40-5200
    litres/kg, depending on the medium and structure of the LAS. LAS
    undergo primary biodegradation in all environmentally relevant
    compartments, such as raw sewage, sewage treatment water, surface
    waters, sediments, and soils. They are readily and ultimately
    mineralized under aerobic conditions in the laboratory and the
    field. They tend not to be biodegraded under methanogenic conditions
    or if the initial LAS concentration is so high that microbial
    degradation is inhibited (> 20-30 mg/litre). Typical half-lives for
    aerobic biodegradation of LAS are 1-8 days in river water, 1-2 days
    in sediments, and 5-10 days in marine systems. The rate of
    biodegradation depends on temperature: biodegradation is rapid
    between 10 and 25°C; at lower temperatures, biodegradation kinetics
    are reduced, in close association with microbial activity. During
    primary sewage treatment, LAS are partially adsorbed onto and
    removed with waste sludge to an extent of about 25% (range, 10-40%).
    LAS are not removed during anaerobic sludge digestion but are
    removed during aerobic treatment with a half-life of about 10 days.
    Application of the sludge to soil generally results in 90%
    degradation within three months, with a half-life of 5-30 days.

        LAS are not bioconcentrated or biomagnified in aquatic
    organisms. They are readily absorbed through the gills and body
    surface of fish and are distributed via the blood to the systemic
    organs. Most LAS-related compounds (parent compound and metabolites)
    have been detected in the gall-bladder and hepatopancreas of fish.
    They are usually cleared rapidly, with a half-life of two to three
    days.

    A4.1  Transport and distribution between media

        Detergent chemicals such as LAS are normally discharged after
    use into sewers in communal wastewater. The proportion of wastewater
    that is subjected to sewage treatment varies widely between
    countries. In most advanced countries, 50 to > 90% may be treated,
    whereas in less developed countries the proportion may be as little
    as 5-30% (Eurostat, 1991). In countries where there is no or

    inadequate sewage treatment, LAS are removed from the environment
    via adsorption and mineralization in the receiving surface waters.

        Anionic surfactants such as LAS can adsorb onto the solid
    substrates associated with sewage, sludge, sediment, and soil; the
    extent of adsorption is dependent on the composition and physical
    nature of the solid matrix. Measured values of the adsorption
    constant (Kd) for LAS on a range of solid substrates were compiled
    by Painter & Zabel (1989), who reported Kd values of 590-1400
    litres/kg for primary sludge, 660-5200 1itres/kg for activated
    sludge, and 40-360 1itres/kg  for river water sediment.

    A4.1.1  Wastewater treatment

        Under certain conditions, up to 50% of the LAS present can be
    biodegraded in sewers before entering sewage treatment (Moreno et
    al., 1990). In large-volume batch biodegradation tests with
    acclimatized sludge, the MBAS levels decreased to 10% of the initial
    concentration within 15 days. During biodegradation, the toxicity of
    the test solution decreased in parallel with the reduction in MBAS.
    A relative enrichment of the shorter chain homologues was observed
    by GC analysis concurrently with the decrease in MBAS levels,
    indicating preferential removal of the higher homologues (Dolan &
    Hendricks, 1976).

        The distribution and fate of LAS have been established in the
    course of mass balance studies at sewage treatment plants in Spain
    (Berna et al., 1989), Italy (Cavalli et al., 1991), Switzerland
    (Giger et al., 1989), Germany (De Henau et al., 1989), and the
    United States (Rapaport & Eckhoff, 1990; McAvoy et al., 1993).
    Efficient, well-operated activated sludge plants generally remove
    most of the LAS during aerobic treatment, and the overall removal of
    LAS in primary settlement and secondary aerobic treatment stages can
    be < 98% (Berna et al., 1991). Smaller amounts of LAS were
    removed (77 ± 15%) in less efficient, trickling filter plants
    (McAvoy et al., 1993).

        The main mechanism for removal of LAS during sewage treatment is
    biodegradation (Berna et al., 1991), but a significant fraction (on
    average, 20-30%) of the LAS entering sewage treatment plants may be
    removed on primary sewage solids and do not undergo aerobic sewage
    treatment (Giger et al., 1989). Instead, the sludge is digested
    under anaerobic conditions, and in some countries a high proportion
    may then be applied raw or digested to agricultural land as a source
    of plant nutrients (Berna et al., 1991). In Germany and the United
    Kingdom, 40-45% of sewage sludge is disposed of in this way (Waters
    et al., 1989). Since LAS do not undergo significant anaerobic
    biodegradation under methanogenic conditions, concentrations of
    3-12 g/kg can be found on dried solids in sludge (see Section 5,
    Table 10). Any LAS in sludge applied to agricultural soil should
    then be rapidly biodegraded, since the receiving soil environment is

    aerobic. In Germany and the United Kingdom a typical application of
    digested sludge was estimated to add LAS at a rate of 7-16 mg/kg
    soil (Waters et al., 1989).

        Adsorption can account for 15-40% of the removal of LAS from raw
    sewage during the primary settlement stage of treatment (Berna et
    al., 1989; Giger et al., 1989). Berna et al. (1989) reported that
    precipitation and adsorption were particularly important in removing
    LAS from wastewater containing high concentrations of calcium and
    magnesium ions.

        The percentage adsorption of C10, C11, C12, and C13 LAS
    onto activated sludge, Amazon clay, and various bacteria and algae
    was directly related to the chain length and phenyl position: longer
    homologues and more terminal phenyl isomers were adsorbed much more
    readily than other forms. Adsorption of LAS at a concentration of
    23 mg/litre was found to be pH-dependent, with adsorption increasing
    as the pH decreased from 7 to 3 (Yoshimura et al., 1984a).

    A4.1.2  Surface waters, sediments, and soils

        The half-life for the removal of LAS by combined sorption and
    settling < 12 km below a sewage outfall in Rapid Creek, South
    Dakota, United States, was 0.25 days. The biodegradation half-life
    was 1.5 days (Rapaport & Eckhoff, 1990). The partition coefficient
    of LAS between natural water and sediment was reported to increase
    with increasing chain length and with the position of the phenyl
    nearer to the end of the chain. Adsorption was increased when either
    the concentration of suspended solids or fractional organic carbon
    was increased (Amano & Fukushima, 1993).

        Freshwater pearl oysters are cultivated in Lake Nishinoko,
    Japan, which has an area of 2.8 km2, an average depth of 1.5 m,
    and a residence period of 27 days. The water of the lake was found
    to contain total concentrations of MBAS of 0.01-0.02 mg/litre and
    LAS concentrations of 0.005-0.018 mg/litre. The partition
    coefficients of LAS (Kd) were 70 litres/kg for bottom
    sediment:water and 11 litres/kg for oyster:water (Sueishi et al.,
    1988). The authors concluded that when a river flows into a
    semi-enclosed lagoon, the fate of the surfactants is dominated by
    mass transfer between media and transformation due to degradation
    rather than spatial transportation.

        LAS were present in Swiss soils that had been treated with
    sludge for 10 years; however, the application rates were six times
    higher than normal. The reported half-lives were 5-80 days. The
    authors noted that it is not entirely correct to use half-life to
    describe the loss of LAS from soils, because there is competition
    between biodegradation and sorption on and into soil particulates,
    and LAS may persist at very low 'threshold' levels. During the

    330-day study, the levels of LAS decreased from 45 mg/kg dry soil to
    a residual level of 5 mg/kg (Giger et al., 1989).

        A comparison of the measured concentration of LAS with detailed
    records on the amount of sludge applied on 51 fields in England
    indicated that loss of LAS  exceeded 98% in fields that had not
    recently been sprayed with sludge; losses from fields that had been
    sprayed recently were calculated to be 70-99% of the estimated
    cumulative load. The calculated half-lives for removal of LAS from
    soil sprayed with sludge were 7-22 days. Examination of the
    distribution of homologues suggested that loss of LAS is the result
    of biodegradation and not leaching (Holt et al., 1989). In a study
    of the disappearance of LAS from sludge-amended soils at two
    locations, the average half-lives were 26 days when sludge was
    applied at a rate of 1.6 kg dry sludge per m2 (giving a
    concentration of LAS of 16.4 mg/kg soil) and 33 days when sludge was
    applied at 5 kg wet sludge per m2 (concentration, 52.5 mg/kg soil)
    (Berna et al., 1989).  In another study, the half-life for LAS in
    soil was more than three months; there was no evidence that they
    accumulate in soil over time (Rapaport & Eckhoff, 1990).

        When C13 LAS were applied to various soil (surface) types at a
    concentration of 0.05 mg/kg under laboratory test conditions, the
    half-lives were 1-5 days, with an average of two days. There was no
    significant variation with regard to soil type. In a second
    experiment, the average half-life of C12 LAS applied to subsurface
    soil was 20 days (Larson et al., 1989).

        After grass, radishes, and garden beans were grown for 76 days
    in soil treated with 14C-LAS at a rate of approximately
    1.2 g/m2, 98% of radioactive residues were recovered, with 63.6%
    released to the atmosphere, 26.8% found in the soil, 6.6% in plant
    biomass, and 0.9% leached out in percolated water. When potatoes
    were grown on the soil for 106 days, 97.9% of  the radioactivity was
    recovered, and 72.3% was released to the atmosphere, 18.3% to the
    soil, 5.9% in plant biomass, and 1.4% leached into percolated water
    (Figge & Schoberl, 1989).

        LAS in a plume of contaminated groundwater on Cape Cod, United
    States, were degraded rapidly and was found only within 0.6 km of
    the sewage disposal bed (Thurman et al., 1986).

        Effects on the biodegradation of LAS applied at 50 mg/litre of
    aqueous dispersion were studied in three Japanese soil types
    inoculated with sewage. The rate of sludge application used in this
    study was not typical of that found in the environment. Primary
    degradation, as measured by the presence of MBAS, reached 70% within
    16 days. Addition of andosol (allophane) and weathered granite
    (kaolin and illite) both reduced primary degradation, and 40-50% of
    the LAS was still present after 30 days, indicating that the rate of
    microbial degradation of LAS adsorbed onto soils containing large

    amounts of allophane  and/or sesquioxides was reduced. A
    montmorillonite soil did not affect the rate of degradation (Inoue
    et al., 1978).

        The behaviour of C10-C13 LAS and C12 LAS at concentrations
    of 50 and 100 mg/litre was studied by HPLC in perfusion tests on two
    types of soil, a clay loam and a sandy loam. The sandy loam, with a
    lower content of humus and clay, adsorbed less LAS with a longer
    lag. During the first three days of perfusion, only adsorption
    occurred, 50% being adsorbed; after nine days, decomposition was
    observed and only 16.6% of the LAS remained; after 15 days, the LAS
    had almost completely disappeared (Abe & Seno, 1987).

        LAS were applied at a rate of 5 g/m2 to three soil types:
    loamy orthic luvisol under agricultural land, sandy acidic dystric
    combisol under a pine forest, and combisol irrigated with
    wastewater. The half-life in loamy soil was five days; 80% was
    degraded after 12 days, and none was detectable after 28 days. With
    45 mm of precipitation, about 8% of the LAS percolated to a depth of
    10-30 cm. The LAS moved significantly more slowly than radioactively
    labelled water. LAS were less mobile in the sandy soil, with a
    maximal percolation depth of 5 cm after two weeks, whereas water
    percolated 15 cm. The half-life in the sandy soil was 10 days, with
    80% degradation after 19 days and total degradation after 28 days.
    The LAS were bound to organic material in the humic litter, which
    probably slowed degradation and reduced mobility. In combisol
    irrigated with wastewater, the LAS were bound mainly in the upper
    5 cm, with some percolation to 10-30 cm after an application of
    180 mm of wastewater. The half-life was 12 days, and 80% was
    degraded within 21 days; however, there was no further degradation
    after 28 days, and the remaining LAS were tightly bound. Increasing
    the application rate to 50 g/m2 had no effect on percolation;
    however, the half-life was doubled. Samples collected during the
    winter showed much slower degradation, with half-lives of 68-117
    days. Percolation was also much deeper; the authors suggest this was
    due to a higher rate of precipitation and extensive evaporation
    (Litz et al., 1987).

         In a study of the adsorption of LAS in aqueous solution onto
    clay grumusol and sandy regosol soils, a linear adsorption isotherm
    was obtained. The release of the surfactant was proportional to the
    initial adsorption and the soil type, suggesting ready desorption.
    More LAS was adsorbed by the clay soil than by the sandy soil (Acher
    & Yaron, 1977).

        Hydroxy aluminium and iron adsorbed LAS more readily and with a
    much larger capacity than other soil constituents, such as organic
    matter, silica gel, layer silicates, and calcium carbonate (Volk &
    Jackson, 1968).

        In a study of the adsorption of LAS applied at a concentration
    of 2 mg/litre to a variety of Wisconsin (United States) soils, a
    highly significant correlation was found between adsorption and
    organic matter content (including the iron and aluminium
    components), phosphate fixing capacity, and aluminium content. The
    removal of sesquioxides reduced the adsorption of LAS to zero;
    however treatment of montmorillonitic soils with H2O2 and
    Na2S2O4 increased adsorption by oxidizing and removing the
    organic matter, indicating that montmorillonite can adsorb LAS.
    Treatment of soils with H2O2 increased adsorption because iron
    and aluminium were released from organic chelates (Krishna Murti et
    al., 1966).

        Adsorption of LAS to microorganisms was found on the basis of
    calculated adsorption isotherms to be more important than adsorption
    to humic substances (Urano et al., 1984; Urano & Saito, 1985).

    A4.1.3  Fate models

        One model of the fate of LAS predicted the sorption coefficient
    to within one order of magnitude. The sorption distribution
    coefficient was consistently underpredicted, so that when the
    concentrations of LAS in interstitial and overlying water were
    predicted from concentrations in sediment they were overestimated.
    The model thus provided conservative estimates for assessing safety
    in aquatic media (Hand et al., 1990).

        The reported concentrations of LAS in Rapid Creek, South Dakota,
    United States, were compared with expected concentrations generated
    by the quantitative water-air-sediment interaction fugacity model,
    which is based on physical, chemical, reactive, and transport
    properties and emission rates into rivers. In general, close
    agreement was reached: in both cases, LAS had a residence time of
    about two days. The authors pointed out that the results might
    differ if the model were applied in situations that differed
    hydrodynamically (Holysh et al., 1986).

        A model to predict surface water concentrations of LAS in German
    and American rivers included the following parameters: river flow
    and velocity, sewage treatment plant location and type, discharge
    volume, and connected population. The values obtained were in
    general agreement with those measured. The authors also investigated
    a septic tank discharge at a Canadian site by applying a groundwater
    model, which was based on hydrogeological, biodegradation, and
    sorption data. The predicted and measured concentrations were in
    good agreement (Hennes & Rapaport, 1989).

        A mathematical model was derived to explain a downstream
    decrease in the concentration of LAS in the Lake Teganuma estuary,
    Japan. The model included the adsorption coefficient, the
    biodegradation rate constant, and the rate of transport (diffusive

    and settling) flux of LAS between water and sediment. The model
    predictions and laboratory findings were used to confirm that
    biodegradation is the predominant mechanism for removal of LAS from
    the estuary (Amano et al., 1991).

        A model based on data from the Lake Biwa basin was devised to
    predict the fate of LAS in Japanese rivers, assuming that complete
    mixing occurs in any given cross-section of a river. The parameters
    included the cross-sectional mean concentration of LAS, time
    elapsed, flow velocity, longitudinal dispersion coefficient, decay
    due to biodegradation and sedimentation, water depth, and river
    width (Sueishi et al., 1988).

        The measured concentrations of LAS in United States river water
    under critical flow conditions were mirrored by the predictions of a
    simple dilution model, which predicts chemical concentrations below
    the mixing zone of wastewater treatment plants. The model is based
    on three large databases, which link river flow, treatment type and
    wastewater discharge volume; the output of the model is a frequency
    distribution of concentrations just below the mixing zone of
    treatment plant outfalls. The model predicted that 95% of the river
    waters below that point would have concentrations of LAS of <
    0.35 mg/litre during critical low-flow periods. The sampling sites
    selected for this study were reported to have a low dilution factor
    for mixing effluent with surface water, however. The predictions
    therefore represent a 'worst-case scenario', since the 95 percentile
    value represents critical low-flow periods, in which the lowest ever
    recorded flow is used for a consecutive period of seven days within
    10 years (McAvoy et al., 1993).

    A4.2  Environmental transformation

    A4.2.1  Biodegradation

    A4.2.1.1  Aerobic degradation

        Studies on aerobic biodegradation of LAS can be divided into
    those of primary degradation and those of ultimate degradation.
    Primary degradation of LAS occurs during the initial reactions in
    the metabolic pathway, and the products are often shorter-chain
    homologues. The ultimate degradation of LAS is that of the entire
    molecule to its biodegradation end-products, CO2, H2O, and
    NH4. These products are used in cell synthesis or, in the case of
    CO2, excreted. The ultimate degradation of LAS normally requires
    the action of several species of bacteria.

        The degradation pathway of LAS has been described (Huddleston &
    Allred, 1963; Swisher, 1963). The steps, shown in Figure 1, are: 
    omega-oxidation of the end of the alkyl chain, rapid ß-oxidation of
    the chain, and oxidation of the ring.

    
    Figure 1.  Postulated metabolic pathway of linear alkylbenzene sulfonates

                                   omega-oxidation
    CH3(CH2)nCH(C6H4SO3H)(CH2)mCH ------------------> COOH(CH2)nCH(C6H4SO3H)CH2)mCH3
    (n>m)                                                           |
                                                                    |
                                                                    |    ß-oxidation
                                                                    |
                                                                    v

                                      ß-oxidation
    COOHCH(C6H4SO3H)(CH2)mCH3     <------------------ COOH(CH2)n-2CH(C6H4SO3H)(CH2)mCH3
               |
               |    Ring
               |    dihydroxylation
               |
               v

    COOHCH(C6H2SO3H)CH2CH3        ------------------> ring fission at the 1-2 position
                                                      of the ring, then desulfonation to
                                                      aliphatic products and sulphate.

    From Painter (1992)
    
        Swisher (1981) pointed out that ultimate biodegradation (at
    least 80%) is achievable under the correct conditions, which
    include:

        (i)   the presence of mixed bacterial species,
        (ii)  free access to new bacteria during the test,
        (iii) acclimatization,
        (iv)  enough growth factors and food, and
        (v)   limitation of the LAS concentration to that found in the
              environment.

        Biodegradation of LAS begins at the terminus of the alkyl chain
    with an omega-oxidation and is followed by successive cleavage of
    C2 fragments (ß-oxidation) (Huddleston & Allred, 1963; Swisher,
    1963). The resulting sulfocarboxylic acids have a chain length of
    four to five carbon atoms (Schöberl, 1989). These intermediates are
    further biodegraded by oxidative scission of the aromatic ring and
    cleavage of the sulfonate group (Setzkorn & Huddleston, 1965;
    Swisher, 1967). Catabolites of further oxidation steps are fed into
    the central metabolic pathways, i.e. the Krebs cycle and glyoxylate
    cycle (Schöberl, 1989).

        LAS degradation begins at the longest end of the linear alkyl
    chain, with omega- and ß-oxidation, and proceeds up to the
    sulfophenylmono-carboxylic acids (one to two CH2 groups) (Divo &
    Cardini, 1980). Under mild conditions, as in river water,
    intermediates such as sulfo-phenylcarboxylic acids are often not
    degraded, as the greater distance between sulfophenyl groups and the
    far end of the hydrophobic group increases the speed of primary
    biodegradation (Swisher, 1976). Once the terminal methyl group has
    been attacked, primary biodegradation is rapid (Swisher, 1970;
    Gledhill, 1975). Short-chain sulfophenylmonocarboxylic acids were
    not degraded by  Pseudomonas but were degraded by mixed cultures of
    microorganisms (Leidner et al., 1976). The initial attack that opens
    the aromatic ring is the rate limiting step for ultimate
    biodegradation: once the ring is opened, degradation is rapid.

        Enzymological methods were used to show that the same sequence
    of steps occurs when ring degradation proceeds via the catechol
    derivative. A variety of microorganisms isolated from soil, sewage,
    and river water showed at least five distinct metabolic routes for
    the degradation of LAS: omega- and ß-oxidation of the side-chain;
    oxidation and desulfonation followed by cleavage of the aromatic
    nucleus; reductive desulfonation of the ring; and metabolic
    alpha-oxidation of the side-chain, followed by ß-oxidation and
    desulfonation. Metabolism of alkyl chains shorter than four carbons
    was initiated through the aromatic nucleus by hydrolytic or
    reductive desulfonation of the ring (Cain et al., 1971). LAS may
    also be cleaved by biochemical mechanisms (Schöberl, 1989).

     Primary degradation

    (i)  Low levels of biomass

        Measurement of MBAS was compared with measurement of total
    organic carbon for detecting biodegradation in shake cultures. With
    the MBAS method, LAS had lost 98% of their activity within five
    days, whereas 34% of the total carbon had disappeared by that time,
    and 70% was lost by the end of the 31-day test (Sekiguchi et al.,
    1975a).

        In a modification of the screening test of the Organisation for
    Economic Co-operation and Development (OECD), accepted by the
    European Commission, the percentage of dissolved organic carbon was
    found to have decreased by more than 80% within four weeks. The
    authors cautioned that the decrease in LAS may not have been due
    solely to biological degradation, since 40-50% of organic carbon was
    also removed from abiotic controls, suggesting that adsorption may
    account for part of the removal of LAS (Canton & Slooff, 1982). When
    aerobic biodegradation of 10 mg/litre LAS was followed during a
    10-day incubation period at 27°C, primary degradation, measured by
    the MBAS method, was complete within 8-10 days, and the theoretical
    CO2 production reached 20-25% within 10 days. At a concentration
    of 20 mg/litre, no degradation was observed, but this elevated
    concenration may have inhibited the microbial inoculum (Itoh et al.,
    1979).

        The rate and degree of biodegradation of LAS are dependent on
    temperature. In an unacclimatized microbial population, no more than
    25% biodegradation was achieved at 5°C during a 28-day test,whereas
    at 15, 25, and 35°C about 90% degradation was achieved within 7-14
    days. At 45°C, the microbial population degraded 75% of the LAS
    within 14 days, but this rate of degradation was not maintained,
    probably because of loss of the acclimatized seed due to the high
    temperature. A clearer effect of temperature was observed when the
    microorganisms were acclimatized to LAS before the test. Under these
    conditions, the rate of biodegradation increased steadily with
    increasing temperature from 15 to 35°C (Hollis et al., 1976).

    (ii)  Wastewater treatment

        In the OECD screening test, there was 95% loss of LAS, measured
    by the MBAS method, and similar losses were measured in OECD
    confirmatory test No. 1 with 20 mg/litre LAS. In the closed-bottle
    test with a concentration of LAS of 2 mg/litre, there was 90-95%
    analytical loss (by the MBAS method) and 60-65% loss of biochemical
    oxygen demand. Coupled-unit tests with 10 mg/litre LAS and a mean
    hydraulic retention time of 6 h showed 94% removal of chemical
    oxygen demand (values > 73% indicate benzene ring opening) (Fischer
    & Gerike, 1975). In activated sludge, 80-90% of dissolved organic

    carbon and benzene rings disappeared within 6 h (Swisher, 1972). A
    bacterium similar to  Klebsiella pneumoniae, isolated from sewage,
    degraded 93% of a concentration of LAS reported as 1% (10 g/litre),
    as measured by the MBAS method (Hong et al., 1984). A direct
    correlation was found between the rate of primary degradation of
    1.5 mg/litre C11.7 LAS and the initial bacterial population size
    (Yediler et al., 1989).

        The biodegradation of C9-C13 LAS at concentrations of 25,
    50, and 65 mg/litre was monitored in activated sludge at
    100 mg/litre over a period of 12 days. Four methods were used: MBAS,
    chemical oxygen demand, dissolved organic carbon, and ultra-violet
    spectrophotometry. The results obtained with the MBAS method showed
    a percentage loss of 94-97% for the three concentrations of LAS,
    whereas the other methods showed losses of approx. 50% at
    25 mg/litre LAS and approx. 70% at 50 and 65 mg/litre. The specific
    rate of biodegradation was calculated to be 3.6 mg/g per h, on the
    basis of loss of chemical oxygen demand (Pitter & Fuka, 1979).

        The degradation ratio (biochemical oxygen demand:total oxygen
    demand) for LAS by a synthetic sewage solution after five days was
    0.81 for a concentration of 3 mg/litre and 0.14 for 10 mg/litre.
    Concentrations of 30 and 100 mg/litre LAS were not degraded during
    the 14-day test. Even after acclimatization to a concentration of
    5 mg/litre LAS for one month, the two higher concentrations were not
    degraded, probably because these levels inhibited the microbial
    inoculum (Urano & Saito, 1985).

        The percentage removal of biochemical oxygen demand and of LAS
    were found to be significantly correlated in activated sludge and in
    a trickling filter system under laboratory and field conditions,
    implying that a well-functioning sewage treatment plant effectively
    removes LAS (Tang, 1974).

        LAS at a concentration of 150 mg/litre were inoculated into
    sewage water collected from French water treatment plants. In six
    out of eight experiments, primary degradation was almost complete
    (90%) within seven days, but in the other two experiments only
    45-55% degradation was achieved. The authors concluded that rapid
    biodegradation of LAS requires the presence of a community of
    several bacterial species, including  Flavobacterium, Pseudomonas,
    and  Acinetobacter (Gard-Terech & Palla, 1986).

        In an extended aeration activated sludge plant, 95-99% of LAS
    was removed. Degradation of LAS and reduction of biochemical oxygen
    demand were strongly correlated, in a 1:1 ratio (Knopp et al.,
    1965). In long-term laboratory tests, 95-97% of LAS was removed by
    activated sludge (Janicke & Hilge, 1979).

        In a wastewater treatment plant where the input water had an
    MBAS concentration of 6.2-9.4 mg/litre, at least 99% of the LAS
    present was removed during treatment, biodegradation accounting for
    85%. The relative composition of long-chain (C12-C13) homologues
    adsorbed on the suspended solids was increased in comparison with
    the relative incidence of short-chain (C10-C11) homologues
    detected in the aqueous phases. Sulfophenylcarboxylates were
    identified as intermediates of the biodegradation of LAS but were
    detected only in the aqueous and not in the adsorbed phases (Cavalli
    et al., 1993b).

        Biodegradation of LAS in field trials with trickling filter
    sewage was 86-95%, and average biochemical oxygen demand removal was
    93.8%. Thus, the LAS appeared to be removed almost as rapidly as the
    naturally occurring organic material. The linear correlation between
    degradation and temperature (7.5-17.5°C) was highly significant.
    Further degradation (94-99%) took place after additional aeration
    (Mann & Reid, 1971).

        MBAS degradation did not correspond to biodegradation of LAS
    (20-200 mg/litre) in laboratory sludge units, because of the
    presence of intermediates not accounted for by analysis of MBAS
    (Janicke, 1971).

    (iii)  Surface waters

        Primary degradation, measured by HPLC, of 5 mg/litre C11 LAS
    in a static lake microcosm was complete within 18 days. The
    sulfo-phenylcarboxylic acid intermediates produced were completely
    degraded within 22 days (Eggert et al., 1979).

        Aerobic degradation of 5 mg/litre LAS in river water, measured
    by MBAS levels, was 100% after seven days at 25°C. Under
    microaerophilic conditions at 25 and 35°C), no degradation took
    place within 10 days (Maurer et al., 1971; Cordon et al., 1972).

        In die-away tests with water from various sites on the Tama
    River, Japan, primary biodegradation (measured by the MBAS method)
    was complete within 7-15 days, but total organic carbon was
    completely removed within an incubation time of 45 days. In a study
    of LAS in seawater collected from the mouth of the Tama River,
    degradation was only 50% complete within 60 days, as measured by
    total organic carbon (Sekiguchi et al., 1975b). In a study to
    monitor detergent-degrading bacteria from the Han River, Republic of
    Korea, the lowest density was found in January and the highest in
    July; the dominant group throughout the year was  Pseudomonas (Bae
    et al., 1982). Mixed and pure isomers of LAS were metabolized
    readily (97.5%) by bacteria collected during the summer from a
    sewage lagoon, but bacteria collected from under the ice during the
    winter were not able to metabolize LAS (Halvorson & Ishaque, 1969).

        Primary biodegradation of C10-C13 LAS was dependent on
    incubation temperature in die-away tests with water from the Tama
    River, Japan: primary biodegradation was complete within two days at
    27°C, within six days at 15°C, and within three days at 21°C; at a
    water temperature of 10°C, however, only 20% of the LAS had been
    degraded within the nine-day test (Kikuchi, 1985). The optimal
    temperature for the biodegradation of LAS in a river water die-away
    test was found to be 25°C (Yoshimura et al., 1984b).

        Degradation of 10 mg/litre LAS in a simulated river model was
    found to be almost complete within 20 days, on the basis of MBAS
    levels in water and sludge; however, ultra-violet spectrophotometry
    showed that 40% of the LAS remained in the water and 25% in the
    sludge. LAS with an alkyl chain length of C10 were degraded more
    slowly than those with a chain length of C14, and LAS compounds
    with sulfylphenyl groups near the terminal part of the alkyl chains
    were degraded more easily than those with such groups further from
    the end (Fujiwara et al., 1975).

        In a study of the biodegradation of LAS (10 mg/litre) and a 1:1
    LAS:ABS (10 mg/litre) mixture in canal water with an unaerated or
    aerated system, LAS were rapidly degraded in the unaerated system,
    by 14.9% within two days and 40.7% within seven days. Biodegradation
    was more rapid in the aerated tanks, with 40.4% degraded within two
    days and 74.5% after seven days. Addition of sewage to the test
    system further increased the rate of degradation in the aerated
    system: addition of 0.5 ml/litre sewage resulted in degradation of
    78.2% after two days and 89.4% after seven days, and addition of
    1.0 ml/litre sewage resulted in degradation of 89.7% after two days
    and 99.8% within three days. No results were reported for the
    unaerated system. The LAS-ABS mixture was degraded more slowly than
    pure LAS: after two days, 12.3% was degraded without aeration, 36.4%
    with aeration, 60.1% with addition of 0.5 ml/litre sewage, and 78.3%
    after addition of 1.0 ml/litre sewage. The corresponding
    degradations calculated after seven days were 32.5, 66.0, 80.7, and
    87.3%. The authors concluded that degradation of these detergents
    was increased by aerating the tank and by increasing the number of
    microflora by adding sewage (Abdel-Shafy et al., 1988).

        In the Lake Teganuma estuary (Japan), an average of 66% of LAS
    is removed, with seasonal variability, ranging from 28% in winter to
    100% in summer. Laboratory studies (based on HPLC methods) of
    estuarine water showed that LAS degraded with a half-life of eight
    days at 5°C and 0.2 days at 25°C. Model calculations and field
    monitoring showed that biodegradation is 10 times more important in
    the removal of LAS from the estuary during summer than is the
    settling of solids or adsorption to bottom sediments. At lower
    temperatures, biodegradation and the other removal mechanisms are of
    equal importance (Amano et al., 1991).

        In well water, biodegradation of all LAS homologues
    (C10-C13) and isomers (maximal concentration, 2.5 mg/litre)
    after an acclimatization period of one day was reported to follow
    zero-order kinetics (Yakabe et al., 1992).

        In seawater, primary biodegradation of 20 mg/litre LAS was 70%
    after 10 days; the half-life was six to nine days (Vives-Rego et
    al., 1987).

    (iv)  Soil

        In soil degradation tests, levels of 2.5 mg/kg MBAS were reached
    within 15 days of the addition of 20 mg/kg LAS (Cordon et al.,
    1972). The biodegradation of LAS in soil was studied by measuring
    the amounts of ferroin reagent-active substance and total organic
    carbon. At 50 mg/litre LAS, total organic carbon disappeared within
    50 days, whereas total ferroin reagent-active substance was
    completely lost after only 10 days. Both chemical and physical
    properties of the soils affected the loss of LAS: more LAS was
    adsorbed onto clay loam than sandy loam, and biodegradation occurred
    more readily in the clay loam (Abe, 1984). In a further study
    (initial concentration not given), loss of  C10-C13 and C12
    LAS was complete within 15 days when measured as ferroin
    reagent-active substances; however, when measured as total organic
    carbon, residues remained until day 50 in the clay loam and beyond
    day 60 in the sandy loam (Abe & Seno, 1987).

     Ultimate degradation

        A number of studies have been conducted of the biodegradation of
    phenyl-radiolabelled LAS, in which 14CO2 production was measured.

    (i)  Screening tests

        In a simple shake-flask system with LAS, CO2 evolution reached
    60% or more of the theoretical value (Gledhill, 1975).

        Four gram-negative bacteria synergistically mineralized
    10 mg/litre 14C-LAS. After 13 days of incubation, 29% of the
    14C-LAS was mineralized to 14CO2. Pure cultures were unable to
    mineralize the LAS, although three of them carried out primary
    biodegradation, measured by the MBAS method (Jimenez et al., 1991).
     Pseudomonas, Alcaligenes, Necromonas, and  Moraxella spp. isolated
    from activated sludge and river water degraded the alkyl chains of
    C12 LAS, while a group of unidentified Gram-negative bacteria cleaved
    the benzene ring.  A mixture of the two groups degraded LAS completely
    (Yoshimura et al., 1984b).

    (ii)  Wastewater treatment

        Mixed cultures of microorganisms found under natural conditions
    or in sewage treatment plants can readily degrade LAS, to 95% of
    MBAS and > 80% of dissolved organic carbon (Schöberl, 1989).

        During a 19-day OECD screening test for the biodegradation of  
    14C-LAS, there was a high degree of ring mineralization, as seen
    by the evolution of 55% as 14CO2. In a continuous system, 80% of
    the LAS was evolved as CO2, with a mean retention time of 3 h;
    2-3% remained as unaltered surfactant and 15-25% as the
    sulfophenylcarboxylic acid intermediates (Steber, 1979).

        Loss of MBAS (primary biodegradation) and ring cleavage were
    found to be nearly complete (> 98%) during simulated waste
    treatment of 14C-LAS. During simulated secondary waste treatment,
    62% of alkyl and ring carbon was converted to CO2, 28-30% was
    assimilated into biomass, and 8-10% remained as soluble residue. In
    die-away tests, 85-100% of the substrates of LAS were converted to
    CO2 within 91 days (Nielsen et al., 1980; Nielsen & Huddleston,
    1981).

        Continuous-flow experiments were conducted with mixed bacterial
    cultures isolated from a detergent plant wastewater containing five
    species of  Achromobacter and two species of  Acinetobacter. All
    were more efficient at primary degradation than ultimate degradation
    of LAS at concentrations of 20 and 50 mg/litre. One species of each
    genus could effect primary degradation even after isolation (Hrsak
    et al., 1982).

        In a semi-continuous activated sludge method, 95% of the phenyl
    ring of radiolabelled LAS  was cleaved, indicating near complete
    biodegradation of the whole molecule. Complete primary degradation
    (MBAS method) of C10, C12, and C14 LAS was followed by 99-100%
    ultimate degradation (HPLC and ultra-violet fluorescence). In
    die-away tests with 10 mg/litre of C10, C12, and C14 LAS,
    primary degradation was rapid and complete; 100% of C12 LAS was
    removed within four days. Almost complete ultimate degradation was
    observed within the 80-day test, with 90% ring cleavage of C10 LAS
    and C11 LAS within 10 days and 70% ring cleavage of C14 LAS
    within 30 days; however, no HPLC analysis was carried out on C14
    LAS after day 30 (Huddleston & Nielsen, 1979).

        The biodegradation of LAS (C9-C14) by a mixed bacterial
    culture was studied in river water, forest soil, and wastewater from
    a detergent plant. The bacteria were acclimatized to 10 mg/litre
    LAS. Under continuous-flow conditions, LAS at a concentration of
    20.8 mg/litre were 96% degraded, and a concentration of 46 mg/litre
    was 64% degraded. Only 8-10% of the breakdown products were
    completely mineralized; however, under the flow-through conditions
    of this test, water-soluble compounds were usually removed via the

    aqueous effluent and were not present long enough to allow
    mineralization. Acclimatization considerably increased the kinetics
    of mineralization (Hrsak et al., 1981).

    (iii)  Surface water and sediment

        Detritus is a significant site of surfactant removal, and LAS
    were found to be the most sorptive of the surfactants tested. In
    wastewater from a pond containing submerged oak leaves, degradation
    followed first-order kinetics, with a half-life of 12.6 days. LAS
    were mineralized more slowly by leaves from a control pond, and an
    S-shaped pattern of degradation was seen (Federle & Ventullo, 1990).

        In river water in which the biomass levels were 10-100 times
    higher below than above a sewage outfall, primary degradation of
    added C11.6 LAS (11 mg/litre) and background LAS (0.37 mg/litre)
    was rapid in water taken from below the outfall, with a half-life of
    0.23 days (based on measurements of MBAS). Mineralization of the
    benzene ring was rapid in water from below the outfall containing
    sediment (500 mg/litre), with a half-life of 0.7 days. Water taken
    above the sewage outfall also underwent ring mineralization, but the
    rate of degradation was about 25% of that seen for water from below
    the outfall, with a half-life of 2.7 days. When samples were
    incubated in the absence of sediment, ring degradation was much
    slower, with half-lives of 1.4 days in water taken from below the
    outfall and approx.14 days in water taken above it. In all cases,
    degradation was immediate in water taken below the outfall, but
    occurred after a three-day lag in water taken above (Larson & Payne,
    1981).

        Degradation of C10-C14 homologues of LAS at concentrations
    of 10 or 100 µg/litre followed first-order kinetics in both river
    water and river water plus sediment; the half-time for
    mineralization of the benzene ring was 15-33 h. The length of the
    alkyl chain and the phenyl position had no significant effect, and
    there was no effect of suspended sediment or competing homologues
    (Larson, 1990).

        LAS were degraded in leaf litter, creek water, periphyton, and
    sediment at temperatures as low as 4°C, with half-lives of 6-11
    days. Temperature changes altered the dependence of the
    biodegradation of LAS: the half-lives increased by less than a
    factor of two over an 18°C temperature range. Under realistic
    conditions, temperature had less effect than was predicted on the
    basis of classical thermodynamic studies in the laboratory
    (Palmisano et al., 1991). The dependence of the biodegradation of
    LAS follows a classical Arrhenius relationship down to about 12°C,
    with a tenfold increase in reaction kinetics for every 2°C drop in
    temperature (Larson, 1990).

        Mineralization of LAS in saturated subsurface sediment from a
    wastewater pond and in a pristine pond was monitored by amending the
    sediment with 14C-LAS and measuring the evolution of 14CO2.
    Mineralization in both sediments exhibited first-order kinetics. LAS
    were mineralized without a lag in wastewater sediment, with
    half-lives of 3.2-16.5 days. In the control pond, LAS were
    mineralized much more slowly, with half-lives of 5.2-1540 days, and
    only after a lag of 2-40 days; the lag tended to increase with
    increasing depth. These findings confirm the assumption that
    acclimatization considerably increases the kinetics of LAS
    mineralization (Federle & Pastwa, 1988).

        A study was conducted of the biodegradation of LAS by
    microorganisms associated with the roots of two aquatic plants,
    duckweed  (Lemna minor) and cattail  (Typha latifola).
    Microorganisms from the roots of cattail mineralized 14C-LAS
    without a lag, attaining 17% evolution of 14CO2 within the
    35-day experiment. Microbiota associated with duckweed roots did not
    mineralize LAS. The fact that the plants came from a pristine pond
    or from a wastewater pond had no effect on the ability of the
    microorganisms to mineralize LAS (Federle & Schwab, 1989).

        More than 70% of parent LAS (20 mg/litre) in natural seawater at
    22°C was biodegraded within 10 days, with an estimated half-life of
    6-9 days (Vives-Rego et al., 1987). In an investigation of the
    primary biodegradation kinetics of LAS (10 mg/litre) in natural
    seawater in the presence of sediments (250 g/litre), 60% remained
    after 20 days at 15°C and almost 100% of LAS at 5°C; however, at 20
    and 25°C, only a small percentage of the original concentration
    remained (Sales et al., 1987). In another study in seawater, 97% of
    parent LAS (10 mg/litre) was biodegraded within two weeks (von Bock
    & Mann, 1971).

        More than 85% of LAS (C11.8) in estuarine water underwent
    primary biodegradation, measured as MBAS removal, after 11 days
    (Arthur D. Little Inc., 1991). In water from Chesapeake Bay, United
    States, 75% of MBAS were removed within three days (Cook & Goldman,
    1974). In a study of effluent-exposed estuarine waters, with
    phenyl-radiolabelled C13 LAS, production of 14CO2 represented
    42% of the added label. Addition of sediment from the site
    (1 g/litre) increased the 14CO2 yield to 60%. In both tests, the
    half-life for mineralization of LAS was about seven days. Up to 54%
    of a radiolabelled control chemical, glucose, was mineralized. Thus,
    mineralization of LAS occurs rapidly in pre-exposed estuarine
    systems, with half-lives shorter than the typical hydraulic
    residence times of such estuaries (Shimp, 1989).

    (iv)  Soils and groundwater

        A simple shake-flask system was used to determine CO2
    evolution in a test to assess the ultimate biodegradability of LAS
    by microorganisms in soil and sewage. At 30 mg/litre, high
    relative-molecular-mass LAS were biodegraded more slowly than those
    with a low relative molecular mass. Ultimate biodegradation could
    not be assessed precisely within the 28-day test period, but CO2
    removal was 37-77% and dissolved organic carbon removal was 59-84%.
    Ultimate biodegradation of the entire molecule (total CO2)
    occurred concomitantly with biodegradation of the benzene ring
    (14CO2). Ring desulfonation, measured as 35S-LAS, was rapid
    and occurred mainly after primary biodegradation (MBAS method)
    (Gledhill, 1975).

        The kinetics of the ultimate biodegradation of C10-C14 LAS
    to CO2 was studied in a sludge-amended soil at 0.1-10 times
    environmental concentrations. All four homologues underwent rapid
    degradation, with half-lives for the breakdown of the benzene ring
    of 18-26 days (Ward & Larson, 1989).

        Microbial mineralization of 50 µg/kg 14C-LAS was examined in
    soil types ranging from a loamy sand impacted with sewage effluent
    to a highly organic alpine soil, by monitoring the evolution of
    14CO2. LAS were mineralized without a lag in all soils;
    mineralization exhibited first-order kinetics in nine of the 11 soil
    types. Asymptotic yields of CO2 ranged from 16 to 70%; the
    half-lives were 1.1-3.7 days. The degradation rates were not
    correlated with microbial activity, pH, total organic content, or
    previous exposure (Knaebel et al., 1990).

        After 14C calcium and sodium salts of LAS were applied to two
    silty loam soils, the distribution of 14C was similar. After 60
    days, 31-47% of the applied 14C had evolved as 14CO2 and
    31-40% was present as soil residue, possibly as a combination of
    parent and metabolized surfactant (Kawashima & Takeno, 1982).

    A4.2.1.2  Anaerobic degradation

        Degradation of LAS (measured as MBAS) was much slower under
    anaerobic conditions in activated sludge than under aerobic
    conditions. No degradation had taken place after one day; up to 20%
    had been degraded between days 3 and 21, and 36% after 28 days. When
    soil and wastewater were used, only 20% of the MBAS had disappeared
    within 28 days (Oba et al., 1967). No significant removal of LAS was
    reported in an anaerobic sludge digester at a Swiss sewage treatment
    plant (Giger at al., 1989).

        In a review of the fate of LAS in anaerobic and aerobic sewage
    treatment plants, it was concluded that drying anaerobic sludge on
    open beds considerably reduces the LAS content. Anaerobic
    degradation of LAS is, however, limited, as the addition of LAS at
    15 g/kg raw sewage (about 15 g/litre raw sewage) may inhibit
    anaerobic degradation. In the laboratory, digestion of LAS was
    impaired at concentrations of > 15-20 g/kg, and a concentration of
    20 g/kg seriously inhibited gas production, especially when other
    potentially inhibitory compounds were present. The concentration of
    LAS normally found in sewage (5-10 g/kg) is, however, unlikely to
    inhibit anaerobic degradation (Painter & Zabel, 1989). About 15-35%
    of LAS in raw sewage is physically removed in primary settlers in
    sewage treatment plants, accounting for most of the LAS found in
    anaerobic sludge. Precipitation of LAS is correlated with water
    hardness, since the solubilities of the calcium and magnesium salts
    of LAS are very low; the solubility products ranged from
    2.2 × 10-10 for C10 LAS to 6.2 × 10-13 for C13 LAS (Berna et
    al., 1989). The effect of water hardness was confirmed by mass
    balance analysis of Na+, Ca2+, and Mg2+ (Berna et al., 1993b).
    The content of total calcium and magnesium in anaerobically digested
    sludge was 43 times higher than that in water. High contents of LAS
    in the sludge (up to 30 g/kg) did not inhibit the anaerobic
    digestion process (Painter & Mobey, 1992), probably because LAS were
    present as calcium and magnesium salts and therefore had reduced
    bioavailability.

        LAS were not degraded in an anaerobic sediment from a pond
    receiving wastewater from a laundromat. Despite an exposure period
    of 25 years, no anaerobic degradation was reported (Federle &
    Schwab, 1992).

        Pre-aerobic treatment of LAS may cause changes in the molecule
    that permit subsequent degradation under anaerobic conditions (Ward,
    1986).

    A4.2.2  Abiotic degradation

        The mechanisms of abiotic degradation of LAS reported below are
    not of environmental significance, since biodegradation and sorption
    are rapid, effective removal mechanisms.

    A4.2.2.1  Photodegradation

        In a study of the kinetics of the photodecomposition of C12
    LAS, using a continuous-flow reactor, the initial concentrations
    were 60-182 mg/litre and the radiation wavelength was 200-450 nm.
    Conversion of LAS to intermediate products occurred within 1 min,
    yielding 7 mol CO2 per mol LAS, and was complete within 20 min.
    The reaction rate was increased by two orders of magnitude by ferric
    perchlorate (Matsuura & Smith, 1970).

        Rapid photodegradation of LAS (50 mg/litre) occurred within
    1-2 h in an aqueous, aerated titanium dioxide suspension without
    noble metal catalysts. There was rapid decomposition of the aromatic
    ring and slower oxidation of the aliphatic ring. Photodegradation
    was dependent on the simultaneous presence of titanium dioxide,
    oxygen, and light (Hidaka et al., 1985).

    A4.2.2.2  Cobalt-60 irradiation

        The decomposition of LAS was studied in distilled water
    irradiated with cobalt-60 gamma rays, which react with water to
    produce oxygen, peroxide, hydrogen peroxide, and other strong
    oxidizing agents. A concentration of 10 mg/litre LAS was reduced to
    7.8 mg/litre by absorption of 10 Gy and to 0.9 mg/litre by
    absorption of 100 Gy. The rate of irradiation was found to be less
    important than the total absorbed energy (Rohrer & Woodbridge,
    1975).

    A4.2.3  Bioaccumulation and biomagnification

        Studies of the bioaccumulation potential of LAS have all been
    carried out with LAS labelled with 14C or 35S. It should be
    noted that as these techniques do not usually allow consideration of
    metabolic transformation the actual bioaccumulation of the parent
    compound may be overestimated. Toxic concentrations of the breakdown
    products of LAS are discussed in section A9.3.7.

    A4.2.3.1  Aquatic organisms

        Bioaccumulation has been studied in daphnids and fish (Table 8).
    LAS are readily absorbed through the gills and body surface of fish
    and are subsequently distributed via the blood to the organs and
    tissues; most LAS accumulate in the gall-bladder and hepatopancreas.
    Clearance is usually rapid, with a half-life of two to three days.
    Short-chain LAS are accumulated to a lesser degree than long-chain
    LAS.

        Only 1% of 0.5 mg/litre LAS added to water was retained in
     Daphnia magna within three or four days after transfer to 'clean'
    water. Almost all of the chemical was in the form of intact LAS. In
    fathead minnows  (Pimephales promelas), metabolic transformation
    occurred. All tissues monitored showed some uptake, with
    concentration factors ranging from 79-372 in muscle to 21 000-70 000
    in gall-bladder. Within four days of transfer to 'clean' water, 85%
    of the LAS had been lost, and almost 100% was lost within 10 days
    (Comotto et al., 1979).

        Table 8.  Bioconcentration factors for linear alkylbenzene sulfonates in aquatic invertebrates and fish
                                                                                                                                              

    Organism           Static/flow   Exposure        Duration   Chain    Steady   Bioconcentration  Tissue           Reference
                                     concentration   of test    length   state    factor
                                     (mg/litre)      (days)
                                                                                                                                              

    Daphnia magna      Flow          0.07            3          C12      ?        490                                Comotto et al.
                                                                                                                     (1979)
                                     0.11                                         560
                                     044                                          720
                                     0.09            3          C13      Yes      1250
                                     0.11                                         1050
                                     0.41                                         1325

    Cyprinus carpio    Static        61.1            1          C12      Yes      4.1               Skin surface     Kikuchi et al.
                                                                                                                     (1978)
                                                                                  1000              Gall-bladder
                       Flow          0.5             4          C12      Yes      20                Whole body       Wakabayashi
                                                                                  30                Hepatopancreas   et al. (1978)
                                                                                  9000              Gall-bladder
                                     0.0091          5          C12      Yes      16                Whole body       Wakabayashi
                                                                                                                     et al. (1981)
                                     0.3                                          400                                
                                     1.0                                          300
    Pimephales         Flow          0.1             11         C12      Yes      551               Whole body       Comotto et al.
    promelas                                                    C13               1223                               (1979)
                                                                C12, C13          269
                                                                                                                                              

    Table 8 (contd)
                                                                                                                                              

    Organism           Static/flow   Exposure        Duration   Chain    Steady   Bioconcentration  Tissue           Reference
                                     concentration   of test    length   state    factor
                                     (mg/litre)      (days)
                                                                                                                                              

    Lepomis            Flow          0.063           28         C12      Yes      260               Whole body       Bishop &
    macrochinus                      0.064                                        120                                Maki (1980)

                       Flow          0.5             35         C11.7    Yes      107               Whole body       Kimerle et al.
                                                                                  5000              Gall-bladder     (1981)
                                                                                                                                              

    Static, water unchanged for the duration of the test; flow, concentration in water maintained continuously
            In an experiment in which the aqueous concentrations of an
    initial concentration of 1.1 mg/litre LAS decreased by 20% during
    the test, the compounds were concentrated in the gills of carp
     (Cyprinus carpio) within 2 h of exposure, with a concentration
    factor of 40. Skin surface, muscle, brain, kidney, hepatopancreas,
    and gall-bladder showed more gradual uptake of LAS over the 24 h of
    exposure, with concentration factors ranging from 4.1 for skin
    surface to 1000 for gall-bladder. Blood, gonads, and spleen also
    took up LAS but were not monitored throughout the period of
    exposure. LAS was lost rapidly from all tissues except the
    gall-bladder during 48 h in 'clean' water (Kikuchi et al., 1978).

        In the bluegill  (Lepomis macrochirus), a steady state was
    reached within 120-168 h. The bioconcentration factor was calculated
    by a kinetic method to be 286 for a concentration of LAS of
    0.8 mg/litre and 132 for 0.08 mg/litre. LAS were cleared rapidly
    after the fish were transferred to 'clean' water, with 99%
    eliminated within 336 h; the time for clearance was 29-30 h (Bishop
    & Maki, 1980). In another study, a steady state was reached within
    seven days; the bioconcentration factor in whole body using a
    kinetic method was reported to be 104; and the half-time for
    clearance was two to five days during a depuration period of 14
    days. The authors postulated that fish excrete LAS in the urine and
    excrete shorter-chain carboxylates with the benzene ring intact
    across the gill membranes. Both forms may also be excreted in the
    faeces (Kimerle et al., 1981).

    A4.2.3.2  Terrestrial plants

        Foliar uptake of the calcium and sodium salts of 14C-LAS
    (chain length not specified) by peanuts was studied seven and 30
    days after application. No movement of LAS was detected: 70-80%
    remained within the same leaf to which the compound was applied, and
    no LAS were detected in other parts of the plant (Kawashima &
    Takeno, 1982).

        Aqueous solutions of 14C-LAS (chain length not specified) were
    applied to soil (orthic luvisol), and ryegrass  (Lolium perenne)
    was grown under laboratory conditions for up to seven days. Uptake
    of LAS after three days was 80 mg/kg at an application rate of
    1 mg/kg dry weight, 370 mg/kg at a rate of 5 mg/kg, and 18 900 mg/kg
    at 50 mg/kg. After seven days, levels of 600, 5000, and 19 300 mg/kg
    were measured at the three dose levels, respectively (Litz et al.,
    1987).

        14C-LAS (chain length not specified) were applied under field
    conditions to both loamy orthic luvisol and sandy dystric cambisol
    soils irrigated with wastewater at rates of 5 and 50 g/m2. After
    49 days, rye grass grown in the loamy soil contained residues of 130
    and 1000 mg/kg dry weight at the two exposure rates, respectively.

    Plants grown in the sandy soil contained 230 and 470 mg/kg,
    respectively, after 54 days (Litz et al., 1987).

        Two plant-soil microcosms were exposed to 14C-LAS (chain
    length not specified), and LAS degradation and percolation were
    followed for up to 109 days. The initial soil concentrations were
    16.2 µg/g dry soil in potato soil (sandy) and 27.2 µg/g in grass,
    bean, and radish soil (clay-like). The concentrations of
    radiolabelled compounds in the plants decreased rapidly: at the end
    of exposure, 39.1-65.8 µg LAS equivalents per g fresh weight of
    plant were found in potatoes (study duration, 76 days) and
    62.1-213.3 µg/g in grass, radishes, and beans (study duration, 109
    days) (Figge & Schoberl, 1989).

    A5.  ENVIRONMENTAL LEVELS AND HUMAN EXPOSURE

     Section summary

        The concentrations of LAS have been quantified by means of a
    specific, sensitive analytical method in almost every environmental
    compartment in which they might be present. The concentrations
    decrease progressively from wastewater to treated effluent and
    surface waters, and low concentrations are found in the sea.

        The environmental concentrations of LAS are directly dependent
    on use patterns, the type and efficiency of sewage treatment, and
    the characteristics of the receiving environment. In areas where LAS
    are the predominant surfactants used, typical concentrations are
    1-10 mg/litre in wastewater, 0.05-0.1 mg/litre in effluents that
    have undergone biological treatment, 0.05-0.6 mg/litre in effluents
    passed through a percolating filter, 0.005-0.050 mg/litre in surface
    waters below sewage outfalls (with concentrations decreasing rapidly
    to 0.01 mg/litre downstream from the outfall), < 1-10 mg/kg in
    river sediments (up to 100 mg/kg in highly polluted sediments near
    discharge zones), 1-10 g/kg in sewage sludge, and < 1-5 mg/kg in
    sludge-amended soils. The initial concentration of LAS in
    sludge-amended soils is 5-10 mg/kg, but up to 50 mg/kg have been
    reported after atypically heavy appli-cations. The concentration of
    LAS in estuarine waters is 0.001-0.010 mg/litre but is higher where
    wastewater is discharged directly. The concentrations in offshore
    marine waters are < 0.001-0.002 mg/litre.

        A wide range of environmental concentrations has been reported,
    owing to use of different analytical methods; differences in
    characteristics of sampling sites, which range from highly polluted
    areas with inadequate sewage treatment to areas where sewage
    undergoes extensive treatment; seasonal differences, which can
    account for a twofold variation; and differences in the use of LAS.

        Monitoring has shown no accumulation of LAS in environmental
    compartments over time. The concentrations in soil do not increase
    with time but are diminished due to mineralization. As LAS are not
    degraded under strictly anaerobic condition, they are not
    mineralized in anaerobic sediments. With current use of LAS, the
    rates of their assimilation in all receiving environmental
    compartments is equal to their rate of input, implying a steady
    state.

    A5.1  Environmental levels

        LAS have been measured in most environmental compartments,
    including discharge (raw sewage), sewers, sewage treatment plants,
    sludge-amended soils and land fill, river water, river sediments,
    subsurface soils, groundwater, and estuaries (Berna et al., 1991).

        A decline in the concentrations of anionic surfactants in the
    environment, as assessed by measurement of MBAS, was seen in Europe,
    Japan, and the United States after ABS was replaced by LAS (Sullivan
    & Evans, 1968; Sullivan & Swisher, 1969; Gerike et al., 1989).
    Similar declines have been observed more recently in countries such
    as Thailand, where the change to LAS detergents is also more recent
    (Berna et al., 1991).

    A5.1.1  Wastewater, sewage effluent, and sludge

        The concentrations of LAS in sewage influent and effluent at
    sewage treatment plants are shown in Table 9; those in sewage sludge
    are given in Table 10.

        The efficiency of wastewater treatment plants in removing LAS is
    reported to exceed that of removal of biochemical oxygen demand. 
    Activated sludge removed an average of 98% LAS, trickling filters
    removed 80%, and primary clarification, 27%. The average
    concentration in raw sewage was 3.5 mg/litre, and those in effluent
    were 2.1 mg/litre after primary treatment and 0.06 mg/litre in
    activated sludge. The average chain length of LAS was C12.5 in
    sewage sludge and C12 in influent sewage (Rapaport & Eckhoff,
    1990).

        The amount of LAS removed in a sewage treatment plant was 93% on
    the basis of total organic carbon and 98.1% on the basis of a
    specific method. The contribution of LAS to the total organic carbon
    was estimated to be 0.93% in treated water and 3.0% in digested
    sludge; 75.9% of LAS present in the raw sewage was mineralized
    during treatment and 7% was in the form of sulfoxyphenyl-
    carboxylates, a product of the biodegradation of LAS, suggesting
    that biodegradation of LAS had reached a steady state. These figures
    were obtained by analysis for sulfoxyphenylcarboxylates (Berna et
    al., 1993b).

        In another study, 40% of LAS was removed in a wastewater
    treatment plant. The half-life for removal from the sewer pipe was
    calculated to be 11 h (Moreno et al., 1990).

    A5.1.2  Sediment

        The concentrations of LAS in sediment are shown in Table 11, and
    those in sediment samples collected at various distances from sites
    of effluent outfall are shown in Table 12.

        Table 9.  Concentrations of methylene blue-active substances (MBAS) and linear alkylbenzene sulfonates (LAS) in sewage
              influent and effluent
                                                                                                                                              

    Location                  Year     Material                      Concentration (mg/litre)                          Reference
                                                                                                                
                                                                     MBAS                           LAS
                                                                                                                                              

    Switzerland (29 sites,    1986     Raw sewage                                                   0.95-3.9           Brunner et al. (1988)
       1 sampling)                     Effluent                                                     0.007-0.33

    Germany (11 sites,        1985     Influent (activated sludge)   5.1 (1-13.3)                   4 (0.54-12.4)      Matthijs & De Henau
       1 sampling)                     Influent (trickling filter)   8.8 (8.1-9.9)                  7.4 (6.8-8.4)      (1987)
                                       Effluent (activated sludge)   0.19 (0.09-0.28)               0.07 (0.05-0.11)   
                                       Effluent (trickling filter)   1.1 (0.84-1.5)                 0.76 (0.61-0.94)

    United Kingdom
       (several samples)      1982     Effluent                      0.69 (0.58-0.81)               0.31 (0.21-0.42)   Gilbert & Pettigrew 
                                                                                                                       (1984)
       River Thames area      1987     Sludge                                                       15.1-341           Holt et al. (1989)
       (5 sites, several
       samples)

    Israel (4 sites)          1983     Influent                      9.6-10.6a                                         Zoller (1985)
                                       Effluent                      0.3-11.0a

    United States             1979     Effluent                                                     0.078-0.303        Eganhouse et al. (1983)
       (4 sites, 45 samples   1976-86  Influent                                                     3.7 ± 1.1          Rapaport & Eckhoff
                                       Effluent (activated sludge)                                  0.05 ± 0.04        (1990)
                                       Effluent (trickling filter)                                  0.6 ± 0.3
                                       Effluent (primary)                                           2.2 ± 0.4
                                                                                                                                              

    Table 9 (contd)
                                                                                                                                              

    Location                  Year     Material                      Concentration (mg/litre)                          Reference
                                                                                                                
                                                                     MBAS                           LAS
                                                                                                                                              

    United States                      Influent                      5.9-6.5                        5.7-6.5            Osburn (1986)
       (1 sampling)                    Influent                      3.7-5.2                        3.8-4.9
                                       Effluent                      0.39-1.02                      0.14-0.60
       (2 sites, 9 samples)   1983     Raw influent                  4.17                           3.73               Sedlak & Booman
                                       Primary influent              3.18                           2.97               (1986)
                                       Primary effluent              1.66-2.82                      1.73-2.51
                                       Final effluent                0.03-0.06                      0.02-0.05

    Canada (4 sites,          1976-86  Influent                                                     2.0 ± 0.6          Rapaport & Eckhoff
       45 samples yearly)              Effluent (activated sludge)   0.09 ± 0.05                                       (1990)
                                       Effluent (primary)                                           1.7-2.3

    Japan
       (5 sites, 60 samples)  1972-73  Influent                      5.1-14.0                                          Oba et al. (1976)
                                       Effluent                      0.3-4.7
       (6 sites, 1-2 samples) 1984     Influent (suspended particles)                               0.236-1.504        Takada & Ishiwatari 
                                       Effluent (suspended particles)                               0.0001-0.001       (1987)
                                                                                                                                              

    a Total anionic surfactants (mainly LAS)

    Table 10.  Concentrations of methylene blue-active substances (MBAS) and linear alkylbenzene sulfonates (LAS) in sewage sludge
                                                                                                                                              

    Location                  Year     Material                      Concentration (mg/litre)                          Reference
                                                                                                              
                                                                     MBAS                           LAS
                                                                                                                                              

    Switzerland
       (8 and 12 sites,                Digested sludge                                              2900-11 900        McEvoy & Giger
                                                                                                                       (1985, 1986)
       1 sampling)
       (29 sites,             1986                                                                  50-13 800a         Brunner et al.
       1 sampling)                                                                                                     (1988)

    Spain
       (5 sites, several               Activated sludge                                             7000-30 200a       Berna et al. (1989)
       samplings)                      (anaerobic digestion)
                                       Aerated, settling system                                     400-700a

    Finland (12 sites,                 Digested sludge                                              3400-6300a         McEvoy & Giger
       1 sampling)                                                                                                     (1986)

    Belgium (11 sites,        1985     Aerobic sludge                5399 (3042-8133)               281 (182-432)      Matthiijs & De
       1 sampling)                     Digested sludge               9017 (3632-17 006)             4917 (1327-9927)   Henau (1987)

    Germany (4 sites,         1981-86                                                               4920 (1330-9930)   Rapaport &
       45 samples yearly)                                                                                              Eckhoff (1990)
                                                                                                                                              

    Table 10 (contd.)
                                                                                                                                              

    Location
                              Year     Material                      Concentration (mg/litre)                          Reference
                                                                                                               
                                                                     MBAS                           LAS
                                                                                                                                              

    United States
       (4 sites, 45           1981-86                                                               4660 ± 1540        Rapaport &
       samples yearly)                                                                                                 Eckhoff (1990)
       12 sites, NY,                   Digested sludge                                              6900a              McEvoy & Giger
       (1 sampling)                                                                                                    (1986)
       (12 sites, CA,                  Digested sludge                                              5200a
       1 sampling)
       (1 sampling)                    Primary sludge                110-126                        107-127            Osburn (1986)
       (2 sites, OK,          1983     Primary sludge                4610-6120                      5340-6310          Sedlak & Booman
       9 samples)                      Secondary sludge              520-990                        410-860            (1986)
                                       Anaerobic digester            6860                           6660
                                       Aerobic digester              3820                           4250
                                       Drying bed (anaerobic)        170                            160
                                       Drying bed (aerobic)          230                            150
    Southern California       1981     Effluent particulates                                        1342               Eganhouse et al.
       (marine)                                                                                                        (1983)
                                                                                                                                              

    a Dry weight

    Table 11.  Concentrations of methylene blue-active substances (MBAS) and linear alkylbenzene sulfonates (LAS) in sediments in
               the United States and Japan
                                                                                                                                              

    Location                                          Year        Concentration (mg/kg)                    Reference
                                                                                                      
                                                                  MBAS              LAS
                                                                                                                                              

    United States
       Rivers (activated sludge)                                                    0.3-3.8                McAvoy et al. (1993)
       Rivers (trickling filter)                                                    0.2-340
       Mississippi River                              1991-92                       < 0.01-5               Tabor et al. (1993)

    Japan
      Tokyo Bay (1 sampling, few samples)             1969        35 (33-37)                               Ambe (1973)
      River (1 sampling, few samples)                             61 (55-65)
      River Sagami estuary (16 sites, 1 sampling)                 7.9-39a           ND-17                  Utsunomiya et al. (1980)
      Sagami Bay (16 sites, 1 sampling)                           5.1-15            ND
      Rivers                                          1977                          < 1-260                Environment Agency Japan
                                                                                                           (1978)
      Lake Suwa (1 site, 3 samples)                   1977                          1.0-7.0
      Rivers (9 sites, 7 samples, 1 year);            1982-83                       107 (ND-567)           Takada & Ishiwatari (1987);
         (1 site 52 samples)                                                                               Takada et al. (1992b)
      Estuaries (1 site, 52 samples)                  1983-84                       4.82 (0.12-36.6)       Takada et al. (1992b)
      Tokyo Bay (9 sites, 7 samples, 1 year)          1980                          71.0                   Takada & Ishiwatari (1987)
      Tokyo Bay                                       1984                          0.02 (ND-0.06)         Takada et al. (1992a)
      Sumida River (12 sites, 1 sampling)             1982                          0.069                  Kikuchi et al. (1986)
      Tama River (3 sites, 8 samples)                 1977                          3.5-86.3               Hon-Nami & Hanya (1980b)
      Tama River (10-12 sites)                        1982                          0.141                  Kikuchi et al. (1986)
      Tokyo Bay (10-12 sites)                         1982                          < 0.001-0.002
                                                                                                                                              

    Table 11 (contd)
                                                                                                                                              

    Location                                          Year        Concentration (mg/kg)                    Reference
                                                                                                      
                                                                  MBAS              LAS
                                                                                                                                              

    Japan (contd).
      Tsurumi River (7 sites, 12 samples)             1984                          17-45a                 Yoshikawa et al. (1985)
      Tama River                                      1981                          2.79-10.72             Yoshimura et al. (1984b)
      Ports and coast                                 1977                          < 1-2.9                Environment Agency Japan
                                                                                                           (1978)
                                                                                                                                              

    ND, not determined
    a  Dry weight

    Table 12.  Concentrations of methylene blue-active substances (MBAS) and linear alkylbenzene sulfonates (LAS) in sediment of rivers in
               Germany and the United States at various distances from effluent outfalls
                                                                                                                                              

    Location                             Year        Sampling site (distance    Concentration (mg/litre)        Reference
                                                     from effluent outfall)                            
                                                                                MBAS              LAS
                                                                                                                                              

    German rivers (14 sites, several     1978-82     Below outfall                                1.5-174a      De Henau et al.
      samples)                                                                                                  (1986)

    United States
      Rivers (4 sites, 45 samples)       1978-82     Below  outfall                               190           Rapaport &
      yearly                                         < 5 miles (8.0 km)                           11.9          Eckhoff
                                                     > 5 miles (8.0 km)                           5.3           (1990)
      (1 sampling)                                   0.5 miles (0.8 km)         118-317           100-322       Osburn (1986)
                                                     4.4 miles (7.1 km)         4.1-19            2.0-5.1
                                                     7.4 miles (11.9 km)        7.5-10.6          1.3-4.4
      Rapid Creek, South Dakota          1979-80     0.8 km                                       44.6-275      Games (1983)
                                                     7 km                                         3.2-9.1
                                                     11.7 km                                      2.1-8.4
                                                     25.3 km                                      2.7-10.1
                                                     48 km                                        1.4
                                                     87.2 km                                      1.5
      Little Miami River, Ohio                       Downstream from sewage                       ND-1.2        Hand et al. (1990)
        4 sites, 1 sampling)                         treatment plants                             24.7-290b
      Rivers (4 sites, 45 samples)       1978-82     Below outfall                                190           Rapaport &
                                                     Above outfallc                               1.0-1.2       Eckhoff (1990);
                                                     Below outfall (left)c                        0.3-1.6       McAvoy et al.
                                                     Below outfall (middle)c                      0.6-3.8       (1993)
                                                                                                                                              

    Table 12 (contd)
                                                                                                                                              

    Location                             Year        Sampling site (distance    Concentration (mg/litre)        Reference
                                                     from effluent outfall)                             
                                                                                MBAS              LAS
                                                                                                                                              

    United States (contd)
      Rivers (4 sites, 45 samples)       1978-82     Below outfall (right)c                       0.8-3.4
      (contd).                                       Above outfalld                               0.2-0.9
                                                     Below outfall (left)d                        0.2-130
                                                     Below outfall (middle)d                      0.6-124
                                                     Below outfall (right)d                       9-340
                                                                                                                                              

    a 13 of the 14 samples contained < 25 mg/kg and 10 contained < 10 mg/kg
    b Suspended solids
    c Activated sludge
    d Trickling filter
             Concentrations of LAS > 10 mg/kg were measured in sediments
    from the upper estuaries near Tokyo Bay and < 1 mg/kg in the lower
    estuaries. The concentrations of LAS in sediments decreased
    offshore, falling below 0.01 mg/kg in sediments sampled 10 km from
    the mouths of the rivers. The authors suggested that loss of LAS was
    due to rapid degradation in the coastal zone (Takada et al., 1992a).

        It was reported in one study that C13 was the most abundant
    homologue of LAS in river sediment (Yoshikawa et al., 1985); another
    group found that C12 was the most abundant of the LAS in estuarine
    sediments and that no C10 were present (Utsunomiya et al., 1980).
    C12 and C13 LAS predominated in sediment and C10 and C11
    homologues were the most abundant in water (Hon-Nami & Hanya,
    1980b). The average chain length of LAS in Japanese river sediments
    was C11.8-C12.2 (Hon-Nami & Hanya, 1980b; Yoshimura et al.,
    1984a).

        In a study of marine sediments from an area adjacent to the
    point of discharge from a submarine sewer, LAS were detected only in
    the vicinity of the discharge, at a concentration of 0.1 mg/kg, and
    not in sediment sampled 50 m outside this area. The average chain
    length was C11.7. In a comparison of the chain lengths of LAS
    detected in various environmental compartments and those used in
    detergent products, the LAS detected in sludge and sediment were
    relatively higher homologues and those in the water phase were
    lighter (Prats et al., 1993).

        The average concentration of LAS in river sediments sampled
    upstream of an activated sludge treatment plant outfall was
    1.1 mg/kg, and those in sediments downstream of the plant were
    0.3-3.8 mg/kg (McAvoy et al., 1993).

    A5.1.3  Surface water

        The concentrations of LAS in water are shown in Table 13 and
    those in samples taken at various distances from sites of effluent
    outfall in Table 14.

        After replacement of branched-chain ABS, which are only
    sparingly biodegradable, with the straight-chain LAS, the
    concentrations of MBAS decreased in many rivers. ABS were replaced
    by LAS in Japan in the late 1960s; the ratio of LAS to total ABS in
    river water rose from 20 to 70% in 1967-70 and had reached 90% by
    1973 (Miura et al., 1968; Ihara et al., 1970; Oba et al., 1975). The
    levels of MBAS were monitored in the Illinois River, United States,
    from 1959 to 1966; those in 1965 and 1966 reflected the change in
    surfactant usage (Sullivan & Evans, 1968), and this trend continued
    in 1967 and 1968 (Sullivan & Swisher, 1969). In the River Rhine, the
    level of anionic detergents, measured as MBAS, fell steadily between
    1971 and 1977 (Hellmann, 1978).  In water samples from 140 sites on

        Table 13.  Concentrations of methylene blue-active substances (MBAS) and linear alkylbenzene sulfonates (LAS) in water
                                                                                                                                              

    Location                                  Year         Water            Concentration (mg/litre)             Reference
                                                           sample                                           
                                                                            MBAS               LAS
                                                                                                                                              

    Freshwater

     United States
     Rivers (4 sites, 45 samples yearly)      1978-86                                          0.041-0.115       Rapaport & Eckhoff
                                                                                                                 (1990)
     Little Miami River, Ohio (4 sites,                                                        < 0.05            Hand et al. (1990)
       one sampling)                                       Interstitial                        ND-0.08
     Illinois River (one sampling)a           1959-65                       0.54                                 Sullivan & Swisher
                                              1965-66                       0.22                                 (1969)
                                              1968                          0.05-0.06
     Rapid Creek, South Dakota                1979-80                                          0.01-0.270        Games (1983)
     Mississippi River (36 sites)             1991-92                                          < 0.01-0.3        McAvoy et al. (1993)
       (350 samples)                                                        < 0.01-0.046       < 0.005           Tabor et al. (1993)

     Japan
     Rivers (23 sites, 51 samples)            1977                                             < 0.01-2.9        Environment
                                                                                                                 Agency Japan (1978)
     Rivers (1 sampling)                                                                       0.018-0.59        Tsukioka &
                                                                                                                 Murakami (1983)
     Oohori River (6 sites monthly)           1987-88                                          approx. 0.5-1.6   Amano et al. (1991)
     Lake Teganuma (6 sites monthly)          1987-88                                          ND-approx. 0.7
     Tama River (3 sites, 8 samples)          1977-78                       0.24-1.24          0.108-0.491       Hon-Nami & Hanya
                                                                                                                 (1980a)
                                                                                                                                              

    Table 13 (contd.)
                                                                                                                                              

    Location                                  Year         Water            Concentration (mg/litre)             Reference
                                                           sample                                           
                                                                            MBAS               LAS
                                                                                                                                              

     Japan (contd)
     Rivers, Hyogo Prefecture (70 sites)                                                       0.004-2.5         Kobuke (1985)
     Tama River (3 sites, 1 sampling)                                                          0.035-0.219       Yoshikawa et al.
                                                                                                                 (1984)
     Tama River (10-12 sites)                 1982                                             0.128             Kikuchi et al. (1986)
     Sumida River (10-12 sites)               1982                                             0.005-0.01        Kikuchi et al. (1986)
     Rivers (1 sampling)                                                    0.06-0.12                            Saito & Hagiwara
                                                                                                                 (1982)
     Rivers, Niigata Prefecture (6 sites,                                   0.02-2.63          0.18 (max)        Motoyama & Mukai
      1 sampling)
                                              (1981)
     Rivers, coastal area, Hiroshima                                                           0.019             Okamoto & Shirane
     Prefecture (20 sites)                                                                     (0.001-0.06)      (1982)
     Inland Sea, Eastern Seto (4 sites,       1975                          0.016-0.077                          Yoshida & Takeshita
      1 sampling)                                                                                                (1978)
      (17 sites, 1 sampling)                  1976                          0.01-0.048
     Tsurumi River, Kanagawa                  1984-76      Surface          0-0.8              0.01-0.29         Yoshikawa et al.
      (7 sites once)                                                                                             (1985)
     Yodo River, Osaka (several sites)        1989         Surface                             0.043-0.089       Nonaka et al. (1990)
     Tama River, Tokyo (2 sites,              1981         Surface                             0.2               Yoshimura et al.
      4 samples)                                                                                                 (1984b)
     Sumidogawa River (2 samples)             1983         Suspended                           0.0048-0.054      Takada & Ishiwatari
     Tomogawa River (5 samples)                            particles                           0.0005-0.0025     (1987)
     Teshiro River, Nagoya (4 sites,          1989         Surface                             0.01-0.27         Kojima (1989)
      4 samples)
                                                                                                                                              

    Table 13 (contd)
                                                                                                                                              

    Location                                  Year         Water            Concentration (mg/litre)             Reference
                                                           sample                                           
                                                                            MBAS               LAS
                                                                                                                                              

     Japan (contd)
     Lake Biwa, Shiga                         1988         Surface                             0.00              Shiga Prefecture
                                                                                                                 (1988)
     Teganuma, Chiba (1 site,                 1988         Surface                             ND-0.423          Amano et al. (1989)
      12 samples)
     River (several sites)                    1988         Surface                             0.019-1.4         Nonaka et al. (1989)
     Nagoya Bay                               1989         Surface                             0.00              Kojima (1989)
     Rivers, Fukuoka City                                                                      ND-1.6            Ohkuma (1981)

     Europe
    River Rhine (several sites)               1971-72      0.08-0.24                                             Hellmann (1978)
    Saar River (11 sites, 1 sampling)         1985                          0.13               0.04              Matthijs & De Henau 
                                                                            (0.03-0.25)        (0.01-0.09)       (1987)
    German rivers (several sites)             1976-79                       0.075-0.5                            Fischer (1980)
    Dutch river (Amsterdam drinking-                                        0.004-0.141        0.003-0.037       Waters (1976)
     water supply) (8 sites)
    Florence, Italy (several samples)         1983         Aqueduct         0 .01-0.1                            Mancini et al. (1984)
     (several sites)                          1982         Well water       0.00-0.01
    United Kigdom
     Rivers                                   1982                          0.04-0.26          0.012-0.08        Gilbert & Pettigrew
                                                                                                                 (1984)
     Rivers (8 sites)                                                       0.035-0.217        0.009-0.097       Waters (1976)
     Rivers (4 sites)                         1977-78                       0.022-0.473        0.007-0.173       Waters & Garrigan
                                                                                                                 (1983)
                                                                                                                                              

    Table 13 (contd)
                                                                                                                                              

    Location                                  Year         Water            Concentration (mg/litre)             Reference
                                                           sample                                           
                                                                            MBAS               LAS
                                                                                                                                              

    Groundwater                               1992                                             < 0.01-0.02       Field et al. (1992)

    Estuarine and marine water

    North Sea (19 sites)                      1989                                             < 0.0005-0.0012   Stalmans et al.
                                                                                                                 (1991)
    Krka River estuary, Croatia               1990         Wastewater                          0.42-0.78         Terzic & Ahel (1993)
     (below 50 m > 50 m)                                   Estuarine water  0.003-0.007
                                                                            0.001-0.002
    Tokyo Bay, Japan (8 samples)              1978                          0.03-0.07          < 0.003-0.014     Hon-Nami & Hanya
                                                                                                                 (1980a)
    Tokyo Bay, Japan (10-12 samples)          1982                                             0.001-0.03        Kikuchi et al. (1986)
    Osaka Bay, Japan (several sites)          1988         Surface                             ND-0.0072         Nonaka et al. (1989)
                                                                                                                                              

    ND, not detected
    a 10-20% of MBAS were LAS

    Table 14.  Concentrations of methylene blue-active substances (MBAS) and linear alkylbenzene sulfonates (LAS) in water at various
               distances from effluent outfalls
                                                                                                                                              

    Location                       Year      Sampling site (distance   Concentration (mg/litre)       Reference
                                             from effluent outfall)                               
                                                                       MBAS             LAS
                                                                                                                                              

    United States
     Rivers (4 sites, 45 samples   1978-86   Below outfall                              0.115         Rapaport & Eckhoff
       yearly)                               < 5 miles (8 km)                           0.079         (1990)
                                             > 5 miles (8 km)                           0.041
       (1 sampling)                          0.5 miles (0.8 km)        0.400            0.270         Osburn (1986)
                                             4.4 miles  (7.1 km)       0.300            0.150
                                             7.4 miles (11.9 km)       0.250            0.120
                                             15.8 miles (25.4 km)      0.240            0.100
                                             30.0 miles (48.3 km)      0.130            0.040
                                             55.0 miles (88.5 km)      0.100            0.010
     Rapid Creek, South Dakota     1979-80   0.8 km                                     0.270         Games (1983)
                                             7 km                                       0.150-0.190
                                             11.7 km                                    0.120
                                             25.3 km                                    0.080
                                             48 km                                      0.040
                                             87.2 km                                    0.010
     Rivers                                  Above outfall                              < 0.01-0.9    McAvoy et al. (1993)
                                             Below outfall (left)                       < 0.01-0.33
                                             Below outfall (middle)                     < 0.01-0.3 
                                             Below outfall (right)                      < 0.01-0.3
                                                                                                                                              

    Table 14 (contd)
                                                                                                                                              

    Location                       Year      Sampling site (distance   Concentration (mg/litre)       Reference
                                             from effluent outfall)                               
                                                                       MBAS             LAS
                                                                                                                                              

    Canadian rivers (4 sites, 45   1978-86   Below outfall                              0.053         Rapaport & Eckhoff
      samples yearly)                                                                                 (1990)

    Rio Grande, Brazil             1979      90 m                      0.05-4.5                       Kantin et al. (1981)
     (1 sampling, 50 samples)

    German rivers (several sites)  1976-79   Unpolluted                0.075                          Fischer (1980)
                                             Polluted                  0.2-0.5
     (4 sites, 45 samples yearly)  1978-86   Below outfall                              0.01-0.09     Rapaport & Eckhoff
                                                                                                      (1990)
    United Kingdom
     Rivers (several samples)      1982      Above discharge           0.04             0.012         Gilbert & Pettigrew
                                                                       (0.02-0.07)      (0.008-0.019) (1984)        
                                             Close to discharge        0.26             0.08 
                                                                       (0.11-0.47)      (0.01-0.17)
                                             5-16 km                   0.16             0.04 
                                                                       (0.08-0.23)      (0.008-0.095)
     Avon River (4 sites)          1977-78   Head water                0.03-0.039       0.009-0.015   Waters & Garrigan
                                             0.5 km                    0.21-0.371       0.056-0.173   (1983)
                                             6 km                      0.095-0.22       0.011-0.095   
     Tean River (4 sites)          1977-78   Head water                0.035-0.073      0.008-0.019
                                             Directly below sewage     0.208-0.473      0.067-0.144
                                             treatment
                                             5 km                      0.145-0.234      0.019-0.07 
                                                                                                                                              

    Table 14 (contd.)
                                                                                                                                              

    Location                       Year      Sampling site (distance   Concentration (mg/litre)       Reference
                                             from effluent outfall)                               
                                                                       MBAS             LAS
                                                                                                                                              

    United Kingdom (contd)
     Trent River (4 sites)         1977-78   Head water                0.022-0.052      0.01-0.011
                                             20-35 km below head       0.08-0.227       0.007-0.072
                                             water
     Nene River tributary          1978                                0.104            0.011
      (4 sites)
                                             In the vicinity of        0.206-0.216      0.035-0.037
                                             sewage effluent disharge
                                             3.5 km                    0.184            0.035
                                             13.5 km                   0.06             0.007
                                                                                                                                              
        four German rivers, MBAS concentrations fell by 90% between 1964 and
    1987 (Gerike et al., 1989).

        The mean level of MBAS in rivers in the United Kingdom was
    0.15 mg/litre. On average, only 26% was attributable to LAS (by
    microdesulfonation and gas-liquid chromatography), but the levels of
    LAS and their contribution to the total MBAS concentration varied
    according to the sampling site, with a higher proportion of LAS in
    samples from sites near sewage effluent discharge points (Waters &
    Garrigan, 1983). Similar findings were reported by Gilbert &
    Pettigrew (1984), who found that LAS represented 45% of total MBAS
    in actual sewage. Sites immediately below sewage outfalls were found
    to have higher MBAS:LAS ratios than sites further downstream
    (Osburn, 1986).

        In Lake Biwa basin, Japan, during the summer months of 1983, LAS
    were found in a wide range of concentrations. The highest, measured
    as MBAS, were > 0.2 mg/litre at river mouths. The levels in rivers
    flowing from densely populated areas were 0.05-0.2 mg/litre MBAS and
    those flowing from less populated areas were < 0.05 mg/litre. The
    middle stream zone of the River Isasa, in a densely populated area,
    contained levels of 0.36-1.91 mg/litre, and surfactant levels in
    residential areas showed daily fluctuations related to discharge
    (Sueishi et al., 1988). Several observations apply to these studies.
    Firstly, the fact that daily fluctuations were observed indicates
    that the samples may have been taken from the actual discharge
    plume, so that the wastewater effluent may not have been completely
    mixed with the recipient surface water. Secondly, in several
    Japanese studies of heavy discharge zones, anionic surfactants could
    not be detected in surface waters, although the analytical detection
    limit of MBAS in the mid-1980s was 0.05-0.1 mg/litre. Thirdly,
    sewage treatment at several of the sites has improved considerably
    over the last decade.

        Seasonal trends in the concentrations of LAS were observed in
    the Oohori River and Lake Teganuma, Japan, in 1987 and 1988, with
    low levels in summer and high levels in winter (Amano et al., 1991).

        The concentrations of LAS were measured in the Tamagawa River,
    Japan, at two-week intervals for two years, by sampling water from
    the boundary between freshwater and brackish zones. The
    concentrations measured in winter were about five times higher than
    those measured in summer, when long-chain homologues tended to be
    depleted. The distribution of isomers also showed a clear seasonal
    trend, with a greater loss of external isomers in summer. The
    seasonal changes are thought to be the result of differences in
    water temperature and microbial activity. The flux of LAS in the
    river was estimated to be 320 tons/year (293 tonnes/year), which
    exceeds the total amount of LAS accumulated in the bay sediment,
    indicating that > 99.9% of LAS in the estuary and the bay was
    degraded (Takada et al., 1992b).

        The concentrations of LAS in suspended particles from
    tributaries of Tokyo Bay, Japan, were 0.5-53.8 µg/litre. Those in
    suspended particles from a wastewater influent were 297-504 µg/litre
    and those in the effluent, 0.1-1.22 µg/litre (Takada & Ishiwatari,
    1987).

        The concentrations of LAS in the estuary of the Krka River,
    Croatia, were 420-780 µg/litre near municipal wastewater outlets; 50
    m from the wastewater outlets, the concentrations were 7.2 µg/litre
    at a depth of 0.5 m and 3.2 µg/litre at a depth of 6 m. The
    concentrations in water sampled more than 50 m from the input area
    were 1-2 µg/litre. The Krka River estuary was reported to be highly
    stratified, with vertical transport of pollutants reduced by the
    freshwater-saline boundary. The concentrations of LAS were
    negatively correlated with salinity; the maximum concentration,
    24 µg/litre, was detected in the surface monolayer. An increase in
    the relative abundance of lower homologues of LAS (C10 and C11)
    was reported in comparison with the original distribution of
    homologues in the wastewater, indicating more rapid depletion of
    higher homologues, possibly by biodegradation and fast settling with
    particles from sewage (Terzic & Ahel, 1993).

        In a comparison of the distribution of homologues of LAS in the
    Tama River, Japan, with those established for active substances used
    in commercial detergents, the levels of C12 and C13 LAS were
    found to decrease over time and those of C10 and C11 to increase
    (Hon-Nami & Hanya, 1980a). C11 was the commonest LAS homologue in
    river water (Kobuke, 1985; Yoshikawa et al., 1985), and no C13 LAS
    were present (Utsunomiya et al., 1980). The average chain length of
    LAS in Japanese rivers was C10.9-C11.2 (Nakae et al., 1980;
    Yoshimura et al., 1984a; Kobuke, 1985).

        Several research groups have confirmed that such changes in
    chain length occur during the environmental passage of LAS. In a
    study in which the concentration of homologues of LAS was measured
    quantitatively by HPLC during activated sludge treatment and lagoon
    treatment of wastewater in Spain, the average chain length decreased
    from C11.7 in raw material, to C11.3 in the dissolved phase of
    raw wastewater, and to C10.3 in the dissolved phase of treated
    effluent. A slight increase in average chain length was reported for
    the solids compartment in each of these systems, adding to
    laboratory findings that the longest homologues adsorb most strongly
    to sediment. The reduction in average chain length in the water
    compartments was environmentally significant, since shorter
    homologues of LAS are less toxic to aquatic organisms. Thus, the
    LC50 values for daphnia were higher for shorter homologues (>
    20 mg/litre for C11 and 10 mg/litre for C11.7) (Prats et al.,
    1993).

        The Japanese Soap & Detergent Association (1992) reported a
    decrease in LAS concentrations in the Tama River near Tokyo, Japan,
    from 2.3 mg/litre in 1967 to 0.2 mg/litre in 1991. The decrease was
    attributed to the development of sewage systems along the river:
    sewage coverage was 26% in 1974 and 89% in 1990. This information
    can be used to estimate concentrations of LAS in developing
    countries with inadequate sewage systems but where detergent use is
    increasing.

        Low levels of LAS were reported in water from the Scheldt River
    estuary and in a series of samples from the North Sea (see Table
    13). The concentrations in the estuary decreased rapidly from about
    0.010-0.012 mg/litre to values below the limit of analytical
    detection (0.5 µg/litre) concurrently with an increase in salinity.
    The concentrations decreased more rapidly than on the basis of
    dilution alone, indicating that removal occurred rapidly. The
    authors did not report whether the removal of LAS was related to
    adsorption onto settling solids, to biodegradation, or to a
    combination of the two. The concentration of LAS in samples taken
    offshore was consistently below the limit of detection (Stalmans et
    al., 1991).

    A5.1.4  Soil and groundwater

        The levels of LAS in sludge-amended soil were 0.9-1.3 mg/kg in
    German soils used for agriculture. A level of 2.2 mg/kg was found in
    the United Kingdom in soil that was used only for the disposal of
    sludge (De Henau et al., 1986). MBAS were found at a level of
    24.7 mg/kg (14.4-37.5 mg/kg) and LAS at 1.4 mg/kg (0.9-2.2 mg/kg) in
    German agricultural soils that had been amended with sludge
    (Matthijs & De Henau, 1987). The levels of LAS in soils near the
    River Thames, United Kingdom, in 1987 to which sludge had been
    applied previously were < 0.2-2.5 mg/kg. Soils that had received an
    application of sludge during 1987 had levels of LAS of <
    0.2-19.8 mg/kg (Holt et al., 1989).

        Levels of 13-47 mg/kg were found on the surface of sludge-
    amended soil in the United States in 1979; < 5 mg/kg were found at
    a depth of 15-90 cm (Rapaport & Eckhoff, 1990).

        A concentration of 22.4 mg/kg LAS was measured in agricultural
    soil that had recently been amended with anaerobically digested
    sludge. The concentration was 3.1 mg/kg six months after application
    of the sludge and 0.7 mg/kg after 12 months (Prats et al., 1993).
    HPLC, fluorescence detection, and mass spectrometry were used to
    analyse samples of a groundwater plume which originated from an
    underground discharge of sewage. It was found that 96% of the LAS
    was removed from the aqueous phase during sewage treatment and an
    additional 3% during infiltration with groundwater. The
    concentrations in ground-water were below the detection limit of
    0.01-0.02 mg/litre. The disappearance of LAS during groundwater

    infiltration was calculated to follow first-order kinetics. LAS were
    detected (by mass spectrometry) at only trace levels in groundwater
    sampled 20-500 m down the gradient from the infiltration zone (Field
    et al., 1992).

    A5.1.5  Drinking-water

        The concentration of LAS reported in Dutch tap-water was
    0.003 mg/litre; MBAS levels were about three times higher. In
    tap-water in the United Kingdom, the concentration of LAS was
    0.007 mg/litre; that of MBAS was again three times higher (Waters,
    1976). The concentrations of LAS in Italian well-water were below
    the analytical limit of detection of 0.0084 mg/litre (Mancini et
    al., 1984). LAS were not detected in Japanese drinking-water in the
    1970s at a limit of detection of 0.001 mg/litre (Yushi, 1978).

    A5.1.6  Biota

        The concentrations of LAS in biota are shown in Table 15.

    A5.2  Environmental processes that influence concentrations of
          linear alkylbenzene sulfonates

        A shift towards LAS of lower chain lengths has been reported in
    environmental samples in comparison with the distribution of chain
    lengths in raw materials. It has also been reported that about 50%
    of the total LAS in samples of water is associated with either
    suspended particles or dissolved organic matter. Reductions in both
    the chain length and the concentration of dissolved LAS will result
    in decreased aquatic toxicity (see also section 9).

    A5.2.1  Changes in chain length distribution during environmental
            removal of linear alkylbenzene sulfonates

        The concentrations of LAS and related compounds were measured in
    350 samples of water and sediment from the Mississippi River, United
    States. Those in surface water were < 0.005 mg/litre. LAS in
    sediment had longer chains than those in the overlying water column
    (Tabor et al., 1993).

        A gradual reduction in the average chain length of homologues
    was observed as they passed through a wastewater treatment plant:
    untreated wastewater, C12.1; treated effluent, C12; surface
    water below a sewage outfall, C11.7 (Castles et al., 1989).
    Isomers of C13 LAS have partition coefficients that are typically
    one order of magnitude higher than those of the corresponding
    isomers of the C12 LAS homologues (Amano et al., 1991).

        Table 15.  Total body concentrations of linear alkylbenzene sulfonates
               in biota in Japan
                                                                               
    Organism       Year      Location   Concentration   Reference
                                        (mg/kg dry
                                        weight)
                                                                               

    Algae          1980-81   River      < 1-368         Katsuno et al. (1983)

    Pond snail     1979      River      0.4-1.81        Tanaka & Nakanishi
      (Sinotaia                                         (1981)
      quadratus
      histrica)

    Gizzard shad   1982      Bay        < 1 or < 2      Tokai et al. (1990)
      (Konosirus   1983                 < 0.1-0.3
      punctatus)
                                                                               
    
    A5.2.2  Specification of linear alkylbenzene sulfonates in
            surface waters

        In most programmes for monitoring LAS in the environment, the
    total sample of waste or surface water is analysed, and separate
    concentrations of LAS in the fractions of dissolved and suspended
    solids are not determined. In a study in which these concentrations
    were reported, the mean levels of dissolved LAS were 8.4 mg/litre in
    raw wastewater (range, 5.6-11.4 mg/litre) and 5.5 mg/litre in the
    suspended solid fraction. In the seven wastewaters studied, an
    average of about 65% was present in the filtered (filtration, <
    1 µm) 'dissolved' fraction and 35% in the 'solids-associated'
    fraction. In treated effluent, 85% of LAS was in the dissolved
    fraction and 15% in the solids-associated fraction (Berna et al.,
    1993b). In wastewater treatment works, 49-63% of the LAS was in the
    dissolved phase and 37-51% in the solids-associated phase (Berna et
    al., 1989). In filtered (0.7 µm) wastewater containing LAS at
    2.55-2.95 mg/litre, 25-30% LAS was dissolved, and the remaining
    70-75% was associated with the solid phase (Cavalli et al., 1991).

        The average chain length of homologues of LAS in raw wastewater
    was lower in the dissolved phase (C11.2-C11.4) than in the
    solids-associated phase (C11.9-C12.0). The authors reported that
    39-43% of LAS was present in the dissolved phase and 57-61% in the
    solids phase (Prats et al., 1993).

        Humic acids extracted from sediments and soils formed strong
    association complexes with LAS under environmental conditions, as
    observed with fluorescence quenching techniques.  The bioavailabilty
    of LAS to aquatic organisms is reduced as a result of these
    complexes (McAvoy et al., 1993).

    A5.3  Estimation of human intake

        Human daily intake has been estimated on the assumption that LAS
    are taken up from drinking-water and from washing food, vegetables,
    dishes, and the skin. The estimates vary from 4.5 to 14.5 mg/day
    (Ikeda, 1965; Tokyo Metropolitan Government, 1974; Sterzel, 1992).
    The higher figure is based on dubious assumptions about the
    concentrations of LAS on vegetables, and the lower value is probably
    a more realistic estimate.

        The human intake of all anionic surfactants is estimated to be
    0.044-0.944 mg/kg per day (Sterzel, 1992), and the maximum daily
    intake of ABS, 0.14 mg/kg per day (Ikeda, 1965).

    A6.  KINETICS

     Section summary

        LAS are readily absorbed by experimental animals in the
    gastrointestinal tract, are distributed throughout the body, and are
    extensively metabolized. The parent compound and metabolites are
    excreted primarily via the urine and faeces, although there are
    marked differences between the isomers in the route of excretion.
    The main urinary metabolites identified in rats are
    sulfophenylbutanoic acid and sulfophenylpentanoic acid, which are
    probably formed through omega-oxidation followed by ß-oxidation of
    LAS, although the metabolic pathways in primates may differ.
    Although few data are available, it would appear that dermally
    applied LAS are not readily absorbed through the skin, although
    prolonged contact may compromise the epidermal barrier and permit
    more extensive absorption.

    A6.1  Absorption, distribution, and excretion

        After oral administration of 2 mg/animal of the calcium or
    sodium salt of 14C-LAS (chain length, C12) to Wistar rats,
    radiolabel was detected in plasma after 0.25 h, reaching maxima at
    2 h (0.86 and 1.00 µg/g of the two salts, respectively), and then
    decreasing gradually with time; the mean biological half-lives were
    calculated to be 10.9 and 10.8 h, respectively. Four hours after
    oral administration of the calcium or sodium salt, the concentration
    of radiolabel was high in the digestive tract (especially in the
    stomach: 22.56 and 31.67 µg/g as the parent compound or metabolites;
    and large intestine: 43.24 and 27.26 µg/g) and in the urinary
    bladder (34.89 and 16.58 µg/g). The concentrations were also high in
    the liver (2.73 and 2.13 µg/g), kidney (1.19 and 1.35 µg/g), testis
    (0.08 and 0.11 µg/g), spleen (1.63 and 0.16 µg/g), and lung (0.49
    and 0.44 µg/g). At 48 and 168 h, there was little further change.
    During the 168-h period after administration, 50% of the radiolabel
    on the calcium salt was excreted in urine and 51% in faeces, and 47%
    of that on the sodium salt was excreted in urine and 50% in the
    faeces (Sunakawa et al., 1979).

        Doses of 1 mg per 200 g body weight of two radiolabelled LAS
    isomers (chain length, C12) with the benzene sulfonate moieties at
    the 2 and 6 positions were administered orally and intravenously to
    rats; the same dose was also administered to anaesthetized rats with
    bile-duct cannulas by intravenous or intraduodenal injection.
    Forty-eight hours after oral or intravenous administration, there
    were marked differences in the disposition of the isomers in the
    urine and faeces: most of the radiolabel associated with the 2
    isomer (75.3%) was in the urine, whereas most of that on the 6
    isomer (77.9%) was present in the faeces. After intravenous
    administration to bile duct-cannulated rats, 88.6% of the 2 isomer
    was recovered in the urine, whereas 83.1% of the 6 isomer was in the

    bile. Studies of absorption after intraduodenal administration
    showed that both isomers were extensively absorbed within 6 h
    (Rennison et al., 1987).

        After a dose of 1.2 mg 35S-LAS in aqueous solution was
    administered by gavage to bile duct-ligated rats, 89% was absorbed
    from the gastro-intestinal tract, as seen by the presence of
    radiolabel recovered in urine. Absorption probably occurred mainly
    via portal venous blood, since only 1.6% was recovered in the
    lymphatic system. When the same dose was administered to bile
    duct-cannulated rats, 46% of the radiolabel was recovered in urine,
    29% in faeces, and 25% in bile after 90 h. Enterohepatic circulation
    was determined in a study in which the bile from one rat was
    transmitted to the intestine of another through a cannula; all of
    the radioactive LAS excreted in the bile was reabsorbed. In a
    separate study, 40-58% of single oral doses of 35S-LAS ranging
    from 0.6 to 40.0 mg was excreted in the urine and 39-56% in the
    faeces within 72 h of administration (Michael, 1968).

        The excretory pattern of 14C-sodium dodecylbenzene sulfonate
    was examined in male rats administered a concentration of 1.4 mg/kg
    of diet daily for five weeks. The total intake was 1213 µg/rat, of
    which 81.8% was excreted during the dosing period, with 52.4% in the
    faeces and 29.4% in the urine. After a further week on a normal
    diet, however, only 7.8% of the estimated residual amount was found
    in excreta. Of a single intraperitoneal injection of 0.385 mg
    14C-sodium dodecylbenzene sulfonate/rat (2.26 mg/kg body weight),
    84.7% was eliminated within the first 24 h and 94.5% within 10 days
    (Lay et al., 1983).

        LAS were not detected in the uterus of pregnant ICR mice
    administered a single oral dose of 350 mg/kg body weight on day 3 of
    gestation (Koizumi et al., 1985).

        14C-LAS (chain length, C10-C14, predominantly C11,
    C12, and C13) were applied at 250 µg/7.5 cm2 in water to
    clipped dorsal skin of rats; the treated area was washed after
    15 min, and the animals were restrained from grooming. Most of the
    radiolabel was rinsed off, but some of the 14C-LAS
    (11 ± 4 µg/cm2) were detected on the treated area; none were
    detected in urine or faeces 24 h after the application. In an
    accompanying study in vitro, there was no measurable penetration of
    14C-LAS (chain length, C12) through isolated human epidermis or
    rat skin 24 or 48 h after application (Howes, 1975).

        A mixture of 35S-LAS and white petrolatum (29 mg/0.3 ml) was
    applied to a 4-cm2 area of the dorsal skin of guinea-pigs, and 24
    h after the application about 0.1% of the applied dose was found in
    urine and about 0.01% in blood and the main organs. After dermal
    application of the same dose to rats and guinea-pigs, the

    concentration of 35S in the liver was 9.7 µg/g equivalent of LAS
    in rats and about 0.4 µg/g in guinea-pigs (Hasegawa & Sato, 1978).

        After a single oral administration of 150 mg/kg 14C-LAS (mean
    relative molecular mass, 349) in aqueous solution to rhesus monkeys
    (Macaca mulatta), plasma concentrations of radiolabel reached a
    maximum equivalent to 41.2 µg/ml at 4 h and then declined over
    6-24 h, with a biological half-life of about 6.5 h. The observed
    peak plasma concentration of radioactivity (33.6 µg/ml) and the
    biological half-life (about 5 h) after seven consecutive daily oral
    administrations of 30 mg/kg body weight were similar to those found
    after a single administration. The highest concentration of 14C
    (238.6 µg/g) was found in the stomach 2 h after the last dose.
    Concentrations were also high in the intestinal tract (108 µg/g),
    kidney (135.6 µg/g), and liver (64.8 µg/g) and were moderately high
    in the lung (19.8 µg/g), pancreas (17.7 µg/g), adrenal glands
    (20.6 µg/g), and pituitary gland (17 µg/g). At 24 h, the
    concentrations were higher in the intestinal tract (255.4 µg/g) and
    liver (10.5 µg/g) than in plasma (2.4 µg/g), whereas those in most
    tissues were lower than those in plasma, indicating that there is no
    specific accumulation or localization of LAS and their metabolites
    in these tissues. After seven subcutaneous doses of 1 mg/kg per day
    of 14C-LAS, most of the radiolabel remained in the skin; the
    concentration was generally highest at the injection site
    (113.96 µg/g). The levels of radiolabel were also high in the
    intestinal tract (2.41 µg/g), kidney (1.83 µg/g), lung (2.45 µg/g),
    spleen (2.43 µg/g), thyroid (1.24 µg/g), and pituitary (1.00 µg/g)
    at 2 h. The concentration in most tissues was generally lower at
    4 h, except in the intestinal tract (3.50 µg/g), liver (1.74 µg/g),
    and kidney (1.92 µg/g). The high level of radiolabel in the
    intestinal tract probably indicates biliary excretion. The average
    rates of excretion of radiolabel in urine and faeces during 120 h
    after administration of single oral or subcutaneous doses of
    14C-LAS to male and female rhesus monkeys are shown in Table 16.
    In animals of each sex, radiolabel was excreted primarily in the
    urine after either route of administration (Cresswell et al., 1978).

        When sodium 35S-dodecylbenzenesulfonate (3.3 mmol/kg body
    weight) was administered in the diet to young pigs, at least 35% of
    the dose was absorbed through the intestinal tract. After 40 h,
    30-40% of the dose had been excreted in urine and > 60% in faeces.
    The concentration of radiolabel after 200 h was relatively high in
    bristles and bones and low in liver, kidney, and spleen
    (quantitative data not presented). After 10 weeks, traceable amounts
    of 35S (0.05% of the administered dose) were found in bristles,
    bones, skin, lung, and brain (Havermann & Menke, 1959).

    Table 16.  Excretion of 14C-linear alkyl benzene sulfonates in
               rhesus monkeys
                                                                 
    Route of administration       Sex        Concentration (%)
                                                                 
                                             Urine        Faeces
                                                                 

    Oral (30 mg/kg body weight)   Male       68.3         25.9
                                  Female     74.0         20.3

    Subcutaneous (1 mg/kg)        Male       63.8         12.5
                                  Female     64.3         9.2
                                                                 

    From Cresswell et al. (1978); values are average rates of excreted
    radioactivity during the 120-h period after a single dose.

    A6.2  Biotransformation

        The main metabolites isolated from the urine of rats
    administered 35S-LAS orally were probably a mixture of sulfophenyl
    butanoic (I) and sulfophenyl pentanoic acids (II):

             CH3-CH-CH2-COOH            CH3-CH-CH2-CH2-COOH
                     |                             |
                     O                             O
                     |                             |
                     SO3H                          SO3H

                     (I)                           (II)

    The material used in the experiment was a mixture of C10-C14 LAS
    (mainly C11, C12, and C13). The compounds in this mixture are
    probably degraded by omega-oxidation, followed by catabolism through
    a ß-oxidation mechanism to form the above metabolites, with
    excretion of four or five carbons in the urine (Michael, 1968).

        After oral administration of the calcium or sodium salt of
    14C-LAS to rats, two metabolites were detected in urine and four
    in faeces by thin-layer chromatography. The two urinary and two of
    the faecal metabolites were believed to be compounds similar to
    metabolites (I) and (II) previously identified by Michael (1968)
    (Sunakawa et al., 1979).

        Thin-layer chromatography of urine extracts after oral or
    sub-cutaneous administration of 14C-LAS to rhesus monkeys showed
    only trace amounts of the unchanged compound, and five metabolites
    more polar than LAS were detected. These metabolites have not been
    identified. Incubation of urine samples with ß-glucuronidase or
    sulfatase did not affect the components, which were therefore
    probably not present as the corresponding conjugates (Cresswell et
    al., 1978).

    A7.  EFFECTS ON LABORATORY MAMMALS AND  IN VITRO TEST SYSTEMS

     Section summary

        The oral LD50 values for sodium salts of LAS are
    404-1470 mg/kg body weight in rats and 1259-2300 mg/kg body weight
    in mice. LAS irritate skin and eyes.

        Minimal effects, including biochemical alterations and
    histopathological changes in the liver, were reported in subchronic
    studies in rats administered LAS in the diet or drinking-water at
    concentrations equivalent to a dose of about 120 mg/kg body weight
    per day. Although ultrastructural changes in liver cells were
    observed at lower doses in one study, these changes appeared to be
    reversible. Effects have not been seen at similar doses in other
    studies, but the organs may have been examined more closely in this
    study. Reproductive effects, including decreased pregnancy rate and
    litter loss, have been reported in animals administered doses >
    300 mg/kg body weight per day. Histopathological and biochemical
    changes have been observed following long-term dermal application on
    rats of solutions of LAS at concentrations > 5% and after 30 days'
    dermal application on guinea-pigs of 60 mg/kg body weight. Repeated
    dermal application of solutions containing > 0.3% LAS induced
    fetotoxic and reproductive effects, although these doses also
    induced maternal toxicity.

        The available long-term studies are inadequate to evaluate the
    carcinogenic potential of LAS in experimental animals, owing to the
    small number of animals used, low or insufficient doses tested, the
    absence of a maximal tolerated dose, and limited histopathological
    examination. The limited studies available in which animals were
    administered LAS orally, however, provide no evidence of
    carcinogenicity.

        Limited data also indicate that LAS are not genotoxic  in vivo
    or  in vitro.

    A7.1  Single exposures

        The LD50 values for the sodium and magnesium salts of LAS
    given orally, subcutaneously, or intravenously are summarized in
    Table 17. Rats appear to be more sensitive than mice to LAS,
    regardless of the route of exposure. The LD50 values for LAS given
    orally were 1259-3400 mg/kg body weight in mice and 404-1900 mg/kg
    body weight in rats. Differences were seen according to the sex,
    strain, and age of the animals and the test material.

    
    Table 17.  Acute toxicity of linear alkylbenzene sulfonates

                                                                                      
    Species/     Sex   Route   LD50a     Test materialb             Reference
    strain                     (mg/kg
                               body
                               weight)
                                                                                      

    Mouse
      NR         NR    Oral    2170      60% active ingredient      Yanagisawa et
                                                                    al. (1964)
      DD         M     Oral    2300      34.55% solution            Tiba (1972)
      ddY        M     Oral    1665      Purified                   Kobayashi et
      ICR-JCL    F     Oral    1950      Purified                   al. (1972)
                 M     Oral    1250      Commercial soln, 19.0%     Kuwano et al.
                 F     Oral    1540      Commercial soln, 19.0%     (1976)
                 M     Oral    1370      Commercial soln, 17.1%
                 F     Oral    1560      Commercial soln, 17.1%
                 M     Oral    2160      99.5% active ingredient    Ito et al. (1978)
                                         of C10-C13
                 F     Oral    2250      99.5% active ingredient
                                         of C10-C13
                 M     Oral    2600      Magnesium salt of above
                 F     Oral    3400      Magnesium salt of above
                 M     s.c.    1250      99% active ingredient      Ito et al. (1978)
                                         of C10-C13
                 F     s.c.    1400      99% active ingredient
                                         of C10-C13
                 M     s.c.    1529      Magnesium salt of above
                 F     s.c.    1550      Magnesium salt of above
                                                                                      

    Table 17 (contd)

                                                                                      
    Species/     Sex   Route   LD50a     Test materialb             Reference
    strain                     (mg/kg
                               body
                               weight)
                                                                                      

      ICR-JCL    M     i.v.     207      99% active ingredient
      (contd)                            of C10-C13
                 F     i.v.     298      99% active ingredient
                                         of C10-C13
                 M     i.v.      98      Magnesium salt of above
                 F     i.v.     151      Magnesium salt of above
      NR         NR    i.v.     120                                 Yanagisawa et al.
                                                                    (1964)

    Rat
      FDRL       M,F   Oral     650      Nominal chain length,      Oser & Morgareidge
                                         C12 (range C9-C15)         (1965)

    Wistar
      6 w        M     Oral     873      Purified                   Kobayashi et
      6 w        F     Oral     760                                 al. (1972)
      10 w       M     Oral     404
      10 w       F     Oral     409
                 M     Oral    1460      99.5% active ingredient    Ito et al. (1978)
                                         of C10-C13
                 F     Oral    1470      99.5% active ingredient
                                         of C10-C13
                 M     Oral    1900      Magnesium salt of above
                 F     Oral    1840      Magnesium salt of above
                                                                                      

    Table 17 (contd)

                                                                                      
    Species/     Sex   Route   LD50a     Test materialb             Reference
    strain                     (mg/kg
                               body
                               weight)
                                                                                      

    CRJ-SD       M     s.c.     840      99.5% active ingredient
                                         of C10-C13
                 F     s.c.     810      99.5% active ingredient
                                         of C10-C13
                 M     s.c.     710      Magnesium salt of above
                 F     s.c.     730      Magnesium salt of above
                 M     i.v.     119      99.5% active ingredient
                                         of C10-C13
                 F     i.v.     126      99.5% active ingredient
                                         of C10-C13
                 M     i.v.      27.2    Magnesium salt of above
                 F     i.v.      35.0    Magnesium salt of above
                                                                                      

    NR, not reported; M, male; F, female; s.c., subcutaneous; i.v., intravenous;
    w, weeks
    a As active ingredient
    b Sodium salt, unless specifically indicated
    
        The main clinical signs observed after oral administration of
    doses near or greater than the LD50 consisted of reduced voluntary
    activity, piloerection, diarrhoea, and weakness. Diarrhoea was more
    severe in rats than mice (Kobayashi et al., 1972). Convulsions,
    torsion, and paralysis of the hind limbs were also observed in some
    of mice (Kobayashi et al., 1972; Kuwano et al., 1976). Death usually
    occurred within 24 h of administration. Transient cardiac arrest,
    dyspnoea, cyanosis, respiratory collapse, and death occurred during
    intravenous injection (Ito et al., 1978).

        At autopsy, hyperaemia and haemorrhage of the stomach and
    intestine, bloating of the intestine with thinning of its wall, and
    congestion of some internal organs were the main macroscopic
    findings; histological examination showed congestion and epithelial
    degeneration of the gastrointestinal mucosa (Kobayashi et al., 1972;
    Kuwano et al., 1976; Ito et al., 1978).

    A7.2  Short-term exposure

    A7.2.1  Mouse

        In a study of the toxicity of a commercial preparation of LAS
    (17.1% active ingredient), 44 male and 16 female C57Bl TW mice were
    given subcutaneous injections according to the following schedule:
    0.02 ml of 1% of the preparation for 10 consecutive days from the
    day of birth, 0.04 ml of the same solution for the following 10
    days, 0.02 ml of a 10% solution five times over the next 10 days,
    and 0.04 ml of the same solution every other day for a further 30 or
    60 days. Eight males and six females served as untreated controls.
    Epilation and dermatitis usually occurred in animals given
    continuous injections of the test material. Adhesions between some
    organs, most frequently between the spleen and kidney, were observed
    in those receiving injections from the day of birth. Neither the
    growth nor the survival of the animals was affected. Although the
    weights of the liver, kidney, and spleen were significantly
    increased in animals receiving treatment for 60 days,
    histopathological examination of the liver, kidney, adrenal glands,
    and thyroid by light and electron microscopy showed no evidence of
    toxicity (Kikuchi, 1978).

    A7.2.2  Rat

    A7.2.2.1  Administration in the diet

        Groups of five male Wistar rats were fed diets containing LAS
    (60% active ingredient; chain length distribution: 10.6% C10, 34.1%
    C11, 27.7% C12, 19.0% C13, 8.7% C14) at a concentration
    of 0, 0.6, 1.2, or 1.8% (equivalent to 180, 360, or 540 mg/kg body
    weight per day) for two and four weeks, and lipids in serum and
    liver were analysed. Body weight gain was suppressed in the group
    receiving 1.8% at four weeks, and the relative liver weight was

    increased at two weeks and thereafter in the groups receiving 1.2
    and 1.8%. The levels of triglyceride and total lipids in the serum
    had decreased markedly at two weeks in all the experimental groups,
    and the levels of phospholipids and cholesterol in the serum had
    decreased significantly at two weeks in the groups given 1.2 and
    1.8%. These changes were less apparent at four weeks, but
    triglyceride, phospholipid, and cholesterol levels in serum were
    significantly decreased in the group given 1.8%. Significant
    increases in triglyceride levels were seen in the liver after two
    weeks in the groups receiving 0.6 and 1.8%, and in cholesterol
    levels in the group given 0.6% (Yoneyama & Hiraga, 1977).

        Technical-grade sodium LAS (87.9% active ingredient; chain
    length distribution: 1.8% C10, 43.2% C11, 32.2% C12, 5.3%
    C14, 1.5% C15) were fed to five groups of 10 weanling
    Sprague-Dawley rats of each sex at a dietary level of 0, 0.02, 0.1,
    or 0.5% (equivalent to 8.8, 44, or 220 mg/kg body weight per day)
    for 90 days. No adverse effects were found on survival, growth, food
    conversion efficiency, haematological values, urinary analytical
    values, or absolute or relative organ weights. There were no gross
    or microscopic histological changes attributable to ingestion of the
    test material (Kay et al., 1965).

        Technical-grade  LAS (normal chain length, C12; range,
    C9-C15; mean relative molecular mass, 346) were fed to three
    groups of weanling FDRL rats, each consisting of 15 males and 15
    females, at a dose of 0, 0.05, or 0.25 g/kg body weight per day for
    12 weeks. No adverse effects were noted on survival, behaviour,
    growth, food conversion efficiency, haematological measurements,
    blood chemistry, urine analytical values, organ weights, or gross or
    microscopic appearance, except for a slight increase in liver weight
    in females given 0.25 g/kg body weight per day (Oser & Morgareidge,
    1965).

        A diet containing LAS at a concentration of 1.5% (equivalent to
    750 mg/kg body weight per day) or a control diet was given to groups
    of five male Wistar rats for 2, 4, or 12 weeks. LAS depressed body
    weight gain, and the relative liver weight was significantly
    increased after two weeks of treatment. The activities of alkaline
    phosphatase and glutamate-pyruvate transaminase in serum were
    significantly increased at each observation period, and cholesterol
    and protein levels were significantly decreased by four weeks. In
    the liver, the activities of glucose-6-phosphatase and
    glucose-6-phosphate dehydrogenase were decreased, and the activity
    of isocitrate dehydrogenase was increased at each observation point.
    Enzymatic examination of the renal cortex showed decreased
    activities of glucose-6-phosphatase and 5'-nucleotidase at each
    observation period, an increase in the activity of lactate
    dehydrogenase at 12 weeks, and increased activity of isocitrate
    dehydrogenase at 2 and 4 weeks. In the renal medulla, the activity
    of Na,K-ATPase was decreased, that of lactate dehydrogenase was

    increased at 12 weeks, and that of isocitrate dehydrogenase was
    decreased at 2 weeks but increased at 12 weeks (Ikawa et al., 1978).

        Groups of five male Wistar rats were given a diet or
    drinking-water containing LAS at a concentration of 0.4% (diet:
    200 mg/kg body weight per day; drinking-water: 560 mg/kg per day)
    for two weeks in order to determine the effects of LAS on the
    synthesis of lipids in the liver. Lipids were thus measured  in the
    liver, and uptake of acetate-1-14C by the lipids was examined.
    Decreases in the levels of total lipids and triglyceride were seen
    in both groups, but there were no significant changes in
    phospholipid or cholesterol levels. Uptake of acetate-1-14C by
    lipids in the liver was increased in both groups; uptake of
    phospholipids and triglycerides tended to increase, and that of
    phospholipids increased significantly in rats given LAS in the diet
    (Yoneyama et al., 1978).

    A7.2.2.2  Administration by gavage

        Groups of 12 male and 12 female Sprague-Dawley rats were given
    the magnesium salt of LAS by gavage at a dose of 0, 155, 310, or
    620 mg/kg body weight for one month. Body weight gain was depressed
    in males and females at 620 mg/kg body weight; one male and two
    females at this dose also had diarrhoea and loss of appetite and
    subsequently died. Haematological examination revealed significant
    decreases in haemoglobin concentration and haematocrit in males at
    620 mg/kg body weight. A significant increase in the activity of
    alkaline phosphatase and a significant decrease in calcium levels
    were seen in males at 310 or 620 mg/kg body weight; and a
    significant increase was seen in the activity of glutamate-oxalate
    transminase and a significant decrease in protein levels in females
    at those doses. Females at all doses had a significant decrease in
    calcium levels. At the highest dose, females had a significant
    increase in the activity of alkaline phosphatase, a significant
    decrease in cholesterol level, and increased weight of the liver,
    but the weight of the thymus decreased. The weight of the heart
    decreased in females at 310 and 620 mg/kg body weight. Histological
    examination of the liver revealed no abnormalities (Ito et al.,
    1978).

        Groups of 12 male and 12 female Sprague-Dawley rats were given
    the sodium salt of LAS (chain length distribution: < 0.1% C9,
    10.1% C10, 33.7% C11, 31.0% C12, 25.1% C13) at a dose of 0,
    125, 250, or 500 mg/kg body weight by gavage once a day. Diarrhoea
    was observed in the group receiving 500 mg/kg, and soft faeces were
    observed in the other two groups. Body weight gain was depressed in
    males of all groups and in females at 500 mg/kg. Haematological
    examination revealed no abnormalities. Serum analysis revealed a
    significant increase in the activity of alkaline phosphatase in
    males at 500 mg/kg, a significant decrease in calcium levels in
    males of all groups, significant increases in the activity of

    gluatamate-oxalate transaminase and in blood-urea nitrogen in
    females at 500 mg/kg, a significant decrease in calcium level in
    females at 250 or 500 mg/kg, and significantly decreased protein and
    albumin levels in females of all groups. At 500 mg/kg, the weights
    of spleen and heart were significantly decreased in males; in
    females, liver weights were increased but the weights of the heart
    and thymus were decreased. No histological abnormalities were seen
    in the liver (Ito et al., 1978).

    A7.2.2.3  Dermal application

        Continued, repeated, or extremely high doses of LAS, like other
    detergents, compromise the integrity of the skin so that penetration
    occurs, causing a variety of anomalies. As the design of the
    following two studies was not adequate, the observations are not
    considered to be relevant to human risk assessment.

        Application of 2 ml of a commercial preparation of LAS (23.4%
    active ingredient) to the thoracic skin of six male Wistar rats
    resulted in redness and wrinkling of the skin after 24 h. The
    redness then increased, the corium was lacerated, and bleeding
    occurred. These effects were most severe after five to seven days,
    but after a further 10 days the skin began to recover. Six rats died
    after 19 days, probably because of the extremely high dose used. The
    livers of three rats were examined by electron microscopy after
    three and 30 days and the findings compared with those in the
    control group. At three days, marked changes were seen in the
    components of the liver parenchymal cells, such as separation of the
    intracellular space, appearance of dark cells with high electron
    density, dysmorphia of mitochondria, extracellular prolapse of
    mitochondria, proliferation of rough-surfaced endoplasmic reticulum,
    lysosome proliferation, and a decrease in the prevalence of fatty
    droplets. At 30 days, many liver parenchymal cells were filled with
    abnormally divided and proliferated mitochondria, and an abnormal
    increase in smooth-surfaced endoplasmic reticula was noted. There
    were no granules of glycogen or fatty droplets. Structures
    resembling necrotic cells were also observed (Sakashita et al.,
    1974).

        A commercial preparation of LAS (23.4% active ingredient) was
    applied dermally to male rats (number not given) at a dose of
    5 mg/kg body weight active ingredient once a day for 30 days, and
    the liver was examined by electron microscopy. Degeneration was seen
    in part of the liver, in the form of atrophy and high density.
    Intra-mitochondrial deposits and deformation of the Golgi apparatus
    were also noted (Sakashita, 1979).

    A7.2.2.4  Subcutaneous injection

        A commercial preparation of LAS (27% active ingredient) was
    given subcutaneously to groups of five male and five female Wistar
    rats at a dose of 2 ml/kg body weight per day of a 0, 0.02, 0.2, or
    2% solution of the preparation for 25 or 50 days. Rats receiving the
    2% solution had reduced body weight gain, increased weights of
    liver, kidney, and spleen, a low serum albumin:globulin ratio, low
    serum protein, and reduced ornithine aminotransferase activity in
    the liver (Hayashi, 1980).

    A7.2.3  Guinea-pig

        Twelve guinea-pigs were treated daily for 30 days with a
    solution of LAS in distilled water equivalent to 60 mg/kg body
    weight, which was applied to a 4-cm2 area of clipped dorsal skin.
    Twelve controls received acetone at 0.5 ml. The animals were
    sacrificed after 30 days, and samples were taken from liver and
    kidney and homogenized for determination of enzymes, lipid
    peroxidation, glutathione, and protein. The activities of
    ß-glucuronidase, gamma-glutamyl transpeptidase, 5-nucleotidase, and
    sorbitol dehydrogenase were increased in liver and kidney. Lipid
    peroxidation was increased in kidney but not in liver, and the
    glutathione content was unchanged in both organs. Extensive fatty
    changes were found in hepatic lobules, with dilation of sinusoids;
    tubular lesions were found in the kidney, predominantly in the
    proximal and distal portions (Mathur et al., 1992).

    A7.2.4  Monkey

        LAS (chain length, C10-C13) were given to four groups of
    three male and three female rhesus monkeys at a daily dose of 0, 30,
    150, or 300 mg/kg body weight orally simultaneously with a dose of
    0, 0.1, 0.5, or 1.0 mg/kg per day subcutaneously, for 28 days.
    Monkeys that received 300 mg/kg orally and 1.0 mg/kg subcutaneously
    vomited frequently, usually within 3 h of administration; these
    animals and those given 150 mg/kg orally and 0.5 mg/kg
    subcutaneously also had an increased frequency of loose or liquid
    faeces. Fibrosis at the injection sites was reported in all test
    animals, and the incidence and severity were related to dose.
    Treatment had no effect on ophthalmoscopic, haematological, or
    urinary parameters, on organ weight, or on histopathological
    appearance (Heywood et al., 1978).

        The studies of short-term exposure to LAS are summarized in
    Table 18.

        Table 18. Summary of studies of short-term exposure to linear alkylbenzene sulfonates (LAS)
                                                                                                                                              

    Species, strain,       Test material       Route          Dosage                  Results                                Reference
    numbers                (specification)
    per group
                                                                                                                                              

    Mouse, C57Bl TW        LAS (a.i. 17.1%)    s.c.           63 or 76 mg/kg          Abdominal adhesions, increased         Kikuchi (1978)
      44 M, 16                                                bw/day, 60-90 days      weights of liver, kidney, and 
                                                                                      spleen after 60-day treatment; 
                                                                                      no histopathological changes
                                                                                      in liver, kidney, adrenal or thyroid 
                                                                                      glands                                 

    Rat, Wistar            LAS, C10-C14        Diet           0, 0.6, 1.2, 1.8%,      Decreased serum triglyceride,          Yoneyama & Hiraga
      5 M                  (a.i. 60%)                         4 weeks                 total lipids, phospholipids, and       (1977)
                                                                                      cholesterol; increased relative 
                                                                                      liver weight at 1.2 and 1.8%;
                                                                                      suppression of body weight gain 
                                                                                      at 1.8%

    Rat, SD                LAS, C10-C15        Diet           0, 0.02, 0.1, 0.5%,     No adverse effects                     Kay et al. (1965)
      10 M, 10 F           (a.i. 8-9%)                        90 days

    Rat, FDRL              LAS, C9-C15         Diet           0, 0.05, 0.25 g/kg bw   Slight increase in liver weight in     Oser & Morgareidge
      15 M, 15 F           (a.i. 39.5%)                       per day, 12 weeks       females at high dose                   (1965)

    Rat, Wistar            LAS (NS)            Diet           1.5%, 24 weeks          Increased activities of serum,         Ikawa et al. (1978)
      4 M                                                                             hepatic, and renal enzymes;
                                                                                      depressed body weight gain;
                                                                                      increased relative liver weight
                                                                                                                                              

    Table 18 (contd)
                                                                                                                                              

    Species, strain,       Test material       Route          Dosage                  Results                                Reference
    numbers                (specification)
    per group
                                                                                                                                              

    Rat, CRJ-SD            LAS, Na, C10-C13    Gavage         125, 250, 500 mg/kg     Altered serum enzyme activity          Ito et al. (1978)
      12 M, 12 F           (a.i. 99.5%)                       bw per day, 1 month     and calcium levels at high doses;
                                                                                      decreased serum protein and 
                                                                                      albumin levels in all treated 
                                                                                      females; decreased spleen and
                                                                                      heart weights in males at highest
                                                                                      dose; increased liver weight and 
                                                                                      decreased heart and thymus 
                                                                                      weights in females at highest dose; 
                                                                                      no histopathological abnormalities
                                                                                      in liver

    Rat, CRJ-SD            LAS Mg, C10-C13     Gavage         155, 310, 620 mg/kg     Altered haemoglobin, haematocrit,      Ito et al. (1978)
      12 M, 12 F           (a.i. 96.9%)                       bw per day, 1 month     serum enzyme activities, calcium 
                                                                                      level at high doses; depressed 
                                                                                      body weight gain at highest dose; 
                                                                                      increased liver weight and 
                                                                                      decreased heart and thymus 
                                                                                      weights in females at highest dose; 
                                                                                      no histopathological abnormalities 
                                                                                      in liver

    Rat, Wistar            LAS detergent       Dermal         2 ml/animal             Skin irritation; liver parenchymal     Sakashita et al.
      6 M                  (a.i. 23.4%)                       3.5 × 4.5 cm, 30 days   changes with necrotic cells; no        (1974)
                                                                                      glycogen granules or fat droplets

    Rat, Wistar            LAS detergent       Dermal         5 mg/kg bw, once/       Degenerative changes in liver          Sakashita (1979)
      6 M                  (a.i. 23.4%)                       day, 30 days
                                                                                                                                              

    Table 18 (contd)
                                                                                                                                              

    Species, strain,       Test material       Route          Dosage                  Results                                Reference
    numbers                (specification)
    per group
                                                                                                                                              

    Rat, Wistar            LAS detergent       s.c.           0, 0.02, 0.2, 2%,       Depressed body weight gain;            Hayashi (1980)
      5 M, 5 F             (a.i. 27%)                         2 ml/kg bw per day,     increased weights of liver, kidney,
                                                              50 days                 and spleen; and altered hepatic
                                                                                      enzyme activities at highest dose

    Rat, Wistar            LAS                 Drinking-      0.4%, 2 weeks           Decreased hepatic total lipids and     Yoneyama et al.
      8 M, 8 F             (a.i. 60.2%)        water                                  triglycerides; increased uptake of     (1978)
                                                                                      acetate-1-14C, phospholipids, and
                                                                                      triglycerides

    Guinea-pig             LAS (NS)            Dermal         60 mg/kg bw,            Altered hepatic and renal enzyme       Mathur et al. (1992)
      12 M, 12 F                                              30 days on 4 cm2        activities; fatty degeneration in
                                                                                      liver; renal tubular lesions

    Rhesus monkey          LAS C10-C13         Gavage         0.30, 150, 300 mg/kg    Vomiting and diarrhoea; no             Heywood et al. 
      3M, 3F               (a.i. 20.5%)        s.c.           0, 0.1, 0.5, 1.0 mg/kg  ophthalmic, haematological or          (1978)
                                                              bw per day, 28 days     urinary changes; no effect on 
                                                                                      organ weights; no histopatho-
                                                                                      logical changes
                                                                                                                                              

    M, male; F, female; a.i., active ingredient; s.c., subcutaneous
        A7.3  Long-term exposure; carcinogenicity

    A7.3.1  Mouse

    A7.3.1.1  Administration in the diet

        Groups of eight or nine ICR mice were given diets containing LAS
    at a concentration of 0.6 or 1.8% for nine months (corresponding to
    intakes of 500 and 1000 mg/kg body weight per day). There was no
    reduction in body weight gain at either dose, but the weight of the
    liver was increased in both males and females. Significant decreases
    were seen in the activities of hepatic lactate dehydrogenase and
    renal acid phosphatase in male mice (Yoneyama et al., 1976).

    A7.3.1.2  Administration in the drinking-water

        Drinking-water containing 100 ppm LAS (corresponding to 20 mg/kg
    body weight per day) was supplied to ddy mice (sex and number not
    stated) for six months, and they were then allowed to recover for
    two months. Mice were killed for electron microscopy of the liver at
    one, two, three, and six months and after the two-month recovery
    period. Hepatic damage was observed at one and six months,
    consisting of the disappearance of the nucleolus, atrophy of the
    Golgi apparatus, degranulation of rough-surfaced endoplasmic
    reticulum, degeneration of mitochondria, and increased numbers of
    primary and secondary lysosomes including autophagic vacuoles with a
    myelinated core. In mice examined after the two-month recovery
    period, some hepatic damage was seen, which was characterized by
    changes in mitochondrial structure and the presence of numerous fat
    droplets. Other cellular effects had reversed, indicating that the
    liver cells had recovered (Watari et al., 1977). Because an
    extremely high dose was used in this study, the observations have
    little relevance to human risk.

        Groups of eight or nine ICR mice were given water containing LAS
    at a concentration of 0.07, 0.2, or 0.6% for nine months,
    corresponding to intakes of about 0.1, 0.25, or 0.6 g/kg body weight
    per day for males and 0.1, 0.25, or 0.9 g/kg body weight per day for
    females. Body weight gain was depressed in males and females at
    0.6%, and there were dose-related increases in liver weight in
    females in all dose groups. In the group given 0.6% LAS, the
    activity of hepatic glutamate-oxalate transaminase was significantly
    decreased in males and the activity of renal glucose-6-phosphatase
    was decreased in animals of each sex (Yoneyama et al., 1976).

    A7.3.2  Rat

    A7.3.2.1  Administration in the diet

        LAS (98.1% active ingredient; chain length distribution,
    C10-C14) were fed to four groups of Charles River weanling rats,
    each consisting of 50 males and 50 females, at a dietary level of 0,
    0.02, 0.1, or 0.5% (corresponding to 10, 50, or 250 mg/kg body
    weight per day) for two years. No adverse effects on growth or feed
    conversion efficiency were observed. Five males and females from
    each group were killed at 8 and 15 months, and all survivors at 24
    months; all animals were necropsied, haematological values were
    determined, and tissues were taken for histological examination. No
    consistent change was seen that could be considered a toxic
    response. Animals that showed significant loss of weight,
    development of tumours, or other evidence of abnormalities were also
    sacrificed and their tissues preserved for study. The incidences of
    tumours and of common incidental diseases were similar in all
    dietary groups (Buehler et al., 1971).

        Diets containing technical-grade LAS (chain length distribution:
    10.6% C10, 34.1% C11, 27.7% C12, 19.0% C13, 8.7% C14; mean
    relative molecular mass, 345.8) at a  concentration of 0, 0.07, 0.2,
    0.6, or 1.8% were given to groups of 10 Wistar rats of each sex for
    six months. The group given 1.8% had diarrhoea, markedly depressed
    growth, increased caecal weight, and marked degeneration of renal
    tubules. The group given 0.6% had slightly depressed growth,
    increased caecal weight, increased serum alkaline phosphatase
    activity, decreased serum protein, and degeneration of renal
    tubules. The group given 0.2% had increased caecal weight and slight
    degeneration of renal tubules. The group given 0.07%, corresponding
    to about 40 mg/kg body weight per day, showed no effects
    attributable to treatment (Yoneyama et al., 1972).

        Groups of eight male and eight female Wistar rats were given
    diets containing LAS at a concentration of 0, 0.6, or 1.8% for nine
    months, corresponding to intakes of 230 or 750 mg/kg body weight per
    day for males and 290 or 1900 mg/kg body weight per day for females.
    In rats given 1.8% LAS, body weight gain was reduced in both males
    and females. Haematological examination revealed a significant
    decrease in leukocytes in males at 0.6% and significant decreases in
    mean corpuscular volume and mean corpuscular haemoglobin in females
    at 1.8%. The activity of glutamate-oxalate transferase and the
    levels of cholesterol and albumin in serum were significantly
    decreased and the activity of alkaline phosphatase and the levels of
    blood-urea nitrogen and cholinesterase were significant increased in
    males at 1.8%; females at that dose had a significant decrease in
    cholesterol level and a significant increase in alkaline phosphatase
    activity. At 0.6%, males had a significant decrease in glucose
    level, and females had a significant decrease in the activity of
    glutamate-pyruvate transaminase. The caecal weight of male rats and

    the liver and caecal weights of female rats at 1.8% were
    significantly increased. Enzymatic examination of the liver revealed
    dose-related decreases in the activities of glucose-6-phosphate
    dehydrogenase and lactate dehydrogenase in male rats. At 1.8%, males
    had significantly decreased activities of glucose-6-phosphatase,
    glutamate-pyruvate transaminase, and glutamate-oxalate transaminase
    and a dose-related decrease in the activity of glucose-6-phosphate
    dehydrogenase; females had significantly decreased activities of
    glucose-6-phosphatase and glutamate-oxalate transaminase. Enzymatic
    examination of the kidneys of females at 1.8% showed significantly
    decreased activities of  glucose-6-phosphatase, Na,K-ATPase, and
    lactate dehydrogenase (Yoneyama et al., 1976).

        Groups of 50 male and 50 female Wistar weanling rats were given
    diets containing LAS (10.6% C10, 34.1% C11, 27.7% C12, 19.0%
    C13, 8.7% C14; mean relative molecular mass, 345.8) at a
    concentration of 0, 0.04, 0.16, or 0.6%. In each group, five rats of
    each sex were fed for one, three, six, or 12 months, and groups of
    15 rats of each sex were fed for 24 months or more. The group fed
    0.6% had slightly increased liver and caecal weights, and increased
    activity of glutamate-pyruvate transaminase and alkaline phosphatase
    in serum. The treatment had no adverse effect on the intake of food,
    body weight gain, general condition, mortality, or mean survival. On
    the basis of these results, it was concluded that a diet containing
    LAS at a concentration of 0.6% (300 mg/kg body weight per day) had
    no adverse effects on the rats (Yoneyama et al., 1977).

        Groups of 50 male and 50 female Wistar rats were fed LAS
    (C10-C14) in the diet at a concentration of 0, 0.04, 0.16, or
    0.6% and were then submitted to a detailed histopathological
    examination. After one month, proliferation of hepatic cells in the
    liver, slight swelling of the renal tubules, and narrowing of the
    tubular lumen were found in treated animals. Since these alterations
    later disappeared, they were considered to represent adaptation to
    the administration of LAS. No histological lesions were seen in the
    organs of rats that were fed for 24 months or more that could be
    attributed to treatment. Various types of tumour were observed in
    both treated and control rats but did not appear to be due to LAS
    (Fujii et al., 1977).

    A7.3.2.2  Administration in the drinking-water

        Groups of eight to nine male and eight to nine female Wistar
    rats were given LAS at a concentration of 0, 0.07, 0.2, or 0.6% in
    drinking-water for nine months. Body weight gain was suppressed in
    males given 0.6%. Haematological examination revealed no significant
    change in any of the experimental groups, but a dose-related
    decrease in cholesterol level was seen in males. No change in organ
    weight was seen that was due to administration of LAS. Significant
    decreases in the activities of glutamate-oxalate transaminase and
    lactate dehydrogenase were seen in males at 0.2% and a dose-related

    increase in the activity of glutamate-oxalate transaminase in
    females. A significant decrease in renal Na,K-ATPase was seen in the
    group given 0.2%. The dose of 0.07% corresponded to intakes of LAS
    of 50 and 120 mg/kg body weight per day in males and females, and
    the dose of 0.2% to intakes of 120 and 170 mg/kg body weight per
    day, respectively (Yoneyama et al., 1976).

        A commercial preparation of LAS (27% active ingredient) was
    given to groups of five male Wistar rats in drinking-water at a
    concentration of 0, 0.3, 3, 30, or 300 ppm (corresponding to 0.007,
    0.07, 0.7, or 7 mg/kg body weight per day) for 60, 124, or 181 days.
    Although a reduction in body weight gain, changes in blood
    biochemistry, and increased ornithine aminotransferase activity in
    the liver were noted in some animals, they were not proportional to
    dose or feeding period (Hayashi, 1980).

        Groups of 20 male Wistar rats were given water containing LAS
    (34.55% commercial solution) at a concentration of 0, 0.01, 0.05, or
    0.1% for two years, the highest dose corresponding to an intake of
    about 200 mg/kg body weight per day. No changes attributable to the
    administration of LAS were seen in terms of growth, mortality, the
    weights of major organs, or histopathological appearance (Tiba,
    1972).

        A group consisting of 62 male and 62 female Wistar rats was
    given drinking-water containing LAS (mean relative molecular mass,
    348; 38.74% active ingredient) at a concentration of 0.1%
    (corresponding to 140 mg/kg body weight per day), and a control
    group of 37 male and 37 females was given normal drinking-water.
    Five to 12 rats in the experimental group and three to 12 rats in
    the control group were killed at 3, 6, 12, and 18 months, and all
    surviving animals were killed at 24-26 months. Administration of LAS
    had no effect on the intake of water, mortality, body weight gain,
    or general condition. Histopathological examination revealed
    atrophy; fatty changes were found in hepatic cells in treated
    animals at six months, when there were also significant increases in
    the activities of glutamate-oxalate and glutamate-pyruvate
    transaminases and in the level of bilirubin. LAS had no effect on
    haematological parameters (Endo et al., 1980).

        A group of 60 male and 60 female rats (strain not specified)
    received drinking-water containing 0.01% of a preparation containing
    51% LAS for 100 weeks; a similar group was untreated. No detrimental
    effects on body weight and no pathological effects, including
    tumours, were reported (Bornmann et al., 1963).

    A7.3.2.3  Administration by gavage

        Groups of 20 male and 20 female Sprague-Dawley rats were given a
    solution of a magnesium salt of LAS at doses of 10, 75, 150, or
    300 mg/kg body weight per day by gavage for six months. Body weight
    gain was suppressed, and slight decreases were observed in serum
    protein, albumin, and calcium ion level, but the changes were within
    the physiological range (Ito et al., 1978).

    A7.3.2.4  Dermal application

        A dose of 0.1 ml/kg body weight of a 0.5, 1.0, or 5.0% solution
    of magnesium LAS (in 3% polyethylene glycol) was applied to the
    backs of 20 male and 20 female Sprague-Dawley rats six times a week
    for six months. Slight redness at the application site was observed
    transiently in males and occasionally in females at 5%. Body weight
    was slightly suppressed in males at that dose, and one male in the
    control group and one at 5.0% died of unknown causes. Treatment had
    no definite effect in terms of food conversion efficiency, urinary,
    haematological, serum biochemistry, or histopathological findings,
    or organ weights (Ito et al., 1978). No systemic toxicity was
    reported in this study. Sakashita et al. (1974) and Sakashita (1979)
    (see section 7.2.2.3) may have obtained positive results because
    they used a shorter period of exposure, during which skin integrity
    may have been compromised, resulting in absorption of the
    preparation of LAS through the skin to produce systemic effects.

        LAS (19.7% active ingredient) were applied to the dorsal skin of
    SLC-Wistar rats three times per week at a dose of 0.005, 0.025, or
    0.125 ml/rat (equivalent to 1, 5, or 25 mg/rat) for 24 months. A
    dose of 0.025 ml of an LAS-based detergent containing 19.9% LAS
    (equivalent to 5 mg LAS per rat) and distilled water was given to
    controls. Each application was washed from the skin with warm water
    after 24 h. Treatment had no effect on organ weights or
    histopathological appearance, and there was no evidence of toxicity
    or carcinogenicity (Taniguchi et al., 1978).

        Long-term studies of exposure to and the carcinogenicity of LAS
    are summarized in Table 19.

    A7.4  Skin and eye irritation; sensitization

        The potential of LAS to irritate the skin depends on the
    concentration applied. On the basis of the criteria of the European
    Commission and the OECD test guideline, LAS were classified as
    irritating to the skin at concentrations above 20% (European
    Committee of Organic Surfactants and Their Intermediates, 1990).

        Table 19. Summary of studies of long-term exposure to linear alkylbenzene sulfonates (LAS)
                                                                                                                                              

    Species, strain,       Test material         Route           Dosage                Results                             Reference
    numbers                (specification)
    per group
                                                                                                                                              

    Mouse, SLC-ICR         LAS (a.i. 60%)        Diet            0, 0.6, 1.8%,         Increased liver weight;             Yoneyama et al.
      8-9 M, 8-9 F                                               9 months              decreased hepatic and renal         (1976)
                                                                                       enzyme activities in males

    Mouse, ddy (NR)        LAS (NS)              Drinking-       20 mg/kg bw per       Degenerative changes in liver,      Watari et al. (1977)
                                                 water           day, 6 months         with partial recovery after
                                                                 end of treatment

    Mouse, ICR             LAS (a.i. 60%)        Drinking-       0, 0.07, 0.2, 0.6,    Depressed body weight gain at       Yoneyama et al.
      8-9 M, 8-9 F                               water           1.8%, 9 months        high dose; dose-related increase    (1976)
                                                                                       in liver weight in all treated
                                                                                       females; changes in hepatic
                                                                                       enzyme activities at high dose

    Rat, Wistar            LAS, C10-C14          Diet            0, 0.07, 0.2, 0.6,    Dose-related depression of          Yoneyama et al.
      10 M, 10 F                                                 1.8%, 6 months        growth, caecal enlargement,         (1972)
                                                                                       and renal tubular degeneration
                                                                                       at > 0.07%

    Rat, Wistar            LAS (a.i. 60%)        Diet            0, 0.6, 1.8%,         Depressed body weight gain          Yoneyama et al.
      8 M, 8 F                                                   9 months              at high dose; changes in            (1976)
                                                                                       haematological parameters, in serum
                                                                                       and hepatic enzyme activities,
                                                                                       and in cholesterol levels at both
                                                                                       doses; changes in renal enzyme
                                                                                       activities in females at high dose
                                                                                                                                              

    Table 19 (contd)
                                                                                                                                              

    Species, strain,       Test material         Route           Dosage                Results                             Reference
    numbers                (specification)                                             
    per group
                                                                                                                                              

    Rat, Wistar            LAS (a.i. 60%)        Drinking-       0, 0.07, 0.2, 0.6%,   Depressed body weight gain in       Yoneyama et al.
      8-9 M, 8-9 F                               water           9 months              males at high dose; no changes      (1976)
                                                                                       in haematological parameters or
                                                                                       organ weight; changes in serum
                                                                                       and renal enzyme activities at 0.2%

    Rat, Wistar            LAS, C10-C14          Diet            0, 0.04, 0.16, 0.6%,  Slight increase in liver and        Yoneyama et al.
      50 M, 50 F           (a.i. 60%)                            24 months             caecal weights and changes in       (1977)
                                                                                       serum enzym activities at high
                                                                                       dose; no effect on body weight
                                                                                       gain

    Rat, Charles River     LAS, C10-C14          Diet            0, 0.02, 0.1, 0.5%,   No treatment-related effects        Buehler et al. 
      50 M, 50 F           (a.i98.1%)                            2 years                                                   (1971)

    Rat, Wistar            LAS, C10-C14          Diet            0, 0.04, 0.16, 0.6%,  Transient changes in liver and      Fujii et al. (1977)
      50 M, 50 F           (a.i. 60%)                            2 years               kidney; no treatment-related
                                                                                       histopathological abnormalities
                                                                                       at end of study

    Rat, SD                LAS Mg, C10-C13       Gavage          75, 150, 300 mg/kg    Depressed body weight gain; no      Ito et al. (1978)
      20 M, 20 F           (a.i. 96.9%)                          bw per day, 6         significant adverse effects
                                                                 months

    Rat, Wistar, 5 M       LAS detergent         Drinking-       0, 0.3, 3, 30, 300    Depressed body weight gain and      Hayashi (1980)
                           (a.i. 27%)            water           ppm, 181 days         changes in blood biochemistry 
                                                                                       and liver enzyme activity considered
                                                                                       not to be related to treatment
                                                                                                                                              

    Table 19 (contd)
                                                                                                                                              

    Species, strain,       Test material         Route           Dosage                Results                             Reference
    numbers                (specification)
    per group
                                                                                                                                              

    Rat, Wistar, 20 M      LAS (a.i. 34.55%)     Drinking-       0, 0.01, 0.05, 0.1%,  No adverse effects                  Tiba (1972)
                                                 water           2 years

    Rat, Wistar            LAS (a.i. 38.74%)     Drinking-       0, 0.1%, 26 months    Fatty changes and atrophy in        Endo et al. (1980)
      62 M, 62 F                                 water                                 liver; changes in hepatic enzyme
                                                                                       activities; no effect on body
                                                                                       weight gain

    Rat                    LAS (Marlon           Drinking-       0, 0.01%,             No adverse effects                  Bornmann et al.
      60 M, 60 F           BW 2043)              water           100 weeks                                                 (1963)

    Rat, SD                LAS Mg, C10-C13       Dermal          0.5, 1.0, 5% in       Slight reduction in body weight     Ito et al. (1978)
      20 M, 20 F           (a.i. 96.9%)                          polyethylene glycol,  gain of males at high dose; no 
                                                                 6 months              other adverse effects

    Rat, SLC-Wistar        LAS (a.i. 19.7%)      Dermal          0, 6.7, 33.3, 167.0   No adverse effects                  Taniguchi et al.
      25 M, 25 F                                                 mg/kg  bw, 3 × per                                        (1978)
                                                                 week, 2 years

    Rat, SLC-Wistar        LAS detergent         Dermal          0, 33.3 mg/kg bw      No adverse effects                  Taniguchi et al.
      25 M, 25 F           (a.i. 19.9%)                          3 × per week, 2 years                                     (1978)
                                                                                                                                              

    M, male; F, female; NS, not specified; a.i.,  active ingredient; SD, Sprague-Dawley
        A7.4.1  Studies of skin

        Solutions of LAS (chain length distribution, C10-C13;
    purity, 99.9%) were applied to the backs of groups of three male
    Wistar rats at a rate of 0.5 g of a 20 or 30% solution once a day
    for 15 days. On the sixteenth day of the experiment, the skin at the
    application site and the tissues of the tongue and oral mucosa (to
    examine the effects of licking) of the rats that received 30% were
    examined histologically. Body weight gain was reduced in the group
    exposed to 20%, and body weight was decreased in animals exposed to
    30%. An infiltrating, yellow-red brown crust was observed after two
    to three days at 20% and after one to two days at 30%; at four to
    six days, the crust was abraded, and erosion was observed.
    Histological examination of the application site revealed severe
    necrosis of the region, from the epidermis cuticle to the upper
    layer of the dermis, severe infiltration of leukocytes in the
    necrotic site, diffuse inflammatory cell infiltration of all of the
    layers of the corium, and swelling of collagenous fibres in the
    dermis. Histological examination of the tongue showed no changes,
    but examination of the oral mucosa revealed atrophy and slight
    degeneration of the epithelium (Sadai & Mizuno, 1972).

        Some batches of a paste of LAS (volume not stated) induced weak
    to moderate sensitization in guinea-pig skin at induction
    concentrations of 2-100% and challenge concentrations of 1-2%. A
    prototype liquid laundry detergent (10% LAS) induced sensitization
    at a challenge concentration of 1% (0.1% as LAS) (Nusair et al.,
    1988).

        The biochemical and pathomorphological effects of LAS on the
    skin of four female albino CDRI guinea-pigs were investigated by
    shaving the abdominal skin and immersing the animals up to the neck
    in a 1% aqueous solution of neutralized LAS for 90 min daily for
    seven consecutive days. A control group was immersed in water
    according to the same schedule. After each immersion, the animals
    were washed and their skin dried. The animals were killed after
    seven days, and skin samples were taken. The skin of guinea-pigs
    exposed to the solution of LAS had increased activity of histidine
    decarboxylase, decreased sulfhydryl groups and histamine, and
    decreased activity of lactic dehydrogenase. It appeared to be
    shrunken, with thinner layers of dermis and epidermis than controls.
    There were also areas of scarring in the epidermis and ridging of
    epidermis and dermis (Misra et al., 1989a).

    A7.4.2  Studies of the eye

        A volume of 0.1 ml of a solution of LAS (relative molecular
    mass, 346.5) at five concentrations ranging from 0.01 to 1.0% was
    instilled into the eyes of rabbits (13 per group). The rabbits were
    observed for 24 h after application. The group receiving 0.01% had
    no abnormalities, but that given 0.05% had slight congestion.

    Concentrations of 0.5% and more induced marked reactions, such as
    severe congestion and oedema, increased secretion, opacity of the
    cornea, and disappearance of the corneal reflex (Oba et al., 1968a).

        Solutions of LAS (chain length distribution, C10-C14; 80.9%
    C11-C13) at six concentrations ranging from 0.01 to 5.0% were
    instilled into the eyes of rabbits (three per group). The rabbits
    were observed for 168 h after application. The group given 0.01% had
    no reaction, but within 2 h those given 0.05% had slight congestion
    and those at 0.1% had considerable congestion or oedema, which had
    disappeared by 24 h. Animals given 0.5% or more had marked
    reactions, such as severe congestion and oedema, increased
    secretion, opacity of the cornea, and disappearance of the corneal
    reflex, for 24 h but then tended to recover; the signs had
    disappeared completely within 120 h (Iimori et al., 1972).

    A7.5  Reproductive toxicity, embryotoxicity, and teratogenicity

        The reproductive toxicity of LAS and formulations of LAS has
    been evaluated in studies by oral (gavage, diet, drinking-water),
    dermal (skin painting), and parenteral (subcutaneous)
    administration. Similar effects were seen, regardless of the route
    of application. The studies had a number of deficiencies, however,
    which are summarized below.

        In some studies, widely separated dose levels were used (Palmer
    et al., 1975a; Takahashi et al., 1975; Tiba et al., 1976; Hamano et
    al., 1976), so that it is difficult to assess dose-response
    relationships and to interpret the results. Some of the studies
    included only one dose (Bornmann et al., 1963; Sato et al., 1972;
    Endo et al., 1980) and some two (Iimori et al., 1973; Nolen et al.,
    1975; Takahashi et al., 1975; Hamano et al., 1976; Tiba et al.,
    1976). The studies done on formulations are difficult to interpret,
    as the effects seen may have been due to another component. In some
    cases, the details of the formulation are not given, so that the
    dose of LAS is also unknown. Certain studies of dermal exposure
    (Sato et al., 1972; Masuda et al., 1973, 1974; Palmer et al., 1975a;
    Nishimura, 1976; Daly et al., 1980) involved levels that compromised
    the integrity of the skin and caused overt toxicity.

        The teratogenic effects of some commercial formulations of LAS
    reported by Mikami and co-workers (1969), mainly in mice, were not
    reproduced in other studies. A number of studies indicated that LAS
    have some reproductive toxicity, but the effects were seen only at
    doses that caused maternal toxicity. No teratogenic effects were
    observed. These studies are summarized in Tables 20-22.

        Table 20.  Studies of the reproductive toxicity and teratogenicity of linear alkylbenzene sulfonates (LAS) and formulations of LAS,
               administered orally
                                                                                                                                              

    Route     Species (no. of   Dose (mg/kg           Length of   Comments and results                          Reference
              animals/group)    bw per day)           treatment
                                                      (days)
                                                                                                                                              

    LAS
    Diet      Charles River     14, 70, 350           84          Combined study of reproduction                Buehler et al. (1971)
              rats (20)         (0.02, 0.1, 0.5%)                 and teratogenicity (three generations);
                                                                  no effects attributable to LAS

    Diet      SD rats (16)      78, 780 (0.1, 1.0%)   0-20        No abnormalities at either dose; few          Tiba et al. (1976)
                                                                  offspring at high dose

    Gavage    ICR mice (NS)     300, 600              6,8,10      High incidence of cleft palate and            Mikami et al. (1969)
                                                                  exencephaly in fetuses at high dose

    Gavage    ICR mice (14)     40, 400 (0.4, 4.0%)   0-6         No effects at low dose; reduced weight        Takahashi et al.
                                                      7-13        gain and pregnancy rate at high dose          (1975)

    Gavage    ICR mice (25-33)  10, 100, 300          6-15        Reduced weight gain at all levels,            Shiobara & Imahori
                                                                  particularly at highest dose; two             (1976)
                                                                  dams died at highest dose;  all
                                                                  fetuses of one dam died  in utero;
                                                                  decreased body weight and delayed
                                                                  ossification in living fetuses but no
                                                                  increase in incidence of malformations
                                                                                                                                              

    Table 20 (contd)
                                                                                                                                              

    Route     Species (no. of   Dose (mg/kg           Length of   Comments and results                          Reference
              animals/group)    bw per day)           treatment
                                                      (days)
                                                                                                                                              

    LAS  (contd).
    Gavage    ICR mice          14, 20, 350           1-3         No effect on implantation rate at             Koizumi et al. (1985)
                                                                  any dose

    Gavage    CD rats (20)      0.2, 2.0, 300, 600    6-15, rats  No effects on any species at two lower        Palmer et al. (1975a)
              CD-1 mice (20)                          and mice    doses
              NZW rabbits (13)                        6-18,       Rats: reduced weight gain and one
                                                      rabbits     death at highest dose
                                                                  Mice: reduced weight gain, seven
                                                                  deaths, and four litter losses at 300 mg/kg
                                                                  bw per day; 18 deaths, one litter loss
                                                                  and one non-pregnancy at 600 mg/kg
                                                                  bw per day

                                                                  Rabbits: reduced weight gain, 11 deaths,
                                                                  two litter losses at 300 mg/kg bw per
                                                                  day; all animals died at highest dose

    Gavage    CD rats (30)      125, 500, 2000        6-15        Two-generation study of reproductive          Robinson &
                                                                  and developmental toxicity; delayed           Schroeder (1992)
                                                                  ossification significant at highest dose,
                                                                  slight at middle dose; no reproductive
                                                                  or developmental toxicity
                                                                                                                                              

    Table 20 (contd)
                                                                                                                                              

    Route     Species (no. of   Dose (mg/kg           Length of   Comments and results                          Reference
              animals/group)    bw per day)           treatment
                                                      (days)
                                                                                                                                              

    LAS  (contd).
    Drinking- Charles River     7 (0.01%)                         Three-generation study of fertility; no       Bornmann et al.
    water     rats (10)                                           teratogenic effects                           (1963)

    Drinking- Wistar rats (20)  70 (0.1%)                         Four-generation study of reproductive         Endo et al. (1980)
    water                                                         toxicity; no effects attributable to LAS

    Drinking- Wistar rats (20)  383 mg/rat (0.1%)     6-15        No effects in rats; rabbits had reduced       Endo et al. (1980)
    water     NZW rabbit (11)   3030 mg/rabbit        6-18        weight gain and delayed ossification
                                (0.1%)                            but no malformations

    17% LAS, 7% alcohol ethoxylate sulfate
    Gavage    CD rats (20)      0.8, 8, 1,200, 2400   6-15        No increase in major malformations            Palmer et al. (1975a)
              CD-1 mice (20)    1.064, 10.64,         6-15        or significant changes in anomalies
                                1600, 320
              NZW rabbits (13)  0.8, 8, 1200, 2400    6-18

    45% LAS
    Diet      CD rats (25)      80, 400, 800          6-15        No treatment-related effects on               Nolen et al. (1975)
                                (0.1, 0.5, 1.0%)                  reproduction or embryonic
                                                                  development
                                                                                                                                              

    Table 20 (contd)
                                                                                                                                              

    Route     Species (no. of   Dose (mg/kg           Length of   Comments and results                          Reference
              animals/group)    bw per day)           treatment
                                                      (days)
                                                                                                                                              

    1% LAS
    Gavage    ICR mice (18-23)  800, 1200, 1500,      6-15        No increase in fetal malformations;           Yamamoto et al.
                                3000                              decreased body weight and delayed             (1976)
                                                                  ossification at 1200 mg/kg bw

    19% LAS
    Gavage    IRC mice (9-13)   125, 4000             6           No effect on fetal viability or               Hamano et al.
                                                                  development                                   (1976)
                                                                                                                                              

    NS, not specified

    Table 21.  Studies of the reproductive toxicity and teratogenicity of linear alkylbenzene sulfonates (LAS) and formulations of
               LAS, administered dermally
                                                                                                                                              

    Species (no. of       Dose (mg/kg             Length of     Comments and results                             Reference
    animals/group)        bw per day)             treatment
                                                  (days)
                                                                                                                                              

    LAS
    CD rats (20)          0.6, 6.0, 60            1-15          Slight reduction in body weight gain at          Palmer et al.
                          (0.03, 0.3, 3.0%)                     highest dose; no effect on litter parameters     (1975a)
                                                                at any dose; no evidence of malformations

    CD-1 mice (20)        5, 50 , 500             2-13          Reduced body weight gain, fewer pregnancies,
                          (0.03, 0.3, 3.0%)                     and total litter loss at highest dose; no
                                                                malformations

    NZW rabbits (13)      0.9, 9, 90              1-16          Marked reduction in body weight gain, fewer
                          (0.03, 0.3, 3.0%)                     pregnancies, and two litter losses at highest
                                                                dose; reduced body weight gain at 9 mg/kg bw
                                                                per day; no malformations

    Wistar rats (20)      20, 100, 400            0-20          Reduced body weight gain, decreased              Nishimura (1976)
                          (1, 5, 20%)                           pregnancy rates and delayed ossification
                                                                at highest dose; no effects at lower doses

    Wistar rats (20)      20, 100, 400            0-20          Irritation at site and reduced body weight       Daly et al. (1980)
                          (1, 5, 20%);                          gain at two higher doses; no change in fetal
                          rinse-off                             parameters at any level
                                                                                                                                              

    Table 21 (contd)
                                                                                                                                              

    Species (no. of       Dose (mg/kg             Length of     Comments and results                             Reference
    animals/group)        bw per day)             treatment
                                                  (days)
                                                                                                                                              

    Wistar rats (contd)
                          0.1, 2, 10              0-20          No change in fetal parameters at any level
                          (0.05, 0.1, 0.5%);
                          leave on

    ddy/s mice (16)       110 (2.22%)             0-13          No abnormalities in dams or fetuses              Sato et al. (1972)

    ddy mice (4-10)       0.084, 0.84, 8.4        2-14          No fetal or reproductive effects                 Masuda et al.
                          (0.017, 0.17, 1.7%)                                                                    (1973, 1974)

    ICR mice              4.2, 8.4, 12.0, 16.5    1-13          Delayed ossification at two highest
    (25-30)               (0.85, 1.7, 2.55, 3.4%)               doses

    ICR mice              15, 150, 1500           6-15          Clear decrease in pregnancy rate and             Imahori et al.
    (27-28)               (0.03, 0.3, 3.0%)                     decrease in fetal weight at highest dose;        (1976)
                                                                no increase in malformations in fetus

    17% LAS, 7% ethanol, 15% urea
    ICR mice              2.5, 25, 75             1-13          Decrease in pregnancy rate at                    Inoue & Masuda
    (11-20)               (0.5, 5, 15%)                         highest dose; no other effects                   (1976)
                                                                                                                                              

    Table 21 (contd)
                                                                                                                                              

    Species (no. of       Dose (mg/kg             Length of     Comments and results                             Reference
    animals/group)        bw per day)             treatment
                                                  (days)
                                                                                                                                              

    16.3% LAS
    ICR mice              25, 50, 100             0-13          Reduced pregnancy rate and                       Nakahara et al.
    (17-50)               (5, 10, 20%)                          some total litter losses at                      (1976)
                                                                highest dose

    Unknown formulation
    ddy/s mice            65 (15%)                0-13          Decreased body weight gain,                      Sato et al. (1972)
    (21)                                                        decreased pregnancy rate,
                                                                decreased fetal weight, and delayed
                                                                ossification

    Unknown formulation
    IRC mice              75, 100                 0-12          Decreased pregnancy rates                        Iimori et al. (1973)
    (27-39)               (15, 20%)                             at both levels

    Unknown formulation
    IRC mice              30, 65, 85,             0-13          Decreased pregnancy rates at all                 Takahashi et al.
    (15-19)               100, 125                              doses; decreased fetal body                      (1975)
                          (13.0, 17.0,                          weight; delayed ossification at all
                          20.0, 25.0%)                          doses except 65 mg/kg bw per day
                                                                                                                                              

    Table 22.  Studies of the reproductive toxicity and teratogenicity of linear alkylbenzene sulfonates (LAS) and LAS formulations,
               administered subcutaneously
                                                                                                                                              

    Species (no. of        Dose (mg/kg          Length of     Comments and results                          Reference
    animals/group)         bw per day)          treatment
                                                (days)
                                                                                                                                              

    LAS
    ICR mice               0.4, 2.0, 10%        7-13          No significant effects on dams; high          Masuda & Inoue  (1974)
    (21-24)                                                   incidence of skeletal variations and
                                                              delayed ossification, not dose-related;
                                                              no abnormalities

    ICR mice               20, 200              0-3           Irritation at injection site and reduced      Takahashi et al. (1975)
    (12-19)                (0.35, 1.00%)        8-11          pregnancy rate at highest dose; no
                                                              malformations or anomalies

    17% LAS, 7% ethanol, 15% urea
    CR mice                30, 150              7-13          No increase in major malformations            Inoue & Masuda (1976)
    (16-17)                                     0-13          or minor anomalies; increase in
                                                              implantations at high dose given on
                                                              days 0-13
                                                                                                                                              
        A7.6  Mutagenicity and related end-points

    A7.6.1  Studies in vitro

        Assays for mutagenicity were performed  in vitro with two
    commercial products containing 17.1 and 19% LAS, either undiluted or
    diluted 10 and 100 times (Oda et al., 1977), 99.5% pure LAS (Fujita
    et al., 1977), 95.5% pure sodium salt, or 96.2% pure calcium salt
    (Inoue & Sunakawa, 1979), using  Bacillus subtilis H17  (rec+) and
    M45  (rec-),  Salmonella typhimurium TA98 and TA100 (including
    a metabolic activation system), and  Escherichia coli WP2  uvrA.
    All of the assays gave negative results. LAS 99.5% pure (Fujita et
    al., 1977) were also tested in  S. typhimurium TA1535 and TA1537,
    again with negative results. Thesodium and calcium salts in the
    presence of various liver homogenates (Sunakawa et al., 1981) and a
    22.2% solution of LAS (C10-C14, 10-200 µg/plate) (Inoue et al.,
    1980) were tested in  S. typhimurium TA98 and TA100. No
    mutagenicity was seen.

    A7.6.2  Studies in vivo

        Groups of male ICR:JCL mice were given LAS at a dose of 200,
    400, and 800 mg/kg body weight per day by gavage for five days and
    were killed 6 h after the final administration for examination of
    chromosomal aberrations in bone-marrow cells. One commercial
    preparation containing 19.0% LAS was also given, at a dose of 800,
    1600, or 3200 mg/kg body weight, and another containing 17.1% LAS at
    a dose of 1000, 2000, or 4000 mg/kg body weight once only by gavage.
    The highest doses were 50% of the respective LD50 values. Bone
    marrow was examined 6, 24 and 48 h after administration. There was
    no significant difference between any of the groups given LAS and
    the negative control group in the incidence of chromosomal
    aberrations. Mitomycin C, used as a positive control at 5 mg/kg body
    weight, induced severe chromosomal aberrations (Inoue et al., 1977).

        Groups of five male Wistar rats, Sprague-Dawley rats, and ICR
    mice were given a diet containing 0.9% LAS for nine months. The
    equivalent doses were 450 mg/kg body weight per day in rats and   
    1170 mg/kg body weight per day in mice. There were no significant
    differences in the incidence of chromosomal aberrations between the
    experimental and control groups (Masubuchi et al., 1976).

        After LAS (C10-C15) were fed to groups of six male and six
    female Colworth/Wistar rats in the diet at concentrations of 0.56 or
    1.13%, equivalent to 280 or 565 mg/kg body weight per day, for 90
    days, no alteratuons were seen in chromosomes in bone marrow (Hope,
    1977).

        In three male ddY mice given LAS at 100 mg/kg body weight by
    intraperitoneal injection, there was no differences between the
    treated animals and a control group in the incidence of
    polychromatic erythrocytes with micronuclei in bone-marrow cells
    (Kishi et al., 1984).

        An assay to detect dominant lethal mutations was performed in
    seven male ICR:JCL mice given a diet containing 0.6% LAS at
    300 mg/kg body weight per day for nine months. Each of the male mice
    was then mated with two female mice that had not been given LAS, and
    11 of the 14 females became pregnant. The pregnant mice were
    laparotomized on day 13 of gestation to determine the numbers of
    luteal bodies, implantations, surviving fetuses, and dead fetuses.
    There were no significant differences in fertility, mortality of ova
    and embryos, the number of surviving fetuses, or the index of
    dominant lethal induction (Roehrborn) between the experimental and
    control groups (Masubuchi et al., 1976).

        LAS were administered as a single oral dose of 2 mg to pregnant
    ICR mice on day 3 of gestation; on day 17 of gestation, each animal
    received a subcutaneous dose of 1, 2, or 10 mg/mouse and was killed
    24 h later. There was no difference among treated groups in the
    incidence of polychromatic erythrocytes with micronuclei in maternal
    bone marrow or fetal liver or blood. No mutagenic effect was found
    in any of the groups (Koizumi et al., 1985).

    A7.7  Special studies

    A7.7.1  Studies in vitro

        The haemolytic action of LAS was investigated by mixing red
    blood cells from rabbits with solutions of LAS at concentrations of
    1-1000 mg/litre at 38°C for 30 min. Haemolysis occurred at
    concentrations > 5 mg/litre (Yanagisawa et al., 1964). Red blood
    cells from rabbits were mixed with solutions of various
    concentrations of LAS (relative molecular mass, 346.5) at room
    temperature for 3 h. The 50% haemolytic concentration of LAS was
    9 mg/litre (Oba et al., 1968a).

        Purified LAS at various concentrations were added to 10 µl of
    normal plasma obtained from male rats, and prothrombin time was
    determined. Prothrombin time was prolonged; the 50% inhibitory
    concentration was about 0.6 mmol/litre. When LAS at various
    concentrations were added to a mixture of 1% fibrinogen and
    thrombin, the time of formation of a mass of fibrin was prolonged by
    inhibition of thrombin activity. The 50% inhibitory concentration
    was about 0.05 mmol/litre (Takahashi et al., 1974).

        LAS influenced the thermal denaturation and decreased the
    fluorescence profile of bovine serum albumin  in vitro, indicating
    protein-LAS interaction (Javed et al., 1988).

        Eggs from female B6C3F1 mice were fertilized  in vitro and
    incubated in culture medium containing LAS at concentrations between
    0.015 and 0.03%; eggs grown in culture medium without LAS served as
    controls. Eggs exposed for 1 h, washed, and then cultured for five
    days developed normally to the blastocyst stage when the
    concentration of LAS was less than 0.025%; at concentrations higher
    than 0.03%, the eggs did not develop beyond the one-cell stage. With
    continuous exposure to LAS for five days, a concentration of 0.01%
    slightly impaired development to the blastocyst stage, and 0.025%
    prevented development to the one-cell stage (Samejima, 1991).

        LAS with a chain length distribution of C10-C14 did not
    induce transformation of cryopreserved primary cultures of Syrian
    golden hamster embryo cells  in vitro (Inoue et al., 1979, 1980).

    A7.7.2  Biochemical effects

        The levels of amylase, alkaline phosphatase, glutamate-oxalate
    transaminase, and glutamate-pyruvate transaminase and of the
    electrolytes Ca, P, and Mg in serum were determined up to 24 h after
    a single oral administration of 2, 5, 50, or 100 mg/kg body weight
    of LAS (60% active ingredient) or dermal application of 5 ml of a 1,
    5, 10, or 20% solution of LAS to rabbits (number not stated). The
    levels of total Ca, Ca2+, Mg, and P were generally lower after
    either type of administration than before. Although there was no
    definite trend, the activities of the enzymes tended to decrease
    regardless of the route of the administration or the dose
    (Yanagisawa et al., 1964).

        Groups of three male mice were given an intraperitoneal
    injection of 0.3 g/kg body weight of LAS (C14) in order to study
    the effects on the formation of methaemoglobin, determined 0.5, 1,
    and 2 h afterinjection of LAS. The level of methaemoglobin in the
    experimental groups was not significantly greater than that in the
    control group at any time (Tamura & Ogura, 1969).

        The effects of LAS (sodium dodecylbenzenesulfonate) on fasting
    blood glucose level and glucose tolerance curves were investigated
    in 40 male and 50 female albino rats pretreated with 0.25 g/kg body
    weight per day of LAS for three months. At the end of this period,
    the rats were divided into four groups and given distilled water,
    6.1 g/kg body weight of glucose, 0.94 g/kg body weight of LAS, or
    6.1 g/kg body weight of glucose plus 0.94 g/kg body weight of LAS by
    gavage. Blood glucose was then estimated at 30-min intervals.
    Administration of LAS in conjunction with glucose resulted in higher
    initial levels of blood glucose in male rats and persistently higher
    levels in females than did administration of glucose alone. Females
    in control and pretreated groups generally had higher blood glucose
    levels in response to administration of glucose or LAS plus glucose
    than did male rats (Antal, 1972).

    A8.  EFFECTS ON HUMANS

     Section summary

        Human skin can tolerate contact with solutions of up to 1% LAS
    for 24 h with only mild irritation. Like other surfactants, LAS can
    delipidate the skin surface, elute natural moisturizing factor,
    denature the proteins of the outer epidermal layer, and increase
    permeability and swelling of the outer layer. LAS do not induce skin
    sensitization in humans, and there is no conclusive evidence that
    they induce eczema. No serious injuries or fatalities have been
    reported following accidental ingestion of LAS-containing surfactant
    preparations.

    A8.1  Exposure of the general population

        Surface-active agents are used in shampoos, dish-washing
    products, household cleaners, laundry detergents, and other
    applications such as industrial cleaners. LAS are major components
    of such products. In general, the concentration of nonionic and
    ionic surfactants is 10-20%.

    A8.2  Clinical studies

    A8.2.1  Skin irritation and sensitization

        LAS are mildly to moderately irritating to human skin, depending
    on the concentration. There is no evidence that they sensitize the
    skin in humans.

        The relative intensity of skin roughness induced on the surface
    of the forearms of volunteers (a circulation method) due to contact
    with LAS of different alkyl chain lengths (C8, C10, C11-C16)
    was characterized mainly by gross visible changes. C12 LAS
    produced more skin roughening than LAS with longer or shorter alkyl
    chains.  The degree of skin roughening  in vivo correlated with the
    extent of protein denaturation measured  in vitro (Imokawa et al.,
    1975a).

        Primary skin irritation induced by an LAS formulation (average
    chain length, C12; relative molecular mass, 346.5), by
    alpha-olefin sulfonates (AOS) (27% C15, 25% C16, 28% C17, 8%
    C18; relative molecular mass, 338.5), and by alkyl sulfates (AS)
    (C12; relative molecular mass, 346.5) was compared in a 24-h
    closed-patch test on the forearms of seven male volunteers. A 1%
    aqueous solution (pH 6.8) of each substance was used, and the
    relative intensity of skin irritation was scored by grading
    erythema, fissuring, and scales. The average score for LAS was
    similar to that for AOS but significantly lower than that for AS
    ( p < 0.05) (Oba et al., 1968a).

        In another comparison, the intensity of skin irritation induced
    by 1% aqueous solutions of LAS (C10-C13), AOS (C14, C16,
    C18), and the sodium salt of AS (C12-C15) was studied in a
    24-h closed-patch test on the forearm and in a test in which the
    substance was dripped onto the interdigital surface for 40 min once
    daily for two consecutive days at a rate of 1.2-1.5 ml/min. Skin
    reactions were scored by grading erythema in the patch test and by
    grading scaling in the drip test. In the patch test, the score for
    LAS was similar to that for AOS but significantly lower than that
    for AS. In the drip test, the score for LAS was similar to that for
    AS but higher than that for AOS (Sadai et al., 1979).

        Repeated patch tests with LAS at aqueous concentrations of 0.05
    and 0.2% produced mild to moderate primary irritation. In a study on
    the sensitization potential of LAS for human skin, a 0.1% aqueous
    preparation caused no sensitization in 86 subjects (Procter & Gamble
    Co., unpublished data).

        No skin sensitization was seen in 2294 volunteers exposed to LAS
    or in 17 887 exposed to formulations of LAS (Nusair et al., 1988).

    A8.2.2  Effects on the epidermis

        The main effects of surface-active agents on the epidermal
    (stratum corneum) are:

        --   delipidation of the skin surface or outer layer;

        --   elution of natural moisturizing factor, which maintains the
             water content of the outer layer;

        --   denaturation of stratum corneum protein; and

        --   increased permeability, swelling of the outer layer, and
             inhibition of enzyme activities in the epidermis.

        These effects and some others present a hazard to the skin; they
    are described below.

        In an investigation of the relationship between the irritating
    potential of LAS  in vivo and its ability to remove lipid from the
    stratum corneum  in vitro, LAS removed detectable levels of lipids
    only at levels above the critical micelle concentration (0.04%). LAS
    removed only small amounts of cholesterol, free fatty acids, the
    esters of those materials, and possibly squalene. At concentrations
    below that level, LAS can bind to and irritate the stratum corneum.
    The clinical irritation produced by LAS is therefore unlikely to be
    directly linked to extraction of lipid, and milder forms of
    irritation may involve binding of LAS to and denaturation of keratin
    as well as disruption of lipid (Froebe et al., 1990).

        The results of the human arm immersion test with measurement of
    eluted amino acids and protein, the skin permeation test, freeing of
    sulfhydryl groups, and the patch test were compared for nine kinds
    of surfactant, including LAS, ABS, AS, alcohol ethoxylate sulfate,
    soap, nonionic surfactant, and amphoteric surfactant. LAS gave
    intermediate reactions in the patch test and the permeation test and
    showed a high level of sulfhydryl group freeing activity. The
    results of the tests for evaluating surfactants did not agree with
    those for the immersion test, which the author considered to provide
    the best simulation of actual use (Polano, 1968).

        In a number of studies, denaturation of outer layer proteins was
    observed  in vitro (Van Scott & Lyon, 1953; Harrold, 1959; Wood &
    Bettley, 1971; Imokawa et al., 1974; Okamoto, 1974; Imokawa et al.,
    1975b; Imokawa & Katsumi, 1976). Sodium dodecylbenzenesulfonate
    stimulated penetration of sodium ions through isolated human
    epidermis, partly because the detergent can denature proteins of the
    epidermal stratum corneum (Wood & Bettley, 1971). Sodium laurate and
    sodium lauryl sulfate were the most effective of several surfactants
    in inducing swelling of the horny layer (Putterman et al., 1977).
    The lysosome labilizing effects of surfactants, measured as the
    release of enzyme from lysosomes, were shown to diminish in the
    order cationic > anionic > nonionic surfactants (Imokawa &
    Mishima, 1979). When ovalbumin was used as a simulated epidermis
    protein, sodium lauryl sulfate was found to denature skin protein
    extensively by exposing concealed sulfhydryl groups in LAS of alkyl
    chain length C8-C16 (Blohm, 1957).

        In immersion tests of the hand and the forearm up to 5 cm above
    the wrist, falling off of skin scales diminished in the order:
     sec-alkane sulfonate > LAS > AOS, alcohol ethoxylate sulfate
    (Okamoto, 1974), but the distribution of carbon chain lengths among
    the samples was not described. In a comparison of skin roughening by
    a circulation method, the effects diminished in the order C12 AS
    > C12 AOS > C12  sec-alkane sulfonate > C12 LAS (Imokawa
    et al., 1974, 1975a,b). Skin roughening caused by several
    surfactants that are components of commercial products was studied
    by the method of Ito & Kakegawa (1972), in which various
    concentrations are dripped onto the fingers. The effects diminished
    in the order C10-C13 LAS = C12-C15 AS > C11, C13, C15
    alcohol ethoxylate sulfate ( n = 0-3) > C14, C16, C18 AOS
    > C11-C15 polyoxyethylene alkylether (Sadai et al., 1979).

    A8.2.3  Hand eczema

        The skin reaction to 0.04, 0.4, and 4.0% aqueous solutions of
    LAS (10.0% C10, 34.3% C11, 31.5% C12, 24.7% C13) was tested
    in a 24-h closed-patch test on the lower backs of 10 healthy
    volunteers and 11 patients with hand eczema (progressive keratosis
    palmaris). The incidence and intensity of skin reactions were

    greater in the group with hand eczema, but the difference was not
    statistically significant (Okamoto & Takase, 1976a,b).

        In order to assess the possible etiological correlation between
    exposure to LAS and hand eczema, 0.04, 0.4, and 4% aqueous solutions
    of LAS were  applied in 48-h closed-patch tests on the lower backs
    of 20 women with hand eczema and 42 with other skin diseases. The
    skin reaction was scored grossly from 0 to 5 on the basis of the
    occurrence or intensity of erythema, papules, and vesicles. The
    average score appeared to increase in parallel with the
    concentration of LAS but did not differ between the groups with hand
    eczema and other skin diseases (Sasagawa et al., 1978).

        Nine proprietary household detergents were tested in 24-h
    closed-patch tests on the lower backs of 160 women with hand eczema.
    The surfactant concentrations in five of the products were: (i) 2%
    ABS-Na, 15% LAS-Na; (ii) 2% ABS-Na, 14% LAS-Na; (iii) 17% LAS-Na,
    12% alcohol ethoxylate sulfate; (iv) 11% ABS-Na, 11% LAS-Na; (v) 19%
    LAS-Na. When the detergents were applied daily (for an unspecified
    period) at an aqueous concentration of 0.175-0.8%, positive
    responses were observed in 3.1% of the women, but they were
    considered not to be allergic because the redness of the skin
    disappeared completely within two days (Kawamura et al., 1970).

        Three proprietary household detergents containing LAS were
    tested in 24-h closed-patch tests on the forearms of 13 women with
    'housewives' dermatitis' and 13 with other skin diseases. The
    detergent was applied either undiluted or in a 0.2% aqueous
    solution. Undiluted solutions of all three detergents caused mild to
    moderate skin reactions, at incidences of 38.5, 48.1, and 73.1%,
    which did not differ between the groups with housewives' dermatitis
    and other skin diseases. The 0.2% aqueous solutions did not induce
    skin reactions (Ishihara & Kinebuchi, 1967).

        Two series of field tests were conducted to estimate if exposure
    to a variety of synthetic detergent formulations was associated with
    causation or aggravation of hand eczema in women. In the first
    series, 162 female volunteers were divided into two groups and
    instructed to wear a rubber glove on either the left or the right
    hand while using the detergents. The test was conducted for one
    month, and the gross appearance of hands before and after the test
    period was compared. The relative intensity of noninflammatory
    keratosis of the hands was increased in individuals in both groups
    on hands that were covered and to a slightly greater extent on hands
    that were uncovered. In the second series of tests, 881 housewives
    were divided into three groups and instructed to use only one brand
    of household detergent, containing LAS, AOS, or ABS during the test
    period and to wear rubber gloves on both hands while using the
    detergent. The test was conducted for 1.5 months, and the gross
    appearance of hands before and after the test period was compared.

    Skin roughness was not worsened in any of the three groups (Watanabe
    et al., 1968).

    A8.2.4  Occupational exposure

        Sixty workers exposed at work to an atmosphere containing LAS at
    8.64 mg/m3 were tested for serum lipid and sugar content and for
    the activities of selected serum enzymes. The levels of total plasma
    lipids and plasma cholesterol were slightly lower in the exposed
    group than in controls, but no differences were noted for blood
    sugar, plasma phospholipid, plasma lipoprotein, alpha-amylase,
    leucine aminopeptidase, or pseudocholinesterase. The duration of
    exposure before testing was not indicated (Rosner et al., 1973).

        In an investigation of the asthmagenic properties of sodium
    isononanoyl oxybenzene sulfonate, detergent industry workers were
    also tested with LAS. Three workers previously exposed to sodium
    isononanoyl oxybenzene sulfonate, three unexposed controls without
    asthma, and three controls with asthma were challenged with
    0.01-100 µg of LAS. No changes were seen after inhalation of LAS in
    any of the subjects; but sodium isononanoyl oxybenzene sulfonate
    induced asthmatic symptoms in the previously exposed workers and not
    in the control groups (Stenton et al., 1990).

    A8.2.5  Accidental or suicidal ingestion

        No symptoms were seen in four cases of accidental ingestion of
    unknown amounts of a household synthetic detergent containing LAS as
    the main component (Hironaga, 1979).

        A 32-year-old woman who had ingested 160 ml of a 21% aqueous
    solution of LAS with suicidal intent showed transient, slight mental
    confusion, vomiting, pharyngeal pain, hypotension, decreased plasma
    cholinesterase activity, and increased urinary urobilinogen, but all
    of these symptoms disappeared rapidly (Ichihara et al., 1967).

        In a review of 1 581 540 cases of human exposure to a wide range
    of chemicals reported by the United States Poison Control Centers in
    1989, 7983 people had been exposed to household automatic dishwasher
    preparations (alkali, anionic or nonionic, other or unknown) and 506
    had required treatment in a health facility; 8950 had been exposed
    to household cleansers, with 894 requiring treatment; 12 876 had
    been exposed to laundry preparations, with 1542 treated; and 621 had
    been exposed to industrial detergents (anionic, cationic, nonionic),
    with 321 cases requiring treatment. There were no deaths, and only
    12 of the treated cases were classified as 'major outcome'.
    Virtually all the reports involved accidental exposure. The
    compositions of the cleaning preparations, routes of exposure, and
    clinical descriptions were not provided (Litovitz et al., 1990).

    A9.  EFFECTS ON OTHER ORGANISMS IN THE LABORATORY AND THE FIELD

     Section summary

        LAS have been tested extensively, both in the laboratory and
    under field conditions, but the following aspects must be considered
    in interpreting test results. Comparison of the results of tests
    carried out on either mixtures of homologues of LAS or LAS of
    specified chain length is restricted, because the toxicity of LAS is
    influenced by the chain length, and homologues of lower chain length
    are less toxic than those with longer chains; furthermore, chain
    length was rarely specified in older studies. Studies of the effects
    of formulations of LAS on environmental biota are not included in
    this section.

        Organisms are not exposed to a constant concentration of LAS in
    water, owing to the high adsorptivity and biodegradability of LAS.
    As LAS are adsorbed on suspended solids or food particles, they have
    reduced bioavailability. The adsorption kinetics of LAS also depend
    on the chain length of the homologues. Studies of aquatic toxicity
    involving flow-through or static renewal (at least daily) should
    therefore be given more prominence than studies based on static
    conditions, although flow-through and static renewal cannot be used
    in (semi-) chronic studies of lower organisms, such as daphnia.
    Studies in which the actual concentration was measured should
    likewise be given more consideration than those that rely on nominal
    concentrations.

        The effects of LAS on the aquatic environment have been studied
    in short- and long-term studies in the laboratory and under more
    realistic conditions: micro- and mesocosm and field studies. In
    general, a decrease in alkyl chain length or a more internal
    position of the phenyl group is accompanied by a decrease in
    toxicity. Data on fish and daphnia indicate that a decrease in chain
    length of one unit (e.g. C12 to C11) is accompanied by an
    approximately 50% decrease in toxicity, but there is no linear
    relationship between chain length and toxicity. In aquatic
    microorganisms, the effects are strongly related to variables such
    as the type of test system and use of mixed cultures as opposed to
    individual species. EC50 values range from 0.5 mg/litre (single
    species) to > 1000 mg/litre.

        In freshwater fish, the acute LC50 values of C8-C15 LAS
    are  0.1-125 mg/litre. The chronic L(E)C50 values of LAS (C11.7 and
    not specified) in two species tested were 2.4 and 11 mg/litre, and
    NOECs ranging from 0.11 to 8.4 mg/litre have been reported for
    C11.2-C13 (or not specified). Marine fish appear to be more
    sensitive, with acute LC50 values for C11.7 (or not specified)
    in six species of 0.05-7 mg/litre, chronic LC50 values for LAS of
    unspecified chain length in two species of 0.01-1 mg/litre, and an
    NOEC for C12 in one species of < 0.02 mg/litre.

        Results in aquatic plants are also species dependent. In
    freshwater plants, the EC50 values for LAS (with chain lengths
    shown in parentheses) were 10-235 mg/litre for green algae
    (C10-C14), 5-56 mg/litre for blue algae (C11.1-C13),
    1.4-50 mg/litre for diatoms (C11.6-C13), and 2.7-4.9 mg/litre
    for macrophytes (C11.8). Marine algae appear to be even more
    sensitive. There is probably no linear relationship between chain
    length and toxicity to algae.

        The effects of LAS on freshwater algae have also been tested
    under realistic conditions in systems with various trophic levels,
    comprising enclosures in lakes (lower organisms),  model ecosystems
    (sediment: water systems), a river below and above a wastewater
    treatment plant outfall, and experimental streams. In general, C12
    LAS were used. Algae were more sensitive in summer, when the 3-h
    EC50 values with regard to photosynthesis were 0.2-8.1 mg/litre,
    whereas studies of model ecosystems showed no effects on the
    relative abundance of algal communities at 0.35 mg/litre. No effects
    were seen in these studies at 0.24-5 mg/litre, depending on the
    organism and parameter tested.

        In aquatic invertebrates, the acute L(E)C50 values were
    4.6-200 mg/litre for molluscs (either C13 or not specified),
    0.12-27 mg/litre for crustaceans (C11.2-C18 or not specified),
    1.7-16 mg/litre for worms (C11.8 or not specified), and
    1.4-270 mg/litre for insects (C10-C15). The chronic L(E)C50
    values were 2.2 mg/litre for insects (C11.8) and 1.1-2.3 mg/litre
    for crustaceans (C11.8-C13). The chronic NOEC for crustaceans,
    on the basis of lethality or reproduction, was 0.2-10 mg/litre
    (C11.8 or not specified). Marine invertebrates are more sensitive,
    with LC50 values of 1 to >100 mg/litre (almost all C12) and
    NOEC values of 0.025-0.4 mg/litre (chain lengths not specified).

        Biodegradation products and by-products of LAS are 10-100 times
    less toxic than the parent compound.

        Fewer data are available on the effects of LAS in the
    terrestrial environment. For the plant species tested, the NOEC
    values were < 10-20 mg/litre in nutrient solutions and 100 mg/kg
    (C10-C13) for growth of plants in soils. The 14-day LC50 for
    earthworms was > 1000 mg/kg.

        One study in which chickens were treated in the diet resulted in
    an NOEC based on egg quality of > 200 mg/kg.

    A9.1  Effect of chain length on the toxicity of linear
          alkylbenzene sulfonates

        The ecotoxicity of homologues of LAS varies according to the
    length of the alkyl chain and the position of the benzene ring on
    this chain. In general, homologues with longer chains are more

    ecotoxic than shorter ones, and ecotoxicity increases with the
    proximity of the benzene ring to the end of the chain. The results
    of studies on the effect of LAS chain length on acute toxicity to
    fish are presented in Table 23.

        The effect of chain length can also be seen on the basis of
    quantitative structure-activity relationships (Roberts, 1989, 1991)
    calculated from the octanol-water partition coefficients of
    homologues of LAS. The slope of the relationship varied from 0.64 to
    0.78; therefore, using an average slope of 0.70, it was calculated
    that a decrease in chain length from C12 to C11 reduced the
    aquatic toxicity of LAS by a factor of 2.4, with a corresponding
    decrease in the octanol-water partition coefficient of 0.54.

    
    Table 23.  Effect of the chain length of linear alkylbenzene sulfonates (LAS)
               on their acute toxicity to freshwater fish

                                                                                      
    Homologue   Fathead minnow    Goldfish       Guppy              Golden orfe
    of LAS      Pimephales        Carassius      Lebistes           Idus idus
                promelas          auratus        reticulatus        melanotus
                48-h LC50         6-h LC50       LC50 (mg/litre)c   96-h LC50
                (mg/litre)a       (mg/litre)b                       (mg/litre)d
                                                                                      

    C10            43.0              61.0             50               16.6
    C11            16.0              22.5                               6.5
    C12             4.7               8.5              5                2.6
    C13             0.4               3.3                               0.57
    C14             0.4                                1                0.26
    C16                               0.087            1                0.68
    C18                               0.38                             15
                                                                                      

    a From Kimerle & Swisher (1977)
    b From Gafa (1974)
    c From Borstlap (1967)
    d From Hirsch (1963)
    
    A9.2  Microorganisms

        No adverse effects were seen on the performance of
    laboratory-scale activated sludge units after addition of <
    20 mg/litre LAS. At 50 mg/litre, nitrification was decreased in
    extended aeration units that were treating synthetic sewage (Janicke
    & Niemitz, 1973). A bacterium similar to  Klebsiella pneumoniae
    isolated from sewage degraded LAS at a concentration of 10 ml/litre,
    but a concentration of 20 ml/litre inhibited the growth of the
    bacterium by 39% (Hong et al., 1984).

        The toxicity of microorganisms in activated sludge increases
    with the length of the alkyl chain up to approximately C12 and
    then decreases (Table 24), presumably because of decreased
    bioavailability (e.g. greater sorption of these higher chain
    lengths) (Verge et al., 1993).

    Table 24.  Results of tests for the inhibition of activated
               sludge by the sodium salt of linear alkylbenzene
               sulfonates (LAS)

                                                             

    LAS               Chain length   3-h EC50 (mg/litre)
                                                             

    Pure homologues      C10         1042-1200
                         C11         740-782
                         C12         500-723
                         C13         700-795
                         C14         900-1045
    Commercial
     formulations        C11         760
                         C11.6       550
                         C13         650
                                                             
    From Verge et al. (1993)

        A mixed bacterial culture was acclimatized to 10 mg/litre LAS  
    (C9-C14) and was then maintained in either river water, forest
    soil, or wastewater from a detergent plant, the concentration of LAS
    being increased every five days. At 20.8 and 46 mg/litre, no effect
    was reported on the specific growth rate of the bacteria; however,
    at 70 mg/litre, the growth rate was inhibited by 18%, and at
    95 mg/litre growth was almost zero. Concentrations of 186 and
    465 mg/litre LAS inhibited growth completely (Hrsak et al., 1981).

        The acute toxicity of LAS (C9-C14) in naturally occurring
    bacteria was studied in freshwater and seawater samples by measuring
    3H-thymidine incorporation. The EC50 values were 0.5-1.66 mg/litre
    for all samples. Toxicity was found to increase with an increasing
    relative abundance of longer carbon chains (Martinez et al., 1989).

    For bacteria collected from the Rhone River plume (an estuarine
    area) and exposed to LAS, the EC50, based on 3H-thymidine
    incorporation, was 11.9 mg/litre (Martinez et al., 1991).

        The 8-h EC50, based on specific growth rate, of  Pseudomonas
     fluorescens in solutions of C11.1 LAS under static conditions
    was 3200-5600 mg/litre (Canton & Slooff, 1982).

        The effect of C11.6 LAS on the structure and function of
    microbial communities was studied in a flow-through model ecosystem
    containing several trophic levels at concentrations of 0.5 or
    5 mg/litre. LAS had no effect on microbial structure at either dose
    level, but at 5 mg/litre it inhibited the degradation of both
    glucose and LAS. In an experiment in which LAS were supplied in
    sewage, neither microbial structure nor function was affected
    (Larson & Maki, 1982).

        The effects of LAS on the microbial activity of soils were
    studied on the basis of Fe[III] reduction. The no-effect-level was
    found to be 250 mg/kg; the EC50 was about 500 mg/kg in a strongly
    adsorbing soil and 33-55 mg/kg in a poorly adsorbing soil (Welp &
    Brummer, 1985).

        LAS at concentrations of 0.8-50 g/m2 had no effect on
    respiration of loamy soil, sandy soil, or sandy soil irrigated with
    wastewater for one or 14 days (Litz et al., 1987).

    A9.3  Aquatic organisms

    A9.3.1  Aquatic plants

    A9.3.1.1  Freshwater algae and cyanobacteria

        The 96-h EC50 values for C13 LAS on population growth were
    116 mg/litre for the green alga  Selenastrum capricornutum,
    5 mg/litre for the blue-green alga  Microcystis aeruginosa, and
    1.4 mg/litre for the diatom  Navicula pelliculosa. The EC50
    values for C12 LAS were 29 mg/litre for  Selenastrum and
    0.9 mg/litre for  Microcystis (Lewis & Hamm, 1986). The EC50 for
    C11.7 LAS on growth of  Selenastrum was reported to be 83
    mg/litre (Konno & Wakabayashi, 1987). The EC50 values for C11.6
    LAS were found to be 50-100 mg/litre for  Selenastrum,
    10-20 mg/litre for  Mycrocystis, and 20-50 mg/litre for the diatom
     Nitzschia fonticola (Yamane et al., 1984). The seven-day EC50
    for C12 LAS in the green alga  Chlorella pyrenoidosa, based on
    growth, was 10 mg/litre (Kondo et al., 1983).

        The 96-h EC50 values in algae grown in solutions of C11.1
    LAS under static conditions, measured as biomass, were
    32-56 mg/litre for  Microcystis aeruginosa and 18-32 mg/litre for
     Chlorella vulgaris (Canton & Slooff, 1982).

        A study of the toxicity of various formulations of LAS to the
    algae  Scenedesmus subspicatus and  Selenastrum capricornutum
    (Table 25) indicated that commercial mixtures are as or slightly
    less toxic than homologues. This finding may be due to a difference
    in the sensitivity of the two algae, since those tested with the
    homologues were of a different origin than those tested with
    commercial LAS (Verge et al., 1993).

    Table 25.  Results of tests for the toxicity of the sodium salt
               of linear alkylbenzene sulfonates (LAS) in algae

                                                                

    LAS               Chain length   72-h EC50 (mg/litre)
                                                                

    Pure homologues      C10             235
                         C11             118
                         C12              62
                         C13              33
                         C14              18
    Commercial
     formulations        C11              80
                         C11.6            80
                         C13              62
                                                                
    From Verge et al. (1993)

        LAS (chain length not specified) significantly reduced the
    growth of the green alga  Selenastrum capricornutum at a
    concentration of 40 mg/litre or more. A significant decrease in
    growth was also noted at 10 mg/litre, but no significant effect was
    observed at 20 or 30 mg/litre (Nyberg, 1988).

    A9.3.1.2  Marine algae

        Growth of Gymnodinium breve was reduced by 69% rafter nine days'
    exposure to C12 LAS (Kutt & Martin, 1977). These results were
    confirmed in a study in which C13 LAS were introduced at the
    bottom or surface of a water column: Exposure to LAS at
    concentrations > 0.025 mg/litre inhibited growth completely within
    two days (Hitchcock & Martin, 1977). These results suggest that
     Gymnodinium breve is more sensitive to the effects of LAS than
    other algae.

        For C11.7 LAS, the seven-day EC50 for growth and the two-day
    EC50 for ATP activity on the marine diatom  Thalassiosira
     pseudonana were both 10 mg/litre (Kondo et al., 1983).

        Exposure of the alga  Porhyra yezoensis, a standard test
    species in Japan, to LAS (C10-C14) under semi-static conditions
    gave a 10-day E50 (based on growth) of 0.56 mg/litre (Takita,
    1985).

    A9.3.1.3  Macrophytes

        The seven-day EC50 values for C11.8 LAS on the duckweed
    Lemna minor under flow-through conditions were 2.7 mg/litre for
    frond count, 3.6 mg/litre for dry weight, and 4.9 mg/litre for root
    length. The time-independent EC50 for growth rate and doubling
    time was 4.8 mg/litre (Bishop & Perry, 1981).

    A9.3.2  Aquatic invertebrates

    A9.3.2.1  Acute toxicity

        The acute toxicity of LAS to aquatic invertebrates is summarized
    in Tables 26 and 27. For marine invertebrates, the 96-h LC50
    values for C12 LAS range from 3 mg/litre for barnacles to >
    100 mg/litre for several other species (Table 26). Freshwater
    invertebrates show a range of 48-h LC50 values from 0.11 mg/litre
    (C16) for a daphnid to 270 mg/litre (C11.8) for an isopod (Table
    27). Several marine invertebrate species are more sensitivite to LAS
    at the larval stage than as adults (Table 26).

        Freshwater mussels  (Anodonta cygnea) were more sensitive to
    LAS during the reproductive period than during the non-reproductive
    period, the 96-h LC50 being reduced from 200 to 50 mg/litre
    (Bressan et al., 1989).

        Studies with  Daphnia magna revealed a correlation between
    chain length and toxicity. The acute toxicity (24-h and 48-h LC50)
    of LAS to  Daphnia magna increased with chain length between C10
    and C14 (Kimerle & Swisher, 1977) and with chain lengths between
    C10 and C16 (Maki & Bishop, 1979), although similar values were
    obtained for C16 and C18 homologues. No significant difference
    in sensitivity was seen between  Daphnia magna and  Daphnia pulex.
    A similar result was obtained with homologue mixtures (Martinez et
    al., 1989): toxicity was correlated with the homologues in which
    long chains were the most abundant.

        Partial biodegradation of LAS significantly reduces the specific
    toxicity (by unit weight) of the remaining LAS to  Daphnia magna.
    For example, LAS with a high relative molecular mass and a 48-h
    LC50 of 2 mg/litre had an LC50 of 30-40 mg/litre after 80-85%
    degradation (Kimerle & Swisher, 1977); the longer homologues and
    more terminal isomers, which are the most toxic, are therefore also
    the more readily biodegraded. Shorter carboxylates formed during the
    degradation of LAS were three to four orders of magnitude less toxic
    than LAS (Swisher et al., 1978). Other workers also found a

        Table 26.  Acute toxicity of linear alkylbenzene sulfonates (LAS) to estuarine and marine invertebrates
                                                                                                                                              

    Organism                    Size or     Static or    Temp.     Salinity    LAS chain    End-point    Concentration   Reference
                                age         flow         (°C)      (%)         length                    (mg/litre)a
                                                                                                                                              

    Sea squirt                  Larva       Static       20                    NS           6-h LC50     1               Renzoni (1974)
    (Ciona intestinalis)

    Common mussel                           Static       6-8       32-34       C12          96-h LC50    > 100           Swedmark et
    (Mytilus edulis)                        Static       15-17     32-34       C12          96-h LC50    50              al. (1971)

    Mussel                                  Staticr      18        35          NS           48-h LC50    39.8            Bressan et al.
    (Mytilus galloprovincialis) Adult                    18        35          NS           96-h LC50    1.66            (1989)

    Cockle                                  Static       6-8       32-34       C12          96-h LC50    5               Swedmark et
    (Cardium edule)             Juvenile    Static       15-17     32-34       C12          96-h LC50    5               al. (1971)

    Clam                                    Static       6-8       32-34       C12          96-h LC50    70
    (Mya arenaria)                          Static       15-17     32-34       C12          96-h LC50    < 25

    Scallop                                 Static       6-8       32-34       C12          96-h LC50    < 5
    (Pecten maximus)

    Scallop                                 Static       15-17     32-34       C12          96-h LC50    < 5
    Decapod                                 Static       15-17     32-34       C12          96-h LC50    50
    (Leander adspersus)         Intermoult  Static       6-8       32-34       C12          96-h LC50    50
                                Postmoult   Static       6-8       32-34       C12          96-h LC50    25
    Hermit crab                             Static       6-8       32-34       C12          96-h LC50    > 100
    (Eupagurus bernhardus)
                                                                                                                                              

    Table 26 (contd)
                                                                                                                                              

    Organism                    Size or     Static or    Temp.     Salinity    LAS chain    End-point    Concentration   Reference
                                age         flow         (°C)      (%)         length                    (mg/litre)a
                                                                                                                                              

    Spider crab                 Larva       Static       6-8       32-34       C12          96-h LC50    9
    (Hyas araneus)              Adult       Static       6-8       32-34       C12          96-h LC50    > 100

    Shore crab                              Static       6-8       32-34       C12          96-h LC50    > 100
    (Carcinus maenus)

    Barnacle                    Larva       Static       6-8       32-34       C12          96-h LC50    3
    (Balanus balanoides)        Adult       Static       6-8       32-34       C12          96-h LC50    50

    Brine shrimp                            Static       25                    C11-C13      24-h LC50    33              Price et al.
    (Artemia salina)                                                                                                     (1974)
                                                                                                                                              

    Static: water unchanged for duration of test; NS, not specified; staticr, static renewal: water changed every 12 h; flow, flow-through
    conditions: LAS concentration in water maintained continuously
    a Based on nominal concentration

    Table 27. Acute toxicity of linear alkylbenzene sulfonates (LAS) to freshwater invertebrates
                                                                                                                                              

    Organism                 Size or     Static or    Temp.    Hardness       pH          LAS chain    End-point    Concn        Reference
                             age         flow         (°C)     (mg/litre)a                length                    (mg/litre)
                                                                                                                                              

    Bivalve mollusc          11 cm       Staticr      18                      8.0         NS           96-h LC50    200b         Bressan et al.
    (Anodonta cygnea)                                 18                      8.0         NS           96-h LC50    50b,c        (1989)

    Bivalve mollusc          9 cm        Staticr      18                      8.0         NS           96-h LC50    182.5b
    (Unio elongatulus)

    Snail                                Static       21       62             7.3         av. C13      24-h LC50    4.6b         Dolan &
    (Gonobasis sp.)                                                                                                              Hendricks (1976)

    Snail (Physa integra)                Flow         15       41-47          7.5-7.7     NS           96-h LC50    9b           Arthur (1970)

    Amphipod (Gammarus                   Flow         15       41-47          7.5-7.7     NS           96-h LC50    7b
    pseudolimnaeus)

    Amphipod                 4.3 mm      Static       22       165            7.9-8.4     C11.8        48-h LC50    3.3b         Lewis &
    (Gammarus sp.)                                                                                                               Suprenant (1983)
    Campeloma decisum                    Flow         15       41-47          7.5-7.7     NS           96-h LC50    27b          Arthur (1970)

    Water flea               < 24 h      Static       20       25                         C11.7        24-h LC50    17           Wakabayashi
    (Daphnia magna)                                                                                                              et al. (1988)
                             < 24 h      Static       21       120            7.4         C10          48-h LC50    9.55d        Maki &
                                                                                                                                 Bishop (1979)
                                                                                                                                              

    Table 27 (contd)
                                                                                                                                              

    Organism                 Size or     Static or    Temp.    Hardness       pH          LAS chain    End-point    Concn        Reference
                             age         flow         (°C)     (mg/litre)a                length                    (mg/litre)
                                                                                                                                              

    Water flea (contd)       < 24 h      Static       21       120            7.4         C11          48-h LC50    1.15d
    (Daphnia magna)          < 24 h      Static       21       120            7.4         C12          48-h LC50    5.88-6.84d
                             < 24 h      Static       21       120            7.4         C13          48-h LC50    2.63d
                             < 24 h      Static       21       120            7.4         C14          48-h LC50    0.68-0.8d
                             < 24 h      Static       21       120            7.4         C16          48-h LC50    0.11-0.2d
                             < 24 h      Static       21       120            7.4         C18          48-h LC50    0.12d
                             < 18 h      Static                                           C13.3        48-h LC50    2.3b         Kimerle &
                             < 18 h      Static                                           C10          48-h LC50    12.3b        Swisher (1977)
                             < 18 h      Static                                           C11          48-h LC50    5.7b
                             < 18 h      Static                                           C12          48-h LC50    3.5b
                             < 18 h      Static                                           C13          48-h LC50    2.0b
                             < 18 h      Static                                           C14          48-h LC50    0.7b
                             < 24 h      Static       19                                  C11.2        48-h LC50    18-32b       Canton &
                                                                                                                                 Slooff (1982)
                             < 24 h      Static       21       131            7.4-7.8     C11.8        48-h LC50    4.8d         Lewis (1983)
                             < 24 h      Static       22       165            7.9-8.4     C11.8        48-h LC50    1.8-5.6b     Lewis &
                                                                                                                                 Suprenant
                                                                                                                                 (1983)
                             < 24 h      Static       21       295-310        7.3-8.4     C11.8        48-h LC50    3.6-4.7b     Taylor (1985)
                             < 48 h      Static       22       241            7.8         C11          48-h EC50    2.2b,e       Barera &
                                                                                                                                 Adams (1983)
                                         Flow                                             C11.8        48-h LC50    4.4d         Bishop &
                                                                                                                                 Perry (1981)
                             < 12 h      Flow         21       120            7.4         C11.8        96-h LC50    23.94d       Maki (1979a)
                             < 12 h      Flow         21       120            7.4         C13          48-h LC50    2.19d
                                                                                                                                              

    Table 27 (contd)
                                                                                                                                              

    Organism                 Size or     Static or    Temp.    Hardness       pH          LAS chain    End-point    Concn        Reference
                             age         flow         (°C)     (mg/litre)a                length                    (mg/litre)
                                                                                                                                              

    Water flea               < 24 h      Static       20       25                         C11.7        24-h LC50    18           Wakabayashi
    (Daphnia pulex)                                                                                                              et al. (1988)
                             < 24 h      Static       21       120            7.4         C12          48-h LC50    8.62d        Maki &
                                                                                                                                 Bishop (1979)
                             < 24 h      Static       21       120            7.4         C14          48-h LC50    0.59d
                             < 24 h      Static       21       120            7.4         C16          48-h LC50    0.15d

    Oligochaete (Dero sp.)   6.0 mm      Static       22       165            7.9-8.4     C11.8        48-h LC50    1.7b         Lewis &
                                                                                                                                 Suprenant
                                                                                                                                 (1983)
    Roundworm (nematode)     0.3 mm      Static       22       165            7.9-8.4     C11.8        48-h LC50    1.7b
    (Rhabditis sp.)

    Flatworm                 3.4 mm      Static       22       165            7.9-8.4     C11.8        48-h LC50    1.8b
    (Dugesia sp.)
    Branchiura sowerbyi                  Staticr      10       25             8.0         NS           96-h LC50    10.8b,f      Bressan et al.
                                                      10       25             8.0         NS           96-h LC50    4.4b         (1989)

    Worm (Limnodrilus                    Staticr      10       25             8.0         NS           96-h LC50    7.8b,f
    hoffmeisteri)                                     10       25             8.0         NS           96-h LC50    2.0b

    Isopod (Asellus sp.)     5.3 mm      Static       22       165            7.9-8.4     C11.8        48-h LC50    1.8b         Lewis &
                                                                                                                                 Suprenant
                                                                                                                                 (1983)
                                                                                                                                              

    Table 27 (contd)
                                                                                                                                              

    Organism                 Size or     Static or    Temp.    Hardness       pH          LAS chain    End-point    Concn        Reference
                             age         flow         (°C)     (mg/litre)a                length                    (mg/litre)
                                                                                                                                              

    Midge (Chironomus        Larva       Flow         22       150            7.8-8.4     C11.8        72-h LC50    2.2d         Pittinger
    riparius)                                                                                                                    et al. (1989)
    Midge (Paratanytarsus    3.6 mm      Static        2       165            7.9-8.4     C11.8        48-h LC50    1.8d         Lewis &
    parthenogenica)                                                                                                              Suprenant
                                                                                                                                 (1983)

    Mosquito (Aedes          Larva       Static                                           C10-13       24-h LC50    6b           Van Emden et
    aegypti)                 Larva       Static                                           C10-15       24-h LC50    2b           al. (1974)
                             3-4 d       Static       23                                  C11.1        48-h LC50    56-100b      Canton &
                                                                                                                                 Slooff (1982)

    Mayfly                   Larva       Static       10       53             7.5-7.8     C11.6        24-h LC50    13.6b        Dolan et al.
    (Isonychia sp.)          Larva       Static       10       53             7.5-7.8     C11.6        48-h LC50    10.4b        (1974)
                             Larva       Static       10       53             7.5-7.8     C11.6        96-h LC50    5.33b
                             Larva       Static       10       53             7.5-7.8     C13.1        24-h LC50    4.19b
                             Larva       Static       10       53             7.5-7.8     C11.6        48-h LC50    12.47b
                             Larva       Static       10       53             7.5-7.8     C11.6        96-h LC50    1.36b
                                                                                                                                              

    Staticr, static renewal: water changed every 12 h; NS, not specified; flow, flow-through conditions: LAS concentration in water maintained
    continuously; static: water unchanged for duration of test
    a mg/litre CaCO3
    b Based on nominal concentration
    c Test performed during the reproductive period
    d Based on measured concentrations
    e Based on immobilization
    f Organism exposed in the presence of sediment

        reduction in the acute toxicity of LAS to  Daphnia magna during
    primary degradation (Gard-Terech & Palla, 1986).

        Increasing hardness also increased the acute toxicity (48-h
    LC50) of C11.8 LAS from a nominal concentration of 7.1 mg/litre
    at 25 mg/litre CaCO3 to 4.0 mg/litre at 350 mg/litre CaCO3;
    however, significant additional physiological stress was induced if
    the hardness of the culture water was significantly different from
    that of the test water. Pre-exposure to 0.4 mg/litre LAS (one-tenth
    of the 48-h LC50) for up to seven generations (14 weeks) had no
    significant effect on the susceptibility of daphnids to acute
    exposures (Maki & Bishop, 1979).

         Loading density, ranging from 10 daphnids per 20 ml to 20
    daphnids per 1000 ml, had no significant effect on the acute
    toxicity of C11.8 LAS for  Daphnia magna (Lewis, 1983). Daphnids
    fed a diet containing Selenastrum  had a significant, twofold
    decrease in acute toxicity due to C11.8 LAS in comparison with
    unfed daphnids (Taylor, 1985). The presence of sediment reduced the
    acute toxicity of LAS to the oligochaete worms  Branchiura sowerbyi
    and  Limnodrilus hoffmeisteri. The NOEC and LOEC for  B. sowerbyi
    were 2.5 times higher in the presence of sediment, and those for
     L. hoffmeisteri were 4-4.5 times higher (Bressan et al., 1989; see
    also Table 27).

        The 96-h EC50 values for duplicate studies of the effect of
    LAS on attachment of the podia of the sea urchin Hemicentrotus
    pulcherrimus were 3.7 and 3.8 mg/litre (Lee & Park, 1984).

        The data from other studies (Lal et al., 1983, 1984a,b; Misra et
    al., 1984; Chattopadhyay & Konar, 1985; Misra et al., 1985; Devi &
    Devi, 1986; Misra et al., 1987, 1989a,b, 1991) could not be
    adequately interpreted because of deficiencies in the data or
    method, including inadequate characterization of the test material
    with regard to chain-length distribution and use of test material in
    an acidified form. The range of values for toxicity reported in
    these studies was 10-100 times greater than that in numerous studies
    of the same or similar species, and the high values have not been
    verified by these or other researchers. As the toxic effects
    reported are not considered to be representative of those of
    commercial LAS, the data were not used in evaluating the
    environmental effects of LAS.

        A 72-h LC50 of 2.2 mg/litre was reported for C11.8 LAS in
    newly hatched larvae of the midge  (Chironomus riparius) (Pittinger
    et al., 1989).

    A9.3.2.2  Short-term and long-term toxicity

        The 21-day LC50 for the water flea  (Daphnia magna) was
    18 mg/litre, and the NOEC, based on survival, was 10 mg/litre under
    static renewal conditions. The 21-day EC50, based on reproduction,
    was estimated to be > 10 mg/litre (Canton & Slooff, 1982). The
    14-day EC50 for C12 LAS in  Daphnia carinata, based on
    reproduction, was 16.8 mg/litre (Hattori et al., 1984).

        Diet had a significant effect on the sensitivity of  Daphnia
     magna to the chronic toxicity of C11.8 LAS. The NOEC values
    showed a threefold variation of 1.2-3.2 mg/litre and the 21-day
    LC50 values a twofold variation of 2.2-4.7 mg/litre with diet. A
    threefold variation in toxicity in tests in  Daphnia is not,
    however, unusual (Taylor, 1985).

        Under continuous-flow conditions, a 21-day LC50 value of
    1.67 mg/litre was found for daphnids  (Daphnia magna) exposed to
    C11.8 LAS and 1.17 mg/litre for those exposed to C13 LAS. The
    EC50 values for reproductive toxicity were 1.5 mg/litre for
    C11.8 LAS and 11.1 mg/litre for C13 with respect to total young
    production, 2.3 mg/litre for C11.8 and 1.4.1 mg/litre for C13
    for average brood size, and 2.31 mg/litre for C11.8 and
    1.29 mg/litre for C13 for percentage of days on which reproduction
    occurred (Maki, 1979a).

         Campeloma decisum, Gammarus pseudolimnaeus, and  Physa integra
    were exposed to LAS at concentrations of 0.2-4.4 mg/litre for six
    weeks; amphipods were exposed for a further 15 weeks. Survival,
    growth, reproduction, feeding, and mobility were studied. The
    maximum acceptable concentrations of LAS were found to be
    0.2-0.4 mg/litre for Gammarus and 0.4-1.0 mg/litre for  Campeloma;
     P. integra were not significantly affected (Arthur, 1970).

        Fertilized eggs of sea urchins  (Paracentrotus lividus) were
    treated with LAS at concentrations of 0-0.5 mg/litre for 40 days.
    The pattern of embryonic development was unaffected, but the mean
    length of the somatic rods of the echinoplutei were reduced
    successively with increasing LAS concentrations. A significant
    reduction in growth occurred at doses between 0.35 and 0.4 mg/litre;
    above 0.45 mg/litre, alterations in skeletal development were
    induced (Bressan et al., 1989).

        Oligochaete worms  (B. sowerbyi) were maintained in LAS at a
    concentration of 0.5, 2.5, or 5.0 mg/litre for up to 140 days in the
    presence of sediment. Exposed worms laid fewer cocoons and eggs, but
    the worms exposed to 5 mg/litre were the least affected. The
    percentage of degenerated cocoons, the percentage of worms hatching,
    the mean number of eggs per cocoon, and the mean embryonic
    development time were all unaffected by treatment. Worms exposed via
    the sediment only were not affected (Bressan et al., 1989).

        Growth of mussels  (Mytilus galloprovincialis) exposed to LAS
    at a concentration of 0.25 or 0.5 mg/litre for 220 days,  expressed
    as mean length of the major axis of the shell, was significantly
    slowed ( p < 0.001). The mean (± SE) increments in growth were:
    control, 3.11 ± 0.34;  0.25 mg/litre, 1.71 ± 0.15;  0.5 mg/litre,
    1.48 ± 0.16 (Bressan et al., 1989).

        Eggs of the common mussel,  M. edulis, were exposed from the
    time of fertilization for 240 h. Fertility was decreased at the
    lowest concentration of 0.05 mg/litre and fertilization did not take
    place at concentrations in excess of 1 mg/litre. LAS at
    concentrations > 0.3 mg/litre inhibited the development of mussel
    larvae by delaying the transitory stages of larval development.
    Reduced growth rates were observed at concentrations > 0.1 mg/litre
    (Granmo, 1972).

        Newly fertilized eggs of American oysters  (Crassostrea
     virginica) were exposed to LAS (chain length not specified, but
    likely to be C13) for 48 h. The percentage of eggs that developed
    normally was significantly reduced at concentrations greater than
    0.025 mg/litre. The percentage survival of oyster larvae hatched in
    'clean' water and exposed to LAS at a concentration of 1 mg/litre
    for 10 days was significantly decreased, and growth (mean length)
    was significantly reduced at 0.5 mg/litre (Calabrese & Davis, 1967).

        Embryos of sea urchins  (P. lividus) were exposed to LAS at
    concentrations of 0.25-0.5 mg/litre from the time of fertilization
    for 40 h. At concentrations > 0.45 mg/litre, skeletal development
    was totally inhibited; a significant decrease was observed at
    0.3 mg/litre. The effect of LAS was found to be maximal at the end
    of gastrulation when calcium uptake is high (Bressan et al., 1991).

        The effects of LAS were studied on the eggs and sperm of the sea
    squirt  Ciona intestinalis. Fertility and hatchability were
    markedly reduced at 0.1 mg/litre when eggs and sperm were exposed
    for the entire developmental period; however, if they were exposed
    only before fertilization, fertility and hatchability were slightly
    reduced at 0.1 mg/litre but markedly at 1 mg/litre. Male gametes
    appeared to be particularly sensitive to the toxic effects of LAS
    (Renzoni, 1974).

        Two marine benthic filter feeders, the sea squirts  Botryllus
     schlosseri and  Botrylloides leachi were exposed at different
    periods of development to LAS. When larvae were exposed from
    spawning for 6 h, the incidence of abnormal metamorphosis was
    significantly increased at 1 mg/litre LAS for  Botryllus and 2
    mg/litre for  Botrylloides. The frequency of spontaneously settled
    larvae of both species also increased with exposure to LAS and
    seemed to be a selective effect of LAS. The frequency was
    significantly different from controls at 1 and 3 mg/litre for the
    two species, respectively. In a second experiment, young colonies

    were exposed to LAS for 15 days immediately after discharge by the
    parental colony. Growth rates were significantly decreased at
    0.5 mg/litre for  Botryllus and at 0.25 mg/litre for  Botrylloides.
    When colonies were exposed from the end of metamorphosis, their
    growth rates were similarly affected, but the mortality rate was
    significantly lower. The effects of LAS thus appear to be exerted
    mainly on the pelagic phase of the life cycle (Marin et al., 1991).

        No significant reduction in egg hatching of midges  (Chironomus
     riparius) was seen at the highest concentration of C11.8 LAS
    tested (18.9 mg/litre), but newly hatched larvae were more
    sensitive, with a 72-h LC50 of 2.2 mg/litre. In bioassays of part
    of the life cycle in a sediment and water system, the percentages of
    winged adults emerging were monitored after continuous exposure of
    larvae and pupae. The NOEC for sediment containing LAS was 319 mg/kg
    (dry weight). In the absence of sediment, the NOEC was
    2.40 mg/litre. Both tests were conducted for about 20 days
    (Pittinger et al., 1989).

    A9.3.2.3  Biochemical and physiological effects

        Juvenile mussels  (M. galloprovincialis) were exposed to LAS at
    a concentration of 0.25 or 0.5 mg/litre for 220 days. Oxygen uptake
    and the retention rate of neutral red (a measure of filtration rate)
    were significantly decreased, but no effect was detected on nitrogen
    excretion (measured as ammonia). When the experiment was repeated
    over a seven-day period at a concentration of LAS of 1 or
    1.5 mg/litre, no significant effect was seen on nitrogen metabolism
    and the results for oxygen uptake were inconclusive. The filtration
    rate was again significantly reduced when compared with that in
    control mussels (Bressan et al., 1989).

        The 48-h LC50 for lugworms  (Arenicola marina) exposed to LAS
    was calculated to be 12.5 mg/litre (95% confidence interval,
    8.6-18.2). When tissues from a lugworm exposed to a concentration
    close to that of the LC50 were examined for changes in morphology
    by both light and electron microscopy, serious damage was reported
    in the caudal epidermis, epidermic receptors, and gills; no effect
    was reported in the thoracic epidermis or the intestine. In the
    caudal epidermis, LAS destroyed the papillae, disrupting the
    internal structure, occasionally displacing the musculature below
    the papillae and thus giving it direct contact with seawater.
    Deciliation of the epidermic receptors was also reported. These
    effects were considered to indicate that the physiological response
    of damaged epidermic receptors was reduced or blocked by exposure to
    LAS. Changes in the morphology of the gills included destruction of
    the epithelium and blood vessels, causing complete solubilization of
    branch apexes, and development of holes at the base of the gills
    (Conti, 1987).

    A9.3.3  Fish

    A9.3.3.1 Acute toxicity

        The acute toxicity of LAS to fish is summarized in Tables 28 and
    29. Only a few studies were available on marine fish, providing two
    96-h LC50 values, 1 and 1.5 mg/litre LAS. Tests in various species
    of freshwater fish gave a wide range of LC50 values: the 48-h
    values ranged from 0.2 mg/litre for brown trout  (Salmo trutta) to
    125 mg/litre for the golden orfe  (Idus idus memanotus), and the
    96-h values ranged from 0.1 mg/litre for brown trout to 23 mg/litre
    for white tilapia  (Tilapia melanopleura).

        The acute toxicity tended to increase with increasing carbon
    chain length. Thus, C14 LAS were more acutely toxic to bluegill
     (Lepomis macrochirus) than C12 compounds (Swisher et al., 1964);
    the acute toxicity of LAS to the golden orfe increased with chain
    length from C8 to C15 but decreased at C16 (Hirsch, 1963).;
    and a similar trend was found for fathead minnows  (Pimephalus
     promelas) exposed to LAS with chain lengths of C10 to C14
    (Kimerle & Swisher, 1977).

        The 96-h LC50 values in bluegill (Lepomis macrochirus) were
    0.64  mg/litre for C14 and 3 mg/litre for C12 LAS but
    75 mg/litre for the intermediate degradation product,
    sulfophenylundecanoic acid disodium salt (Swisher et al., 1964).
    Biodegradation of LAS with a high relative molecular mass
    progressively shifted the homologue distribution in favour of
    shorter chain lengths and reduced the acute toxicity of the compound
    to bluegill (Dolan & Hendricks, 1976). Similar findings were
    reported for fathead minnow (Swisher et al., 1978), goldfish
     (Carassius auratus) (Divo & Cardini, 1980) and zebra fish
     (Brachydanio rerio) (Gard-Terech & Palla, 1986).

        In rainbow trout  (Oncorhynchus mykissi), addition of LAS
    (C10-C15) to activated sludge plant effluent increased the
    nominal 96-h LC50 from 0.36 to 29.5 mg/litre (Brown et al., 1978).
    No deaths were observed among bluegill exposed for 4-11 days to
    effluent from continuous-flow activated sludge units fed
    100 mg/litre LAS (Swisher et al., 1964).

        Water hardness was found to be the most significant
    environmental factor in the acute toxicity of LAS to bluegill,
    increasing with the level of hardness. At a water hardness of
    15 mg/litre CaCO3, the mean LC50 was 4.25 mg/litre; at
    290 mg/litre CaCO3, the LC50 was reduced to 2.85 mg/litre
    (Hokanson & Smith, 1971). Similarly, when water hardness was
    increased from 0 to 500 mg/litre CaCO3, the LC50 for C18 LAS
    in goldfish was reduced from 15 to 5.7 mg/litre (Gafa, 1974).
    Exposure of the freshwater bleeker  (Puntius gonionotus) to LAS
    gave 96-h LC50 values of 13.6 mg/litre at a water hardness of

    50 mg/litre CaCO3, 11.8 mg/litre at 110 mg/litre CaCO3, and
    11.4 mg/litre at 260 mg/litre CaCO3 (Eyanoer et al., 1985).

        The toxicity of C11.7 LAS to the medaka  (Oryzias latipes)
    increased with increasing salinity, but the effect was less
    pronounced than that of water hardness (Wakabayashi & Onizuka,
    1986).

        Temperature was reported to have no significant effect on the
    acute toxicity of LAS (Hokanson & Smith, 1971), but in another study
    increasing the water temperature from 28 to 35°C marginally
    decreased the 96-h LC50 for the bleeker, from 11.8 to
    11.5 mg/litre (Eyanoer et al., 1985).

        A reduction in the dissolved oxygen concentration from 7.5 to
    1.9 mg/litre reduced the 24-h LC50 in bluegill from 2.2 to
    0.2 mg/litre. When the fish were first acclimatized to reduced
    oxygen levels, the effect was less pronounced (Hokanson & Smith,
    1971).

        No significant effect on the acute toxicity of LAS to bluegill
    was observed after a bentonite suspension was added to water at
    concentrations of 0, 50, or 200 mg/litre (Hokanson & Smith, 1971).
    Addition of gluten, however, reduced the 24-h and 48-h acute
    toxicity of LAS to both himedaka  (Oryzias latipes) and cobalt
    suzume  (Chrysiptera hollisi) (Iimori & Takita, 1979).

    A9.3.3.2  Chronic toxicity

        Exposure of the eggs of fathead minnows (Pimephales promelas) to
    LAS from laying until all surviving eggs had hatched under
    flow-through conditions gave a nine-day LC50 of 2.4 mg/litre,
    which would result in an LC50 of 3.4 mg/litre after 24 h of
    exposure (Pickering, 1966).

        Eggs of cod  (Gadus morhua) were exposed to LAS at a
    concentration of 0.005, 0.02, 0.05, or 0.1 mg/litre from
    fertilization until hatching under flow-through conditions. There
    were no significant effects at 0.005 mg/litre. At a concentration of
    0.02 mg/litre, only 42% of the embryos completely developed into
    larvae, and there was an increased occurrence of tail malformations
    in comparison with controls. At 0.05 mg/litre, few eggs developed to
    embryos. No eggs developed to the blastula stage at a concentration
    of 0.1 mg/litre. In a repetition of the test at 0.05 mg/litre, fewer
    eggs and larvae died, but there was an increased frequency of
    abnormal embryos and inactive and crippled larvae (Swedmark &
    Granmo, 1981).

        Eggs, larvae, and immature adult fathead minnows  (Pimephales
     promelas) were exposed to LAS at a concentration of 0.34, 0.63,
    1.2, or 2.7 mg/litre for up to four months. No significant effect
    was observed on the number of spawnings, the total number of eggs
    produced, the mean number of spawnings per female, the mean number
    of eggs per spawning, or the percentage hatchability; however, the
    two highest concentrations significantly reduced the survival of fry
    (Pickering & Thatcher, 1970).

        The effects of C11.8 and C13 LAS on the number of females,
    the number of spawnings, total number of eggs produced, and number
    of eggs per female were also studied in the fathead minnow over a
    period of one year. As C11.8 LAS had no significant effect on
    these parameters at a concentration of 1.09 mg/litre and a water
    hardness of 120 mg/litre CaCO3, the NOEC was 0.9 mg/litre; C13
    LAS were more toxic, and the NOEC was 0.15 mg/litre. At a lower
    water hardness (39 mg/litre), however, survival of larvae was
    impaired at 0.74 mg/litre (Maki, 1979a). NOECs in the fathead minnow
    in life-cycle and embryo-larval tests were dependent on mean alkyl
    chain length: 5.1-8.4 mg/litre for C11.2, 0.48 mg/litre for
    C11.7, and 0.11-0.25 mg/litre for C13.3 (Holman & Macek, 1980).

        The LC50 value of LAS in the eggs of carp  (Cyprinus carpio)
    exposed from spawning to hatching was 11 mg/litre. In determinations
    of the sensitivity of eggs at different stages of development after
    spawning, the 24-h LC50 values were 15 mg/litre for eggs exposed
    between 2 and 26 h, 25 mg/litre for exposure between 26 and 50 h,
    and 32 mg/litre for exposure between 50 h and hatching (Kikuchi et
    al., 1976).

        Bluegill  (Lepomis macrochirus) were exposed to LAS from
    fertilization to yolk-sac resorption at a concentration of 1.8, 3.5,
    4.6, or 5.5 mg/litre. The lowest concentrations did not affect
    hatchability or survival. Survival among those exposed to
    3.5 mg/litre which hatched successfully was significantly reduced
    within two days of hatching, and 95% were dead by the end of the
    experiment. Eggs exposed to 4.6 or 5.5 mg/litre failed to hatch
    (Hokanson & Smith, 1971).

        The NOEC of LAS in guppies  (Poecilia reticulata), based on
    mortality, behaviour, and growth over 28 days, was 3.2 mg/litre
    (Canton & Slooff, 1982).

        Studies of the short- and long-term toxicity of LAS to
    freshwater and marine fish are summarized in Tables 28 and 29.

    A9.3.3.3  Biochemical and physiological effects

        The main injury to the gills of catfish  (Heteropneustes
     fossilis) exposed to LAS at 1 or 2.5 mg/litre was progressive
    separation of the lamellae from their vascular components.

        Table 28.  Toxicity of linear alkylbenzene sulfonates (LAS) to freshwater fish
                                                                                                                                              

    Organism                 Size or     Static or    Temp.    Hardness       pH          LAS chain    End-point    Concn        Reference
                             age         flow         (°C)     (mg/litre)a                length                    (mg/litre)
                                                                                                                                              

    Brown trout                          Flow         15       26-30                      NS           48-h LC50    5.3          Reiff et al.
    (Salmo trutta)                       Flow         15       26-30                      NS           96-h LC50    4.6          (1979)
                                         Flow         15       26-30                      NS           48-h LC50    2.3
                                         Flow         15       26-30                      NS           96-h LC50    1.4
                                         Flow         15       26-30                      NS           48-h LC50    0.4
                                         Flow         15       26-30                      NS           96-h LC50    0.4
                                         Flow         15       250                        NS           48-h LC50    2
                                         Flow         15       250                        NS           96-h LC50    0.9
                                         Flow         15       250                        NS           48-h LC50    0.7-0.9
                                         Flow         15       250                        C10-C15      48-h LC50    0.2
                                         Flow         15       250                        C10-C15      96-h LC50    0.1

    Masu trout               2 mo        Staticr      8.5-9.6  30                         C11.7        96-h LC50    4.4          Wakabayashi et
    (Oncorhynchus masou)                                                                                                         al. (1984)

    Rainbow trout                        Flow         15       250                        C12.6        96-h LC50    0.36b        Brown et al.
    (Oncorhynchus mykiss)                                                                                                        (1978)
                             40 d        Staticr      8.8-10.9 25                         C11.7        96-h LC50    4.7          Wakabayashi et
                                                                                                                                 al. (1984)
                             4 d         Staticr      10       25                         C11.7        96-h LC50    2.1          Wakabayashi &
                             19 d        Staticr      10       25                         C11.7        96-h LC50    3.4          Onizuka (1986)

    Goldfish                             Static       20                                  C16          6-h LC50     61           Gafa (1974)
    (Carassius auratus)                  Static       20                                  C17          6-h LC50     22.5
                                         Static       20                                  C18          6-h LC50     8.5
                                                                                                                                              

    Table 28 (contd)
                                                                                                                                              

    Organism                 Size or     Static or    Temp.    Hardness       pH          LAS chain    End-point    Concn        Reference
                             age         flow         (°C)     (mg/litre)a                length                    (mg/litre)
                                                                                                                                              

    Goldfish (contd)                     Static       20                                  C19          6-h LC50     3.3
    (Carassius auratus)                  Static       20                                  C16-C19      6-h LC50     7.6
                                         Static       20                                  C16-C19      6-h LC50     10
                                         Static       20                                  C16-C19      6-h LC50     12.2
                                         Static       20       100                        NS           6-h LC50     8.2          Reiff et al. 
                                         Static       20       100                        NS           6-h LC50     7            (1979)
                                         Static       20       100                        NS           6-h LC50     4.3
                             3.1-6.0     Flow         20-23    45-96          7.1-9.3                  24-h LC50    7.6          Tsai & McKee
                             cm          Flow         20-23    45-96          7.1-9.3                  48-h LC50    7.5          (1978)
                                         Flow         20-23    45-96          7.1-9.3                  72-h LC50    7.0
                                         Flow         20-23    45-96          7.1-9.3                  96-h LC50    6.2

    Bluegill sunfish         1.6 g       Static       23       76             7.5         av. C13      48-h LC50    0.72b        Dolan &
    (Lepomis macrochirus)    1.6 g       Static       23       76             7.5         av. C13      96-h LC50    0.72b        Hendricks
                                                                                                                                 (1976)
                                         Flow         23       50             7.5         av. C13      96-h LC50    4c           Thatcher &
                                                                                                                                 Santner (1967)
                             Finger      Static       25       15                         C11.2        48-h LC50    4.0-4.5b     Hokanson &
                             Finger      Static       25       290                        C11.2        48-h LC50    2.8-2.9b     Smith (1971)
                                         Flow                                             C11.8        96-h LC50    1.7c         Bishop & Perry
                                                                                                                                 (1981)

    Fathead minnow                       Static                                           C13.3        48-h LC50    1.7b         Kimerle &
    (Pimephales promelas)                Static                                           C10          48-h LC50    43b          Swisher (1977)
                                         Static                                           C11          48-h LC50    16b
                                                                                                                                              

    Table 28 (contd)
                                                                                                                                              

    Organism                 Size or     Static or    Temp.    Hardness       pH          LAS chain    End-point    Concn        Reference
                             age         flow         (°C)     (mg/litre)a                length                    (mg/litre)
                                                                                                                                              

    Fathead minnow (contd)               Static                                           C12          48-h LC50    4.7b
                                         Static                                           C14          48-h LC50    0.4b
                             2-3 mo      Static                40                         C11.2        96-h LC50    12.3c        Holman & Macek
                             2-3 mo      Static                40                         C11.7        96-h LC50    4.1c         (1980)
                             2-3 mo      Static                40                         C13.3        96-h LC50    0.86
                                         Static       25                                               48-h LC50    4.6          Pickering & 
                                         Static       25                                               96-h LC50    5.0          Thatcher (1970)
                                         Flow         15       43             7.2-7.9                  96-h LC50    3.4          McKim et al.
                                                                                                                                 (1975)
                                         Flow         23       50             7.5                      96-h LC50    4.2          Thatcher &
                                                                                                                                 Santner (1967)
                                         Flow         25                                               96-h LC50    4.2-4.5      Pickering &
                                                                                                                                 Thatcher (1970)
                             2.5 cm      Flow         18       116            7.9         C12          96-h LC50    3.5          Solon et al.
                                                                                                                                 (1969)

    Harlequin fish                       Flow         20       20                         NS           48-h LC50    7.6          Reiff et al. 
    (Rasbora heteromorpha)               Flow         20       20                         NS           96-h LC50    6.1          (1979)
                                         Flow         20       20                         NS           48-h LC50    5.1
                                         Flow         20       20                         NS           96-h LC50    4.6
                                         Flow         20       20                         C10-C15      48-h LC50    0.9
                                         Flow         20       20                         NS           96-h LC50    0.7
    Carp (Cyprinus carpio)   4.4  mg     Static       22       25             7           C11.7        12-h LC50    5.6          Kikuchi et al.
                                         Static       22       25             7           C11.7        48-h LC50    5.6          (1976)
                                                                                                                                              

    Table 28 (contd)
                                                                                                                                              

    Organism                 Size or     Static or    Temp.    Hardness       pH          LAS chain    End-point    Concn        Reference
                             age         flow         (°C)     (mg/litre)a                length                    (mg/litre)
                                                                                                                                              

    Carp (contd)             3.5-5.5     Static       21                      7.5-7.8     NS           48-h LC50    6.8          Lopez-Zavala
                             cm          Static       21                      7.5-7.8     NS           96-h LC50    5.0          et al. (1975)
                             7 d         Staticr      22       25             7.0         C11.7        48-h LC50    5.6          Arima et al.
                             6 mo        Staticr      22       25             6.5-7.1     C11.7        48-h LC50    10           (1981)
                             50 d        Staticr      21       75                         C11.7        96-h LC50    4.4          Wakabayashi et
                                                                                                                                 al. (1984)
                             2 d         Staticr      20       25                         C11.7        96-h LC50    4.6          Wakabayashi &
                             15 d        Staticr      20       25                         C11.7        96-h LC50    2.6          Onizuka (1986)
    White tilapia            5-7 cm      Static       21                      7.5-7.8     NS           48-h LC50    26           Lopez-Zavala
    (Tilapia melanopleura)   5-7 cm      Static       21                      7.5-7.8     NS           96-h LC50    23           et al. (1975)

    Guppy                    3-4 wk      Staticr      23                                  C8-C14       96-h LC50    5.6-10       Canton & Slooff
    (Poecilia reticulata)                                                                                                        (1982)

    Northern pike                        Flow         15       43             7.2-7.9                  96-h LC50    3.7          McKim et al.
    (Esox lucius)                                                                                                                (1975)

    White sucker                         Flow         15       43             7.2-7.9                  96-h LC50    4            McKim et al.
    (Catostomus commersoni)                                                                                                      (1975)

    Golden orfe                          Static       18-20                               C8           48-h LC50    125          Hirsch (1963)
    (Idus idus melanotus)                Static       18-20                               C9           48-h LC50    88
                                         Static       18-20                               C10          48-h LC50    16.6
                                                                                                                                              

    Table 28 (contd)
                                                                                                                                              

    Organism                 Size or     Static or    Temp.    Hardness       pH          LAS chain    End-point    Concn        Reference
                             age         flow         (°C)     (mg/litre)a                length                    (mg/litre)
                                                                                                                                              

    Golden orfe (contd)                  Static       18-20                               C11          48-h LC50    6.6
                                         Static       18-20                               C12          48-h LC50    2.6
                                         Static       18-20                               C13          48-h LC50    0.57
                                         Static       18-20                               C15          48-h LC50    0.23
                                         Static       18-20                               C16          48-h LC50    0.68
                             1.2-1.8 g   Static       20                                  NS           48-h LC50    3.94         Mann (1976)
                                         Static       20                                  NS           48-h LC50    1.85
                                         Static       20                                  NS           48-h LC50    1.24
                                         Flow         20       150                        NS           48-h LC50    4.9          Reiff et al.
                                                                                                                                 (1979)
                                         Flow         20       150                        NS           48-h LC50    2.4
                                         Flow         20       150                        NS           48-h LC50    1.2
                                         Flow         20       268                        NS           48-h LC50    2.1-2.9
                                         Flow         20       268                        NS           96-h LC50    1.9-2.9
                                         Flow         20       268                        NS           48-h LC50    1.3-1.7
                                         Flow         20       268                        NS           96-h LC50    1.2-1.3
                                         Flow         20       268                        NS           48-h LC50    0.8-0.9
                                         Flow         20       268                        NS           96-h LC50    0.4-0.6
    Himedaka (killifish)     4-5 wk      Staticr      23                                  C8-C14       96-h LC50    10-18        Canton & Slooff
    (Oryzias latipes)                                                                                                            (1982)
                             323 mg      Staticr      23-24                   5.6-6.1     C11.7        48-h LC50      15         Kikuchi et
    al.
                             323 mg      Staticr      23-24                   5.6-6.1     C11.7        48-h LC50      10         (1976)
                        approx. 262 mg   Staticr      21-22                   6.7-7.1     C12          48-h LC50      12         Kikuchi &
                        approx. 262 mg   Staticr      21-22                   6.7-7.1     NS           48-h LC50      10         Wakabayashi
                                                                                                                                 (1984)
                                                                                                                                              

    Table 28 (contd)
                                                                                                                                              

    Organism                 Size or     Static or    Temp.    Hardness       pH          LAS chain    End-point    Concn        Reference
                             age         flow         (°C)     (mg/litre)a                length                    (mg/litre)
                                                                                                                                              

    Himedaka (contd)                                                                      C161         48-h LC50    > 50         Tomiyama (1974)
                                                                                          C6           48-h LC50    > 50
                                                                                          C8           48-h LC50    > 50
                                                                                          C10          48-h LC50    > 50
                                                                                          C12          48-h LC50    4
                                                                                          C14          48-h LC50    4            Iimori &
                                                                                                                                 Takita
                                                                                                                                 (1979)
                                                      25                      7.2-7.9                  48-h LC50    7.6          Hidaka et al.
                                                                                                                                 (1984)
                                                      25                      7.2-7.9                  96-h LC50    7.3
                             Adult       Staticr      20       5                          C11.7        96-h LC50    13           Wakabayashi &
                             Adult       Staticr      20       25                         C11.7        96-h LC50    8.8          Onizuka (1986)
                             Adult       Staticr      20       125                        C11.7        96-h LC50    4.8
                             Adult       Staticr      20       625                        C11.7        96-h LC50    3.2
                             Adult       Staticr      20       0                          C11.7        48-h LC50    6.7          Wakabayashi &
                             Adult       Staticr      20       1                          C11.7        48-h LC50    4.8          Onizuka (1986)
                             Adult       Staticr      20       5                          C11.7        48-h LC50    4.7
                             Adult       Staticr      20       10                         C11.7        48-h LC50    3.5
                             Adult       Staticr      20       15                         C11.7        48-h LC50    3.8
                             Adult       Staticr      20       20                         C11.7        48-h LC50    2.5
                             Adult       Staticr      20       25                         C11.7        48-h LC50    1.9
                             Adult       Staticr      20       30                         C11.7        48-h LC50    1.6
                             Adult       Staticr      20       35                         C11.7        48-h LC50    1.4
                                                                                                                                              

    Table 28 (contd)
                                                                                                                                              

    Organism                 Size or     Static or    Temp.    Hardness       pH          LAS chain    End-point    Concn        Reference
                             age         flow         (°C)     (mg/litre)a                length                    (mg/litre)
                                                                                                                                              

    Cobalt suzume                                                                                      48-h LC50    1.3          Iimori &
    (Chrysiptera hollisi)                                                                                                        Takita (1979)

    Smallmouth bass                      Flow         15       43             7.2-7.9     NS           96-h LC50    3.7          McKim et al.
    (Micropterus dolomieu)                                                                                                       (1975)

    Black bullhead                       Flow         23       50             7.5         NS           96-h LC50    6.4          Thatcher &
    (Ictalurus melas)                                                                                                            Santner (1967)

    Common shiner                        Flow         23       50             7.5         NS           96-h LC50    4.9          Thatcher &
    (Notropis cornutus)                                                                                                          Santner (1967)

    Emerald shiner                       Flow         23       50             7.5         NS           96-h LC50    3.3          Thatcher &
    (Notropis atherinoides)                                                                                                      Santner (1967)

    Bleeker                  0.3 g       Static       28                                  NS           96-h LC50    11.8         Eyanoer et al.
    (Puntius gonionotus)     0.3 g       Static       35                                  NS           96-h LC50    11.5         (1985)
                             0.3 g       Static                50                         NS           96-h LC50    13.6
                             0.3 g       Static                110                        NS           96-h LC50    11.8
                             0.3 g       Static                260                        NS           96-h LC50    11.4
                                                                                                                                              

    Table 28 (contd)
                                                                                                                                              

    Organism                 Size or     Static or    Temp.    Hardness       pH          LAS chain    End-point    Concn        Reference
                             age         flow         (°C)     (mg/litre)a                length                    (mg/litre)
                                                                                                                                              

    Ayu                      0.26 mg                  1                                   NS           48-h LC50    0.86         Sueishi et al.
    (Plecoglossus altivelis) 0.29 g                   1                                   NS           48-h LC50    0.53         (1988)
                             1.24 g                   1                                   NS           48-h LC50    0.77
                             6.51 g                   1                                   NS           48-h LC50    1.45
                             27.98 g                  1                                   NS           48-h LC50    1.17
                                                                                                                                              

    Flow, flow-through conditions: LAS concentration in water maintained continuously; NS, not specified; staticr, static renewal: water changed
    periodically; static, water unchanged for the duration of test; finger, fingerling 
    a mg/litre CaCO3
    b Based on nominal concentration
    c Based on measured concentrations

    Table 29.  Toxicity of linear alkylbenzene sulfonates (LAS) to marine fish
                                                                                                                                              

    Organism                 Size or     Static or    Temp.    Salinity       LAS chain   End-point    Concn        Reference
                             age         flow         (°C)     (%)            length                   (mg/litre)
                                                                                                                                              

    Cod (Gadus morhua)       30 cm       Static       6-8      32-34          C12         96-h LC50    1a           Swedmark et al. 
                             30 cm       Static       15-17    32-34          C12         96-h LC50    < 1a         (1971)

    Flounder                             Static       6-8      32-34          C12         96-h LC50    1.5a
    (Pleuronectes flesus)                Static       15-17    32-34          C12         96-h LC50    < 1a

    Plaice (Pleuronectes                 Static       6-8      32-34          C12         96-h LC50    > 1 -< 5a
    platessa)

    Mosbled sole             Newly                                            NS          48-h LC50    0.5-1        Yasunaga (1976)
    (Limanda yokohamae)      hatched
                             10 days                                          NS          48-h LC50    0.1-0.5
                             30 days                                          NS          48-h LC50    0.5-1
                             40 days                                          NS          48-h LC50    < 0.1
                             Newly                                            NS          48-h LC50    0.05-0.1
                             hatched

    Olive flounder           5 days                                           NS          48-h LC50    < 0.1
    (Paralichtys olivaceus)  10 days                                          NS          48-h LC50    0.1-0.5
                             30 days                                          NS          48-h LC50    0.1-0.5

    Himedaka (killifish)     Adult       Staticr      20       0              C11.7       48-h LC50    6.7          Wakabayashi &
    (Oryzias latipes)        Adult       Staticr      20       1              C11.7       48-h LC50    4.8          Onizuka (1986)
                             Adult       Staticr      20       5              C11.7       48-h LC50    4.7
                                                                                                                                              

    Table 29 (contd)
                                                                                                                                              

    Organism                 Size or     Static or    Temp.    Salinity       LAS chain   End-point    Concn        Reference
                             age         flow         (°C)     (%)            length                   (mg/litre)
                                                                                                                                              

    Himedaka (contd)         Adult       Staticr      20       10             C11.7       48-h LC50    3.5
                             Adult       Staticr      20       15             C11.7       48-h LC50    3.8
                             Adult       Staticr      20       20             C11.7       48-h LC50    2.5
                             Adult       Staticr      20       25             C11.7       48-h LC50    1.9
                             Adult       Staticr      20       30             C11.7       48-h LC50    1.6
                             Adult       Staticr      20       35             C11.7       48-h LC50    1.2
                                                                                                                                              

    Static: water unchanged for duration of test; staticr, static renewal: water changed periodically; NS, not specified
    a Based on nominal concentration
        The activity of the enzymes of aerobic metabolism was decreased, and
    that of lactate dehydrogenase was strongly increased (Zaccone et
    al., 1985). Concentrations of 2.19 mg/litre C11.8 LAS and
    0.39 mg/litre C13 LAS significantly increased the 24-h mean
    ventilation rate (number of opercular closures per minute) of
    bluegill  (Lepomis macrochirus) (Maki, 1979b).

        A  concentration of 36 mg/litre LAS severely affected the
    viability of the perfused gills of rainbow trout  (Oncorhynchus
     mykissi). Vascular resistance increased gradually during
    perfusion, with a concomitant decrease in oxygen transfer. LAS at
    0.05 mg/litre more than doubled cadmium transfer (0.8 µg/litre)
    through the perfused gills; and at concentrations of 36 mg/litre LAS
    and 0.9 mg/litre cadmium, there was a marked reduction in cadmium
    transfer (Pärt et al., 1985).

    A9.3.3.4  Behavioural effects

        Hidaka and co-workers have reported several studies of the
    avoidance of surfactants by fish (Hidaka et al., 1984; Hidaka &
    Tatsukawa, 1989; Tatsukawa & Hidaka, 1978). The results should be
    interpreted with caution, since the environmental relevance and the
    reproducibility and sensitivity of these tests is unclear;
    furthermore, no effect was seen after removal of the olfactory
    organs. Another study (Maki, 1979a) showed no adverse toxicological
    effects at concentrations two times greater than those reported to
    cause avoidance reactions.

        Hidaka et al. (1984) found that the minimal avoidance
    concentration of LAS, i.e. the concentration at which fish spent 65%
    of a 5-min period in clean water in order to avoid LAS, was
    13.5 µg/litre for medakas  (Oryzias latipes). Medakas exposed to
    LAS at concentrations of 5-50 µg/litre for 10 min showed significant
    avoidance to 10, 20, and 30 µg/litre. No significant avoidance of
    concentrations of 10-50 µg/litre LAS was found after removal of the
    olfactory organs (Hidaka & Tatsukawa, 1989).

        The threshold concentrations for avoidance of LAS by ayu
     (Plecoglossus altivelis) were 0.11 µg/litre of a formulation and
    1.5 µg/litre of pure reagant LAS (Tatsukawa & Hidaka, 1978).

    A9.3.3.5  Interactive effects with other chemicals

        The chronic toxicity of  para, para-DDT (50 mg/litre) to
    goldfish  (Carassius auratus) was increased by prior exposure to
    LAS at 4 mg/litre for 37 days (Dugan, 1967).

        The toxicity of 1 mg/litre LAS solution to mosquito fish exposed
    under static conditions was not affected by allowing the LAS
    solution to react with excess chlorine (Katz & Cohen, 1976).

        A concentration of 1 mg/litre LAS significantly increased the
    toxicity of fuel oil to bluegill  (Lepomis macrochirus), reducing
    the 24-h LC50 from 91 to 51 mg/litre. The authors concluded that
    sublethal concentrations of LAS increased the toxicity of fuel oil
    by increasing its penetration (Hokanson & Smith, 1971). The toxicity
    of No. 2 and No. 4 fuel oils in six species of freshwater fish was
    increased in the presence of 1-5 mg/litre LAS (Rehwoldt et al.,
    1974).

        The uptake of cadmium by freshwater trout  (Salmo gairdneri)
    exposed to 0.14 µmol/litre LAS was more than two times greater than
    in controls. Reduced cadmium uptake was reported in fish exposed to
    100 µmol/litre LAS. The authors reported that trout exposed to low
    levels of both LAS and cadmium could take up lethal cadmium
    concentrations. LAS were reported to interact with the gill proteins
    involved in cadmium transport, resulting in increased permeability
    to cadmium (Pärt et al., 1985).

        Fathead minnows  (Pimepheles promelas) were exposed to various
    pesticides in the presence and absence of 1 mg/litre LAS. Parathion
    acted synergistically with LAS, reducing the 96-h LC50 from 1410
    to 720 µg/litre. Endrin and LAS showed no synergism, and no
    consistent results were obtained for DDT (Solon et al., 1969).
    Methyl parathion, ronnel, trithion, and trichloronat were also found
    to act synergistically with LAS, but neither  ortho-ethyl-ortho-4-
    nitrophenyl phenylphos-phonothioate nor dicapthon exhibited
    synergism. The synergistic relationship does not appear to be
    exclusive to a general structural group (Solon & Nair, 1970).

        Goldfish  (Carassius auratus) were exposed to mixtures of LAS
    and chloramines and LAS and copper at ratios of 1:1, 2:1, and 1:2,
    and toxicity curves and 24-h and 96-h LC50 values were compared.
    LAS and chloramines had an additive effect at a ratio of 1:1, but at
    2:1 and 1:2 synergistic effects were seen. LAS and copper at ratios
    of 1:1 and 2:1 had additive effects; however, at 1:2, high
    concentrations and longer exposure times had additive effects, and
    low concentrations and shorter exposure times had synergistic
    effects (Tsai & McKee, 1978).

        When eggs of cod  (Gadus morhua) were exposed to mixtures of
    LAS and zinc or copper from fertilization to hatching, zinc had a
    weak synergistic affect on the toxicity of LAS, but LAS had a strong
    synergistic affect on the toxicity of copper (Swedmark & Granmo,
    1981).

        In a study of the effect of polyoxyethylene (20) on the acute
    toxicity of C12 LAS, red killifish  (Oryzias latipes) and carp
     (Cyprinus carpio) were exposed to the 48-h LC50 of LAS for the
    respective species and to 5-40 mg/litre of either a polyoxyethylene
    sorbitan ester, a polyethylene glycol, a polypropylene glycol, or a
    protein (albumin, kaolin, or bentonite). Addition of most of these

    substances decreased mortality. No mortality was observed in carp
    exposed to LAS and 14 or 28 mg/litre polyoxyethylene (20) sorbitan
    monooleate (SMOE20) or to other nonionic surfactants with a similar
    polyoxyethylene sorbitan ester structure-polyoxyethylene (6)
    sorbitan monolaurate, polyoxy-ethylene (6) sorbitan monooleate,
    polyoxyethylene (20) sorbitan monolaurate, and polyoxyethylene (20)
    sorbitan monostearate-or to albumin. No significant effect on
    mortality induced by LAS was reported after simultaneous exposure to
    polyoxyethylene (6) sorbitan monostearate, polyethylene glycol,
    polypropylene glycol, kaolin, or bentonite. The authors also
    examined the histological effects of these chemicals on the gills of
    carp exposed to high concentrations of LAS, including the 48-h
    LC50 of 3.5 mg/litre and the LC100 of 7 mg/litre. Histological
    changes in fish exposed only to 3.5 mg/litre LAS included the
    appearance of mucous cells and agglutination of the secondary
    lamellae; carp exposed to a mixture of LAS and SMOE20 showed only
    slight swelling of the secondary lamellae and slight proliferation
    of the gill epidermal cells. Exposure only to LAS at 7 mg/litre
    resulted in marked proliferation of the epidermal cells and
    agglutination of secondary lamellae; exposure to both LAS and SMOE20
    induced only swelling of the secondary lamellae. No effects were
    reported on the gills of control fish or on other organs of the
    exposed fish; and no significant differences from controls were
    reported in haematological or serum biochemical parameters for fish
    exposed to either LAS or the LAS:SMOE20 mixture. When the
    distribution of LAS in the tissues and organs of carp was examined,
    higher levels were found in the blood and most organs after exposure
    to LAS only than after exposure to the mixture; the differences were
    statistically significant in blood, muscle, and gill but not in
    spleen or gall-bladder. Adsorption of the 5- and 6-phenyl isomers of
    LAS was similar when they were given alone or in conjunction with
    SMOE20, but more of the 4- and (especially) the 2-phenyl isomers was
    adsorbed by fish receiving LAS alone, indicating that SMOE20
    decreases the acute toxicity of LAS to fish by decreasing the
    adsorption on the gills of the more toxic isomer (Toshima et al.,
    1992).

    A9.3.4  Amphibia

        No reliable data were available.

    A9.3.5  Studies of the mesocosm and communities

        Diversity and similarity indices were used in many studies to
    assess the effects of LAS on phytoplankton communities, usually on
    the basis of taxonomy, mean number of species, and density. Mean
    density and similarity indices were then compared with those of
    controls. In general, these indices are not sensitive to change, as
    the densities of some species may decrease while the indices do not.

        The effects of C12 and C13 LAS on short-term photosynthetic
    activity were studied in plankton sampled from Acton Lake, Ohio,
    United States, during May-October in the laboratory and  in situ.
    Toxicity increased with the temperature of the water, the most
    sensitive period being June-August, and LAS were less toxic during
    periods of diatom dominance and low phytoplankton density. Thus the
    density of diatoms decreased during June-August, and that of green
    and blue algae increased. The comparison of the results of
    laboratory and field tests was highly dependent on species and the
     in-situ end-point. Short-term tests for photosynthetic activity in
    situ gave 3-h EC50 values of 0.2-8.1 mg/litre (mean, 1.9 mg/litre)
    for C13 LAS and 0.5-8.0 mg/litre (mean, 3.4 mg/litre) for C12
    LAS (Lewis & Hamm, 1986). (See also section 9.3.1.1.)

        In another study of the effect of LAS on phytoplankton
    communities in Acton Lake, Ohio (Lewis, 1986), phytoplankton were
    exposed  in situ to LAS at a concentration of 0.01, 0.02, 0.24,
    0.80, 27, or 108 mg/litre for 10 days. The LOEL for LAS, based on
    community similarity indices and the mean number of species, was
    108 mg/litre. The similarity index (coefficient of community)
    decreased as the concentration of LAS increased, with calculated
    values of 0.62 at 0.01 mg/litre and 0.43 at 108 mg/litre. No
    significant effects were seen on the community diversity index or
    phytoplankton density. Green algae were the species least affected,
    on the basis of abundance, followed in order of decreasing tolerance
    by blue-green algae and diatom species.  Chlorophyta species were
    the most abundant at higher concentrations of LAS, comprising 74% of
    the total cell volume at 108 mg/litre; their abundance tended to
    increase to a maximum at this concentration and then decrease to
    values similar to those of the controls.  Chlorophyta species of
    the genera  Chlamydomonas, Oocystis, and  Sphaerocystis were not
    found after exposure to higher concentrations of LAS.  Chlamydomonas
    was found only in waters with a concentration of LAS <
    0.8 mg/litre, and Oocystis and Sphaerocystis were found only at
    concentrations < 27 mg/litre. The peak density of blue-green
    phytoplankton (56% of cell volume) was achieved at 0.24 mg/litre
    LAS, declining to 17% at 108 mg/litre. The density of the major
    species, Schizothrix calcicola, was greatest at 27 mg/litre LAS but
    declined to a level below that of controls at 108 mg/litre LAS. The
    abundance of diatoms was low at all concentrations of LAS. At
    concentrations < 0.24 mg/litre, the average density of diatoms
    was 23% of the total cell volume, similar to that of controls; at
    concentrations of 0.24-0.8 mg/litre, the diatom density was 10% of
    the cell volume. The mean densities of the major diatom species,
    such as  Cyclotella glomerata, Cyclotella pseudostelligera, and
     Nitzschia frustulum v. perminuta, followed the overall trend for
    diatoms, reaching a peak at low LAS concentrations and declining to
    control values at higher concentrations.

        In the same study, the laboratory-based 96-h EC50 values for
    exposure to C11.8 LAS were calculated to be 29.0 mg/litre for
     Selenastrum and 0.0096 mg/litre for Microcystis, on the basis of
    population growth. The lowest concentration of LAS that produced a
    significant effect on algal growth in the laboratory was
    0.05-1.0 mg/litre, which is considerably lower than the
    27-108 mg/litre value found to be the lowest that altered the
    structure of a natural phytoplankton community. The differences
    between the results of laboratory and field tests were smaller for a
    laboratory-based EC50 than for an LOEL. Calculations based on the
    EC50 give a 30-fold difference for Microcystis but essentially no
    difference for  Selenastrum (Lewis, 1986).

        The toxic effects of LAS were also examined on periphyton
    communities above and below the outfall of a wastewater treatment
    plant on Little Miami River, Ohio, United States. The dominant
    species at both test sites were diatoms,  Amphora perpusilla and
     Navicula minima accounting for at least 80% of the total cell
    volume. The tests were conducted  in situ, with 21-day
    continous-flow exposure to LAS (average chain length, C11.9) in
    river water entering submerged exposure tubes at a concentration of
    0.2, 1.1, 9.8, or 28.1 mg/litre, after a four-week colonization
    period. The delivery rate of LAS was adjusted daily according to
    measurements of river flow in order to maintain the desired test
    concentrations. The periphyton at the site below the treatment plant
    outfall were exposed to LAS in the presence of 20-30% treated
    municipal effluent. No effects on the structure or function of the
    periphyton community above the outfall were reported after exposure
    to an average concentration of LAS < 1 mg/litre. The lowest
    concentration that had an effect on the upstream periphyton
    community was 9.8 mg/litre, which reduced photosynthesis by 16%; a
    concentration of 28.1 mg/litre reduced photosynthesis by 64%, with a
    noticeable reduction in chlorophyll a. No effects on community
    similarity or diversity were reported in comparison with control
    communities. Mean cell densities were increased by 26% after
    exposure to 0.2 mg/litre LAS and by 17% after exposure to
    1.1 mg/litre; exposure to 28.1 mg/litre reduced mean cell density by
    28%. Exposure to LAS had no significant effects on the abundance of
    the three main species in the upstream community. Increased
    photosynthesis (by 12-39%) and chlorophyll  a (50-51%), were
    reported after exposure to 1.1 or 9.8 mg/litre LAS, but exposure to
    28.1 mg/litre resulted in a 52% decrease in photosynthesis and a 71%
    decrease in chlorophyll  a. No effects on the similarity or
    diversity of the periphyton community were reported at any
    concentration of LAS tested. Cell densities of periphyton were
    increased by 34% after exposure to 9.8 mg/litre LAS and by 13% after
    exposure to 28.1 mg/litre. The abundance of the three main species
    in the downstream periphyton community was not affected. The lowest
    concentration of LAS that induced an effect was 3.3 mg/litre for the
    upstream periphyton community and 16.6 mg/litre for the downstream
    community. The authors suggested that the difference between the two

    values was due to the presence of 20-30% sewage downstream, which
    reduced the bioavailability of LAS (Lewis et al., in press).

        When an aquatic ecosystem was exposed to LAS at concentrations
    of 0.25-1.1 mg/litre for 90 days, the numbers of phytoplankton were
    unaffected but primary productivity was significantly reduced at all
    concentrations. The zooplankton population showed a more variable
    response: the number of rotifers was reduced at all concentrations,
    and those of  Diaptomus and  Cyclops were reduced at >
    0.51 mg/litre. The number of ostracods was decreased at
    0.38 mg/litre but was increased at 0.51 and 1.1 mg/litre. The
    chironomid population was significantly reduced at concentrations
    > 0.38 mg/litre (Chattopadhyay & Konar, 1985). Exposure of an
    aquatic ecosystem consisting of phytoplankton, zooplankton, and
    benthic organisms to 1 mg/litre of a preparation of LAS for 90 days
    significantly reduced the numbers of phytoplankton and zooplankton
    per litre but did not significantly affect the numbers of chironomid
    larvae (Panigrahi & Konar (1986).

        The effect of C12 LAS on microbial communities was studied in
    a model ecosystem consisting of a 19-litre glass tank containing
    sediment from Winton Lake, Ohio, United States, and several trophic
    levels, comprising bacteria, algae, macrophytes  (Elodea canadensis,
     Lemna minor), macroinvertebrates  (Daphnia magna, Parantanytarsus
     parthenogenica), and blugill sunfish  (Lepomis macrochirus).
    After a four-week equilibrium period, LAS were added at 0.5 or
    5.0 mg/litre to a flow-through system with six to 10 replacements
    per day for 26 days. The structure of the microbial communities was
    not affected, and no differences were reported in mean biomass or
    number of colony-forming units between the microorganisms exposed at
    the two levels. The function of the microbial communities, assayed
    by measuring the degradation of both LAS and D-glucose, was reduced
    only at 5.0 mg/litre. In a similar system, in which the same
    concentrations of LAS were added in the form of sewage effluent, no
    effect was seen on the structure of the microbial community or on
    their function, measured only as the degradation of LAS (Larson &
    Maki, 1982).

        Addition of LAS (average chain length, C11.8) at a measured,
    relatively uniform concentration of 0.36 ± 0.05 mg/litre to 50-m
    outdoor experimental streams had no effect on total density, species
    richness, percentage similarity, or dominance of macroinvertebrates
    or periphyton or on the processing of organic matter of leaf discs.
    Fathead minnows  (Pimephales promelas) and amphipods  (Hyallela
     azteca) were exposed in groups of 10 and 20 per box placed in the
    streams at three locations. The mortality rates of the amphipods
    were 17-25% after exposure to LAS and 47% among controls; no effects
    were seen on the survival or weights of the fish, although minor
    effects were found on length (Fairchild et al., 1993).

        A study of the fate and effects of surfactants in outdoor
    artificial streams addressed the effect of LAS on drift and
    population densities of macroinverebrates, the reproductive
    behaviour of an amphipod, the scud  (Gammarus pulex), the survival
    of a fish, the three-spined stickleback  (Gasterosteus aculeatus),
    and photosynthesis by the community. The concentration of LAS in
    sediment was reported to increase with increasing water
    concentration, and selective adsorption of longer-chain LAS
    homologues to sediment was reported. The microbial populations of
    both the water and the sediment adapted to LAS, resulting in a
    reduction in its half-life during the test. LAS at concentrations
    < 1.5 mg/litre did not affect macroinverebrate drift, population
    density, or community photosynthesis. Survival of the fish and
    reproduction by the amphipod were affected at concentrations of
    1.5-3.0 mg/litre (Mitchell & Holt, 1993).

    A9.3.6  Field studies

        The effect of LAS downstream of a sewage outflow was studied by
    monitoring sediment, water, and the distribution of invertebrates at
    an upstream control site, a site near the discharge point, and a
    site 200 m downstream of the outflow. The concentrations of LAS in
    sediment were 1-40 mg/kg dry weight, with concentrations < 2 mg/kg
    at the control site and 200 m downstream. No effect of LAS in the
    effluent or in the streambed sediments could be discerned on the
    invertebrate populations (Ladle et al., 1989).

    A9.3.7  Toxicity of biodegradation intermediates and impurities
            of linear alkylbenzene sulfonates

        Tests of degradation products and impurities of LAS show that
    they are less toxic than LAS themselves.

    A9.3.7.1  Individual compounds

        The 48-h LC50 values in Daphnia magna were 208 ± 85 mg/litre
    for sulfophenylundecanoic acid, disodium salt (mixed isomers, 6-10
    phenyl); about 6000 mg/litre for 3-(sulfophenyl) butyric acid,
    disodium salt; and about 5000 mg/litre for 4-(sulfophenyl) valeric
    acid, disodium salt. The equivalent 48-h LC50 values in the
    fathead minnow  (Pimephales promelas) were 77 ± 12, about 10 000,
    and about 10 000 mg/litre, respectively (Kimerle & Swisher, 1977).

        The 24-h LC50 values in Daphnia were about 22 000 mg/litre for
    3-sulfophenylbutyric acid, disodium salt; about 12 000 mg/litre for
    3-sulfophenylheptanoic acid, disodium salt; > 22 000 mg/litre for
    3-sulfophenylbutyric acid, disodium salt; and 2 000 mg/litre for
    sulfophenylundecanoic acid, disodium salt. Other tests were carried
    out with the last two compounds, giving 96-h LC50 values of about
    28 000 and 1200 mg/litre in fathead minnows  (Pimephales promelas);

    28-day NOELs of > 2000 and > 200 mg/litre for survival and
    reproduction of  Daphnia; and 30-day NOECs of > 1400 and >
    52 mg/litre for survival of the fry of fathead minnows (egg
    hatchability and fry growth were less sensitive) (Swisher et al.,
    1978).

        The 96-h LC50 for mixed isomers of sulfophenylundecanoic acid
    disodium salt in bluegill  (Leponis macrochirus) was 75 mg/litre
    (Swisher et al., 1964). The 24-96-h LC50 values in fathead minnows
    were 1000-1500 mg/litre for sulfophenylundecanoic acid (C11) and
    25 000-32 000 mg/litre for sulfophenyl butyrate (C4) (Swisher et
    al., 1978).

        The 48-h LC50 for the alkanoic acid derivatives of
    2-sulfophenyl C13 LAS and 4-sulfophenyl C13 LAS in nearly pure
    form was > 800 mg/litre in goldfish  (Carassius auratus) (Divo &
    Cardini, 1980).

        The 24-h LC50 values for  Daphnia magna exposed to
    dialkyltetralin sulfonates, which are trace contaminants of LAS,
    were 420, 195, 110, 50, and 27 mg/litre for tetralin sodium
    sulfonates of chain lengths C10, C11, C12, and C13,
    respectively (Arthur D. Little Inc., 1991).

    A9.3.7.2  Effluents

        Interpretation of tests on effluents must take into account the
    following:

    -- As concentrations arwe often reported as MBAS, testing of
    effluent from a sewage treatment plant may result in overestimation
    of the actual concentrations of LAS, owing to interference (see
    section 2.3).

    -- The bioavailability of LAS is decreased by the presence of high
    concentrations of suspended solids; thus, as effluents are diluted
    in the environment, availability is usually increased, although
    biodegradation occurs.

        Addition of LAS (C10-C15) to detergent-free activated sludge
    plant effluent (95% was removed as MBAS) gave a nominal 96-h LC50
    in rainbow trout  (Oncorhynchus mykiss) of 0.36 mg/litre. After
    treatment, the 96-h LC50 was 29.5 mg/litre,  expressed in terms of
    the concentration of the surfactant in the influent (Brown et al.,
    1978).

        When bluegill were exposed to effluent from continuous-flow
    activated sludge units fed 100 mg/litre LAS, none died during
    4-11-day exposure (Swisher et al., 1964).

    A9.4  Terrestrial organisms

    A9.4.1  Terrestrial plants

        Young seedlings of tomato, lettuce, radish, pea, cucumber, and
    barley were grown in a soil-based compost and were watered and given
    a foliar spray of a preparation of LAS. No effects were noted at
    concentrations up to 100 mg/litre (Gilbert & Pettigrew, 1984). In
    another study, barley, tomato, and bean plants were grown from seed
    and watered with a solution containing LAS at a concentration of 10,
    25, or 40 mg/litre. Plants that received the lowest dose germinated
    at the same time as controls, but plants watered at 25 or
    40 mg/litre germinated three days later. The growth of barley plants
    was inhibited at all three concentrations; however, the dose of
    25 mg/litre increased the growth rate of beans, and the highest dose
    increased the growth rate of both tomatoes and beans (Lopez-Zavala
    et al., 1975).

        The 21-day EC50 values for LAS (C10-C13), based on the
    emergence of seedlings and early stages of growth, were 167 mg/litre
    in sorghum, 289 mg/litre in sunflower, and 316 mg/kg in mung bean.
    The highest concentration that caused no significant reduction in
    the growth of any of the three species was 100 mg/kg  (Holt et al.,
    1989; Mieure et al., 1990). In a second study, 407 mg/kg C11.36 or
    393 mg/kg C13.13 LAS were mixed with sewage sludge, and nine
    common plant species, including five crop plants, were exposed as
    seed either at the same time or two weeks after application of the
    sludge to soil at a rate of 9000 kg/ha. There was no significant
    effect on seed germination and no significant inhibition of growth
    (Mieure et al., 1990).

        Orchid seedlings  (Phalaenopsis or  Epidendrum sp.) were grown
    in culture media containing either the sodium or the ammonium salt
    of LAS at a concentration of 10, 100, or 1000 mg/litre. The lowest
    dose had no effect on growth, and that of ammonium LAS had no effect
    on germination. At 100 mg/litre, survival was halved and germination
    completely inhibited (Ernst et al., 1971). A concentration of
    1000 mg/litre caused drastic changes in morphology, loss of
    membranes, swelling of thylakoids, and the appearance of dense
    osmophilic granules in chloroplasts (Healey et al., 1971).

        The growth of pea seedlings grown for 26 days in quartz sand to
    which 0.005% (50 mg/kg) LAS had been added was significantly
    reduced, as measured by the fresh weight of roots and the length and
    fresh weight of pea greens (Lichtenstein et al., 1967).

        LAS were not toxic with respect to growth at the early life
    stages of radish, Chinese cabbage, and rice when added in hydroponic
    culture at concentrations of 10, 20, and 20 mg/litre, respectively;
    concentrations of 20, 35, and 35 mg/litre were toxic (Takita, 1982).

        When seeds of  Pisum sativum and  Crotolaria juncea were
    exposed to LAS for 24 h before sowing, the percentage germination
    was reduced at concentrations of 1 ml/litre for  P. sativum and
    10 ml/litre for C. juncea, although no statistical analysis was
    presented. No germination occurred after exposure to LAS at
    concentrations of 20 ml/litre for  P. sativum and 40 ml/litre for
     C. juncea. Radicle length was reduced at > 0.1 ml/litre in both
    species (Sharma et al., 1985).

        Application of LAS at 50 g/m2 under field conditions to loamy
    and sandy soils (corresponding to 0.47-1 mg/kg dry weight,
    respectively) led to considerable physiological damage, including
    leaf necrosis, chlorosis, and turgescence, to ryegrass  (Lolium
     perenne) after 14 days; however, there was no difference in the
    fresh weight yield after harvesting at 45-54 days (Litz et al.,
    1987).

    A9.4.2  Terrestrial invertebrates

        When the earthworm  Eisenia foetida was exposed to C11.36 LAS
    incorporated into soil at nominal concentrations of 63-1000 mg/kg
    dry weight, the 14-day LC50 was > 1000 mg/kg. On the basis of a
    statistical analysis of body weights, the no-effect concentration
    was 250 mg/kg; this was confirmed by HPLC to be 235 mg/kg. In a
    second study, C11.36 and C13.13 LAS were incorporated into
    sludge and applied to soil, and the earthworm  Lumbricus terrestris
    was exposed to the subsequent mixture, which contained LAS at
    concentrations of 84-1333 mg/kg. The 14-day LC50 was again found
    to be greater than the highest concentration (> 1333 mg/kg). The
    no-effect concentration, based on weight and burrowing behaviour,
    was the nominal concentration of 667 mg/kg, measured by HPLC as
    613 mg/kg. The worms were exposed, however, to LAS under conditions
    of continuous light, which would inhibit them from surfacing to feed
    and thus increase their exposure to and the toxicity of the test
    over that of the same concentration in the field (Mieure et al.,
    1990).

        Topical application to house flies  (Musca domestica) of LAS at
    the same time as parathion, diazinon, or dieldrin in ratios of 1:1
    and 1:10 had no effect on the toxicity of the insecticides. When LAS
    were added to soil treated with parathion or diazinon, however, a
    significant synergistic effect was observed on the toxicity of the
    insecticides to the fruit fly  Drosophila melanogaster. The optimal
    concentration of LAS that resulted in synergy was 23 mg/kg
    (Lichtenstein, 1966).

    A9.4.3  Birds

        No significant effect on egg quality was found after Leghorn
    chickens were fed a diet containing 200 mg/kg LAS for 45 days
    (Lopez-Zavala et al., 1975).

    B.  alpha-Olefin sulfonates

    B1.  SUMMARY

        See Overall Summary, Evaluation, and Recommendations (pp. 7-21).

    B2.  IDENTITY, PHYSICAL AND CHEMICAL PROPERTIES, AND
         ANALYTICAL METHODS

    B2.1  Identity

    Chemical formula:        CnH2nO3S Na, CnH2n+1O4S Na ( n = 14-18)

    Chemical structure:      CH3(CH2)jCH:CH(CH2)kSO3- Na+
                             CH3(CH2)mCH(CH2)nSO3- Na+
                             OH ( m,n, integers)

    Common names:            Sodium alpha-olefinsulfonate,
                             alpha-olefin-sulfonic acid sodium salt, AOS
                             sodium salt

    Common trade names:      Bioterge AS 40 F, Elfan OS 46, Geropon
                             MLS/A, Hostapur OS Brands, Lipolan, Lipomix
                             G, Lipon PB-800, Lutensit A-PS, Nansa
                             LSS38/AS, Sawaclean, Sermul EA 214,
                             Sulframin AOS, Witconate (McCutcheon, 1989)

    Abbreviations:           AOS, AOS-Na

    CAS Registry numbers:    29963-33-5  Sodium 1-tetradecenesulfonate
                             29734-60-9: Sodium hexadecenesulfonate

                             13513-23-0: Sodium 3-hydroxyhexadecyl-1-
                                         sulfonate
                             26446-92-4: Octadecene-1-sulfonic acid
                                         sodium salt
                             13513-42-3: 3-Hydroxy-1-octadecanesulfonic
                                         acid, sodium salt

    Specifications:          AOS are mixtures consisting of about 60-65%
                             alkene sulfonates, 30-35% hydroxylalkane
                             sulfonates, and 5-10% disulfonates. Various
                             positional isomers of alkene sulfonates and
                             hydroxyalkane sulfonates have been reported
                             (Gentempo et al., 1985; Williamson, 1993).
                             Sodium C14-C16 AOS are typically
                             shipped as solutions containing 35-40%
                             active matter in water. Sodium C16-C18
                             AOS are typically slurries containing
                             28-30% active matter in water at ambient
                             temperature.

    B2.2  Physical and chemical properties

        AOS are white crystalline solids consisting of various chemical
    compounds and their isomers, with different properties. Typical
    properties of AOS are given in Table 30. Two ranges are usually
    offered; the commonest are based on C14-C16 olefin and the other

    on C16-C18 olefin. Detergency is maximal with alkyl chain
    lengths of C15-C18. Maximal detergency is also obtained with the
    same range of alkyl chain lengths in a detergent formulation that
    includes alkali builders and chelating agents (Yamane et al., 1970).
    AOS are stable, even in hot acidic media.

    Table 30.  Relationship between alkyl chain length, Krafft point,
               critical micelle concentration (CMC), and surface
               tension of alpha-olefin sulfonates

                                                                 

    Alkyl chain   Krafft pointa   CMCal       Surface tension
    length        (°C)            (g/litre)   (dyne/cm)
                                                                 

    12            -               4.0         -
    14            -               1.0         30
    16            10              0.3         33
    18            30              0.1         35
    20            40              -           -
                                  (25°C)      (25°C)
                                                                 

    From Ohki & Tokiwa (1970)

    a The solubility of surfactants in water, defined as the
    concentration of dissolved molecules in equilibrium with a
    crystalline surfactant phase, increases with rising temperature. For
    surfactants, there is a distinct, sharp bend (break-point) in the
    solubility-temperature curve.  The steep increase in solubility
    above the sharp bend is caused by micelle formation. The point of
    intersection of the solubility and critical micelle curves, plotted
    as a function of temperature, is referred to as the Krafft point.
    This is a triple point at which surfactant molecules coexist as
    monomers, micelles, and hydrated solids. The temperature
    corresponding to the Krafft point is called the Krafft temperature.
    At above the Krafft temperature and critical micelle concentration,
    a micellar solution is formed. Under these conditions, higher levels
    than the aqueous solubility may be obtained.

    B2.3  Analytical methods

        There is no officially recognized specific procedure for the
    analysis of AOS in environmental samples. The methods commonly used
    to analyse anionic surfactants are also used for AOS, except those
    involving high-performance liquid chromatography (HPLC), which has
    limited use in environmental analyses for AOS, because they do not
    absorb ultra-violet radiation as effectively as do linear
    alkylbenzene sulfonates (LAS). A modified version of the methylene
    blue-active substance (MBAS)-HPLC method described in the monograph
    on LAS has been developed (Takita & Oba, 1985).

        Nonspecific methods used in the analysis of anionic surfactants
    in general, such as the MBAS method, can be used to analyse
    materials for AOS (see section 2.3 of the monograph on LAS).

    B3.  SOURCES OF HUMAN AND ENVIRONMENTAL EXPOSURE

    B3.1  Natural occurrence

        AOS do not occur naturally.

    B3.2  Anthropogenic sources

    B3.2.1  Production levels and processes

        AOS are synthesized industrially. Although they have been
    available since the 1930s, production for use in commercial
    surfactant formulations was somewhat limited until recently owing to
    a lack of suitable feedstock. Development of continuous and
    short-contact sulfur trioxide sulfonation processes and the
    increased availability of highly pure Ziegler-derived alpha-olefin
    feedstock has recently made AOS surfactants competitive with other
    surfactants on the market (Arthur D. Little Inc., 1977, 1981).

        The estimated world consumption of AOS in 1988 was 50 200 tonnes
    (Colin A. Houston & Associates Inc., 1990). In 1990, that group
    estimated that world consumption would be 51 900 tonnes; an
    alternative estimate (Hewin International Inc. 1992) was 76 000
    tonnes (Table 31).

    Table 31.  Estimated worldwide consumption of alpha-olefin
               sulfonates (tonnes)
                                                                      

    Region           Household   Personal   Industrial and   All uses
                     products    care       institutional
                                 products   use
                                                                      

    North America      3 000      7 000          4 000        14 000
    Western Europe     2 000      3 000          3 000         8 000
    Japan             24 000      7 000          2 000        33 000
    Rest of the       18 000      3 000              -        21 000
    world

    Total             57 000     20 000          9 000        76 000
                                                                      
    From Hewin International Inc. (1992)

        AOS are prepared commercially by direct sulfonation of linear
    alpha-olefins with a dilute stream of vaporized sulfur trioxide in a
    continuous thin-film reactor. The olefin is obtained by wax cracking
    or ethylene polymerization with a Ziegler-type catalyst (Tomiyama,
    1970). The reaction is complex and follows several paths, forming
    large amounts of various sultones as intermediates which hydrolyse
    during subsequent quenching and neutralization. Commercial AOS

    products contain a mixture of two major components, alkene sulfonate
    and hydroxyalkane sulfonate, with smaller amounts of alkene
    disulfonates, hydroxyalkane disulfonates, and saturated sultones.

    B3.2.2  Uses

        AOS are good detergents, have good foaming characteristics in
    hard water and are used in heavy-duty laundry detergents, light-duty
    dishwashing detergents, shampoos, and cosmetics. Table 31 indicates
    the use patterns for AOS.

    B4.  ENVIRONMENTAL TRANSPORT, DISTRIBUTION, AND TRANSFORMATION

     Section summary

        It can be inferred that AOS are transported into the environment
    in a similar manner to that established for LAS, alkyl sulfates, and
    other detergent surfactants. Fewer data are available on the
    environmental transport, distribution, and transformation of AOS
    than for LAS. The environmental fate of AOS is similar to that of
    LAS and alkyl sulfates: it is readily biodegraded under aerobic
    conditions, and primary biodegradation is complete within 2-10 days,
    depending on the temperature. At temperatures below 5-10°C,
    biodegradation kinetics are reduced, owing to a reduction in
    microbial activity. No data were available on abiotic degradation.
    There was no evidence of bioaccumulation or bioconcentration in a
    study of fish in which the uptake and distribution of AOS were
    examined.

    B4.1  Transport and distribution between media

        In the same manner as other detergent compounds, AOS are
    discharged into the environment in wastewater. The wastewater may
    undergo sewage treatment if such facilities are available. In
    countries where there are no adequate wastewater treatment
    facilities, AOS released to the environment are removed by
    biodegradation and adsorption mechanisms (see section 4.2 of the
    monograph on LAS).

        Limited studies of the adsorption of AOS are available. In a
    study of the adsorption of C12 AOS on river sediments, the
    equilibrium quantities adsorbed were proportional to the organic
    carbon content of the sediments, with a sorption coefficient Koc
    (dimensionless; normalized for the level of organic matter) of 0.65.
    This indicates that adsorption of C12 AOS is slightly weaker,
    than, for example, that of C12 LAS or C12 alkyl sulfonates
    (Urano et al., 1984). Like other detergent chemicals, AOS are
    adsorbed onto sewage sludge and river sediments in the environment.

    B4.2  Biotransformation

    B4.2.1  Biodegradation

    B4.2.1.1  Aerobic biodegradation

        Primary biodegradation of AOS, studied in die-away tests in
    water from various sites on the Tama River, Japan, was complete
    within three to five days when measured by the MBAS method; however,
    total organic carbon was completely removed after an incubation time
    of 20 days. In a study of AOS in seawater collected from the mouth
    of the Tama River, 99% of MBAS was removed within one day, and 90%

    of organic carbon was removed within five days (Sekiguchi et al.,
    1975b).

        In a comparison of the MBAS and total organic carbon methods for
    measuring biodegradation with the shake-culture method, AOS lost 99%
    of their activity as measured by the MBAS method and 90% of total
    carbon within one day; 100% was lost within five days (Sekiguchi et
    al., 1975a). In another study, complete loss of parent AOS (initial
    concentration, 100 mg/litre) as determined by the MBAS method was
    seen within 15 days, and 90% of total organic carbon was removed
    within eight days (Miura et al., 1979). In a static die-away test
    system, 90% biodegradation of three commercial AOS products,
    comprising 100% C14-C16 AOS and > 95% C15-C18 AOS (determined
    as MBAS), was reported within four days (Gafa & Lattanzi, 1974).

        In a shake-culture test in Bunch-Cambers medium, C15-C18 AOS
    were degraded by 99% (determined as MBAS) or 90% (removal of total
    organic carbon) within one day; 100% total organic carbon was
    removed within five days. The authors did not verify whether the
    removal was the result of adsorption or mineralization (Sekiguchi et
    al., 1972). The biodegradation of C15 AOS and three C15-C18
    compounds with disulfonate contents of < 4, 15, and 50% in a
    shake-flask culture system was reported to be 96% (determined as
    MBAS), with no significant difference between compounds (Oba et al.,
    1968b).

        In a modified OECD screening test, 85% of C14-C18 AOS
    (measured as chemical oxygen demand) was removed. Measurement of
    MBAS in the same test indicated 99% removal (Gerike, 1987).

        The aerobic biodegradation of 20 mg/litre AOS at 27°C was
    followed during a 10-day incubation period. Primary degradation,
    measured by the MBAS method, was complete within 10 days. The
    theoretical CO2 production had reached 30-40% within that time
    (Itoh et al., 1979).

        The oxygen uptake of C14-C18 AOS was reported to be 85% of
    the theoretical oxygen demand in a closed-bottle test (Gerike,
    1987). The average biochemical oxygen demand for C12-C18 AOS
    containing up to 40% hydroxylalkane sulfonates was 51.6% at five
    days, while glucose under the same conditions had a biochemical
    oxygen demand of 69.6% (Procter & Gamble Co, unpublished data).

        The primary and ultimate biodegradability of a series of pure
    AOS homologues (C12, C14, C16, and C18) was determined by
    measuing CO2 production. Primary biodegradation was 98-99% within
    three days, the rate of degradation varying with chain length.
    Degradation of C12 and C14 AOS occurred at a similar rate (65%
    within 30 days), but C18 AOS degraded more slowly. Mineralization
    of all AOS samples was reported to be at least 50% within two weeks,

    whereas mineralization of glucose during that time was 75-80%
    (Kravetz et al., 1982). In a study of the biodegradation of the two
    major breakdown products of AOS, alkene sulfonate and hydroxyalkane
    sulfonate, AOS homologues (C15, C16, C17, C18) were degraded
    to about 50%, and in each case the alkene sulfonate was degraded at
    least twice as fast as the hydroxyalkane sulfonate (Sekiguchi et
    al., 1975c).

        The biodegradation of C18 AOS at a concentration of
    28 mg/litre was studied in activated sludge (concentration, 100 mg
    dry matter per litre) over 12 days: 90% was lost within eight days,
    as measured by removal of chemical oxygen demand. The specific rate
    of biodegradation was calculated to be 5.3 mg/g per h (Pitter &
    Fuka, 1979).

        In the OECD confirmatory test with activated sludge, 20 mg/litre
    AOS were degraded, as follows: 97% C14 AOS within 17 days, 98%
    C16 AOS within seven days, and 94% C14-C18 AOS within eight
    days (Maag et al., 1975).

        Primary biodegradation of C15-C18 AOS was dependent on
    incubation temperature in die-away tests with water from the Tama
    River, Japan. Primary biodegradation was complete within two days at
    27°C, within five days at 15°C, and within two days at 21°C;
    however, at a water temperature of 10°C about 20% of the AOS had
    still not been degraded within the nine-day test (Kikuchi, 1985).

        When C15-C18 AOS were added to seawater, no MBAS activity
    was present after five days (Marquis et al., 1966).

    B4.2.1.2  Anaerobic degradation

        The primary anaerobic biodegradation of C15-C18 AOS
    (measured as MBAS) by bacteria on sludge sampled from a sewage
    treatment plant was 19% within 14 days and 31% within 28 days. More
    parent AOS were degraded by bacteria from the bottom of a private
    cesspool, with 34% lost within 14 days and 43% within 28 days. The
    anaerobic degradation reported may have been due to the presence of
    hydroxyalkane sulfonate compounds (Oba et al., 1967). AOS and LAS
    were reported to be the two surfactants that were least degraded
    anaerobically (Itoh et al., 1987).

    B4.2.2  Abiotic degradation

        No information was available.

    B4.2.3  Bioaccumulation and biomagnification

        Rapid, significant absorption of 14C-AOS by the gills of
    goldfish  (Carassius auratus) was seen after exposure to AOS at a
    concentration of 10 mg/litre. The concentration of AOS in the gills

    increased from 0.3 mg/kg after 0.5 h of exposure to 48.3 mg/kg after
    3 h. AOS were not detected in the alimentary canal (Tomiyama, 1975).
    Three hours is a relatively short exposure, and the authors did not
    determine whether a steady state of adsorption had been achieved.
    Tomiyama (1978) reported that AOS accumulated to the greatest extent
    in the gills of exposed fish, with additional accumulation in the
    gall-bladder. Only limited conclusions can be drawn from this study,
    however, owing to the short exposure period.

    B4.3  Interaction with other physical, chemical, and biological
          factors

        No information was available.

    B5.  ENVIRONMENTAL LEVELS AND HUMAN EXPOSURE

        Few data are available on environmental concentrations of AOS
    because of the lack of an accepted analytical method for this
    purpose. A modified analytical method based on MBAS-HPLC measurement
    has been used to measure AOS (Takita & Oba, 1985). The concentration
    in the Tama River, Japan, was calculated to be < 0.0016-0.002
    mg/litre.

        The annual average concentration of AOS in wastewater was
    0.160-0.164 mg/litre on the basis of total MBAS concentrations of
    8.4 and 8.2 mg/litre. AOS was not detected in the effluent from a
    treatment plant outfall (Oba et al., 1976).

        AOS can be expected to mineralize rapidly in all environmental
    compartments and to be removed to a large extent during sewage
    treatment. Environmental concentrations in receiving surface waters,
    sediments, soils, estuaries, and the marine environment can also be
    expected to be low.

    B6.  KINETICS

     Section summary

        AOS administered orally are readily absorbed by the
    gastrointestinal tract of rats and are distributed throughout the
    body; they are eliminated primarily in the urine and, to a lesser
    extent, in the faeces within 24 h of administration. AOS applied
    dermally are absorbed only minimally by intact skin. Several
    metabolites have been isolated, but their chemical structures have
    not been identified.

    B6.1  Absorption, distribution, and excretion

        14C-AOS were synthesized by sulfonation and hydrolysis of
    tetradecene-1-14C. The labelled compound was composed of a
    mixture of about 55% sodium 3-hydroxyalkane sulfonate
    [C11H23CH(OH)-CH2SO3Na] and about 45% sodium 2-14C alkenyl sulfonate
    [C11H23CH2CH214CH2SO3Na]. After oral administration of
    100 mg/kg 14C-AOS (50 µCi/kg) in water to rats, the level of
    radiolabel in blood reached a peak at 3 h (0.08% of the dose/ml) and
    then rapidly decreased, since little radioactivity was detected 24 h
    after the administration. At 4 h after administration, 0.45% of the
    dose per gram of tissue was detected in liver and 0.65% in kidney,
    but the levels in tissues other than the gastrointestinal tract were
    < 0.1%. Thereafter, the radiolabel in organs and tissues decreased
    rapidly, and 24 h after administration, about 0.8% was detected in
    the caecal contents and < 0.02% in other tissues. No specific
    accumulation was observed in any tissue. Within 24 h of
    administration, 72% of the dose was excreted in urine and 22% in
    faeces. At the end of the experiment, after four days, no 14C
    residue (< 0.1% of the dose) was detected in urine or faeces.
    Cumulative excretion in the bile within 12 h after administration
    was about 4.3% of the radioactivity administered (Inoue et al.,
    1982).

        The biological half-lives of AOS and their metabolites in blood
    after intravenous administration of 10 mg/kg 14C-AOS in rats were
    15 and 1 h, respectively. The marked difference in half-life can be
    accounted for by the fact that the binding of AOS to plasma
    proteins, especially serum albumin, increased in proportion to its
    concentration while that of the metabolites did not increase to any
    appreciable extent. The volume of distribution of AOS was
    8 litres/kg, and that of the metabolites was 0.5 litres/kg (Inoue et
    al., 1982).

        A dose of 0.5 ml of a 0.2% aqueous solution of 14C-AOS was
    applied to the dorsal skin (4 × 3 cm) of rats with bile-duct and
    bladder cannulae. The total amount absorbed through the skin was
    estimated to be about 0.6% on the basis of the recoveries of 14C
    in urine, bile, and the main organs over 24 h. At that time, the

    level of radiolabel was higher in the liver (0.123% of dose) than in
    the kidney (0.059%), spleen (0.004%), brain (0.01%), or lung
    (0.012%). A total of about 0.24% of the applied dose was recovered
    in these organs. After 24 h, 0.33% of the radiolabel was excreted in
    the urine and 0.08% in the bile. When the solution was painted on
    skin damaged by 20 applications of cellophane adhesive tape to
    remove the stratum corneum, the rates of excretion were 36.3% in the
    urine and 1.8% in the bile (Minegishi et al., 1977).

    B6.2  Biotransformation

        AOS and its metabolites were investigated in tissues and
    excrement after oral administration of 100 mg/kg 14C-AOS to rats.
    AOS and a metabolite more polar than AOS were detected in blood,
    liver, kidney, bile, and urine by thin-layer chromatography. As most
    of the 14C-labelled compounds in urine were alcoholic,
    unsaturated, and of sulfonic functionality, the metabolite may be a
    hydroxylated or polyhydroxylated sulfonic acid with a shorter chain
    than AOS, although the precise chemical structure remains to be
    elucidated (Inoue et al., 1982).

    B7.  EFFECTS ON LABORATORY MAMMALS AND  IN VITRO TEST SYSTEMS

     Section summary

        The oral LD50 for AOS sodium salt in mice was 3000 mg/kg. AOS
    are skin and eye irritants. Data from studies in experimental
    animals are limited, but no effects were observed in a long-term
    study in which  oral doses of 250 mg/kg body weight per day were
    administered to rats. Fetotoxicity was observed in the progeny of
    rabbits administered a maternally toxic dose of 300 mg/kg body
    weight per day.

        The available long-term studies are inadequate to evaluate the
    carcinogenic potential of AOS in experimental animals; however, in
    the limited studies available in which animals were administered AOS
    orally or on the skin, there was no evidence of carcinogenicity.

        The limited data available also indicate that AOS are not
    genotoxic  in vivo or  in vitro.

    B7.1  Single exposures

        The LD50 values for AOS (sodium salt of sulfonated C15-C18 
     n-olefin) in male ddy mice were 3000 mg/kg body weight by oral
    administration, 1660 mg/kg by subcutaneous injection, 170 mg/kg by
    intraperitoneal injection, and 90 mg/kg by intravenous injection.
    The toxic effects seen at high oral doses were reduced voluntary
    activity, diarrhoea, anaemia, dyspnoea, and respiratory collapse.
    Clonic convulsions followed by respiratory collapse were seen in
    animals given the material intravenously (Oba et al., 1968a).

    B7.2  Short-term exposure

        No data were available.

    B7.3  Long-term exposure; carcinogenicity

    B7.3.1  Mouse

        The skin of Swiss-Webster mice was painted with 20% C14-C18
    AOS, 25% C14-C18 AOS, 20% C14-C16 AOS, 25% C14-C16 AOS,
    6.7 or 8.3% C16 1,4-sultone, water, or acetone, or remained
    untreated. Animals were treated with 0.02 ml of test material on
    about 1 cm2 of exposed skin three times per week for 92 weeks.
    Final necropsies were conducted when the survival of each group
    reached 30% (approx. 19 months). Histopathological examination
    showed no evidence of carcinogenicity with any test material (Haar,
    1983).

    B7.3.2  Rat

        AOS (97.93% of a 60.4:39.6% (w/w) mixture of alkenyl sulfonate
    and hydroxyalkane sulfonate; chain-length distribution, 25% C14,
    45% C16, 30% C18) were fed to four groups of 50 male and 50
    female CFY rats at a dietary level of 0, 1000, 2500, or 5000 ppm,
    corresponding to 49, 122, or 245 mg/kg body weight per day, for two
    years. No adverse clinical signs were seen, and survival rates were
    not affected by treatment. The rate of body weight gain was
    marginally lower during the second trimester of the study in both
    males and females receiving 5000 ppm, and food intake was marginally
    lower during the first year among females receiving 5000 ppm. During
    the remainder of the study, body weight gain and food consumption
    were similar to those of the control animals. Investigation of the
    eyes, blood, and urine of controls and of those receiving 5000 ppm
    several times during the experiment revealed no reaction to
    treatment; and no changes related to treatment were seen in gross
    appearance or organ weights of rats in any group killed after 104
    weeks. Histological examination of a limited range of tissues did
    not provide evidence of toxicity or tumour induction that could be
    attributed to treatment (Hunter & Benson, 1976).

        Groups of 40 male and 40 female Wistar rats were fed the
    following materials in the diet for 24-27 weeks: 1, 0.75, or 0.5%
    C14-C18 AOS (corresponding to 500, 375, or 250 mg/kg body weight
    per day); 1, 0.75, or 0.5% C14-C18 AOS (corresponding to 500,
    375, or 250 mg/kg body weight per day); or 0.33, 0.25, or 0.16%
    C161,4-sultone (corresponding to 165, 125, or 80 mg/kg body weight
    per day). One control group consisted of 100 males and 100 females
    and another of 40 males and 40 females. No excess of tumours over
    that in controls was observed with any treatment (Haar, 1983).

        In 70-week studies on Wistar rats, 0.5 ml of a 1.0, 10, or 30%
    aqueous solution of AOS or 0.5 ml of a 50% aqueous solution of a
    detergent based on AOS was applied dermally; 24 h after the
    application, each site was washed with warm water. No abnormal gross
    or histopathological findings were reported (Tomizawa, 1978).

        These studies are summarized in Table 32.

    B7.4  Skin and eye irritation; sensitization

        AOS (C10; purity, 99.21%) were applied as 0.5 g of a 20 or 30%
    solution once a day for 15 days to the backs of three male Wistar
    rats. The skin at the application site and the tissues of the tongue
    and oral mucosa of animals receiving the 30% solution were examined
    histologically 16 days after application. Body weight gain was
    reduced in the group given the 20% solution, and body weight was
    decreased in the group at 30%. Macroscopically, there were no
    abnormalities at the application site. Histologically, although
    atrophy of the stratum spinosum was noted, neither necrosis nor

        Table 32.  Carcinogenicity of alpha-olefin sulfonates (AOS) after long-term exposure
                                                                                                                                    

    Species, strain,          Test material    Route      Dosage                 Results                          Reference
    numbers per group         (specification)
                                                                                                                                    

    Mouse, Swiss-Webster      AOS, C14-C18     Dermal     0, 200, 250 mg/kg      No gross or histopathological    Haar (1983)
       40 M, 40 F                                         (water, acetone)       adverse effects on skin
                                                                                 3 times/week,
                                                                                 92 weeks

    Mouse, Swiss-Webster      AOS, C14-C16     Dermal     0, 200, 250 mg/kg      No gross or histopathological    Haar (1983)
       40 M, 40 F                                         (water, acetone)       adverse effects on skin
                                                                                 3 times/week,
                                                                                 92 weeks

    Rat, CFY, 50 M, 50 F      AOS, C14-C18     Oral       0, 0.1, 0.25, 0.5%,    No adverse effects               Hunter & Benson
                              (a.i., 97-93%)   (diet)                            2 years                          (1976)

    Rat, X-MRC, 40 M, 40 F    AOS, C14-C18     Oral       0, 0.5, 0.75, 1.0%,    No excess of tumours in          Haar (1983)
                                               (diet)     24-27 months           comparison with controls

    Rat, X-MRC, 40 M, 40 F    AOS, C14-C16     Oral       0, 0.5, 0.75, 1.0%,    No excess of tumours in          Haar (1983)
                                               (diet)     24-27 months           comparison with controls

    Rat, Wistar, 10 M, 10 F   AOS, C16-C19     Dermal     0, 250, 2500, 7500     No gross or histopathological    Tomizawa (1978)
                                                          mg/kg bw, 3 times      abnormalities
                                                          per week, 70 weeks

    Rat, Wistar, 10 M, 10 F   AOS-based        Dermal     12.5 g/kg bw           No gross or histopathological    Tomizawa (1978)
                              detergent                   3 times/week,          abnormalities
                                                          70 weeks
                                                                                                                                    

    M, male; F, female; a.i., active ingredient
        inflammatory cell infiltration was present. No abnormalities of the
    tongue were observed, but severe atrophy was observed in the mucosa
    of the oral cavity. The local lesions caused by application of AOS
    were reported to be minimal in comparison with those induced by
    application of linear dodecylbenzenesulfate or lauryl sulfate (Sadai
    & Mizuno, 1972).

        Solutions of 0.05-4% AOS (sodium salt of sulfonated C15-C18  
     n-alpha-olefin) were instilled at a dose of 0.1 ml into the eyes
    of one to three rabbits, and the eyes were examined after 24 h. No
    abnormal findings were observed with the 0.05% solution, but slight
    congestion was observed with 0.1% and marked reactions, including
    severe congestion and oedema, increased secretion, opacity of the
    cornea, and absence of the corneal reflex, were observed at > 1%
    (Oba et al., 1968a).

        Solutions of C14-C19 olefin (84% C15-C17) and five other
    solutions consisting mainly of C10, C12, C14, C16, or C18
    were instilled into the eyes of three rabbits at one of six
    concentrations ranging from 0.01 to 5%. The rabbits were examined
    over a period of 168 h. The materials elicited similar reactions. No
    abnormal reaction was seen with 0.05%; slight congestion was
    observed with 0.1% within 2 h after application of the solution; and
    marked congestion or oedema was observed with 0.5%, which
    disappeared by 24 h. In the groups treated with 1 or 5%, marked
    reactions, including severe congestion and oedema, increased
    secretion, turbidity of the cornea, and disappearance of the corneal
    reflex, continued for 24 h but had usually completely disappeared by
    120 h (Iimori et al., 1972).

        In 1973, the apparent sensitizing potential of AOS attracted
    attention (Haar, 1983). AOS can contain unsaturated gamma-sultones
    when manufactured under certain conditions, and these are strong
    sensitizers in guinea-pigs (Haar, 1983; Roberts & Williams, 1983;
    Roberts et al., 1990). When the levels of these sultones were
    reduced to low levels by altering the manufacturing techniques, AOS
    no longer caused sensitization (Haar, 1983; Oba et al., 1985;
    Roberts et al., 1990).

        Skin sensitization was studied in guinea-pigs with pastes made
    of C14-C16 AOS, a light-duty dishwashing detergent containing
    AOS, some consumer products containing AOS, and mixtures of these
    products with alkyl unsaturated sultone in sodium lauryl sulfate or
    hypochlorite bleach. The pastes, the dishwashing detergent, most of
    the consumer products, and the mixtures with hypochlorite bleach
    induced sensitization, the degree of response being related to the
    amount of unsaturated gamma-sultone present in the material tested
    (Bay & Danneman, 1985).

    B7.5  Reproductive toxicity, embryotoxicity, and teratogenicity

        AOS (C14-C18) were administered at a concentration of 0.2,
    2, 300, or 600 mg/kg body weight per day to CD rats, CD-1 mice, and
    NZW rabbits orally once a day by gavage. Groups of 20 rats and mice
    were  given AOS on days 6-15 of pregnancy, and groups of 13 rabbits
    were treated on days 6-18 of pregnancy. The doses of 0.2 and 2 mg/kg
    were estimated to be equivalent to 1-2 and 10-20 times the maximal
    amount of AOS to which humans are exposed. No adverse effects were
    seen in rat dams, even at the maximal dose. Mouse dams given 300 or
    600 mg/kg showed piloerection, decreased movement, and inhibition of
    body weight gain; six dams at 600 mg/kg died. All rabbits given
    600 mg/kg and one given 300 mg/kg died; anorexia and decreased body
    weight were seen initially in surviving dams given 300 mg/kg. Both
    mouse and rabbit dams given 0.2 or 2 mg/kg showed only initial
    inhibition of body weight gain. No adverse effects were seen on
    litter parameters of rats at any dose. In mice, total litter loss
    was found in five dams given 600 mg/kg and in six dams given
    300 mg/kg; however, the average number of live fetuses in the other
    dams was no different from that in controls. The average body
    weights of the fetuses of dams given 300 or 600 mg/kg was
    significantly lower than that of controls. The incidence of major
    malformations was not significantly increased in rats, mice, or
    rabbits. There were no significant minor anomalies or skeletal
    variations (extra ribs) in rats at any dose. The offspring of mice
    at 600 mg/kg had a significant increase in delayed ossification.
    Those of rabbits at 300 mg/kg had a significant increase in skeletal
    anomalies and variations, although the incidence of skeletal
    variations was within the normal background range, and there was no
    delayed ossification. The effects of AOS on the fetuses, such as
    changes in litter parameters and delayed ossification, were
    considered to reflect the effects of AOS on the dams. There were no
    adverse effects on fetuses of mouse or rabbit dams given 0.2 or
    2 mg/kg or on fetuses of rat dams given 0.2, 2, 300, or 600 mg/kg,
    where effects on the dams were either not observed or were minimal
    (Palmer et al., 1975b).

        AOS and AOS-S (a synthetic detergent with AOS as the main
    ingredient) were applied to the shaven dorsal skin of mice at a dose
    of 0.5 ml/mouse per day of a 0.1% (the concentration of AOS usually
    found in detergents), 1%, or 5% aqueous solution of AOS or a 0.5%
    (equivalent to 0.1% AOS), 5%, or 25% aqueous solution of AOS-S on
    days 0-14 of pregnancy. Adverse effects on the dams and fetuses were
    found in a few cases. None of the dams died; the viability, body
    weight, and sex ratio of the fetuses did not differ from those of
    controls; and there were no malformations (Sawano, 1978).

    B7.6  Mutagenicity and related end-points

        AOS did not cause differential toxicity in  Bacillus subtilis
    rec at a concentration of 20 µg/disc or reverse mutation in
     Salmonella typhimurium TA98 or TA100 at 10-100 µg/disc, in the
    presence or absence of metabolic activation (Oda et al., 1980).

        One batch of AOS (C14-C16; 28.4% active ingredient) induced
    host-mediated mutagenicity at 283 mg/kg body weight in rats
    inoculated with  S. typhimurium TA1530 but not in an assay with
    TA1534 or in plate incorporation assays with either strain (Arthur
    D. Little Inc., 1993).

    B7.7  Special studies

        Rabbit erythrocytes were mixed with solutions containing various
    concentrations of AOS (sodium salt of sulfonated C15-C16
     n-alpha-olefin; average relative molecular mass, 338.5) at room
    temperature for 3 h. The 50% haemolytic concentration was
    1.5 mg/litre (Oba et al., 1968a). The effects of AOS on
    methaemoglobin formation were studied in groups of three male mice
    given an oral or intraperitoneal dose of 0.3 or 3.0 g/kg body weight
    C15-C18 AOS. The level of methaemoglobin in blood was measured
    0.5, 1, 2, 3, and 24 h after administration of AOS. No significant
    increase was observed (Tamura & Ogura, 1969).

        In an immunological study of AOS, a complex (HA) prepared by
    mixing AOS with human serum albumin (HSA) containing 30 mg of total
    protein was injected subcutaneously or intravenously into rabbits
    during a period of 2.5 months, and the anti-serum produced was
    subjected to the ordinary precipitation reaction. As a control,
    anti-AOS-serum, similarly prepared, was subjected to the same
    reaction. Minor positive reactions were seen in the HA-anti-HA and
    HSA-anti-HSA systems but not in the AOS-anti-HA or AOS-anti-AOS
    systems (Iimori & Ushiyama, 1971).

    B8.  EFFECTS ON HUMANS

     Section summary

        In patch tests, human skin can tolerate contact to solutions
    containing up to 1% AOS for 24 h with only mild irritation. AOS can
    cause delipidation of the skin surface, elution of natural
    moisturizing factor, denaturation of the outer epidermal layer
    proteins, and increased permeability and swelling of the outer
    layer. AOS did not induce skin sensitization in volunteers. There is
    no conclusive evidence that AOS induce eczema. No serious injuries
    or fatalities have been reported following accidental ingestion of
    detergent formulations that could contain AOS.

    B8.1  Exposure of the general population

        AOS surface-active agents are found in shampoos, dishwashing
    products, household cleaners, and laundry detergents. The
    composition of nonionic and ionic surfactants in these products
    varies between 10 and 30%. Surface-active agents can affect human
    skin and eyes.

    B8.2  Clinical studies

    B8.2.1  Skin irritation and sensitization

        AOS are mildly to moderately irritating to human skin, depending
    on the concentration.

        The relative intensity of skin roughness induced on the surface
    of the forearm was evaluated in volunteers by a circulation method
    consisting of contact with 1% solutions of C12, C14, C16, and
    C18 AOS for 10 min. The skin response was characterized mainly on
    the basis of gross visible changes. C12 AOS induced more skin
    roughening than compounds with longer or shorter alkyl chains. The
    relative degree of skin roughening  in vivo was correlated with the
    extent of protein denaturation measured  in vitro (Imokawa et al.,
    1975a).

        Primary skin irritation induced by a 1% aqueous solution
    (pH 6.8) of AOS containing 27% C15, 25% C16, 28% C17, and 18%
    C18 (relative molecular mass, 338.5) was studied in a 24-h
    closed-patch test on the forearms of seven male volunteers. The
    intensity of skin irritation was scored by grading erythema,
    fissuring, and scales. The average score for AOS was 3.97 and that
    for a control (water) was 1.79. The same compound was evaluated at
    0.3% for the relative intensity of skin lesions produced on the
    surface of the hands by an immersion test involving 30 repetitions
    of a 1-min dip and 1-min dry. The average score for AOS with regard
    to erythema, irritation, fissuring, scaling, and loss of suppleness

    was 5.75, while that for the water control was 2.5 (Oba et al.,
    1968a).

        Skin irritation induced by a 1% aqueous solution of C14,
    C16, and C18 AOS was studied in a 24-h closed-patch test on the
    forearm and in a test in which the compound was dripped onto the
    interdigital surface for 40 min once daily for two consecutive days
    at a rate of 1.2-1.5 ml/min. Skin reactions were scored by grading
    erythema in the patch test and by grading scaling in the drip test.
    The score for AOS was 1 (slight erythema) in the patch test and 0.35
    (minimal scaling) in the drip test (Sadai et al., 1979).

        In sensitization tests on volunteers, AOS in a paste or in a
    detergent mixture containing up to 0.06% AOS and up to 0.002 ppm
    unsaturated g-sultone did not produce sensitization, although one
    subject had a strong dermal response, which was considered to be due
    to pre-existing sensitization. Two out of 264 subjects using a
    light-duty detergent containing AOS  developed hand dermatitis and
    had positive reactions to AOS paste and/or unsaturated gamma-sultone
    in sodium lauryl sulfate in a patch test. Use of a hand dishwashing
    liquid containing AOS  did not cause sensitization provided the
    level of unsaturated g-sultones was kept low (Bay & Danneman, 1985).
    Patch tests on 790 volunteers after four months' use of a
    dishwashing liquid showed no evidence of sensitization (Oba et al.,
    1985).

    B8.2.2  Effects on the epidermis

        The effects of AOS on the epidermal outer layer (stratum
    corneum) are similar to those of other surface-active agents (see
    section 8.2.2 of the monograph on LAS), including delipidation of
    the skin surface, elution of natural moisturizing factor,
    denaturation of stratum corneum protein, increased permeability,
    swelling of the stratum corneum, and inhibition of enzyme activities
    in the epidermis (Wood & Bettley, 1971; Imokawa et al., 1974;
    Okamoto, 1974; Imokawa et al., 1975a,b).

        The effects of anionic surfactants on various types of proteins
    were studied using skin keratin as a filamentous protein, bovine
    serum albumin as a globular protein, acid phosphatase as an enzyme
    protein, and membrane lysosome as a membrane protein. The denaturing
    effects of surfactants were measured as liberation of sulfhydryl
    groups and enzyme inhibition. AOS were less potent than LAS or alkyl
    sulfates. A relationship was observed between denaturing potency,
    skin irritant action, and alkyl chain length (Imokawa & Katsumi,
    1976; Imokawa & Mishima, 1976).

    B8.2.3  Hand eczema

        Skin reactions to a 0.04, 0.4, or 4.0% aqueous solution of AOS
    (25.0% C14, 45.0% C16, 30.0% C18)were evaluated in a 24-h
    closed-patch test on the lower back of 10 healthy volunteers and 11
    patients with hand eczema (progressive keratosis palmaris). The
    incidence and intensity of skin reactions were significantly higher
    in the group with hand eczema than in a control group with normal
    skin (Okamoto & Takase, 1976a,b).

    B8.2.4  Accidental or suicidal ingestion

        No data were available that related specifically to AOS.

    B9.  EFFECTS ON OTHER ORGANISMS IN THE LABORATORY AND THE FIELD

     Section summary

        Limited data are available on the effects of AOS on
    environmental organisms. The 24-h LC50 values for daphnids were
    19-26 mg/litre; the 48-h LC50 values ranged from 0.3 mg/litre for
    brown trout  (Salmo trutta) to 6.8 mg/litre for golden orfe  (Idus
     idus melanotus), and the 96-h LC50 was 0.5-5.0 mg/litre for
    brown trout. One study suggested that AOS have little toxicity for
    birds.

    B9.1  Microorganisms

        No information was available.

    B9.2  Aquatic organisms

    B9.2.1  Aquatic plants

        The EC50 values for C16.4 AOS in the green alga  Selenastrum
     capricornutum exposed for two to three days, based on growth, fell
    within the range 45-65 mg/litre (Yamane et al., 1984). The EC50
    for C16-C18 AOS on the growth of  S. capricornutum was >
    20 mg/litre (Konno & Wakabayashi (1987).

    B9.2.2  Aquatic invertebrates

         Daphnia magna and  Dapghnia pulex less than 24 h old were
    exposed to C16-C18 AOS under static conditions, in which the
    water was unchanged for the duration of the test, at a temperature
    of 20°C and a water hardness of 25 mg/litre CaCO3. The 6-h LC50
    values were > 64 and > 130 mg/litre, and the 24-h LC50 values
    were 19 and 26 mg/litre, for the two species respectively
    (Wakabayashi et al., 1988).

    B9.2.3  Fish

        The acute toxicity of AOS to fish is summarized in Table 33. The
    48-h LC50 values ranged from 0.3 mg/litre for brown trout  (Salmo
     trutta) to 6.8 mg/litre for golden orfe  (Idus idus melanotus);
    the 96-h LC50 for brown trout was 0.5-5.0 mg/litre. Acute toxicity
    tended to increase with carbon chain length.

        When eggs of rainbow trout  (Oncorhynchus mykiss) and carp
     (Cyprinus carpio) were exposed to C16-C18 AOS, the EC50
    values, based on hatchability, were 4.9 for rainbow trout and
    3.0 mg/litre for carp (Wakabayashi & Onizuka, 1986). In one-month
    old rainbow trout under semi-static conditions, the 14- and 28-day
    LC50 values for C16-C18 AOS were 0.62 and 0.58 mg/litre. The

    EC50 based on growth was 0.35 mg/litre (Wakabayashi & Mizorogi,
    1989).

        The time to lethality in goldfish  (Carassius auratus) exposed
    to AOS was 2 h at a concentration of 5 mg/litre and 1 h at
    10 mg/litre. Addition of 2100 mg/litre egg albumin increased the
    time to 100% lethality to 3 h and addition of 4200 mg/litre albumin
    increased the time to 6 h (Tomiyama, 1974).

    B9.3  Terrestrial organisms

    B9.3.1  Terrestrial plants

        AOS were not toxic with respect to growth at the early life
    stages of radish, Chinese cabbage, and rice when added in hydroponic
    culture at concentrations of 56, 56, and 32 mg/litre, respectively;
    concentrations of 100, 100, and 56 mg/litre were toxic (Takita,
    1982).

    B9.3.2  Terrestrial invertebrates

        No information was available.

    B9.3.3  Birds

        No significant effect on egg quality was found after Leghorn
    chickens were fed a diet containing 200 mg/kg AOS for 45 days
    (Lopez-Zavala et al., 1975).

        Table 33.  Toxicity of alpha-olefin sulfonates (AOS) to fish
                                                                                                                                              

    Species           Length,        Static or     Temp.         Hardness        pH     AOS chain     End-point     Concn        Reference
                      weight,        flow          (°C)          (mg/litre)a            length                      (mg/litre)
                      or age
                                                                                                                                              

    Masu trout        2 mo           Staticr       8.5-9.6       30              NS     C16-C18       96-h LC50     0.56        
    Wakabayashi
    (Oncorhynchus                                                                                                                et al. (1984)
    masou)

    Rainbow trout     40 d           Staticr       8.8-10.9      25              NS                   96-h LC50     0.78         Wakabayashi
    (Oncorhynchus                                                                                                                et al. (1984)
    mykiss)           4 d            Staticr       10            25              NS     C16-C18       96-h LC50     0.61         Wakabayashi
                      19 d           Staticr       10            25              NS     C16-C18       96-h LC50     0.98         & Onizuka
                                                                                                                                 (1986)

    Brown trout       2.8-5.8 cm     Flow          15            26-30           NS     C14-C16       48-h LC50     2.5-5.0b     Reiff et al.
    (Salmo trutta)    2.8-5.8 cm     Flow          15            26-30           NS     C14-C16       96-h LC50     2.5-5.0b     (1979)
                      2.8-5.8 cm     Flow          15            26-30           NS     C16-C18       48-h LC50     0.6b
                      2.8-5.8 cm     Flow          15            26-30           NS     C16-C18       96-h LC50     0.5b
                      2-4 cm         Flow          15            250             NS     C14-C16       48-h LC50     3.5b
                      2-4 cm         Flow          15            250             NS     C16-C18       96-h LC50     3.1b
                      2-4 cm         Flow          15            250             NS     C14-C16       48-h LC50     0.3-0.5b

    Goldfish                         Static        20                            NS     C12-C16       6-h LC50      11.2c        Gafa (1974)
    (Carassius auratus)              Static        20                            NS     C14-C18       6-h LC50      3.0c
                                                                                                                                              

    Table 33 (contd)
                                                                                                                                              

    Species           Length,        Static or     Temp.         Hardness        pH     AOS chain     End-point     Concn        Reference
                      weight,        flow          (°C)          (mg/litre)a            length                      (mg/litre)
                      or age
                                                                                                                                              

    Golden orfe       1.2-1.8 g      Static        20                            NS     C14-C16       48-h LC50     5.08         Mann (1976)
    (Idus idus        1.2-1.8 g      Static        20                            NS     C16-C18       48-h LC50     1.44
    melanotus)        5-7 cm         Flow          20            150             NS     C14-C16       48-h LC50      5.7b         Reiff et al.
                      5-7 cm         Flow          20            150             NS     C16-C18       48-h LC50      1.9b         (1979)
                                     Flow          20            268             NS     C14-C16       48-h LC50     3.7-6.8b
                                     Flow          20            268             NS     C16-C18       48-h LC50     1.0b
                                     Flow          20            268             NS     C14-C16       96-h LC50     3.4-4.9b
                                     Flow          20            268             NS     C16-C18       96-h LC50     0.9b

    Harlequin fish                   Flow          20            20              NS     C14-C16       48-h LC50     4.8b         Reiff et al.
    (Rasbora                         Flow          20            20              NS     C16-C18       48-h LC50     0.9b         (1979)
    heteromorpha)                    Flow          20            20              NS     C14-C16       96-h LC50     3.3b
                                     Flow          20            20              NS     C16-C18       96-h LC50     0.5b

    Medaka            175-332 mg     Static        21-22         25            6.7-7.1  C14-C18       6-h LC50      6.2b         Kikuchi &
    (Oryzias latipes) 175-332 mg     Static        21-22         25            6.7-7.1  C14-C18       48-h LC50     1.8b         Wakabayashi
                      175-332 mg     Static        21-22         25            6.7-7.1  C16-C18       6-h LC50      2.7b         (1984)
                      175-332 mg     Static        21-22         25            6.7-7.1  C16-C18       48-h LC50     0.81b

    Carp              3.5-5.5 cm     Static        21                          7.5-7.8  Technical     24-h LC50     3.2c         Lopez-Zavala
    (Cyprinus carpio) 3.5-5.5 cm     Static        21                          7.5-7.8  Technical     96-h LC50     3.0c         et al. (1975)
                      2 d            Staticr       20            25              NS     C16-C18       96-h LC50     > 1.4        Wakabayashi
                      15 d           Staticr       20            25              NS     C16-C18       96-h LC50     1.5          & Onizuka
                                                                                                                                 (1986)
                                                                                                                                              

    Table 33 (contd)
                                                                                                                                              

    Species           Length,        Static or     Temp.         Hardness        pH     AOS chain     End-point     Concn        Reference
                      weight,        flow          (°C)          (mg/litre)a            length                      (mg/litre)
                      or age
                                                                                                                                              

    Carp (contd).     50 d           Staticr       21            75              NS                   96-h LC50     1.0          Wakabayashi
    (Cyprinus carpio)                Staticr                                                                                     et al. (1984)

    White tilapia     5-7 cm         Static        21                            7.5-7.8   Technical  24-h LC50     2.0c         Lopez-Zavala
    (Tilapia melan    5-7 cm         Static        21                            7.5-7.8   Technical  96-h LC50     2.0c         et al. (1975)
    opleura)

    Grey mullet                      Static        20.6-22.0                                          96-h LC50     0.70         Wakabayashi
    (Mugil cephalus)                                                                                                             et al. (1984)
                                                                                                                                               

    Staticr, static renewal:  water changed at regular intervals; flow, flow-through conditions: concentration in water maintained
    continuously; static:  water unchanged for duration of test
    a mg/litre CaCO3
    b Measured concentration
    c Nominal concentration
        C.  Alkyl sulfates

    C1.  SUMMARY

        See Overall Summary, Evaluation, and Recommendations (pp. 7-21)

    C2.  IDENTITY, PHYSICAL AND CHEMICAL PROPERTIES, AND
         ANALYTICAL METHODS

    C2.1  Identity

    Chemical formula:        CnH2n+1O4S Na ( n = 10-8)

    Chemical structure:      CnH2n+1OSO3- Na+ ( n, integer)

    Common names:            Sodium alkylsulfate, sulfuric acid alkyl
                             ester sodium salt, alkylsulfate sodium salt,
                             alcohol sulfuric ester sodium salt, sodium
                             dodecyl sulfate, sodium lauryl sulfate

    Common trade names:      Akyporox SAL SAS, Akyposal, Alphenate TFC
                             76, Alscoap LN, Aremsol, Berol, Cosmopon,
                             Dehydag, Elfan, Emal, Empicol, Gardinol,
                             Genapol CRT 40, Manro, Marlinat KT 50,
                             Melanol LP 1, Monogen, Montopol CST,
                             Montovol, Neopon LT, Nikkol, Nissan Persoft
                             SK, Perlankrol ATL-40, Perlankrol, Polystep
                             B, Rewopol, Sactipon, Sactol, Sandopan KD,
                             Sermul, Stepanol WA 100, Sufatol, Sufetal,
                             Sulfopon, Sunnol, Surfax, Swascol, Teepol HB
                             7, Tensopol Tesapon, Texapon, Ufarol AM 70,
                             Zoharpon, Zorapol LS-30, (McCutcheon, 1993)

    Abbreviations:           AS, AS-Na, SDS

    CAS Registry numbers:    151-21-3 (C12 AS), 1120-04-3 (C18 AS),
                             68130-43-8 (C8-C18 AS)

    Specification:           AS are higher alcohol sulfuric ester salt
                             types of anionic surfactants. Depending on
                             which precursor alcohol is used as the raw
                             material, the alkyl group is linear or
                             branched, may contain a single homologue or
                             a mixture of chain lengths, and is usually
                             primary. The data presented are applicable
                             mainly to linear alcohol sulfates and AS
                             with predominantly single or similar type of
                             branching.

    C2.2  Physical and chemical properties

        AS are white crystalline powders. Their physical properties differ
    widely depending on their alkyl groups, and they are usually produced
    and used as mixtures. The relationships between the critical micelle
    concentration, solubility, and alkyl chain length are shown in Table
    34.

    Table 34.  Relationships between alkyl chain length, critical
               micelle concentration (CMC), and solubility
                                                                 

    Alkyl chain      CMC × 10-3       Solubility/°Cb,c
      length         mol/litrea,c
                                                                 
         8               136                 -
        12               8.6                15
        14               2.4                28
        16              0.58                42
        18              0.16                55
                                                                 

    a  From Evans (1956)
    b  Temperature at which 10 g of AS dissolve in 1 litre of water
       (Gotte, 1954)
    c  The solubility of surfactants in water, defined as the
       concentration of dissolved molecules in equilibrium with a
       crystalline surfactant phase, increases with rising temperature.
       For surfactants, there is a distinct, sharp bend (break-point) in
       the solubility-temperature curve. The steep increase in solubility
       above the sharp bend is caused by micelle formation. At above the
       critical micelle concentration, a micellar solution is formed.
       Under these conditions, higher levels than the aqueous solubility
       may be obtained.

        AS are readily hydrolysed in hot acidic media. Compounds with an
    alkyl chain length of C10 (27°C), C12 (25°C), C14 (40°C), or
    C16 (40°C) have a surface tension of 40 dyne/cm at the temperatures
    shown in parentheses at concentrations greater than the critical
    micelle concentration, indicating a good ability to reduce surface
    tension (Dreger et al., 1944).

        Cleansing capacity at 25°C increases with alkyl chain length up to
    C13 and then becomes constant up to C16. In an actual detergent
    containing alkali builders and chelating agents, however, maximal
    detergency was obtained with C14 compounds (Yamane et al., 1970).

    C2.3  Analysis

    C2.3.1  Isolation

        Since AS are readily susceptible to hydrolysis in acidic media,
    special attention is required.

    C2.3.2  Analytical methods

        There is no officially recognized, specific procedure for the
    analysis of AS in environmental samples. The methods used for
    analysing linear alkylbenzene sulfonates (LAS) are commonly used for
    AS, except those involving high-performance liquid chromatography
    (HPLC), which is of limited use for detecting AS in environmental
    samples because AS do not effectively absorb ultra-violet radiation.
    An HPLC method for the analysis of AS after its conversion by
    derivatization into an ultra-violet-active species has been proposed
    (Utsunomiya et al., 1982). A modified analytical method has been
    developed that is based on measurement of methylene blue-active
    substances (MBAS) by HPLC. This method permits determination of AS at
    concentrations as low as 0.05 mg/litre (Takita & Oba, 1985). Trace
    enrichment followed by gas chromatography and flame ionization
    detection have been proposed for the sensitive determination of AS as
    their trimethylsilyl ethers in environmental samples (Fendinger et
    al., 1992a).

        Non-specific methods used in the analysis of anionic surfactants
    in general, such as the methylene blue method, may be used for the
    analysis of AS (see also section 2.3 of the monograph on LAS).

    C3.  SOURCES OF HUMAN AND ENVIRONMENTAL EXPOSURE

     Section summary

        Few quantitative data are available on AS in the environment, but
    AS can be expected to mineralize rapidly in all environmental
    compartments and to be removed to a large extent during sewage
    treatment. Environmental concentrations in receiving surface waters,
    sediments, soils, estuaries, and the marine environment can be
    expected to be low.

    C3.1  Natural occurrence

        AS do not occur naturally.

    C3.2  Anthropogenic sources

    C3.2.1  Production levels and processes

        AS are synthesized industrially. Worldwide consumption of AS in
    1987 was about 117 000 tonnes in the United States, 56 000 tonnes in
    western Europe, and 46 000 tonnes in Japan (Richtler & Knaut, 1988).
    In western Germany in 1987, some 10 000 tonnes of AS and 87 000 tonnes
    of LAS were used (Schöberl et al., 1988). Worldwide consumption was
    estimated to be 289 000 tonnes in 1990 (Hewin International Inc.,
    1992; see Table 35).

    Table 35.  Estimated worldwide use of alkyl sulfates in
               1990 (tonnes)
                                                                 

    Region            Household   Personal care  Industrial and
                      products    products       institutional
                                                 use
                                                                 

    North America      140 000       33 000           9 000
    Western Europe      49 000       12 000           7 000
    Japan               21 000        6 000           4 000
    Rest of the              -        4 000           4 000
      world

    Total              210 000       55 000          24 000
                                                                 

    From Hewin International Inc. (1992)

        AS were originally made by the sulfation of natural fatty
    alcohols. They are currently produced from both natural and synthetic
    fatty alcohols. Primary AS are usually manufactured by conventional
    sulfation of the parent alcohol with either sulfur trioxide or
    chlorosulfonic acid. The product of this reaction is then neutralized
    with an appropriate base (NaOH, Na2CO3, NH4OH, or
    triethanolamines).

    C3.2.2  Uses

        Initially, AS were used as washing agents for wool or as active
    ingredients in heavy-duty laundry detergents. They are now used mainly
    in personal care products (shampoos, toothpastes, toiletries),
    household detergents (light-duty dishwashing detergents, heavy-duty
    laundry detergents), and industrial applications.

    C4.  ENVIRONMENTAL TRANSPORT, DISTRIBUTION, AND TRANSFORMATION

     Section summary

        AS can be expected to be transported into the environment by
    mechanisms similar to those that operate for LAS and alpha-olefin
    sulfonates (AOS). AS are readily biodegradable under aerobic
    conditions, both in laboratory tests and under environmental
    conditions, and primary biodegradation is complete within two to five
    days. Less information is available on the effect of temperature on
    the biodegradation of AS than for LAS. The biodegradation kinetics of
    AS appear to be less affected by temperature than those of other
    surfactants. The whole-body bioconcentration factors are 2-73,
    depending on chain length. AS are taken up by fish mainly through the
    gills and are subsequently distributed to the liver and gall-bladder.
    After biotransformation, AS are excreted rapidly. They are not
    bioconcentrated or biomagnified in aquatic organisms.

    C4.1  Transport and distribution between media

        After use, AS are discharged into the environment in wastewater,
    like other detergent compounds, where they can undergo sewage
    treatment if such facilities are available. In countries where
    adequate wastewater treatment facilities are not available, AS
    released to the environment are removed by biodegradation and
    adsorption in the receiving surface water (see section 4.2 of the
    monograph on AOS).

        Sorption equilibria were obtained rapidly (within 20 min) for pure
    homologues of AS (> 99%) with chain lengths of C8, C9, C10,
    C11, C12, C13, and C14, suggesting that sorption is due to a
    hydrophobic bonding mechanism, as has been observed for other
    surfactants. Thus, sorption of AS to sediment is likely to be stronger
    for longer chain homologues than for shorter ones. The KD values for
    C12 AS were 70 and 100 for two river sediments, whereas for C12
    LAS on the same sediments they were 310 and 330 (Marchesi et al.,
    1991). Adsorption of AS therefore competes in kinetic terms with
    biodegradation as a mechanism for removal of AS from the environment,
    as is seen for surfactants in general.

    C4.2  Biotransformation

    C4.2.1  Biodegradation

    C4.2.1.1  Biodegradation pathway; mechanism

        Several species of bacteria have been found that can mineralize
    AS. AS with chains longer than six carbons are degraded by the initial
    action of a sulfatase enzyme, producing sulfate and the corresponding

    alcohol. The alcohol is readily oxidized by formation of an aldehyde,
    to produce carboxy acid, which can be further oxidized by ß-oxidation
    and in the citric acid cycle. Secondary ketones and hydroxy ketones of
    AS are produced as metabolites but have not been detected in simulated
    activated sludge. Biodegradation of short-chain homologues of AS may
    proceed by oxidation of the chain before hydrolysis of the ester bond
    by the sulfatase enzyme.

        The metabolic pathway for biodegradation of C12 AS by
     Pseudomonas strains has been described (Hsu, 1965; Thomas & White,
    1989). Initial liberation of the sulfate head produces dodecanol,
    which is further transformed into more polar metabolites, including
    dodecanal and dodecanoic acid. These products may be further
    metabolized by ß-oxidation, or they may be elongated to C14, C16,
    or C18 fatty acyl residues, which are then incorporated into lipid
    fractions such as phospholipids (Thomas & White, 1989).

    C4.2.1.2  Biodegradation in the environment

        The aerobic biodegradation of 20 mg/litre AS at 27°C was followed
    during a 10-day incubation period. Primary degradation, measured by
    the MBAS method, was complete within five days. The theoretical
    production of CO2 reached 60-90% within 10 days (Itoh et al., 1979).

        The biodegradation of AS at a concentration of 30 mg/litre was
    studied in a vessel containing activated sludge at a concentration of
    100 mg/litre over a period of 12 days, by measuring chemical oxygen
    demand. All of the AS were lost within two days; the specific rate of
    biodegradation was calculated to be 20 mg/g per h (Pitter & Fuka,
    1979).

        The biodegradation of an initial concentration of 6 mg/litre C12
    AS was studied by the die-away method, in which disappearance of the
    compound is followed over a given period. Less than 10% of the
    original amount remained in river water in the test vessel after 12
    days' exposure, and complete degradation was reported within 21 days
    (Okpokwasili & Nwabuzor, 1988).

        The capacity of epilithic (sampled from the surface of pebbles)
    and planktonic river bacterial populations to degrade C12 AS was
    studied under simulated environmental conditions. Samples were
    collected from four polluted sites and one clean site in a polluted
    river in South Wales, United Kingdom. In die-away tests, AS were
    degraded after an apparent lag at all four polluted sites, but
    degradation by the bacterial populations at the clean site was
    relatively slow. Quantification of the kinetic components that
    contributed to the die-away curves demonstrated that biodegradation of
    AS occurred at concentrations below its Km by bacteria with
    exponential growth that are unaffected by addition of the test
    substrate. Degradation of AS in the clean sample followed a

    different pattern, but there was generally little or no growth on
    endogenous carbon. The authors concluded that the capacity of
    epilithic bacterial populations to degrade C12 AS is more stable
    than that of planktonic populations (Anderson et al., 1990).

        Riverine bacteria that can grow in the presence of
    0.5 mmol/litre C12 AS are widespread, and a greater incidence of
    isolates resistant to C12 AS was recorded at a polluted site than in
    clean water. The ability of each culture to produce alkyl sulfatases,
    the enzymes that initiate degradation of AS, was also determined.
    Bacteria containing alkyl sulfatases were widespread, but a greater
    alkyl sulfatase yield was obtained from polluted site. The authors
    concluded that more strains at the polluted site had constitutive
    rather than inducible enzymes. An increased incidence of strains
    containing multiple alkyl sulfatases was also recorded at the polluted
    site (White et al., 1985).

        In another study in South Wales, the distribution of planktonic
    bacteria capable of degrading 98.5% C12 was examined in water
    samples at sites along a river. The annual mean prevalence of such
    bacteria was 8.1-16.0% of the total number of isolates. The proportion
    of  isolates that degrade AS in clean water was no different from that
    at polluted sites, and a lower density was recorded at the source
    owing to a reduction in overall numbers. A higher percentage of
    bacteria capable of degrading C12 AS was recorded in estuarine
    samples than in samples from the middle of the polluted river;
    however, when cell numbers were taken into account, the cell density
    was similar at all polluted sites on the river, including the estuary.
    The incidence of these isolates was not correlated with either
    biochemical oxygen demand or oxygen concentration, but the incidence
    tended to increase at the end of the summer. More than half of the
    isolates contained constitutive alkyl sulfatase enzymes, while they
    were induced or repressed in the remainder after exposure to AS. No
    variation in the proportions of type of enzyme regulation was seen
    between sampling sites or times (White et al., 1989).

        The biodegradation of AS was also examined at three sites, above,
    at, and below a sewage works outfall on the South Wales river. Samples
    capable of degrading C12 AS after only one day's exposure were found
    at each site. No biodegradation of AS was reported at a pristine
    source site. The onset of biodegradation was more rapid following
    longer exposure of the river, suggesting the existence of an adaptive
    mechanism. A model of the die-away kinetics of degradation suggested
    that C12 AS were biodegraded by a bacterial population growing at
    the expense of endogenous carbon. The activity of the epilithic
    samples in degrading AS increased during the first four days of
    exposure at each site. The stabilized values (days 4-14) increased
    from the upstream site to the outfall, decreasing to intermediate
    values downstream. The sewage input had less effect on activities

    in degrading AS than on bacterial cell densities. Little variation in
    growth characteristics was seen throughout colonization at the three
    sites. The authors concluded that the adaptation seen during exposure
    in the river was attributable to colonization of the epilithon by an
    existing population that degradedC12 AS and not to acquisition or
    adaptation of biodegrading capacity (Russell et al., 1991).

        The half-life for primary degradation of 20 mg/litre C12 AS in
    seawater varied over a range of 0.26 to 0.34 days, and degradation was
    reported to follow first-order kinetics. Primary degradation was
    followed by an immediate increase in bacterial number and thymidine
    incorporation (Vives-Rego et al., 1987). C12 AS was found to be
    degraded rapidly in seawater, and 250 g/litre were found in sediment;
    at 25°C, 90% was degraded within five days. No lag phase was reported,
    and the degradation kinetics were reported to be first-order (Sales et
    al., 1987).

        C15-C16 AS were 98% removed at 15°C and 99% removed at 8°C
    (Gilbert & Pettigrew, 1984). Similarly, C12-C15 and C12-C14 AS
    were found (by the MBAS method) to be  biodegraded during winter and
    spring in a trickling filter sewage treatment plant (Mann & Reid,
    1971). These results suggest that temperature has no major effect on
    the removal of alkyl sulfates under environmental conditions.

        Primary biodegradation of C12 AS was less affected by incubation
    temperature than that of other anionic surfactants in die-away tests
    with water from the Tama River, Japan. Primary biodegradation was
    complete within one day at temperatures of 21 and 27°C, within two
    days at 15°C, and within three days at 10°C (Kikuchi, 1985).

        Over 99% of MBAS activity in activated sludge was lost in a 19-day
    OECD screening test and in the 28-day OECD confirmatory test.
    Mineralization of both C12-C14 and C16-C18 AS was complete,
    with 90-95% degradation for C12-C14 AS and 77-88% for C16-C18
    AS in the two test systems (Steber & Wierich, 1987).

    C4.2.1.3  Anaerobic degradation

        Biodegradation of AS under anaerobic conditions has been reported
    in several studies, with 88% degradation of stearyl sulfate containing
    C14 AS in an anaerobic screening test (Birch et al., 1989) and 95%
    ultimate degradation of the same compound (Steber & Wierich, 1987).

    C4.2.2  Abiotic degradation

        No information was available.

    C4.2.3  Bioaccumulation and biomagnification

        Carp  (Cyprinus carpio) were exposed to 35S-C12 AS at a
    concentration of 0.85 mg/litre for up to 24 h. Within 1 h, AS was
    concentrated in the gills, hepatopancreas, and kidneys with
    concentration factors of 1.6, 1.4, and 1.5, respectively. After the
    initial uptake in the gills, the levels of AS fell, and other organs
    and tissues, such as the skin surface, muscle, brain, kidney,
    hepatopancreas, and gall-bladder showed gradual uptake over the
    exposure period. The concentration factors after 24 h ranged from 2.0
    for the skin surface to 43 for gall-bladder. Blood and kidney also
    showed uptake, but the levels after 24 h were less than those after 4
    and 8 h, respectively. AS were lost rapidly from all tissues except
    the gall-bladder when the fish were kept in 'clean' water for 48 h
    (Kikuchi et al., 1978).

        Carp maintained in water containing 0.5 mg/litre 35S-C12 AS
    absorbed the compound within 1 h, and an equilibrium for the whole
    body and gall-bladder was reached within 24 h, with concentration
    factors of about 4 and 700, respectively. After 24 h, the levels of AS
    in hepatopancreas had decreased from the initial level. When the fish
    were transferred to 'clean' water, 50% of the AS was still present
    after 72 h (Wakabayashi et al., 1978).

        When carp were exposed to 35S-C12 AS at concentrations between
    2.7 µg/litre and 40 mg/litre for up to 120 h, equilibrium was reached
    within 72 h, at concentration factors of 3.9-5.3, which were
    independent of the concentration of AS in solution (Wakabayashi et
    al., 1981).

        In a study of the effect of chain length on the uptake of AS, carp
    were exposed to 0.5 mg/litre of 35S-C12, 35S-C14, or
    35S-C16 AS for 24 h. Absorption of AS reached a maximum within the
    exposure period. The whole-body concentration factors were 2.1, 11,
    and 73 for the three surfactants respectively, and thus increased with
    alkyl chain length. This tendency was also observed in gills and
    hepatopancreas, but the factors in the gall-bladder were almost the
    same for the three homologues. When fish were transferred to 'clean'
    water, the elimination rate decreased with increasing carbon chain
    length, and 50% of C16 AS was retained after 120 h (Wakabayashi et
    al., 1980).

        The absorption, tissue distribution, metabolism, and route of
    excretion of 50 mg/litre C12 AS were studied in goldfish  (Carassius
    auratus) exposed for 24 h. AS was absorbed mainly through the gills
    and was distributed rapidly throughout the body; it was absorbed to a
    lesser extent (20% of total) by cutaneous absorption and orally (8%).
    The highest concentration of AS was measured in the gall-bladder,
    mainly because of its small size. The greatest proportion of the
    absorbed AS was located in the body, gut, liver, and gall-bladder. The
    level of AS in the tissues fell by 38% over 24 h in unfed fish and by

    68% in fed fish. The high concentration of AS in the liver and
    gall-bladder was thought to indicate metabolism of the compound in the
    liver. The metabolites of AS that were identified included successive
    products of ß-oxidation of the alkyl chain and butyric-4-sulfate
    (Tovell et al., 1975).

    C4.3  Interaction with other physical, chemical, and biological
          factors

        The presence of 1 mg/litre AS (chain length unspecified) had no
    significant effect on the uptake of mercury by phytoplankton
    ( Diogenes sp.) or mussels ( Mytilus sp.) (Laumond et al., 1973).

        Exposure of bacteria to 20 mg/litre phenol and 0.5 mg/litre C12
    AS resulted in a directly additive effect. Exposure to 2.5 mg/litre
    phenol and 0.5 mg/litre AS resulted in a synergistic effect. No
    interactive effects were reported between sodium cyanide and AS in the
    same test protocol (Dutka & Kwan, 1982).

    C4.4  Ultimate fate following use

        As no specific analytical method is available for AS, their
    concentrations in environmental samples have not been established.
    Like detergent compounds, AS are present in wastewater after use. A
    large proportion is removed during treatment of wastewater, mainly as
    a result of a combination of biodegradation and adsorption processes.
    As for other surfactants, these processes continue when AS are
    released into the environment.

    C5.  ENVIRONMENTAL LEVELS AND HUMAN EXPOSURE

     Section summary

        Data on the environmental concentrations of AS are limited. At
    sewage treatment plants where the influent concentrations of AS were
    < 0.01-0.7 mg/litre, the effluent contained predominantly C12 AS,
    at concentrations of < 0.005-0.1 mg/litre. Surface waters receiving
    treated wastewater contained AS at concentrations below the detection
    limit of 0.005 mg/litre.

     Environmental levels

        AS were measured at two sewage treatment plants in the United
    States where the influent concentrations were < 0.01-0.7 mg/litre,
    which were at least 2.4 times lower than those predicted on the basis
    of use of AS and per-capita wastewater in the United States. The
    predominant homologues of AS in untreated wastewater were C12,
    C14, and C15. The effluent contained predominantly C12 AS, at
    concentrations of < 0.005-0.1 mg/litre, showing that removal exceeded
    98% during rotating biological contact and activated sludge treatment.
    Surface waters receiving treated wastewater contained AS at
    concentrations below the detection limit of 0.005 mg/litre (Fendinger
    et al., 1992a,b).

    C6.  KINETICS

     Section summary

        AS are readily absorbed by the gastrointestinal tract after oral
    administration and are excreted principally in the urine, only minor
    amounts being eliminated in the faeces. Penetration of AS through
    intact skin appears to be minimal. AS are extensively metabolized in
    various species to several metabolites. Butyric acid-4-sulfate has
    been identified as their major metabolite.

    C6.1  Absorption, distribution, and excretion

        In a study of the absorption of higher alcohol sulfates,
    14C-hexadecyl sulfate salts were administered orally to humans and
    dogs. After a single dose of 14.4 mg/kg bw of the salts to dogs, the
    maximal plasma concentration of hexadecyl sulfate (1.22-2.45 µg/ml)
    was reached within 30-60 min; 6 h later, the plasma concentration had
    decreased to about one-tenth of the peak value. Within 72 h, 50-79% of
    the administered dose had been excreted in the urine and 12-41% in the
    faeces. After a single dose of 360 mg to humans, the maximal plasma
    concentration was reached at 2 h, although there was marked variation
    between individuals (range, about 3.1-23 µmol/ml) (Merits, 1975).

        Potassium dodecyl 35S-sulfate was injected intravenously or
    intraperitoneally  at 1 mg/ml to male and female rats. The proportions
    of the administered dose excreted in the urine and faeces and the
    amounts retained in the carcass after 24 h are shown in Table 36. Most
    of the radiolabel appeared in the urine of both male and female rats,
    although some was present as inorganic 35S-sulfate. The intestinal
    flora do not play a significant role in the metabolism of potassium
    dodecyl 35S-sulfate, since the distribution of radiolabel in the
    urine and faeces was similar in rats pretreated with antibiotics and
    in untreated rats. Whole-body autoradiograms of rats killed 5 min
    after administration of the compound by intraperitoneal injection
    showed significant amounts of radiolabel in the liver; the
    concentrations increased up to 30 min and then gradually declined,
    only trace amounts remaining after 4 h. The kidney was the only other
    organ in which any appreciable accumulation was reported (quantitative
    data not presented) (Denner et al., 1969).

        In order to investigate the percutaneous absorption of AS,
    0.5 ml of 25 mmol/litre sodium 14C-dodecyl sulfate in water was
    applied to the dorsal skin (10 cm2) of rats for 15 min. Heavy
    deposition of the surfactant on the skin surface and in the upper
    regions of the hair follicles was observed. The 14C level in urine
    was calculated to be equivalent to a penetration of 0.26 µg/cm2 per
    24 h (Howes, 1975).

        Table 36.  Excretion of 14C-alkyl sulfates by rats after injection
               of 1 mg/ml
                                                                      

    Route of          Sex                    Excretion (%)
    administration                                                     
                               Urine                  Faeces
                               (total 35S)                            
                                             Inorganic 35S   Total35S
                                                                      
    Intraperitoneal   Male     86.3          14.4            0.2
                      Female   93.2          18.1            0.9

    Intravenous       Male     95.6          23.5            -
                      Female   97.4          11.4            -
                                                                      
    From Denner et al. (1969)
            In young swine administered sodium dodecyl 35S-sulfate
    (3.3 mmol/animal) orally, the labelled compound was well absorbed from
    the intestine. Traces of radiolabelled sulfur were found only in
    bristles, bones, and bone marrow. The total amounts of 35S retained
    in organs and tissues were 1.7% of the dose at 82 h, 0.6% at 200 h,
    and 0.18% at 10 weeks. About 90% of the sodium dodecyl sulfate was
    recovered in urine and about 10% in faeces at 140 h (Havermann &
    Menke, 1959).

        Similar results were obtained in guinea-pigs in a study of the
    percutaneous absorption of 3 µmol sodium lauryl 35S-sulfate in water
    through skin  in vivo. Less than 0.4% of the dose was found to have
    penetrated the skin, on the basis of recovery of radiolabel in the
    urine, faeces, and expired air. The permeability constant was
    calculated to be 0.65 × 10-6 cm/min (Prottey & Ferguson, 1975).

        In a study of the dermal absorption of some homologues of AS,
    ranging from octyl to octadecyl sulfate, by isolated human abdominal
    skin, no penetration of the dermis was detected (Blank & Gould, 1961).

        The rates of excretion in urine and faeces after oral,
    intravenous, or intraperitoneal administration of 14C- or
    35S-labelled C10-C18 AS to rats, dogs, and humans are summarized
    in Table 37.

    C6.2  Biotransformation

        Potassium dodecyl 35S-sulfate was extensively metabolized in
    rats to yield a single ester sulfate, identified as butyric acid
    4-35S-sulfate (III in scheme below), and inorganic 35S-sulfate.

        Table 37.  Excretion of alkyl sulfates (AS) in the urine and faeces of rats, dogs, and humans
                                                                                                                

    ASa               Species    Treatment         Length of     Excretion (%)         Reference
                                                   treatment                      
                                                   (h)           Urine       Faeces
                                                                                                                

    35S-AS(C10)-K     Rat        1 mg/rat ip       48            82.9        1.2       Burke et al. (1975)
                                                                 79.5        1.0

    35S-AS(C11)-K     Rat        1 mg/200 g ip     48            98.2        2.5       Burke et al. (1976)
                                                                 90.6        7.3
                      Rat        1 mg/200 g po     48            75.1        14.3
                                                                 88.7        5.7
                      Rat        1 mg/200 g iv     48            85.9        5.9
                                                                 74.8        18.5

    35S-AS(C12)-K     Rat        1 mg/rat ip       48            86.3        0.2       Denner et  al. (1969)
                                                                 93.2        0.9
                      Rat        1 mg/rat po       48            98.7        0.7
                                                                 106.9       0.5

    35S-AS(C16)-EM    Rat        14.4 mg/kg po     96            94          5         Merits (1975)

    14C-AS(C16)-EM    Rat        14.4 mg/kg po     72            87          3

    35S-AS(C16)-Na    Dog        2.9 mg/kg iv      72            83          3

    14C-AS(C16)-TMA   Dog        4.4 mg/kg iv      48            50          41
                                                                                                                

    Table 37 (contd)
                                                                                                                

    ASa               Species    Treatment         Length of     Excretion (%)         Reference
                                                   treatment                       
                                                   (h)           Urine       Faeces
                                                                                                                

    35S-AS(C16)-EM    Dog        14.4 mg/kg po     72            52          37

    14C-AS(C16)-EM    Dog        14.4 mg/kg po     72            65          26

    14C-AS(C16)-EM    Human      250 mg po         72            80          7
                                                                 20          73

    35S-AS(C18)-K     Rat        1 mg/rat ip       48            77.1        1.1       Burke et al. (1975)
                                                                 73.9        2.6
                      Rat        1 mg/200 g po     48            76.7        4.1
                                                                 68.8        6.1

    35S-AS(C18)-Na    Rat        4 mg/rat po       48            95.3        2.2       Adachi et al. (1979)
                                                                                                                

    a  K, potassium salt; EM, erythromycin salt; TMA, trimethylammonium salt
        These compounds were degraded by a process involving initial
    omega-oxidation followed by ß-oxidation of fatty acids with successive
    elimination of a C2 fragment. The final product of degradation of
    potassium dodecyl 35S-sulfate was potassium butyric acid
    4-35S-sulfate, which was excreted in urine. When this product was
    injected intraperitoneally into rats, it was mostly eliminated
    unchanged in the urine, but about 20% of the dose was present as an
    inorganic 35S-sulfate. These findings suggest that the sulfate ester
    is hydrolysed  in vivo (Denner et al., 1969).

        Butyric acid 4-sulfate was hydrolysed nonenzymatically  in vitro
    at pH 5.0 and above, and the 4-butyrolactone (IV) and inorganic
    SO42- ion were liberated in approximately equimolar amounts (Ottery
    et al., 1970).

        After administration of 14C-hexadecyl sulfate to rats, dogs, and
    humans, the main metabolite was identified as the sulfate ester of
    4-hydroxybutyric acid. A minor metabolic product,  tert-14C-
    butyrolactone, was also isolated from the urine of rats, dogs, and
    humans. The urine of dogs contained still another metabolite, which
    was isolated and identified as glycollic acid sulfate (V) (Merits,
    1975).

    HOOC-CH2-CH2-CH2OSO3H  OC-CH2-CH2CH2  HOOC-CH2OSO3H

       Butyric acid 4-sulfate   4-Butyrolactone     Glycollic acid sulfate

              (III)                 (IV)                      (V)

        Qualitative analysis of 35S in the urine of rats administered
    potassium decyl 35-sulfate or potassium octadecyl 35-sulfate
    intravenously showed that butyric acid 4-35-sulfate was the major
    metabolite and inorganic 35-sulfate a minor metabolite; no unchanged
    compound was detected (Burke et al., 1975).

        Similar results were obtained when sodium octadecyl 35-sulfate
    was administered orally to rats . It was suggested that alkylsulfates
    with even-numbered carbons, like C10, C12, C16, and C18, are
    degraded by a common pathway involving omega-oxidation followed by
    ß-oxidation, and finally excreted in urine as metabolized forms with
    C4 or C2 (Adachi et al., 1979).

        The metabolism of surfactants with odd-numbered carbon chains,
    like C11 potassium undecyl 35-sulfate, was also investigated in
    rats. Propionic acid 3-35-sulfate was identified as the major
    metabolite in urine; pentanoic acid 5-35-sulfate and inorganic
    35-sulfate were identified as minor metabolites (Burke et al., 1975,
    1976).

    C7.  EFFECTS ON LABORATORY MAMMALS AND IN VITRO TEST SYSTEMS

     Section summary

        The oral LD50 values for AS in rats ranged from 1000 to
    4120 mg/kg bw. AS irritate the skin and eye at concentrations of about
    0.5% or more. Although the effects of short- and long-term exposure to
    AS in animals have been investigated, most of the studies are limited
    by inadequate histopathological examination or small group size. Toxic
    effects have been reported in rats administered AS in the diet or
    drinking-water at concentrations equivalent to > 200 mg/kg per day.

        Maternal toxicicity and fetotoxic effects have been observed at a
    dose equivalent to 200 mg/kg per day.

        The available long-term studies are inadequate to evaluate the
    carcinogenic potential of AS in experimental animals; however, in the
    limited studies available, in which animals were administered AS in
    the diet, there was no evidence of carcinogenicity.

        On the basis of limited data, AS also do not appear to be
    genotoxic  in vivo or  in vitro.

    7.1  Single exposures

        The oral, intraperitoneal, intravenous, and dermal LD50 values
    for AS are summarized in Table 38. The acute oral toxicity of AS in
    rats and guinea-pigs may vary with the length of the alkyl chain, and
    compounds with shorter chains are less toxic. The low LD50 value for
    sodium lauryl sulfate after dermal application to rabbits may indicate
    rapid skin penetration.

        There were no overt signs of poisoning, except diarrhoea in rats
    given sodium coconut alcohol sulfate orally (Brown & Muir, 1970);
    however, signs of central nervous stimulation, including tremors,
    tonic-clonic convulsions, and respiratory collapse, were observed in
    rabbits, guinea-pigs, and rats given lauryl sulfate dermally and in
    rabbits given the compound intravenously (Carson & Oser, 1964).

        In animals that died after receiving large doses of AS, the main
    gross pathological findings were haemorrhage and congestion of the
    stomach wall and bloodstained urine. Histopathological examination of
    rats given the sodium sulfate derivative of 3,9-diethyltridecane-
    4-ol orally revealed congestion, cloudy swelling of convoluted tubules
    with marked toxic degeneration of the cells, and granular detritus in
    the kidneys of animals killed by the LD50, whereas only congestion
    and cloudy swelling were seen in the kidneys of animals that survived
    the LD50. At larger doses, similar severe kidney injury and necrosis
    of the intestinal villi of the entire mucosal surface of the small
    intestine were observed. Only minor injury was seen in the liver, and
    the other organs examined were normal (Smyth et al., 1941).

        Table 38.  Acute toxicity of alkyl sulfates (AS)

                                                                                          

    Species   Sex   Route    LD50a         Test material                  Reference
                                                                                          

    Mouse     NS    po       2900          C8 sodium AS                   Gloxhuber
                             2200          C10 sodium AS                  (1974)
                             2700          C12 sodium AS
                             3000          C14 sodium AS
                             > 8000        C16 sodium AS
                             > 8000        C18 sodium AS

    Rat       M     po       4120          40% solution of sodium         Smyth et
                                           2-ethylhexanol sulfate         al. (1941)
              M     po       1250          25% solution of sodium
                                           7-ethyl-2-methyl
                                           undecanol-4 sulfate
              M     po       1425          25% solution of sodium
                                           3,9-diethyl tridecanol-6
                                           sulfate
              M     po       2730          30% solution of sodium
                                           lauryl  sulfate
              F,M   po       1280          86% sodium laury sulfate       Walker et
                             (C12-C15)                                    al. (1967)
              F,M   po       1000-2000     Sodium coconut alcohol         Brown &
                                           sulfate (mainly C12)           Muir (1970)
              F,M   ip       210           Sodium lauryl sulfate          Epstein et
                                                                          al. (1939)
              F,M   Dermal   2000 (100%    30% slurry of sodium lauryl    Carson &
                             deaths)       sulfate                        Oser (1964)
                                                                                          

    Table 38 (contd)

                                                                                          

    Species   Sex   Route    LD50a         Test material                  Reference
                                                                                          

    Guinea-   F,M   po       1520          40% solution of sodium         Smyth et
    pig                                    2-ethylhexanol sulfate         al., (1941)
              F,M   po       650           25% solution of sodium
                                           7-ethyl-2-methyl
                                           undecanol-4 sulfate
              F,M   po       425           25% solution of sodium
                                           3,9-diethyl tridecanol-6
                                           sulfate
              F,M   Dermal   1200          33% slurry of sodium lauryl    Carson &
                             (no deaths)   sulfate                        Oser (1964)
              F,M   Dermal   2000 (100%    33% slurry of sodium lauryl
                             deaths)       sulfate

    Rabbit    F,M   Dermal   580           33% slurry of sodium lauryl
                                           sulfate
              F,M   iv       121 (100%     33% slurry of sodium lauryl
                             deaths)       sulfate
                                                                                          

    M, male; F, female
    a As active ingredient
    
    C7.2  Short-term exposure

        The results of short-term tests for toxicity with repeated doses
    are summarized in Table 39.

    C7.2.1  Rat

    C7.2.1.1  Administration in the diet

        Groups of five male and five female Wistar rats were fed diets
    containing technical-grade sodium lauryl sulfate (purity, 98%) at a
    concentration of 0, 0.5, 1, or 2% (equivalent to 245, 490, or
    980 mg/kg of diet per day) for two or four weeks. No abnormalities
    were seen in behaviour or food intake; but body weight gain was
    significantly suppressed in females at the highest dose, and
    haematological examination revealed a significant decrease in red
    blood cells at two weeks. Biochemical examination of the serum
    revealed a significant increase in the glucose level at two weeks in
    males given 2%, a significant increase in glutamate-oxalate
    transaminase at two weeks in females given 1 or 2%, significant
    increases in glutamate-pyruvate transaminase and alkaline phosphatase
    activities at four weeks in all females, and a significant decrease in
    cholinesterase activity at four weeks in females given 2%. Both the
    absolute and relative weights of the liver and thyroid were increased
    at two weeks in males and females given 2%, and those of the liver and
    left kidney were increased at four weeks in all females; the weights
    of the thymus were decreased in males given 2% at four weeks.
    Histopathological examination of rats with increased liver weight
    revealed slight swelling of liver cells and increased numbers of
    dividing liver cells. This finding was considered to be an adaptation
    to administration of the test material. Cylinders in the renal
    tubules, vacuolar degeneration of the epithelial cells of the renal
    tubules, periodic acid-Schiff stain-positive substances in the renal
    tubules, and atrophy of the renal glomeruli were observed mainly in
    rats given 1 or 2% (Oishi et al., 1974).

        Groups of 25 albino rats (sex not specified) were given diets
    containing a sodium lauryl sulfate formulation (Iriumr) at a dose of
    0, 30, or 60 mg/animal per day for eight weeks. The only abnormal sign
    in the experimental groups was soft stools. Histological examinations
    of the livers of four rats in each group revealed swelling of liver
    cells, compression of cellular cords, and prominent nuclei. These
    effects were particularly marked in rats given the high dose (Hatton
    et al., 1940).

        Table 39.  Results of short-term exposure of experimental animals to alkyl sulfates (AS)
                                                                                                                                    

    Species, strain,    Material           Route       Dosage                Results                           Reference
    numbers per group
                                                                                                                                    

    Rat, Wistar, 10     AS, C12 (a.i. 98%) Diet        0, 0.5, 1.0, 2.0%,    Changes in haematological         Oishi et al.
                                                       4 weeks               parameters, serum enzyme          (1974)
                                                                             activities, and liver; depressed
                                                                             body weight gain in females at
                                                                             highest dose; increased weights
                                                                             of liver, thyroid and kidney at
                                                                             highest dose; decreased thymus
                                                                             weight in males
    Rat, 25             AS, C12 (Irium(R)   Diet       30, 60 mg/rat per     Dose-related hepatic effects      Hatton et al.
                                                       day, 5 weeks                                            (1940)
    Rat, Wistar, 5      AS, C12            Diet        1.5%, 12 weeks        Changes in serum, renal, and      Ikawa et al.
                                                                             hepatic enzyme activities;        (1978)
                                                                             depressed body weight gain;
                                                                             increased liver weight
    Rat, Osborne-       AS, C12            Diet        9, 2, 4, 8%,          Diarrhoea, abdominal bloating;    Fitzhugh &
       Mendel, 5 M                                     4 months              depressed body weight gain        Nelson (1948)
    Rat, Carworth,      AS, C12-C15        Diet        9, 0.04, 0.02, 0.1,   Increased liver weight in         Walker et al.
       24               (a.i. 86%)                     0.5%, 13 weeks        females at highest dose           (1967)
    Rat, Wistar,        AS                 Drinking-   0, 0.25, 0.5, 1.0,    Renal changes; proteinuria;       Smyth et al.
       5, 10                               water       2.0, 4.0%, 30 days    depressed body weight gain at 4%  (1941)
                                                                             sodium 2-ethylhexanol sulfate
    Rat, Wistar         AS (a.i.22.5%)     Dermal      5 mg/kg per day,      Dermal irritation; hepatic        Sakashita et
       15 M                                            30 days               effects                           al. (1974)
                                                                                                                                    

    Table 39 (contd)
                                                                                                                                    

    Species, strain,    Material           Route       Dosage                Results                           Reference
    numbers per group
                                                                                                                                    

    Rat, Wistar         AS (a.i. 22.5%)    Dermal      5 mg/kg per day,      Hepatic degeneration              Sakashita
       (NS) M                                          30 days                                                 (1979)
    Rabbit              AS, sodium lauryl  Dermal      6, 60, 150 mg/kg,     Dermal irritation                 Carson & Oser
       3 M, 3 F         sulfate                        5 times/week,                                           (1964)
                                                       3 months
                                                                                                                                    

    a.i., active ingredient; M, male; F, female; NS, not specified
            Groups of five male Wistar SPF rats were fed a diet containing
    sodium dodecyl sulfate at a concentration of 1.5% (equivalent to
    750 mg/kg of diet per day) for 2, 4, or 12 weeks, and were compared
    with a control group. Body weight gain was suppressed and relative
    liver weight significantly increased from two weeks. Biochemical
    analysis of serum revealed increased activities of alkaline
    phosphatase and glutamate-pyruvate transaminase and a decreased level
    of cholesterol. Enzymatic examinations of the liver showed decreased
    activity of glucose-6-phosphatase at 12 weeks, decreased activity of
    glucose-6-phosphate dehydrogenase and increased activity of lactate
    dehydrogenase at each observation time, and increased isocitrate
    dehydrogenase activity at 4 and 12 weeks. Examination of the renal
    cortex showed decreased activities of 5'-nucleotidase and Mg-ATPase at
    12 weeks and increased isocitrate dehydrogenase activity at 4 and 12
    weeks. Examination of the renal medulla showed decrease activities of
    Mg- and Na,K-ATPases and increased isocitrate dehydrogenase activity
    at 12 weeks (Ikawa et al., 1978).

        Groups of five male Osborne-Mendel rats were given diets
    containing sodium lauryl sulfate at a concentration of 0, 2, 4, or 8%
    (equivalent to 1000, 2000, or 4000 mg/kg of diet per day) for four
    months. Significant inhibition of growth was observed with 4%; severe
    diarrhoea and marked abdominal bloating were noted at 8%, and all the
    rats died within two weeks. Autopsy revealed irritation of the
    gastrointestinal tract in rats fed 8% (Fitzhugh & Nelson, 1948).

        Technical-grade sodium lauryl sulfate (86% w/w active ingredient;
    chain length distribution, C12-C15) was fed to four groups of 12
    male and 12 female Carworth Farm 'E' rats at a dietary level of 0, 40,
    200, 1000, or 5000 ppm (corresponding to 2, 10, 50, or 250 mg/kg bw
    per day) for 13 weeks. No abnormalities were observed in behaviour,
    body weight, food intake, haematological parameters, urinary pH or
    osmolality, serum urea or protein, or organ weights, except for a
    significant increase in the absolute weight of the liver in females
    fed 5000 ppm (Walker et al., 1967).

    C7.2.1.2  Administration in the drinking-water

        Groups of five or 10 male Wistar rats were given water containing
    sodium 2-ethylhexanol sulfate, sodium 7-ethyl-2-methyl undecanol-4
    sulfate, or sodium 3,9- diethyl tridecanol-6 sulfate at a
    concentration of 0, 0.25, 0.5, 1, 2, or 4% for 30 days. Water intake
    was decreased at concentrations >  2% of sodium 2-ethylhexanol
    sulfate and sodium 7-ethyl-2-methyl undecanol-4 sulfate and at > 1%
    sodium 3,9-diethyl tridecanol-6 sulfate. Body weight gain was
    suppressed at 4% sodium 2-ethylhexanol sulfate. None of the rats died,
    and no haematological abnormalities were observed during the
    experiment. Proteinurea was seen at 2 and 4% sodium 2-ethylhexanol
    sulfate. The major histopatho-logical findings were renal changes,
    including light cloudy swelling and secretion in the renal tubules and
    congestion or dilation of Bowman's capsule. The no-effect doses were

    0.44 g/kg bw per day of sodium 2-ethylhexanol sulfate, 0.1 g/kg bw per
    day of sodium 7-ethyl-2-methyl undecanol-4 sulfate, and 0.25 g/kg bw
    per day of sodium 3,9- diethyl tridecanol-6 sulfate (Smyth et al.,
    1941).

    C7.2.1.3  Dermal application

        A group of 15 male Wistar rats received 2 ml of a commercial
    preparation of AS (22.5% active ingredient) on their backs, and the
    livers of three rats were examined under the electron microscope three
    and 30 days later; a control group was available. Redness of the skin
    and wrinkles were observed in treated animals at 24 h; the redness
    subsequently increased, the dermis became lacerated, and bleeding
    occurred. These lesions reached a peak at 57 days but tended to
    regress about 10 days later. Five rats died within the first 19 days.
    Electron microscopy at three days revealed separation of the
    intercellular space, cells with a high electron density, elongation of
    mitochondria, swelling of the smooth-surfaced endoplasmic reticulum,
    and a decreased prevalence of fatty droplets. Electron microscopy at
    30 days showed liver parenchymal cells filled with mitochondria,
    apparently abnormally divided and proliferated smooth-surfaced
    endoplasmic reticulum, abnormally rough-surfaced cells, a typical
    Golgi apparatus, myelin-like structures in bile canaliculi, and
    extracellular prolapse of mitochondria (Sakashita et al., 1974).

        Electron microscopy of the liver was also performed after dermal
    application of a commercial preparation of AS (22.5% active
    ingredient) to male Wistar rats (number not specified) at a dose of
    5 mg/kg active ingredient once a day for 30 days. Hepatic
    degeneration, seen as atrophy and a high density of liver cells, was
    observed; in cells, there was deformation of nuclei, mitochondria, and
    the Golgi apparatus, an increased number of lysosomes, and swelling of
    endoplasmic reticula (Sakashita, 1979).

        As no information was given on the method of application (occluded
    or non-occluded), these results were not interpretable in terms of
    risk to human health.

    C7.2.2  Rabbit

        Sodium lauryl sulfate was applied dermally to three groups,
    consisting of two male and two female rabbits with intact skin and one
    male and one female rabbit with abraded skin, at a dose of 6, 60, or
    150 mg/kg bw five times per week for three months. A control group
    consisted of one male and one female with intact skin and one male
    with abraded skin. Dose-related irritation of the skin was observed in
    all treated animals (Carson & Oser, 1964).

    C7.3  Long-term exposure; carcinogenicity

    C7.3.1  Mouse

        In a study of the effects of AS on the carcinogenicity of
    benzo[a]pyrene (BaP), a 10% AS solution, a 0.3% BaP solution, and a
    10% AS:0.3% BaP solution were applied to the backs of groups of 10
    male and 20 female mice twice a week for one year. Skin tumours
    appeared in all mice treated with BaP or AS:BaP. The average ages at
    the appearance of skin tumours were 119 days in the group exposed to
    BaP and 102 days in that exposed to AS:BaP. It was concluded that AS
    accelerated the induction of tumours by BaP ( p < 0.1). Untreated
    mice and vehicle (acetone) controls had no skin tumours; one female
    exposed to AS had a skin tumour, but this finding was not considered
    to be related to treatment (Yamamoto, 1977).

    C7.3.2  Rat

    C7.3.2.1  Administration in the diet

        Three groups of 12 weanling male Osborne-Mendel rats were given
    food containing sodium lauryl sulfate at a concentration of 0.25, 0.5,
    or 1.0% for two years; there was a similar sized control group. No
    effects attributable to the test material were observed on growth,
    mortality, or the macroscopic or histopathological appearance of
    organs. No tumours were reported (Fitzhugh & Nelson, 1948). As there
    were few animals per group and no toxic effects at any dose, the
    observations are considered to be of limited value.

    C7.3.2.2  Administration in the drinking-water

        Groups of 4-11 white rats were given drinking-water containing
    sodium lauryl sulfate at a concentration of 0, 0.1, 0.25, 0.5, 1, 5,
    or 10% for 120 or 160 days. Dose-related increases in mortality
    occurred at doses > 0.25%; at doses > 5%, all rats died.
    Histological examination of rats exposed to doses > 0.25% revealed
    marked inflammatory changes of the lumen of the oesophagus in those
    that died, but the changes were slight in surviving animals. No
    abnormalities were seen in the liver, kidney, or intestine. The intake
    of the materials was about 30 mg/animal per day in those given 0.1%
    and 150 mg/animal per day in those given 1.0% (Epstein et al., 1939).

        Groups of 9 or 10 weanling male Wistar rats were given
    drinking-water containing technical-grade sodium lauryl sulfate at a
    concentration of 0, 0.05, or 0.25% for five months. Growth was not
    suppressed, even at the higher concentration, and the activities of
    serum enzymes, including glutamate-oxalate and glutamate-pyruvate
    transaminases, alkaline phosphatase and cholinesterase, were not
    affected. At 0.25%, the triglyceride level increased in the liver but
    decreased in serum, while hepatic and serum levels of cholesterol,

    phospholipids, and free fatty acids were unchanged. Increased weights
    of spleen, lung, and kidney were noted at 0.25%. Histopathologically
    diagnosed broncho-pneumonia, observed in all animals given 0.25% and
    two animals given 0.05%, was considered to be a characteristic effect
    of the test material (Fukazawa et al., 1978).

        The results of long-term studies are shown in Table 40.

    C7.4  Skin and eye irritation; sensitization

    C7.4.1  Local irritation

    C7.4.1.1  Skin

        Groups of two to six white rats received a subcutaneous injection
    of 1 ml of one of 10 solutions of sodium AS, ranging from 0.125 to 10%
    and were observed for one week after the injection. No reactions
    occurred at 0.125%, but  sloughing and subcutaneous lumps in the skin
    appeared in rats given doses > 0.19%. In a study in which the
    diffusibility of trypan blue was used as an index of irritation,
    groups of five to nine white rats were given subcutaneous injections
    of 0.2 ml sodium AS at one of six concentrations ranging from 0.15 to
    5%. Two hours after the injection, slight reactions were seen in
    animals given 0.15% and marked reactions in those given 2.5 or 5%
    (Epstein et al., 1939).

        Groups of three albino rabbits received closed-patch applications
    of 5 ml of 1, 5, or 25% sodium lauryl sulfate solution on intact and
    abraded areas of shaven abdominal skin. Over a 14-day period, 10
    applications were made to intact skin and three to abraded skin;
    additionally, small amounts of the material were applied daily to the
    intact ears of groups of three rabbits. Occluded application to the
    abdomen produced erythema and blistering, which was more severe on
    abraded skin. Application to the intact ear resulted in very slight
    erythema at the 1% concentration, very slight to slight erythema at
    5%, and slight erythema with moderate to severe burns at 25% (Olson et
    al., 1962).

        Sodium alcohol (coconut alcohol, mainly C12) sulfate solutions
    of 0.1, 1.0, and 2.5% were applied in occluded tests in rabbits as
    1 ml of each solution on the back three times on three days.
    Macroscopic and histological examination seven days after application
    revealed no abnormalities at 1.0% and moderate irritation at 2.5%. In
    open tests, 1 ml of each of the solutions was applied to the backs of
    rabbits and 0.5 ml to the backs of guinea-pigs five times a week for
    4.5 weeks. No abnormal findings were seen in animals receiving 0.1 or
    1.0% groups, but there was moderate irritation at 2.5% (Brown & Muir,
    1970).

        Table 40.  Results of long-term exposure of experimental animals to alkyl sulfates (AS)
                                                                                                                                              

    Species, strain,         Material          Route      Dosage                 Results                    Reference
    numbers per group
                                                                                                                                              

    Mouse, ddy/SLC           10% AS, 3%        Dermal     Twice per              Skin tumours               Yamamoto (1977)
       10 M, 20 F            benzo[ a]pyrene               week, 1 year

    Rat, Osborne-Mendel      1.0%AS, C12       Diet       0, 0.25, 0.5, 1.0%,    No effects                 Fitzhugh & Nelson
       10-12 M                                            2 years                                           (1948)

    Rat, Wistar, 9-10        AS, C12           Diet       0, 0.05, 0.25%,        Increased weights of       Fukuzawa et al.
                                                          5 months               spleen, lung, and liver    (1978)
                                                                                 at highest dose

    Rat, 4-11                AS, C12           Diet       0, 0.1, 0.25, 0.5      Oesophageal irritation     Epstein et al.
                                                          1.0, 5.0%, 160 days                               (1939)
                                                                                                                                              
            Groups of three male Wistar rats received applications of 0.5 g of
    a 20 or 30% solution of linear lauryl sulfate (C12; purity, 98.91%)
    on the back once a day for 15 days. The skin at the application site
    and the tissues of the tongue and oral mucosa (to determine the
    effects of licking) of animals receiving the 30% solution were
    examined histologically 16 days after application. Body weight gain
    was inhibited in the group given the 20% solution; body weight was
    decreased in the group at 30%, and two rats had died by the end of the
    experiment. A dry, thick, yellowish-white or reddish-brown crust was
    observed after two to three days in animals given 20% and after one to
    two days in those given 30%. When the crust was abraded several days
    later, ulcers occurred at the abraded site, which remained unchanged
    for 16 days in animals at 20% group and were aggravated in those at
    30%. Histological examination of the application site revealed severe
    necrosis extending from the epidermis to the upper layer of the
    dermis, dense inflammatory-cell infiltration into the upper layer of
    the dermis just below the necrotic area, diffuse inflammatory-cell
    infiltration throughout the dermis, swelling of collagenous fibres in
    the dermis, and sloughing. Histological examination of the tongue
    revealed necrosis extending from the surface to the middle epithelial
    layer of the mucosa, inflammatory-cell infiltration into the upper
    layer of the dermis, and sloughing. Histological examination of the
    mucosa of the oral cavity revealed thickening of the stratum corneum
    and germinative and slight degeneration (pale staining) of epithelial
    cells (Sadai & Mizuno, 1972).

        The effects of sodium lauryl sulfate on oesophageal and gastric
    mucosa were studied in cats by irrigation and pledget techniques. In
    the irrigiation technique, the stomachs and oesophaguses of two cats
    were filled with 10 and 20% solutions of sodium lauryl sulfate,
    respectively, for 15 min, and then tissues were taken for histological
    examination. Pledgets soaked in 10 or 20% sodium lauryl sulfate
    solution were applied to the exposed oesophageal and gastric mucosa of
    two other cats for 10 min, and specimens were taken 90 min later. The
    10% solution produced moderate injury to the oesophagus, consisting of
    intramucosal oedema and congestion and loss of superficial epithelial
    layers; in the stomach, there was hydropic degeneration, loss of
    surface mucosal cells, vascular congestion with submucosal oedema, and
    occasional focal ulceration. Treatment with the 20% solution resulted
    in more extensive damage, and particularly extensive submucosal oedema
    and disruption and erosion of the superficial mucosa of both the
    oesophagus and stomach (Berensen & Temple, 1976).

    C7.4.1.2  Eye

        Three drops of one of nine solutions of sodium lauryl sulfate
    ranging from 0.019 to 5.0% were instilled into the eyes of rabbits
    three times at 10-min intervals, and the rabbits were observed for
    48 h. There were no abnormal findings at 0.038%, but slight chemosis
    and redness were seen at 0.075% and marked chemosis and redness at 5%
    (Epstein et al., 1939).

        The minimal concentration of sodium lauryl sulfate that caused
    corneal necrosis (detected by fluorescein staining) after instillation
    into the eyes of rabbits was 0.1% (Smyth et al., 1941). In another
    study, two drops of a 1, 5, or 25% solution of sodium lauryl sulfate
    were instilled into both sides of the eyes of groups of three rabbits;
    30 min later, one of the eyes was washed. Moderate corneal injury was
    observed in unwashed eyes of animals receiving the 5 or 25% solution;
    in washed eyes, either slight conjunctivitis or moderate corneal
    injury was observed at 25%, slight conjunctivitis at 5%, and only very
    slight conjunctivitis at 1% (Olson et al., 1962).

        In an irritation test based on a method developed by the United
    States Food and Drug Administration, 0.1, 1, or 25% solutions of
    sodium coconut alcohol sulfate were instilled into the eyes of
    rabbits. No reaction was seen at 0.1%; mild conjunctivitis lasting for
    48 h was seen at 1%, and severe conjunctivitis lasting for 72 h was
    observed at 25% group, but there was no permanent damage (Brown &
    Muir, 1970). Solutions of a synthetic alkyl sulfate and five AS
    consisting mainly of C10, C12, C14, C16, or C18, were instilled
    at concentrations of 0.01-5% into the eyes of three rabbits, which
    were observed for 168 h. The materials caused similar reactions. No
    abnormalities were seen at 0.01%. Slight congestion and marked
    congestion or oedema were observed at 0.05 and 0.1% within 2 h, but
    these effects had disappeared 24 h later. In the groups given >
    0.5%, marked reactions were seen for 24 h, including severe congestion
    and oedema, increased lachrymal secretion, turbidity of the cornea,
    and disappearance of the corneal reflex, but these tended to regress
    and had disappeared completely by 120 h (Iimori et al., 1972).

    C7.4.2  Skin sensitization

        A 0.1% solution of a sodium lauryl sulfate derivative of coconut
    alcohol was applied to the skin or injected intradermally into groups
    of 10 guinea-pigs three times per week for three weeks. Ten days later
    the animals received challenge doses and were observed for 48 h. No
    reaction occurred in the group treated dermally, but a slight reaction
    was observed 24 h after the challenge in some of the guinea-pigs
    treated intradermally (Brown & Muir, 1970).

    C7.5  Reproductive toxicity, embryotoxicity, and teratogenicity

         Daily doses of 0.2, 2, 300, or 600 mg/kg bw of AS were
    administered by gavage to CD rats, CD-1 mice, and NZW rabbits. Groups
    of 20 rats and mice were given AS on days 6-15 of pregnancy, and
    groups of 13 rabbits were treated on days 6-18 of pregnancy. The doses
    of 0.2 and 2 mg/kg bw per day were estimated to be equivalent to 1-2
    and 10-20 times the maximal amount of AS to which humans are exposed.
    Three rats given 600 mg/kg bw died during the study, but the surviving
    rats and those given 300 mg/kg bw had only mild to moderate inhibition
    of body weight gain. Mice given 600 mg/kg bw showed severe effects,
    including anorexia and inhibition of body weight gain, and four
    animals died during the study; in those given 300 mg/kg bw, inhibition
    of body weight gain was mild to moderate. Rabbits given 600 mg/kg bw
    showed severe effects, including diarrhoea, anorexia, and reduced rate
    of body weight gain, and 11 died during the study; those given
    300 mg/kg bw showed mild to moderate reduction of body weight gain. No
    toxic effects were seen in any of the animals given 0.2 or 2 mg/kg bw.
    No adverse effects were seen on litters of rats at any dose. Some mice
    and rabbits at each dose had total litter loss, but the other litter
    parameters did not differ from those of controls. No major
    malformations were seen at any dose in offspring of rats, mice, or
    rabbits, and the incidence of skeletal variations in offspring of rats
    given 600 mg/kg bw was significantly low. A high incidence of skeletal
    anomalies was seen in litters of mice given 600 mg/kg bw, and those of
    rabbits at 2.0 mg/kg bw had a significantly higher incidence of
    skeletal variations; however, the incidences of anomalies and
    variations were within the background range (Palmer et al., 1975a).

        Groups of 21 ICR mice received applications of 15 mg/kg bw per day
    of a 0.4, 4, or 6% aqueous solution of AS (98% sodium dodecyl sulfate,
    0.5% N2SO4, 0.1% NaCl, and 0.1% H2O) to a 3 × 3-cm2 area of
    shaven dorsal skin on days 6-13 of pregnancy. The 0.4% solution was
    equivalent to about 10-12 times the specified concentration used by
    humans, and the application area was equivalent to about one-seventh
    of the total surface area of the mouse. The body weight gain of dams
    exposed to the 4 or 6% solution was reduced; there were no deaths. The
    numbers of dams with surviving young were 19/21 in the control group,
    20/20 at 0.4%, 17/20 at 4%, and 11/21 at 6%; the decrease in dams at
    6% was significant. Fetal weights were significantly lower in dams at
    4 and 6%, but there were no other differences from the control values.
    The incidence of cleft palate was fairly high in offspring of dams
    exposed to the 4 or 6% solution, and a tendency to delayed
    ossification was seen; however, none was significant (Takahashi et
    al., 1976).

        A dose of 0.1 ml/day of a 2% aqueous solution of AS was applied to
    a 2 × 3-cm2 area of shaven dorsal skin in groups of 20-26 ICR mice
    on days 1-17 of pregnancy. The same dose of a 20% solution was applied
    to a similar group up to the 10th day of pregnancy, and implantation
    was examined on the 11th day. In addition, 14 mice were injected
    subcutaneously with 2 mg/kg bw per day of AS on days 8-10 of
    pregnancy. The numbers of dams with implantations were 18/20 controls,
    14/22 at 2%, 1/26 at 20%, and 13/14 at 2 mg/kg bw; the decrease at 20%
    was significant. There were no significant changes in litter
    parameters and no significant changes in the incidences of major
    malformations, minor anomalies, or skeletal variations. AS thus
    disturbed implantation and caused abortion at maternally toxic doses,
    but in surviving litters it had no effect on the size or numbers of
    fetuses, although low fetal weight and delayed ossification were
    observed. At doses that had no or only mild effects on the dams, no
    adverse effects were seen on the fetuses. The effects of AS on the
    fetus therefore appear to be secondary to the toxic effects on the
    dams (Nomura et al., 1980).

    C7.6  Mutagenicity and related end-points

        Sodium lauryl sulfate did not cause differential toxicity in
     Bacillus subtilis H17 ( rec+) or M45 ( rec-) at concentrations
    of 20-2000 µg/plate, and it did not induce reverse mutations in
     Salmonella typhimurium TA98 or TA100 at 1-500 µg/plate or in
     Escherichia coli WP2  trp at 10-1000 µg per plate (Inoue &
    Sunakawa, 1979).

        Sodium lauryl sulfate, Dobanol 25 sulfate LCU, and Dobanol 25
    sulfate HCB (aliphatic alcohol sulfates with chain lengths of
    C10-C15) were fed in the diet to groups of six male and six female
    Colworth/Wistar rats for 90 days at a concentration of 0.56 or 1.13%,
    the latter being the maximal tolerated dose. No effect was seen on
    chromosomes in bone-marrow cells (Hope, 1977).

        After dodecyl sulfate was administered to male ddY mice
    intra-peritoneally at 50 mg/kg bw, the incidence of polychromatic
    erythrocytes with micronuclei in the bone marrow was similar in
    treated and control groups (Kishi et al., 1984).

    C7.7  Special studies

        Intravenous injection of 1 mg/min sodium decyl sulfate or        
    5.7 mg/min sodium dodecyl sulfate to cats increased pulmonary arterial
    pressure, caused a small increase in systemic vascular resistance, and
    reduced the ventilation volume per minute after about 5 min.
    Intravenous injection of 4.6 mg/min sodium octyl sulfate or 6.3 mg/min
    sodium tetradecyl sulfate had similar effects. The increase in
    pulmonary arterial pressure was considered to be due to a direct

    effect on the smooth muscle of blood vessels and bronchi. The blood
    sugar level was unchanged (Schumacher et al., 1972).

        The effects of sodium lauryl sulfate on histamine release from
    mast cells were studied  in vitro in peritoneal mast cells isolated
    from rats. Histamine was released at a concentration of
    0.03 mmol/litre, and the critical micelle concentration in buffer at
    22°C was 1.0 mmol/litre. Sodium lauryl sulfate and its mono- and
    tri-ethoxy derivatives had the most potent histamine releasing
    capacity of nine surfactants with a chain length of C12 (Prottey &
    Ferguson, 1975).

    C8.  EFFECTS ON HUMANS

     Section summary

        In patch tests, human skin can tolerate contact with solutions
    containing up to 1% AS for 24 h with only mild irritation. AS caused
    delipidation of the skin surface, elution of natural moisturizing
    factor, denaturation of the proteins of the outer epidermal layer, and
    increased permeability and swelling of the outer layer. They did not
    induce skin sensitization in volunteers, and there is no evidence that
    they induce eczema. No lasting injuries or fatalities have been
    reported following accidental ingestion of detergent formulations
    containing AS.

    C8.1  Exposure of the general population

        Surface-active agents are found in shampoos, dishwashing products,
    household cleaners, and laundry detergents, and AS are major
    components of these products. The composition of nonionic and ionic
    surfactants varies between 10 and 30%. Surface-active agents can
    affect human skin and eyes.

    C8.2  Clinical studies

    C8.2.1  Skin irritation and sensitization

        AS can be mildly to moderately irritating to human skin. No data
    were available on sensitization.

        The relative intensity of skin erythema produced on the lower back
    of volunteers was evaluated by applying concentrations of 0.2-5.4% of
    C8, C10, C12, C14, or C16 AS under a closed patch for 24 h
    or under a closed patch re-applied once daily for 10 days. C12 AS
    were more potent than AS with other alkyl chain lengths (Kligman &
    Wooding, 1967).

        A circulation method was used to evaluate the relative intensity
    of skin roughness induced on the surface of the forearms of volunteers
    after application for 1 min of 1% aqueous solutions of AS with an
    alkyl chain length of C8, C10, C12, or C14. The potential to
    cause skin roughness increased with alkyl chain length, reaching
    maximal intensity at C12 (Imokawa et al., 1974, 1975a). In other
    studies, the relative degree of skin roughening was correlated with
    the extent of protein denaturation but not with irritating potential
    determined in a closed-patch test (Imokawa et al., 1975b).

        Primary skin irritation induced by a 1% aqueous solution (pH 6.8)
    of dodecyl sulfate (relative molecular mass, 288.5) was studied in a
    24-h closed-patch test on the forearms of seven male volunteers. The
    relative intensity of skin irritation was scored by grading erythema,

    fissuring, and scaling. The average score for AS was 4.86, whereas
    that for a water control was 1.79. Dodecyl sulfate was more irritating
    than either LAS or AOS (Oba et al., 1968a).

         The intensity of skin irritation produced by a 1% aqueous
    solution of sodium AS was studied in a 24-h closed-patch test on the
    forearm and in a 40-min drip test on the interdigital surface in which
    the compound was dripped once daily for two consecutive days at a rate
    of 1.2-1.5 ml/min. Skin reactions were scored by grading erythema in
    the patch test and by grading scaling in the drip test. The average
    scores were 2.5 for primary skin irritation at 24 h in the patch test
    and 1 for scaling at two days in the drip test; in both tests, the
    control value was 0. AS was more irritating than LAS or AOS in the
    patch test, whereas the score of AS for skin scaling in the drip test
    was similar to that of LAS but higher than that of AOS (Sadai et al.,
    1979).

        Moderate to intense erythema was produced on the forearms of     
     10 volunteers in a 24-h closed-patch test by a 10% aqueous solution
    of AS with an average chain length of C12. The mean irritation
    scores were significantly higher at 26 h (2.85 out of 8 possible
    points) and at 28 h (2.88) than at 24 h (2.00), when the patches were
    removed. Irritation had decreased by 48 h, and a significant decrease
    in the intensity of inflammation was apparent at 96 h (Dahl & Trancik,
    1977).

        In a 48-h patch test on the upper arms of 100 pairs of twins
    (54 monozygotic, 46 dizygotic) with a solution of 0.5% C12 AS, no
    reaction was seen in 50% of the subjects, and slight reaction, ranging
    from noninflammatory changes to mild erythema, in the other 50%. The
    response was not related to the type of twin (Holst & Moller, 1975).

        Application of aqueous 0.5, 1, or 2% solutions of AS with an
    average chain length of C12 to the backs of healthy male volunteers
    produced epidermal hyperplasia. Treatment with the 1% solution induced
    an approximately 30-fold increase in mitotic activity, which peaked 48
    h after treatment. Application of either the 0.5 or the 2% solution
    induced similar but milder changes (Fisher & Maibach, 1975).

        Skin permeability to C8, C10, C12, C14, C16, and C18
    AS prepared as 0.02, 0.5, and 1% solutions (0.58% C8 and 0.74%
    C18) was studied by a circulation method on the forearms of healthy
    male and female volunteers. C12 AS attained maximum permeation,
    whereas the permeation of C8 and C18 AS was of the same order as
    that of water. The authors pointed out the close relationship between
    permeation and irritation (Szakall & Schulz, 1960).

    C8.2.2  Effects on the epidermis

        The effects of AS on the stratum corneum include delipidation of
    the skin surface, elution of natural moisturizing factor, denaturation
    of protein of the stratum corneum, increased permeability, swelling of
    the stratum corneum, and inhibition of enzyme activities in the
    epidermis. These effects, and some others, constitute a potential
    hazard to the epidermis.

        The water-holding capacity of thin sheets of callus isolated from
    the plantar surface of the human foot, with relative moisture contents
    of 76, 88, and 97%, was compared before and after immersion in water,
    AS, or soap solution. Water-holding capacity was measured as the
    weight of water taken up from each solution. The relative moisture
    content decreased after treatment with AS or soap solution (Blank &
    Shappirio, 1955).

        Elution of natural moisturizing factor was compared for nine kinds
    of surfactants, including AS, in the arm immersion test, in patch
    tests, and by measuring eluted amino acids and protein, skin
    permeation, and freeing of sulfhydryl groups. AS induced a strong
    reaction in the immersion test and relatively strong reactions in the
    other tests. The author concluded that the immersion test was the best
    simulation of actual use (Polano, 1968).

        A detergent consisting of long-chain AS was shown to denature
    stratum corneum protein and thus expose enclosed sulfhydryl groups
    (Anson, 1941). AS readily released sulfhydryl groups from stratum
    corneum obtained from abdominal skin taken at autopsy within 12 h of
    death, but there was no correlation between changes in epidermal
    permeability and the amounts of sulfhydryl released (Wood & Bettley,
    1971). AS were the most effective surfactants with regard to
    denaturation of protein, measured as inhibition of invertase activity
    (Imokawa et al., 1974; Okamoto, 1974). AS were found to denature skin
    keratin (a filamentous protein), bovine serum albumin (a globular
    protein), acid phosphatase (an enzyme protein), and membrane lysozymes
    (membrane protein) (Imokawa & Katsumi, 1976). Sodium laurate was
    reported to produce swelling of the stratum corneum (Putterman et al.,
    1977).

        AS with a hydrophobic chain length of C12 were maximally
    absorbed on human callus. Extraction of proteins from human callus was
    also a function of chain length: C12 and C14 AS were much more
    active than C8, C10, and C18 AS (Dominguez et al., 1977).

    C8.2.3  Hand eczema

        In a 24-h closed-patch test of 0.2-0.5% aqueous solutions of AS on
    the fingers of nine women with hand eczema, skin lesions were not
    exacerbated, although four women felt slight itching at the patch site
    (Sasagawa, 1963).

    C8.2.4  Accidental or suicidal ingestion

        Four members of a family accidentally ingested unknown quantities
    of a household detergent containing 24% lauryl sulfate, 60% sodium
    tripolyphosphate, and 16% anhydrous soap. Shortly after ingestion, all
    of the family members experienced abdominal pain and nausea. The
    10-year-old daughter and 13-year-old son felt oropharyngeal pain, and
    the son was found at endoscopic examination to have a 2.5 × 2 cm
    oropharyngeal burn in the right posterior pharynx and first-degree
    burns of the oesophagus. The mother had erythema, friability, erythema
    and a few superficial erosions of the distal oesophagus, and gastritis
    evidenced by exudate and petechial lesions on the mucosa. The father
    had haematemesis on a few occasions. The mother, father, and son were
    examined about one month after the incident by an X ray examination
    after a barium meal; no strictures were found (Berenson & Temple,
    1974).

    C9.  EFFECTS ON OTHER ORGANISMS IN THE LABORATORY AND THE FIELD

     Section summary

        AS have been studied in short- and long-term studies in the
    laboratory and in one study carried out under more realistic
    conditions. Their toxicity is dependent on alkyl chain length, but no
    data were available on the differential toxicity of linear and
    branched AS.

        In aquatic organisms, the EC50 values for C12 AS in a
    community of marine microorganisms were 2.1-4.1 mg/litre. The NOEC
    values were 35-550 mg/litre (C16/C18) for  Pseudomonas putida and
    14-26 mg/litre (C12-C16/C18) for green algae; and the EC50
    values were > 20-65 mg/litre (C12-C13) for green algae and 18-43
    mg/litre (C12) for macrophytes.

        In aquatic invertebrates, the L(E)C50 values were 4-140 mg/litre
    (C12/C15-C16/C18) for freshwater species and 1.7-56 mg/litre
    (all C12) for marine species. The long-term NOECs were 16.5 mg/litre
    (C16-C18) for  Daphnia magna and 0.29-0.73 mg/litre (chain length
    not specified) for marine species.

        In fish, the LC50 values were 0.5-5.1 mg/litre (C12-C16 or chain
    length not specified) for freshwater species and 6.4-16 mg/litre
    (all C12) for marine species. In a 48-h study of  Oryzias latipes,
    chain length influenced LC50 values, the measured concentrations being
    46 mg/litre for C12, 2.5 mg/litre for C14, and 0.61 mg/litre
    for C16. This and other studies indicate that toxicity differs by a
    factor of five for two units of chain length.

        In a flow-through study of the effect of C16-C18 AS on a
    biocenosis, an NOEC of 0.55 mg/litre was observed. Many of the studies
    of toxicity in aquatic environments were carried out under static
    conditions. As AS are readily biodegraded, this design may result in
    underestimates of toxicity.

        Few data were available on the effects of AS on terrestrial
    organisms. An NOEC of > 1000 mg/kg (C16-C18) was reported for
    earthworms and turnips.

    C9.1  Microorganisms

        During tests of biodegradation, marine bacteria used 20 mg/litre
    AS as a nutrient source. It was therefore concluded that its toxicity
    for the bacterial community studied is nil or very low (Vives-Rego et
    al., 1987). In a study of the effect of C12 AS on the metabolic
    activity of a marine microbial community, the EC50 values for toxic
    effects on thymidine incorporation and glucose metabolism were
    reported to be 4.1 and 2.1 mg/litre, respectively. AS also increased
    exoproteolytic activity (Vives-Rego et al., 1986).

        The 30-min EC50 for C16-C18 AS, based on oxygen consumption,
    was 35 mg/litre in  Pseudomonas putida (Robra, 1976). The NOEC for
    cell reproduction in  Pseudomonas putida exposed to C16-C18 AS
    was 550 mg/litre (Bringmann & Kühn, 1977).

    C9.2  Aquatic organisms

    C9.2.1  Aquatic plants

    C9.2.1.1  Freshwater algae

        The phytoflagellate alga  Poterioochromonas malhamensis was
    exposed to C12 AS at sublethal concentrations of 28.8, 57.6, 72,
    86.4, 100.8, and 115.2 mg/litre (100, 200, 250, 300, 350, and
    400 µmol/litre), being transferred every three to four days into fresh
    medium with a higher test concentration. The initial cell density in
    each medium was 0.1 × 106 cells/ml; the final cell density, after
    exposure to the highest concentration of AS, was 0.05 × 106 cells/ml,
    which was similar to that reached after exposure of unacclimatized
    algal cultures to 200 µmol/litre AS. Exposure to AS at 57.6 mg/litre
    (240 µmol/litre) was reported to affect mitosis and cytokinesis, with
    the formation of cells containing up to 12 nuclei. Exposure of the
    alga to 50.4 mg/litre (175 µmol/litre) AS resulted in a 24% increase
    in telophases (binucleated cells). Cells with eight nuclei were also
    reported in this culture (Röderer, 1987).

        The green alga  Selenastrum capricornutum was exposed to analytical
    grade C12 AS at a concentration of 10, 20, 30, 40, 50, or
    100 mg/litre in synthetic medium for three weeks. Growth was reduced
    by 30% at the lowest concentration (Nyberg, 1988).

        The green alga  Chlamydomonas reinhardi was exposed to 0.02, 0.2,
    or 2.0 mmol/litre of C10, C12, C14, C16, or C18 AS for 7-10
    days. Photometric absorption (652 nm) by the exposed cultures was no
    different from that by controls for the first six days of exposure,
    although it was reduced slightly at 2 mmol/litre. The authors
    concluded that the AS were present at below the critical micelle
    concentration at all concentrations tested (Ernst et al., 1983).

        The EC50 for growth of the green alga  Selenastrum capricornutum
    exposed to C12 AS for two to three days was within the range 45-65
    mg/litre (Yamane et al., 1984). An EC50 of 9 mg/litre C14 AS was
    found for growth of S. capricornutum (Konno & Wakabayashi, 1987).

    C9.2.1.2  Macrophytes

        The seven-day EC50 values for C12 AS in the duckweed Lemna
    minor under flow-through conditions were 43 mg/litre for frond count,
    29 mg/litre for dry weight, and 18 mg/litre for root length.

    The time-independent EC50 for growth rate/doubling time was
    44 mg/litre (Bishop & Perry, 1981).

    C9.2.2  Aquatic invertebrates

        The acute toxicity of AS to aquatic invertebrates is summarized in
    Table 41. The 48-h LC50 values were 8-60 mg/litre for daphnids; the
    96-h LC50 values ranged from 3.2 to 4.2 mg/litre for marine
    invertebrates.

        The 48-h LC50 for lugworms  (Arenicola marina) exposed to AS
    was calculated to be 15.2 mg/litre (95% confidence interval,
    13.2-17.6). Tissues from lugworms exposed to AS at a concentration
    close to that of the LC50 were examined for changes in morphology by
    both light and electron microscopy: serious damage was found in the
    epidermic receptors and less serious damage in the caudal epidermis
    and gills. No morphological effects were reported on the thoracic
    epidermis or intestine. AS caused separation inside the caudal
    epithelial layer, resulting in holes in some caudal papillae.
    Deciliation of the epidermic receptors was also reported. The authors
    concluded that the physiological response of damaged epidermic
    receptors was reduced or blocked after exposure to AS. AS also induced
    fissures in the epithelial layer of the gills (Conti, 1987).

         Caeriodaphnia dubia were exposed to C12 AS for three
    generations under static renewal conditions, with the following mean
    water parameters: temperature, 26.2°C; pH, 8.2; hardness,
    94.4 mg/litre CaCO3; and alkalinity, 82.2 mg/litre CaCO3. The
    water was changed every second day. The LC50 for survival of three
    broods of  C. dubia was calculated to be 41 ± 3.2 mg/litre. The mean
    EC50, based on progeny produced, was calculated to be 36 ± 3.2
    mg/litre. No statistically significant effects were reported after
    exposure to 83 mg/litre AS, although the size of later broods was
    reduced (Cowgill et al., 1990).

        The effect of 0.25-10 mg/litre AS was studied on the growth and
    survival of eggs and larvae of oysters  (Crassostrea virginica) and
    clams  (Mercenaria mercenaria). The minimal concentrations that
    caused a significant reduction in the number of fertilized eggs which
    developed into normal larvae two days after hatching were
    0.73 mg/litre for clams and 0.29 mg/litre for oysters. The minimal
    concentration that caused a significant reduction in growth and
    survival between two and 12 or 14 days after hatching was
    1.46 mg/litre for both species. The EC50 values, based on the
    development of fertilized clam and oyster eggs to normal
    straight-hinge larvae after 48 h, were calculated to be
    0.47 mg/litre for clams and 0.37 mg/litre for oysters (Hidu, 1965).

        After snails  (Lymnaea peregra) were exposed to C12 AS at
    measured concentrations of 0.6-12 mg/litre for six days, a
    significant, dose-related reduction in the dry weight of shells was
    observed, but the organic content of shells was not significantly
    affected at any concentration (Tarazona & Nunez, 1987).

    C9.2.3  Fish

        The acute toxicity of AS to fish is also summarized in Table 41.
    The 48-h LC50 values were 0.5-51 mg/litre for medaka  (Oryzias
     latipes). A 96-h LC50 value of 1.7 mg/litre was reported for both
    rainbow trout  (Salmo gairdneri) and sheepshead minnow  (Cyprinodon
    variegatus). The acute toxicity of AS to fish tends to increase with
    increasing carbon-chain length.

        Rainbow trout  (Oncorhynchus mykiss) and goldfish  (Carrasius
     auratus) were exposed to C12 AS at a concentration of 70 mg/litre
    at different levels of water hardness. Trout treated in hard water
    (300 mg/litre CaCO3) died within 40-45 min; those treated in soft
    water (60 mg/litre CaCO3) died after 3 h. Goldfish treated in hard
    water died within 90-110 min, whereas those treated in distilled water
    (no CaCO3) were alive and apparently normal after 24 h (Tovell et
    al., 1974). When yearling rainbow trout were maintained in water
    containing C12 AS at a concentration of 100 mg/litre, the time to
    50% lethality was calculated to be 4.9 h. The changes seen in the
    gills were typical of an acute inflammatory reaction: The gill
    epithelium was lifted away from the underlying tissue, and lymphocytes
    and granulocytes invaded the subepithelial spaces. Large numbers of
    epithelial cells died, but the epithelium was not punctured (Abel &
    Skidmore, 1975).

        After exposure of the eggs of carp  (Cyprinus carpio) to AS  of
    various chain lengths from spawning to hatching, the LC50 values
    were calculated to be 18 mg/litre for C12 AS, 2.9 mg/litre for C14
    AS, and > 1.6 mg/litre for C16 AS (Kikuchi et al., 1976).

        The minimal avoidance concentration of AS, i.e. the concentration
    at which fish spend 65% of a 5-min period in clean water in order to
    avoid AS, was 7.1 µg/litre for medakas  (Oryzias  latipes) (Hidaka et
    al., 1984). The threshold concentrations for avoidance of AS by ayu
     (Plecoglossus altivelis) were 4.0 µg/litre of a formulation and 8.4
    µg/litre of pure reagant AS (Tatsukawa & Hidaka, 1978). The
    environmental relevance of avoidance studies is questionable (see also
    section A9.3.3.4 of the monograph on LAS).

        Larvae of the fathead minnow (Pimephales promelas) were exposed to
    C12 AS at a concentration of 1.2, 2.3, 4.6, 9.2, or 18.4 mg/litre
    for seven days under static renewal conditions. Survival and final dry
    weight were not significantly affected at concentrations up to and
    including 4.6 mg/litre; however, at 9.2 and 18.4 mg/litre, no fish

        Table 41.  Toxicity of alkyl sulfates (AS) to aquatic organisms
                                                                                                                                              

    Species                 Size or      Static or    Temp.     Hardness        pH          AS chain    End-point      Concn      Reference
                            age          flow         (°C)      or salinity                 length                     (mg/litre)
                                                                                                                                              

    Eastern oyster          Embryo       Static       20        25a                         C12         48-h LC50      1.7b       Mayer (1987)
    (Crassostrea virginica)

    Mysid shrimp            Juvenile     Static       25        30a                         C12         96-h LC50      3.2b
    (Metamysidopsis swifti)

    Mysid shrimp            Juvenile     Static       25        20a                         C12         96-h LC50      4.2b
    (Mysidopsis bahia)      Adult        Static       22                                    C12         96-h LC50      6.62       Roberts et al.
                                                                                                                                  (1982)
    Shrimp                  Adult        Static       22        20.0 ± 0.5a                 C12         96-h LC50      7.24
    (Neomysis americana)

    Copepod                 Adult        Static                 10a                         C12         96-h LC50      2.6
    (Eurytemora affinis)
    (Acartia tonsa)         Adult        Static                                              C12        96-h LC50      0.55

    Scud                                                                                    NS          72-h LC50      9-46       Gilbert &
    (Gammarus pulex)                                                                                                              Pettigrew
                                                                                                                                  (1984)

    Water flea                           Static       20                                    C12         24-h EC50      17.4       Snell &
    (Daphnia magna)                                                                                                               Persoone
                                                                                                                                  (1989)
                                         Static       20                                    C12         24-h EC50      27.5       Persoone et
                                                                                                                                  al. (1989)
                                                                                            C16-C18     24-h EC50      27.5       Steber et al.
                                                                                                                                  (1988)
                                                                                            C12         24-h EC50      10.5-24.3  Cowgill et
                                                                                                                                  al. (1990)
                                                                                                                                              

    Table 41 (contd)
                                                                                                                                              

    Species                 Size or      Static or    Temp.     Hardness        pH          AS chain    End-point      Concn      Reference
                            age          flow         (°C)      or salinity                 length                     (mg/litre)
                                                                                                                                              

    Water flea                                                                              C12         24-h LC50      15.0       Snell &
    (Daphnia pulex)                                                                                                               Persoone
                                                                                                                                  (1989)
                                                                                            C12         24-h LC50      9.5-20.5   Cowgill et 
                                                                                                                                  al. (1990)

    Mosquito                2nd/3rd      Static       25                                    C12-C15     24-h LC50      4          van Emden et
    (Aedes aegypti)         stage                                                                                                 al. (1974)

    Rainbow trout                        Flow         15        350-375c        8.3-8.5     NS          96-h LC50      4.62       Fogels &
    (Salmo gairdneri)                                                                                                             Sprague (1977)
                                                                                            NS          96-h LC50      1.7        Gilbert &
                                                                                                                                  Pettigrew
                                                                                                                                  (1984)

    Atlantic silverside     59 mm        Static       22        10a                         C12         96-h LC50      6.4        Roberts et al.
    (Menidia menidia)                                                                                                             (1982)

    Medaka (killifish)                                                                                  48-h LC50      10         Tomiyama
    (Oryzias latipes)                                                                                                             (1974)
                            323  mg      Staticr      23-24                     5.6-5.8     C12         24-h LC50      70b        Kikuchi et al.
                            323  mg      Staticr      23-24                     5.6-5.8     C12         48-h LC50      51b        (1976)
                            323  mg      Staticr      19-21                     5.6-5.8     C14         24-h LC50      5.9b
                            323  mg      Staticr      19-21                     5.6-5.8     C16         24-h LC50      0.78b
                            323  mg      Staticr      19-21                     5.6-5.8     C12         48-h LC50      0.5b
                         approx. 262 mg  Staticr      21-22                     6.7-7.1     C12         48-h LC50      46d        Kikuchi &
                         approx. 262 mg  Staticr      21-22                     6.7-7.1     C12         48-h LC50      2.5d       Wakabayashi
                         approx. 262 mg  Staticr      21-22                     6.7-7.1     C12         48-h LC50      0.61d      (1984)
                                                                                                                                              

    Table 41 (contd)
                                                                                                                                              

    Species                 Size or      Static or    Temp.     Hardness        pH          AS chain    End-point      Concn      Referenceage
    flow                    (°C)         or salinity            length                      (mg/litre)
                                                                                                                                              

    Sheepshead minnow       Juvenile     Static       25        20a                         C12         96-h LC50      1.7b       Mayer (1987)
    (Cyprinodon variegatus)

    Fathead minnow          NS           Static       NS        80-400          7.4-8.2     NS          96-h LC50      5-6        Henderson et
    (Pimephales promelas)                                                                                                         al. (1959)
                            < 30 d       Static       20                                    C15         48-h LC50      7.8        Cowgill et al.
                            <30 d                     17                                    C12         24-h LC50      7.7-9.7    (1990)
                            <30 d                     17                                    C12         96-h LC50      7.0-9.0
                            30±2 d                    20                                    C12         48-/96-h LC50  38.0

    Carp                    4.4 mg       Static       22        25              7           C10         12-h LC50      180b       Kikuchi et al.
    (Cyprinus carpio)       4.4 mg       Static       22        25              7           C10         48-h LC50      13b        (1976)
                            4.4 mg       Static       22        25              7           C12         12-h LC50      46b
                            4.4 mg       Static       22        25              7           C14         48-h LC50      5.0b
                            4.4 mg       Static       22        25              7           C16         12-h LC50      0.69b
                            4.4 mg       Static       22        25              7           C16         48-h LC50      0.69b
                                                                                                                                              

    Static, water unchanged for duration of test; NS, not specified; flow, flow-through conditions: AS concentration in water maintained
    continuously; staticr,  static renewal: water changed at regular intervals
    a Salinity (%)
    b Based on nominal concentrations
    c Hardness expressed as mg/litre CaCO3
    d Based on measured concentrations
        survived. When the test was repeated over an eight-day period,
    significantly reduced survival was seen at 4.6 mg/litre, but this
    result was variable, as some replicates did not show significant
    effects. The mean of the geometric means of the NOEC and LOEC values
    for the embryo-larval test was 3.8 mg/litre; the mean LC50 value was
    5.5 mg/litre (Pickering, 1988).

        An LC50 value of 38 mg/litre was reported for fathead minnows
    exposed to C12 AS for either 48 or 96 h. The authors suggested that
    the same value was obtained because the tests were not carried out
    aseptically and the C12 AS had degraded completely within 48 h
    (Cowgill et al., 1990).

    C9.2.4  Tests in biocenoses

        In a flow-through biocenosis test, 13 species of aquatic organisms
    were exposed to C16-C18AS. The species used represented several
    trophic levels: seven species of algae, four species of protozoa, and
    two species of rotifers. An NOEC of 0.55 mg/litre was reported for
    'biocenotic toxicity'. The lowest concentration at which biocenotic
    toxicity was reported was 1.65 mg/litre (Guhl, 1987).

    C9.3  Terrestrial organisms

        No information was available.


        APPENDIX I

    APPENDIX I.

    Reference values for intakes and body weights of laboratory animals, with conversion factors for
    deriving no-observed-adverse-effect levels (NOAELs) in milligrams per kilogram per day from
    doses administered as parts per million
                                                                                                         

    Species          Body       Inhalation      Water          Food           Dose conversiona
                  weight (kg)      rate      consumption    consumption                             
                                                                           Air      Water     Food
                                                                         (m3/day)  (litres/  (g/day)
                                                                                    day)
                                                                                                        

    Mouse            0.03b         0.04b        0.006b         4b          1.33      0.20     0.13
    Rat              0.35b         0.11d        0.05b          18b         0.31      0.14     0.05
    Hamster          0.14b         0.13b        0.03b          12b         0.93      0.21     0.09
    Guinea-pig       0.84b         0.40b        0.20b          34b         0.48      0.24     0.04
    Rabbit           3.8b          2.0b         0.41b          186b        0.53      0.11     0.05
    Rhesus monkey    8.0b          5.4c         0.53b          320b        0.68      0.07     0.04
    Dog              12b           4.3b         0.61b          300b        0.36      0.05     0.03
    Cat              1.5d          0.75d        0.15e          168e        0.50      0.10     0.11
    Pig              80e           -            5.5e           2250e                 0.07     0.03
                                                                                                        

    From Health Canada (in press); most values have been rounded to two significant figures.
    a Air: 1 mg/m3 in air =  x in mg/kg bw per day; water: 1 ppm (mg/litre) =  x in mg/kg bw per day;
      food: 1 ppm in food =  x in mg/kg bw per day
    b From Calabrese & Kenyon (1991)
    c Calculated from the minute volume of 220 ml/kg bw reported by Flecknell (1987)
    d From Flecknell (1987); values are average of the ranges reported.
    e From Canadian Council on Animal Care (1980-84); values are average of the ranges reported.
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    ALKYLBENZENESULFATES A CHAINE DROITE ET COMPOSES VOISINS

    1.  RECAPITULATION, EVALUATION ET RECOMMANDATIONS GENERALES

    1.1  Identité, propriété et méthodes d'analyse

        Les alkylbenzènesulfonates à chaîne droite (appelé aussi
    alkylbenzènesulfonates linéaires ou ASL, les alpha-oléfine-
    sulfonates (AOS) et les alkylsulfates (AS)) sont des tensio-actifs
    anioniques dont les molécules sont caractérisées par la présence d'un
    groupement hydrophobe et d'un groupement hydrophile (polaire). Les
    produits du commerce sont des mélanges d'isomères et d'homologues de
    produits voisins, qui different par leurs propriétés physicochimiques
    et qui, sous leurs diverses formes, ont des applications variées.

        L'analyse des ASL, des AOS et des AS peut se faire par des
    méthodes non spécifiques. On utilise généralement l'essai au bleu de
    méthylène, qui permet de mettre en évidence tout composé contenant un
    groupement anionique et un groupement hydrophobe. On peut donc être
    gêné par la présence d'autres substances lorsqu'on travaille sur des
    échantillons prélevés dans l'environnement; en outre, la sensibilité
    de la méthode n'est que de 0,02 mg/litre. On a mis au point d'autres
    méthodes non spécifiques qui peuvent se substituer à celles-ci mais on
    ne les utilise guère. En ce qui concerne les échantillons prélevés
    dans l'environnement, il n'existe de méthodes spécifiques que pour les
    ASL et les AS. En ce qui concerne les AOS, on dispose d'une méthode
    améliorée qui repose sur la réaction au bleu de méthylène et la
    chromatographie en phase liquide à haute performance (HPLC).

        Les ASL sont des composés non volatils que l'on obtient par
    sulfonation des alkylbenzènes à chaîne droite. Les produits du
    commerce sont toujours constitués de mélanges d'homologues ayant des
    chaînes alkylées de différentes longueurs (C10-C13 ou C14) et
    d'isomères qui différent par la position du point d'attache de la
    chaine sur le noyau phényle (positions 2 à 5). Tous les homologues et
    isomères des ASL peuvent être dosés dans des échantillons
    environnementaux ou d'autres matrices au moyen de méthodes d'analyse
    spécifiques comme la HPLC, la chromatographie en phase gazeuse et la
    chromatographie en phase gazeuse couplée à la spectrométrie de masse.

        Les AOS sont également des dérivés non volatils produit par
    sulfonation des alpha-oléfines. Ils consistent dans le mélange de deux
    types de composés, les alcène-sulfonates de sodium et les
    hydroxyalcane-sulfonates de sodium, avec une chaine alkylée en
    C14-C18.

        Egalement non volatils, les AS s'obtiennent en traitant par
    l'acide sulfurique, les alcools d'origine oléochimique ou
    pétrochimique. Ce sont des mélanges d'homologues avec une chaîne
    alkylée en C10-C18.  On met actuellement au point des méthodes
    d'analyse spécifiques pour la surveillance de l'environnement.

    1.2  Sources d'exposition humaine et environnementale

        On utilise les ASL, les AOS et les AS comme principes actifs de
    divers produits d'entretien ou d'hygiène personnelle, ou encore, pour
    certaines applications spéciales. Après usage, ces détergents sont
    rejetés dans l'environnement avec les eaux usées.

        Il peut y avoir exposition professionnelle à ces composés. Quant
    à l'exposition de la population humaine en général et des êtres
    vivants dans leur milieu naturel, elle dépend du type d'application de
    ces substances (ou d'autres tensio-actifs), des pratiques locales en
    matière de traitement des effluents et des caractéristiques du milieu
    récepteur.

        En 1990, la consommation mondiale de ces produits d'établissait à
    2 millions de tonnes pour les ASL, 86 000 tonnes pour le AOS et 289
    000 tonnes pour les AS.

    1.3  Concentrations dans l'environnement

    1.3.1  Alkylbenzènesulfonates à chaîne droite

        On peut doser les ASL à l'aide de méthodes spécifiques et
    sensibles dans pratiquement tous les compartiments du milieu où ils
    sont susceptibles de se trouver. Leur concentration diminue
    progressivement selon la séquence suivante: eaux usées > effluents
    traités > eaux de surface > mer.

        Dans les zones où l'on utilise principalement des ASL comme
    tensio-actifs, leur concentration est généralement de 1-10 mg/litre
    dans les eaux usées, de 0,05-0,1 mg/litre dans les effluents traités
    par voie biologique, de 0,05-0,6 mg/litre dans les effluents traités
    sur lit filtrant, de 0,005-0,05 mg/litre dans les eaux de surface
    situées au-dessous de déversoirs d'égouts (avec des concentrations qui
    tombent rapidement à 0,01 mg/litre en aval du déversoir), de < 1-10
    mg/kg dans les sédiments de cours d'eau (< 100 mg/kg dans les
    sédiments très pollués à proximité des zones de décharge), de 1-10
    g/kg dans les boues d'égouts, de < 1 5  mg/kg dans les sols amendés
    à l'aide de boues d'égouts (initialement 5-10 mg/kg; on a trouvé des
    concentrations < 50 mg/kg après d'importants épandages de boues,
    d'ailleurs non représentatifs). La concentration des ASL dans les eaux
    estuarielles varie de 0,001 à  0,01 mg/litre, mais elle peut être
    beaucoup plus élevée là où il y a déversement direct d'eaux usées. En
    mer, à distance du rivage, les concentrations vont de <  0,001 à
    0,002 mg/litre.

        Il est à noter que la concentration de ASL varie considérablement
    dans l'environnement. Ces variations sont dues à la diversité des
    méthodes d'analyse, des points de prélèvement (qui vont de zones très
    polluées où sont déversés des effluents insuffisamment traités à des
    secteurs où l'effluent a subi un traitement intensif), des périodes de
    prélèvement (ce qui selon le cas peut signifier une différence du
    simple au double) et enfin, des volumes de ASL consommés.

        La surveillance de l'environnement montre que les ASL ne
    s'accumulent pas au cours du temps dans les différents compartiments
    du milieu. La concentration dans le sol, loin d'augmenter, diminue au
    contraire par suite de la minéralisation. Comme les ASL ne se
    décomposent pas en anaérobiose stricte (pour donner naissance à du
    méthane), on ne peut pas en conclure qu'ils subissent une
    minéralisation dans les sédiments anaérobies. Au taux actuel
    d'utilisation, les ASL parviennent dans les différents compartiments
    de l'environnement à un rythme sensiblement égal à celui de leur
    assimilation, ce qui crée les conditions d'un état stationnaire.

    1.3.2  Les alpha-oléfine-sulfonates et alkyle-sulfates

        Les données dont on dispose sur la concentration des AOS dans
    l'environnement sont limitées en raison de la difficulté à analyser
    les échantillons prélevés dans le milieu. En général, on peut déceler
    la présence des tensio-actifs anioniques au moyen de méthodes
    colorimétriques non spécifiques (comme celles qui sont basées sur la
    réaction au bleu de méthylène), mais la présence d'autres substances
    est gênante et ces méthodes ne permettent pas de procéder à un dosage
    spécifique des alpha-oléfine-sulfonates. Une méthode spécifique de
    dosage des AS dans l'environnement est en cours de mise au point.

        Les études effectuées en laboratoire indiquent que les AOS et les
    AS sont rapidement minéralisés dans tous les compartiments de
    l'environnement et presque totalement éliminés des effluents au cours
    du traitement de ces derniers. Leur concentration dans les eaux de
    surface, les sédiments, le sol, les eaux estuarielles et le milieu
    marin est probablement faible. C'est précisément ce que l'on a
    constaté pour la concentration des AOS dans l'eau des rivières.

    1.4  Transport, distribution et transformation dans l'environnement

        Aux températures inférieures à 5-10°C, la cinétique de
    biodégradation des ASL, des AOS et des AS est ralentie en raison de la
    réduction de l'activité microbienne.

    1.4.1  Alkylbenzène-sulfonates à chaîne droite

        Les voies de pénétration des ASL dans l'environnement varient
    selon les pays, mais la porte d'entrée principale est constituée par
    la décharge des stations d'épuration des eaux usées. Lorsque ces
    stations sont inexistantes ou fonctionnent mal, il peut y avoir
    décharge directe dans les rivières, les lacs et la mer. L'épandage de
    boues d'égout sur les terrains agricoles peut également constituer une
    voie de pénétration de ASL dans l'environnement.

        A mesure qu'ils pénètrent dans l'environnement, les ASL en sont
    éliminés par divers mécanismes qui vont de l'adsorption à la
    biodégradation ultime. Les ASL sont adsorbés sur les surfaces
    colloïdales et les particules en suspension, et l'on a mesuré des
    coefficients d'adsorption de 40-5200  litres/kg selon le milieu et la
    structure des ASL en cause. Ils subissent une biodécomposition dans
    les eaux de surface (demi-vie 1-2  jours), dans les sédiments aérobies
    (1-3  jours) ainsi que dans les écosystèmes marins et estuariels (5-10 
    jours).

        Lors du traitement primaire des effluents, environ 25% des ASL (de
    10-40%) s'adsorbent sur les boues résiduelles et sont rejetés avec
    elles. Ils ne sont pas éliminés au cours de la digestion anaérobie des
    boues mais au cours du traitement aérobie, leur demi-vie étant alors
    de 10 jours. Après épandage des boues sur le sol, les ASL sont
    générale-ment décomposés à hauteur de 90% en l'espace de trois mois,
    la demi-vie étant de l'ordre de 5-30 jours.

        Le facteur de concentration des ASL dans le corps entier varie de
    100 à 300 pour l'ensemble des 14C-ASL et 14C-métabolites. Ils sont
    captés par les poissons essentiellement à travers les branchies et se
    répartissent ensuite dans le foie et la vésicule après
    biotransformation. Les ASL sont rapidement excrétés et rien n'indique
    par conséquent qu'ils subissent une bioamplification.

    1.4.2  alpha-Oléfine-sulfonates

        Les données relatives au transport, à la distribution et à la
    transformation des AOS dans l'environnement sont encore moins
    nombreuses que dans le cas des ASL. On peut toutefois penser que les
    AOS sont transportées dans l'environnement à peu près comme les ASL,
    les AS et les autres détergents tensio-actifs et que leur destinée y
    est analogue à celles des ASL et des AS. En aérobiose, elles subissent
    une biodécomposition rapide et cette biodécomposition primaire est
    achevée en 2  à 10  jours, en fonction de la température. On ne
    dispose que de données limitées sur la bioaccumulation des AOS; en
    tout état de cause elles ne s'accumulent pas chez les poissons. On ne
    dispose d'aucune donnée sur leur décomposition en milieu abiotique.

    1.4.3  Alkylsulfates

        Les AS sont transportés dans l'environnement par des mécanismes
    analogues à ceux qui sont à l'oeuvre dans le cas des ASL et des AOS.
    Ils sont facilement biodégradable en aérobiose ou en anaérobiose, que
    ce soit au laboratoire ou dans l'environnement; la biodécomposition
    primaire est achevée en l'espace de 2 à 5  jours. Les facteurs de
    bioconcentration pour le corps entier varient de 2 à 73 ainsi qu'avec
    la longueur de la chaîne des différents homologues. Chez les poissons,
    les AS sont captés, distribués, biotransformés et excrétés de la même
    manière que les ASL et ne se concentrent pas dans les autres
    organismes aquatiques.

    1.5  Cinétique

        Les ASL, les AOS et le AS sont facilement résorbés dans les voies
    digestives, après quoi ils se répartissent dans l'ensemble de
    l'organisme où ils sont largement métabolisés. Les ASL subissent une
    omega- et une ß-oxydation. Les composés initiaux et leurs métabolites
    sont principalement excrétés par la voie rénale, encore qu'une
    certaine proportion de la dose absorbée puisse l'être également pas la
    voie fécale, après métabolisation et passage dans les voies biliaires.
    Les ASL, les AOS et les AS ne sont absorbés qu'en quantités minimes
    par voie percutanée lorsque la peau est intacte, mais un contact
    prolongé peut altérer l'intégrité de la barrière épidermique, ce qui
    permet une résorption plus importante; à fortes concentrations, il
    peut y avoir réduction du temps de pénétration.

    1.6  Effets sur les animaux de laboratoire et sur les systèmes
         d'épreuve  in vitro

        On a relevé, pour la DL50 des sels de sodium des ASL, des
    valeurs allant de 404 à 1470  mg/kg de poids corporel chez le rat et
    de 1259 à 2300  mg/kg de poids corporel chez la souris, ce qui incite
    à penser que les rats sont plus sensibles que les souris à l'action
    toxique des ASL. Chez la souris, on a obtenu une DL50 de 3000 mg/kg
    de poids corporel pour un sel de sodium d'AOS. Chez le rat, les
    valeurs de la DL50 par voie orale allaient de 1000 à 4120 mg/kg
    de poids corporel pour les AS. Les ASL, les AOS et les AS sont
    irritants pour la peau et les yeux.

        Lors d'études subchroniques au cours desquelles on a administré à
    des rats des ASL dans leur nourriture ou leur eau de boisson à des
    concentrations quotidiennes correspondant à plus de 120  mg/kg de
    poids corporel, on a observé des effets minimes, qui consistaient
    notamment en modifications des paramètres biochimiques et altérations
    histopathologiques au niveau du foie. Bien que lors d'une étude, on
    ait observé des modifications ultrastructurales dans les hépatocytes
    à des doses plus faibles, ces modifications se sont révélées
    réversibles. D'ailleurs, les autres études n'ont pas révélé de tels

    effets aux mêmes doses, mais il n'est pas exclu que lors de l'étude
    initiale, les organes aient fait l'objet d'un examen plus minutieux.
    Des effets ont également été observés sur la fonction de reproduction
    chez des animaux auxquels on avait administré des doses quotidiennes
    > 300 mg/kg; il s'agissait d'une réduction du taux de grossesse et
    d'une certaine mortalité dans les portées. Après application cutanée
    de longue durée à des rats de solutions de ASL à plus de 5% et
    application, également cutanée, du même type de solution à des cobayes
    à raison de 60 mg/kg de poids corporel pendant 30 jours, on a observé
    des modifications biochimiques et histopathologiques. Des applications
    cutanées répétées de solutions de teneur > 0,3% de ASL ont
    produit des effets toxiques sur les foetus ainsi que sur la
    reproduction, mais les doses étaient également toxiques pour les
    femelles gestantes.

        On n'a guère de données résultant d'études sur des animaux de
    laboratoire qui permettraient d'évaluer les effets potentiels des AOS
    chez l'homme. Aucun effet n'a été observé sur des rats ayant reçu,
    pendant une longue durée, des doses quotidiennes de 250 mg/kg de poids
    corporel en administration orale; toutefois une dose quotidienne de
    300 mg/kg de poids corporel, toxique pour les femelles gestantes, a
    entraîné des effets foetotoxiques chez des lapins. L'application
    topique d'AOS sur la peau et les yeux de divers animaux de laboratoire
    a produit des effets localisés.

        Les effets d'une exposition à long et à court terme aux AS ont été
    étudiés à plusieurs occasions sur l'animal mais la plupart des études
    en question pêchent par les insuffisances des examens
    histopathologiques ou la trop petite taille des groupes; en outre, les
    doses les plus élevées utilisées dans les études à long terme n'ont
    pas produit le moindre effet toxique, de sorte qu'il n'a pas été
    possible d'établir la valeur de la dose sans effets nocifs
    observables. Cependant, lorsqu'on a administré à des rats des
    concentrations quotidiennes de ces substances correspondant à
    200 mg/kg de poids corporel ou davantage, par incorporation à leur
    nourriture ou à leur eau de boisson, on a systématiquement observé un
    certain nombre d'effets. En outre, l'application topique sur la peau
    ou les yeux d'AS à des concentrations égales ou supérieures à environ
    0,5%, a donné lieu à une irritation localisée. Par ailleurs à fortes
    concentrations, on observe des effets toxiques sur les femelles
    gestantes ainsi que sur les foetus.

        La plupart des études à long terme ne se prêtent pas à
    l'évaluation du pouvoir cancérogène des ASL, des AOS et des AS chez
    l'animal de laboratoire en raison de facteurs tel que le nombre trop
    faible d'animaux, un nombre de doses limité, la non détermination de
    la dose tolérée maximale, et, en outre, un examen histopathologique
    limité dans la majorité des cas. Dans les travaux où les effets
    anatomo-pathologiques ont été convenablement étudiés, on n'a pas
    déterminé la dose tolérée maximale et les doses employées n'ont pas
    produit d'effets toxiques. Toutefois et compte tenu de ces réserves,

    on peut retenir que les études au cours desquelles on a administré à
    des animaux des ASL, des AOS et des AS par voie orale, n'ont pas
    révélé de signes de cancérogénicité; quant aux études à long terme
    consistant en applications topiques d'AOS par badigeonnage cutané,
    elles n'ont pas non plus révélé la présence d'effets imputables à ces
    substances.

        Sur la base de ces données limitées, il ne semble pas que ces
    composés soient génotoxiques  in vivo ou  in vitro.

    1.7  Effets sur l'homme

        L'application d'un timbre cutané imprégné de solution contenant
    jusqu'à 1% de ASL, d'AOS ou d'AS pendant 24  heures montre que la peau
    humaine supporte le contact avec cette substance au prix d'une légère
    irritation. Ces tensio-actifs provoquent une délipidation de
    l'épiderme, une élution du facteur d'humidification naturelle, ainsi
    qu'une dénaturation des protéines de la couche épidermique externe,
    dont ils augmentent la perméabilité et dont ils provoquent le
    gonflement. Ni les ASL, ni les AOS, ni les AS n'ont provoqué de
    sensibilisation cutanée chez les volontaires et rien n'indique de
    façon concluante qu'ils puissent provoquer un eczéma. On n'a pas
    signalé de lésions graves ou mortelles consécutives à l'ingestion
    accidentelle de ces tensio-actifs.

    1.8  Effets sur l'environnement

    1.8.1  Alkylbenzène-sulfonates à chaîne droite

    1.8.1.1  Milieu aquatique

        Les ASL ont été très largement étudiés tant au laboratoire (études
    à court et à long terme) que dans des conditions plus proches de la
    réalité (études sur le micro- et le mésocosme et études en situation
    réelle). En général, la diminution de la longueur de la chaîne alkylée
    ou une plus grande intériorisation du groupement phényle
    s'accompagnent d'une diminution de la toxicité. Les observations
    effectuées sur des poissons et sur des daphnies montrent que lorsque
    la longueur de la chaîne diminue d'une unité (par exemple lorsqu'elle
    passe de C12 à C11), la toxicité est approximativement divisée par
    deux.

        Les résultats des tests en laboratoire sont les suivants:

        --  Microorganismes: Les résultats sont très variables en raison
    de l'utilisation de systèmes d'épreuve très divers (par exemple
    inhibition des boues activées, cultures mixtes et espèces
    individuelles). Les valeurs de la CE50 vont de 0,5 mg/litre (une
    seul espèce) à > 1000 mg/litre. Dans le cas des microorganismes, il
    n'existe pas de relation linéaire entre la longueur de la chaîne et la
    toxicité.

        --  Plantes aquatiques: Les résultats dépendent largement de
    l'espèce. En ce qui concerne les plantes d'eau douce, les valeurs de
    la CE50 se situent entre 10 et 235 mg/litre (C10-C14), dans le
    cas des algues vertes; entre 5 et 56 mg/litre (C11,1-C13), dans le
    cas des algues bleu-vert; entre 1,4 et 50 mg/litre (C11,6-C13)
    pour les diatomées et entre 2,7 et 4,9 mg/litre (C11,8) pour les
    macrophytes. Il semble que les algues marines soient même encore plus
    sensibles. Dans le cas des algues, il n'y a probablement pas non plus
    de relation linéaire entre la longueur de la chaine et la toxicité.

        --  Invertébrés: Les valeurs de la CE50 et de la CL50
    (exposition aiguë) pour au moins 22 espèces d'eau douce se situent
    entre les limites suivantes: 4,6-200 mg/litre (longueur de chaine non
    précisée; C13) dans le cas des mollusques; 0,12-27 mg/litre
    (longueur de chaine non précisée; C11,2-C18) dans le cas des
    crustacés; 1,7-16 mg/litre (longueur de chaine non précisée; C11,8)
    dans le cas des vers et enfin 1,4-270 mg/litre (C10-C15) dans le
    cas des insectes. Dans le cas d'une exposition chronique, les valeurs
    de la CE50 et de la CL50  sont de 2,2 mg/litre (C11,8) pour les
    insectes et de 1,1-2,3 mg/litre (C11,8-C13) pour les crustacés. La
    concentration sans effets chroniques observables (basée sur la
    mortalité ou des effets sur la fonction de reproduction) est de 0,2 à
    10 mg/litre (longueur de chaîne non précisée; C11,8) pour les
    crustacés. Il semble que les invertébrés marins soient plus sensibles,
    avec des valeurs de la CL50 allant de 1 à plus de 100 mg/litre (dans
    presque tous les cas, C12) pour 13 espèces et avec une concentration
    sans effets observables de 0,025 à 0,4 mg/litre (longueur de chaine
    non précisée dans l'ensemble des tests) dans le cas des sept espèces
    étudiées

        --  Poissons: Pour 21 espèces d'eau douce, les valeurs de la
    CL50 aiguë se situent entre 0,1 et 125 mg/litre (C8-C15); les
    valeurs de la CE50 et/ou de la CL50 pour une exposition chronique
    sont, pour deux espèces, respectivement égales à 2,4 et à 11 mg/litre
    (longueur de chaîne non spécifiée; C11,7); quant à la concentration
    sans effets observables, elle va de 0,11-8,4 à 1,8 mg/litre (longueur
    de chaine non précisée; C11,2-C13) pour deux espèces. Dans ce cas
    encore, les poissons de mer se révèlent plus sensibles, avec des
    valeurs de la CL50  aiguë allant de 0,05 à 7 mg/litre (longueur de
    chaîne non spécifiée; C11,7) pour six espèces et des valeurs de la
    CL50  chronique allant de 0,01 à 1 mg/litre (longueur de chaîne non
    précisée) pour deux espèces. Dans la plupart des publications, la
    longueur de la chaine n'est pas précisée. Pour des espèces marines, on
    a également fait état d'une concentration sans effets observables <
    0,02 mg/litre (C12).

        Les produits communément utilisés dans le commerce ont en moyenne,
    une chaîne latérale en C12. Des composés ayant diverses longueurs de
    chaîne ont été étudiés sur  Daphnia magna et sur des poissons, mais
    dans le cas des autres organismes d'eau douce, c'est en général des

    composés dont la longueur de chaine moyenne est de C11,8 qui ont été
    utilisés. Les valeurs caractéristiques de la CE50 et de la CL50  aiguë
    pour les ASL en C12 sont 3-6 mg/litre chez  Daphnia magna et
    2-15 mg/litre chez les poissons d'eau douce; celles de la
    concentration sans effets observables pour une exposition chronique
    sont de 1,2 à 3,2 mg/litre pour  Daphnia magna et de 0,48-0,9
    mg/litre pour les poissons d'eau douce. Chez les poissons de mer, les
    valeurs caractéristiques de la CL50  aiguë pour des ASL en C12
    sont de < 1-6,7 mg/litre.

        Les organismes halophiles et en particulier les invertébrés, se
    révèlent être plus sensibles aux ASL que les organismes d'eau douce.
    Chez les invertébrés, l'action séquestrante des ASL sur le calcium
    peut affecter la biodisponibilité de cet ion pour la morphogénèse. Les
    ASL exercent un effet général sur le transport ionique. Les produits
    de biodécomposition et les sous-produits des ASL sont 10 à 100 fois
    plus toxiques que les composés de départ.

        Les résultats obtenus dans des conditions plus proches de la
    réalité sont les suivants: on a étudié les ASL au moyen de toute sorte
    de tests en eau douce et à plusieurs niveaux trophiques, notamment
    dans des enceintes lacustres (organismes inférieurs), dans des
    écosystèmes modèles (sédiments et réseaux hydrographiques), des cours
    d'eau en aval et en amont des déversoirs de stations d'épuration des
    eaux usées et enfin, des cours d'eau expérimentaux. Dans presque tous
    les cas on a utilisé des ASL en C12. Les algues se sont révélées
    être plus sensibles en été qu'en hiver, les valeurs de la CL50 à 3
    heures étant de 0,2  à 8,1 mg/litre après la photosynthèse, alors que
    dans les écosystèmes modèles, on n'observait aucun effet sur
    l'abondance relative des populations d'algues à la concentration de
    0,35 mg/litre. Selon ces études, la valeur de la concentration sans
    effets observables se situe de 0,24 à 5 mg/litre selon l'organisme et
    le paramètre étudié. Ces résultats sont en assez bon accord avec ceux
    des épreuves en laboratoire.

    1.8.1.2  Milieu terrestre

        On dispose de données sur les végétaux et les lombrics. Pour sept
    espèces de plantes étudiées dans des solutions nutritives, on a obtenu
    des valeurs de la concentration sans effets observables qui se situent
    dans les limites < 10-20 mg/litre; pour trois espèces étudiées sur
    sol d'après leur croissance, on a obtenu 100 mg/kg (C10-C13). Pour
    les lombrics, la CL50 à 14 jours était > 1000 mg/kg.

    1.8.1.3  Oiseaux

        Une étude sur des poulets qui recevaient une nourriture contenant
    de ces substances, a permis de fixer à > 200 mg/kg la dose sans
    effets observables (d'après la qualité des oeufs).

    1.8.2  alpha-Oléfine-sulfonates

        On dispose de données limitées concernant les effets des AOS sur
    les organismes aquatiques et terrestres.

    1.8.2.1  Milieu aquatique

        On ne dispose que des résultats des épreuves en laboratoire:

        --  Algues: Valeur de la CE50 : > 20-65 mg/litre (C16-C18)
    pour les algues vertes

        --  Invertébrés: Valeur de la CL50 : 19 et 26 mg/litre
    (C16-C18) pour la daphnie

        --  Poissons: Pour neuf espèces de poissons on a obtenu des
    valeurs de la CL50 aiguë de 0,3-6,8 mg/litre (C12-C18). Sur la
    base d'études à court terme effectuées sur la truite de mer  (Salmo
     trutta), l'ide rouge  (Idus melanotus) et le rasbora (Rasbora
    heteromorpha), on peut conclure que la toxicité des composés en
    C14-C16 est environ cinq fois plus faible que celle des composés
    en C16-C18, avec des valeurs de la CL50 (à toutes les
    concentrations mesurées) de 0,5-3,1 (C16-C18) et de
    2,5-5,0 mg/litre (C14-C16). Deux études à long terme effectuées
    sur la truite arc-en-ciel ont montré que le paramètre le plus sensible
    était la croissance, et qu'il permettait d'obtenir une CE50 de
    0,35 mg/litre. Pour ce qui est des poissons de mer, on a obtenu pour
    le mulet gris ou muge  (Mugal cephalus), une valeur de la CL50 à 96
    heures de 0,70 mg/litre.

    1.8.2.2  Milieu terrestre

        Une étude portant sur des végétaux en solution nutritive a montré
    que la concentration sans effets observables se situait dans les
    limites 32-56 mg/litre. Dans une autre étude, portant cette fois sur
    des poulets qui recevaient les AOS dans leur nourriture, on a obtenu
    une valeur > 200 mg/kg pour la concentration sans effets observables
    (d'après la qualité des oeufs).

    1.8.3  Alkyl-sulfates

    1.8.3.1  Organismes aquatiques

        Les AS ont fait l'objet d'études à court et à long terme et d'une
    étude dans des conditions plus proches de la réalité. On constate
    encore que leur toxicité dépend de la longueur de la chaîne latérale
    alkylée; par contre on ne dispose d'aucune donnée qui indiquerait
    l'existence d'une différence de toxicité entre les AS à chaine droite
    et les AS à chaîne ramifiée.

        Les résultats des épreuves de laboratoire sont les suivants:

        --  Microorganismes: Les valeurs de la CE50 dans une communauté
    marine étaient de 2,1-4,1 mg/litre (C12). Pour  Pseudomonas putida,
    les concentrations sans effets observables étaient de 35-550 mg/litre
    (C16-C18).

        --  Végétaux aquatiques: Les valeurs de la CE50 s'établissaient
    comme suit: > 20-65 mg/litre (C12-C13) pour les algues vertes et
    18-43 mg/litre (C12) pour les macrophytes. Les concentrations sans
    effets observables s'établissaient à 14-26 mg/litre (C12-C16/C18)
    chez les algues vertes.

        --  Invertébrés: Les valeurs de la CE50 et de la CL50 se
    situaient entre 4 et 140 mg/litre (C12/C15-C16/C18) pour les
    espèces d'eau douce et entre 1,7 et 56 mg/litre (tous les composés en
    C12) chez les espèces marines. La concentration sans effets
    observables pour  Daphnia magna était de 16,5 mg/litre (C16/C18)
    en exposition chronique, les valeurs se situant entre 0,29 et
    0,73 mg/litre (longueur de chaine non précisée) pour les espèces marines.

        --  Poissons: Les valeurs de la CL50 se situaient entre 0,5 et
    5,1 mg/litre (longueur de chaine non précisée ou C12-C16) pour des
    espèces d'eau douce et entre 6,4 et 16 mg/litre (tous les composés en
    C12) pour les espèces marines. On n'a pas eu connaissance d'études
    à long terme.

        Il est à noter que nombre de ces travaux ont été effectués dans
    des conditions statiques. Comme les AS sont facilement biodégradables,
    il est possible qu'on en ait sous estimé la toxicité. Lors d'une étude
    de 48 heures sur  Oryzias latipes, on a obtenu pour la CL50  des
    valeurs respectivement égales à 46, 2,5 et 0,61 mg/litre (mesures de
    concentrations) pour des composés en C12, C14 et C16. Cette
    étude et d'autres, montrent que la toxicité s'accroît d'un facteur 5
    lorsque la longueur de la chaîne augmente de deux unités. Une étude
    dynamique sur une biocénose, avec des composés en C16-C18 a permis
    d'obtenir une concentration sans effets observables de 0,55 mg/litre.

    1.8.3.2  Organismes terrestres

        On a fait état, pour les lombrics et les navets, de concentrations
    sans effets observables de valeur > 1000 mg/kg (C16-C18).

    1.9  Evaluation des risques pour la santé humaine

        Les ASL sont les tensio-actifs les plus largement utilisés pour la
    fabrication de détergents et de produits de nettoyage; les AOS et les
    AS entrent également dans la composition des détergents et des

    produits destinés à l'hygiène personelle. La principale voie
    d'exposition humaine est donc le contact cutané. Cependant de petites
    quantités de ASL, d'AOS et d'AS peuvent être ingérées avec l'eau de
    boisson ou sous forme de résidus subsistant sur les ustentsiles de
    cuisine et dans les aliments. Bien que les données sur ce point soient
    limitées, on peut estimer à environ 5 mg/personne la quantité de ASL
    ingérée quotidiennement de cette manière. Quant à l'exposition
    professionnelle à ces trois catégories de produits, elle peut
    intervenir lors de la préparation des différentes substances qui en
    contiennent, mais on ne dispose d'aucune donnée sur les effets qu'une
    exposition chronique à ces composés pourrait avoir sur l'homme.

        Les ASL, les AOS et les AS peuvent irriter la peau par suite d'un
    contact répété ou prolongé aux concentrations qui sont celles des
    produits non dilués. Chez le cobaye, les AOS peuvent provoquer une
    sensibilisation cutanée lorsque la concentration en sultone
    gamma-insaturée dépasse environ 10 ppm.

        Les études à long terme sur animaux de laboratoire dont on connaît
    les résultats sont insuffisantes pour permettre d'évaluer le pouvoir
    cancérogène des ASL, des AOS et des AS, et ce, pour différentes
    raisons: conception même de ces études, trop petit nombre d'animaux
    utilisés et doses administrées trop faibles, enfin examens
    histopathologiques trop succints. Compte tenu de ces réserves, les
    résultats fournis par les études au cours desquelles les animaux ont
    reçu des ASL, des AOS ou des AS par voie orale, ne comportent aucun
    signe de cancérogénicité; par ailleurs l'application d'AOS aux animaux
    par badigeonnage cutané, a également donné des résultats négatifs. Ces
    composés ne se révèlent pas non plus génotoxiques  in vivo ou  in
     vitro, encore que peu d'études aient été publiées sur ce point.

        Des études sub-chroniques au cours desquelles des rats avaient
    reçu des ASL dans leur nourriture ou leur eau de boisson à des
    concentrations quotidiennes correspondant environ à 120 mg/kg de poids
    corporel, ont révélé la présence d'effets minimes, notamment des
    altérations biochimiques et des modifications histopathologiques au
    niveau du foie; toutefois d'autres études au cours desquelles des
    animaux avaient été exposés plus longtemps à des doses plus élevées
    n'ont pas mis d'effets en évidence. L'application cutanée de ASL a
    provoqué une intoxication générale ainsi que des effets localisés.

        La dose journalière moyenne de ASL absorbée par la population
    générale, telle qu'on peut l'évaluer sur la base d'estimations de
    l'exposition de cette population par l'intermédiaire de l'eau de
    boisson, des ustensiles de cuisine et des aliments, est probablement
    beaucoup plus faible (de l'ordre de trois ordres de grandeur) que les
    concentrations qui se révèlent produire des effets insignifiants sur
    les animaux de laboratoire.

        Les effets des AOS observés sur l'homme à l'occasion des quelques
    études dont on a connaissance, rapellent ceux qui ont été mis en
    évidence chez des animaux de laboratoire exposés aux ASL. Comme on ne
    dispose pas de données suffisantes pour évaluer la dose journalière
    moyenne d'AOS absorbée par la population générale ni sur les
    concentrations susceptibles de produire des effets chez l'homme et
    l'animal, il n'est pas possible de savoir avec certitude si
    l'exposition aux AOS présentes dans l'environnement représente un
    risque pour la santé humaine. Les concentrations d'AOS présentes dans
    les milieux auxquels l'homme pourrait être exposé, sont de toute
    manière plus faibles que celles des ASL, du fait de la moindre
    utilisation des AOS.

        Des effets ont été observés systématiquement à l'occasion de
    quelques études à portée limitée effectuées sur des rats à qui l'on
    avait fait ingérer quotidiennement des AOS soit avec leur nourriture,
    soit dans leur eau de boisson à des concentrations supérieures ou
    égales à 200 mg/kg de poids corporel. Des applications topiques
    répétées ou prolongées produisent également des effets localisés sur
    la peau et les yeux. On ne dispose pas non plus de données suffisantes
    pour évaluer la dose journalière moyenne d'AS absorbée par la
    population générale. Toutefois, étant donné que les tensio-actifs à
    base d'AS ne sont pas utilisés aussi abondamment que ceux qui
    contiennent des ASL, il est probable que la dose d'AS absorbée est au
    moins mille fois plus faible que celle qui produit des effets sur
    l'animal.

    1.10  Evaluation des effets sur l'environnement

        Les ASL, les AS et les AOS sont utilisés en grandes quantités et
    rejetés dans l'environnement avec les eaux usées. Pour évaluer le
    risque qui leur est attaché, il faut comparer les concentrations
    auxquelles l'exposition peut se produire avec celles qui ne provoquent
    aucun effet indésirable, cette comparaison pouvant être faite pour un
    certain nombre de milieux présents dans l'environnement. En ce qui
    concerne les tensio-actifs anioniques en général, les plus importants
    de ces milieux sont constitués par les stations de traitement des eaux
    usées, les eaux de surface, les sols amendés au moyen de sédiments et
    de boues d'égout, ainsi que les eaux estuarielles et marines. Les
    composés subissent une biodécomposition (depuis les premiers stades
    jusqu'à leur dégradation ultime) ainsi qu'une adsorption, qui
    réduisent leur concentration dans l'environnement ainsi que leur
    biodisponibilité. Le racourcissement de la chaîne latérale alkylée et
    la disparition de la structure du composé initial conduisent à des
    composés qui sont moins toxiques que les molécules de départ. Il
    importe d'en tenir compte lorsqu'on compare les résultats des épreuves
    en laboratoire aux effets qui pourraient se produire dans
    l'environnement. En outre, lorsqu'on évalue le risque associé à
    l'exposition, dans l'environnement, à ces trois types de tensio-

    actifs anioniques, il faut que les comparaisons entre les
    différentes épreuves de toxicité portent sur des composés dont la
    chaîne latérale à la même longueur.

        Les effets des ASL sur les organismes aquatiques ont été très
    largement étudiés. Lors des épreuves de laboratoire effectuées en eau
    douce, ce sont les poissons qui se sont révélés les plus sensibles;
    ainsi la concentration sans effets observables pour un cyprin
    d'Amérique du Nord,  Pimephales promelas, est d'environ
    0,5 mg/litre (C12); tous ces résultats ont été confirmés lors
    d'épreuves effectuées dans des conditions plus proches de la réalité.
    Pour ce qui est du phytoplancton, des épreuves de toxicité aiguë
    sur trois heures ont donné, pour la CE50, des valeurs de
    0,2-0,1 mg/litre (C12-C13), alors qu'on n'a constaté aucun effet
    sur l'abondance relative du plancton dans d'autres tests effectués à
    la concentration de 0,24 mg/litre (C11,8). Il semble que les espèces
    marines soient légèrement plus sensibles que la plupart des autres
    groupes taxonomiques.

        Ces trois types de composés anioniques se retrouvent dans
    l'environnement à des concentrations qui varient dans de larges
    limites. De ce fait, il n'est pas possible de procéder à une
    évaluation du risque écologique qui soit d'une portée générale. Toute
    évaluation du risque doit s'appuyer sur une connaissance suffisante de
    l'exposition et des concentrations agissantes dans l'écosystème
    étudié.

        Pour ce qui est de l'évaluation du risque imputable à la présence
    d'AS et d'AOS dans l'environnement, il faudra encore réunir des
    données précises sur l'exposition à ces composés. C'est pourquoi on
    utilise des modèles pour étudier l'exposition à ces produits dans les
    différents milieux qui en sont les récepteurs. En ce qui concerne les
    organismes aquatiques, les données toxicologiques sur les AS et les
    AOS sont relativement rares, notamment dans les cas d'exposition
    chronique à des concentrations constantes. Celles dont on dispose
    montrent que cette toxicité est analogue à celle des autres
    tensio-actifs anioniques.

        Les organismes aquatiques halophiles se révèlent plus sensibles
    que les organismes dulçaquicoles à ces composés; toutefois leur
    concentration est plus faible dans l'eau de mer, sauf au débouché des
    émissaires d'eaux usées. La destinée et les effets de ces composés,
    qui sont présents dans les effluents déversés en mer, n'ont pas été
    étudiés en détail.

        Pour évaluer la sûreté écologique de tensio-actifs tels que les
    ASL, les AOS et les AS, il faut comparer les concentrations effectives
    dans l'environnement à celles qui ne produisent aucun effet. Les
    besoins en matière de recherche sont déterminés non seulement par les
    propriétés intrensèques de tel ou tel produit chimique mais aussi par
    les modalités ou les tendances de sa consommation. Tous ces facteurs

    peuvent varier fortement d'une région à l'autre, aussi l'appréciation
    et l'évaluation des risques doivent-elles être effectuées région par
    région.

    1.11  Recommandations pour la protection de la santé humaine
          et de l'environnement

    1.  Comme il peut y avoir exposition à des poussières sur les lieux de
    travail (au cours de la fabrication et de la préparation des
    différentes formules), il faut veiller à ce que les précautions
    habituelles d'hygiène et sécurité du travail soient respectées afin
    d'assurer la protection des travailleurs.

    2.  La composition des préparations destinées à la consommation des
    ménages et à l'usage industriel doit être étudiée pour éviter tout
    danger, en particulier lorsqu'il s'agit de produits destinés au
    nettoyage ou au lavage du linge à la main.

    3.  L'exposition à ces produits dans l'environnement et les effets
    qu'ils peuvent avoir doivent faire l'objet d'une surveillance
    appropriée afin que l'on puisse reconnaître à temps la présence de
    tout concentration excessive dans tel ou tel milieu.

    1.12  Recommandations pour les recherches futures

         Santé humaine

    1.  Etant donné que le contact cutané est la principale voie
    d'exposition humaine aux ASL, aux AOS et aux AS et que l'on ne dispose
    pas d'études à long terme suffisantes sur la toxicité cutanée ou la
    cancérogénicité de ces produits chez les animaux de laboratoire, il
    est recommandé de procéder à des études à long terme convenablement
    conçues au cours desquelles il sera procédé à l'application de ces
    composés sur la peau des animaux.

    2.  En raison de l'absence de données définitives sur la génotoxicité
    des AOS et des AS, il conviendrait de procéder à des études
    supplémentaires  in vivo et  in vitro.

    3.  En raison de l'insuffisance des études existantes concernant les
    effets toxiques de ces produits sur la reproduction et le
    développement, il conviendrait d'effectuer, sur des animaux de
    laboratoire, des études qui permettent d'obtenir des résultats
    définitifs sur la valeur des concentrations agissant ou au contraire,
    sans effets des ASL, des AOS et des AS.

    4.  Etant donné que l'on ne connaît pas de façon suffisamment précise
    l'exposition aux ASL, aux AOS et aux AS, il faudrait surveiller
    l'exposition de la population générale à ces produits, en particulier
    lorsque ces tensio-actifs sont utilisés pour le nettoyage et le lavage
    du linge à la main.

    5.  Etant donné que les ASL, les AOS et les AS peuvent favoriser le
    transport d'autres produits chimiques dans les différents milieux qui
    composent l'environnement et en faire varier la biodisponibilité et la
    toxicité dans les eaux de surface, les sédiments, les cours d'eau et
    les sols auxquels l'être humain pourrait se trouver exposé, il
    conviendrait d'étudier les interactions de ces produits avec d'autres
    substances présentes dans l'environnement et les conséquences qui en
    découlent pour la santé humaine.

     Sûreté écologique

    6.  Des études supplémentaires devraient être effectuées afin
    d'élucider les mécanismes de l'adsorption et de la désorption des AOS
    et des AS. Elles devraient également porter sur le partage des ASL,
    des AOS et des AS entre les particules colloïdales en solution ou en
    suspension dans l'eau. Il faudrait effectuer une modélisation
    mathématique des coefficients de sorption et valider les modèles
    obtenus en fonction des paramètres physicochimiques.

    7.  En cas d'exposition à des sols amendés à l'aide de boues d'égout
    ou à des sédiments de rivière, il faudrait étudier la biodécomposition
    des AOS et des AS dans ces milieux. L'étude des sédiments (dans les
    zones d'aérobiose et d'anaérobiose) devrait s'effectuer en aval des
    points où sont rejetées des eaux traitées ou non traitées ou des
    émissaires d'évacuation.

    8.  Il faudrait surveiller au niveau régional et national les
    concentrations en ASL, AOS et AS dans l'environnement afin d'obtenir
    des données sur l'exposition. Il faudrait également mettre au point
    des méthodes d'analyse permettant de déceler la présence de faibles
    teneurs en AOS et en AS dans les compartiments appropriés de
    l'environnement.

    9.  Il faudrait établir des bases de données nationales sur la
    concentration des ASL, AOS et AS dans les eaux usées et les cours
    d'eau ainsi que sur les différents types de stations d'épuration, leur
    implantation et leur efficacité, afin de mieux étudier l'impact des
    décharges dans l'environnement.

    10.  Il faudrait effectuer des études à long terme sur la toxicité des
    AOS et des AS pour les poissons (espèces d'eau douce et espèces
    marines) et des invertébrés aquatiques, afin d'en établir la
    sensibilité relative.

    ALKILSULFONATOS LINEALES Y SUSTANCIAS RELACIONADOS

    1.  RESUMEN GENERAL, EVALUACION Y RECOMENDACIONES

    1.1  Identidad y métodos analíticos

        Los alkilsulfonatos lineales (ASL), los alpha-olefinsulfonatos
    (AOS) y los alkilsulfatos (AS) son sustancias tensioactivas aniónicas
    con moléculas que se caracterizan por tener un grupo hidrófobo y uno
    hidrófilo (polar). Las mezclas comerciales están formadas por isómeros
    y homólogos de compuestos relacionados entre sícon distintas
    propiedades fisicoquímicas, obteniéndose formulaciones con diversas
    aplicaciones.

        Los ASL, los AOS y los AS se pueden analizar por métodos no
    específicos. El ensayo que se suele utilizar es el de las sustancias
    que reaccionan con el azul de metileno, es decir, todas las que
    contienen un grupo aniónico e hidrófobo. Por consiguiente, si se
    utiliza para muestras del medio ambiente se producen interferencias
    analíticas; por otra parte, la sensibilidad de este método es de unos
    0,02 mg/litro. Aunque se han buscado alternativas no específicas a
    este método, su uso no es habitual. En el análisis del medio ambiente
    sólo hay métodos específicos para los ASL y los AS. Para el análisis
    de los AOS se dispone de un método mejorado basado en la reactividad
    del azul de metileno y la cromatografía líquida de alto rendimiento
    (HPLC).

        Los ASL son sustancias no volátiles que se forman por la
    sulfonación del alkilbenceno lineal. Los productos comerciales son
    siempre mezclas de homólogos con la cadena alkilo de distintas
    longitudes (C10-C13 o C14) e isómeros que difieren en las
    posiciones del anillo de fenilo (2-5 fenil). En las muestras del medio
    ambiente y en otras matrices se pueden determinar todos los homólogos
    e isómeros de los ASL por medio de métodos analíticos específicos como
    la HPLC, la cromatografía de gases y la cromatografía de
    gases-espectrometría de masas.

        Los AOS son sustancias no volátiles producidas por la sulfonación
    de las alpha-olefinas. Son mezclas de dos compuestos, el
    alkensulfonato de sodio y el sulfonato de hidroxialkano, con
    longitudes de la cadena alkilo de C14-C18.

        Los AS son compuestos no volátiles producidos por la sulfatación
    de alcoholes oleoquímicos o petroquímicos. Son mezclas de homólogos
    con longitudes de la cadena alkilo de C10-C18. Se están
    perfeccionando métodos analíticos específicos para la vigilancia del
    medio ambiente.

    1.2  Fuentes de exposición humana y ambiental

        Los ASL, los AOS y los AS se utilizan como ingredientes activos en
    productos de uso doméstico y de aseo personal y en aplicaciones
    especializadas. Una vez utilizadas, dichas sustancias detergentes
    pasan al medio ambiente en las aguas residuales.

        Se dan casos de exposición en el trabajo a estas sustancias. La
    exposición de la población humana general y de los organismos del
    medio ambiente depende de la aplicación de los ASL, los AOS y los AS
    (y de otras sustancias tensioactivas), de las prácticas de tratamiento
    de las aguas residuales y de las características del medio ambiente al
    que llegan.

        En 1990, el consumo mundial fue de unos dos millones de toneladas
    de ASL, 86 000 toneladas de AOS y 289 000 toneladas de AS.

    1.3  Concentraciones en el medio ambiente

    1.3.1  Alkilsulfonatos lineales

        Las concentraciones de ASL se han determinado cuantitativamente
    por medio de un método analítico sensible específico en casi todos los
    compartimentos del medio ambiente en los que pueden estar presentes.
    Las concentraciones disminuyen progresivamente en el siguiente orden:
    aguas residuales > efluente tratado > aguas superficiales > mar.

        En las zonas donde los ASL son las sustancias tensioactivas
    predominantes utilizadas, las concentraciones suelen ser de
    1-10 mg/litro en las aguas residuales, 0,05-0,1 mg/litro en los
    efluentes sometidos a un tratamiento biológico, 0,05-0,6 mg/litro en
    los efluentes tratados con un filtro de goteo, 0,005-0,05 mg/litro en
    las aguas superficiales por debajo de los desagües de aguas residuales
    (con concentraciones que disminuyen con rapidez a 0,01 mg/litro
    corriente abajo del desagüe), < 1-10 mg/kg en los sedimentos
    fluviales (< 100 mg/kg en los sedimentos muy contaminados cerca de
    las zonas de vertido), 1-10 g/kg en los fangos de alcantarillado y <
    1-5 mg/kg en los suelos tratados con fangos (al principio 5-10 mg/kg;
    se ha registrado una concentración de < 50 mg/kg después de
    aplicaciones anormalmente elevadas de fangos). Las concentraciones de
    ASL en las aguas de estuario son de 0,001-0,01 mg/litro, aunque hay
    niveles más elevados en los lugares donde se vierten directamente
    aguas residuales. Las concentraciones en el agua marina cercana a la
    costa son < 0,001-0,002 mg/litro.

        Hay que señalar que las concentraciones de ASL en el medio
    ambiente varían mucho. Esto se debe a diferencias en los métodos
    analíticos, las características de los lugares de muestreo (que van
    desde zonas muy contaminadas con un tratamiento inadecuado de las
    aguas residuales hasta zonas donde dichas aguas se someten a un

    tratamiento a fondo), la estación (los valores pueden ser en una el
    doble que en otra) y el consumo de ASL.

        La vigilancia del medio ambiente pone de manifiesto que no se ha
    producido acumulación de ASL en sus compartimentos a lo largo del
    tiempo. Las concentraciones en el suelo no aumentan con el tiempo,
    sino que disminuyen debido a la mineralización. Los ASL no se degradan
    en condiciones estrictamente anaerobias (para formar metano), por lo
    que no se puede concluir que estén mineralizados en sedimentos
    anaerobios. Con la utilización presente, el ritmo de asimilación de
    ASL en todos los compartimentos del medio ambiente que los reciben es
    igual al ritmo de entrada, por lo que la situación es estable.

    1.3.2  alpha-Olefinsulfonatos y alkilsulfatos

        Los datos disponibles sobre las concentraciones de AOS en el medio
    ambiente son limitados debido a la dificultad para analizarlos en las
    muestras de dicho medio. Hay métodos colorimétricos no específicos
    (como el basado en el azul de metileno) que permiten detectar
    sustancias tensioactivas aniónicas en general, pero se ven afectados
    por interferencias analíticas y no son idóneos para determinar
    concentraciones determinadas de AOS. Se está preparando un método
    específico para medir los AS en muestras del medio ambiente.

        En estudios de laboratorio se ha observado que los AOS y los AS se
    mineralizan con rapidez en todos los compartimentos del medio ambiente
    y prácticamente se eliminan del todo de las aguas residuales durante
    el tratamiento. Las concentraciones en el agua superficial, los
    sedimentos, el suelo, el agua de estuario y el medio marino son
    probablemente bajas. Se ha comprobado que la concentración de AOS en
    el agua fluvial es pequeña.

    1.4  Transporte, distribución y transformación en el medio ambiente

        A temperaturas por debajo de 5-10°C, la cinética de la
    biodegradación de los ASL, los AOS y los AS se reduce debido a la
    disminución de la actividad microbiana.

    1.4.1  Alkilsulfonatos lineales

        Las vías de entrada de los ASL en el medio ambiente varían de un
    país a otro, pero la principal es el vertido de las depuradoras de
    aguas residuales. Cuando no hay depuradoras o son inadecuadas, las
    aguas residuales se pueden verter directamente en los ríos, los lagos
    o el mar. Otra vía de entrada de ASL en el medio ambiente es la
    dispersión de fangos de alcantarillado en las tierras cultivadas.

        Durante su recorrido hasta llegar al medio ambiente, los ASL se
    eliminan mediante una combinación de adsorción y biodegradación
    primaria y final. Los ASL se adsorben sobre superficies coloidales y
    partículas en suspensión, con unos coeficientes medidos de adsorción
    de 40-5200 litros/kg, en función de los medios y de la estructura de
    los ASL. Se biodegradan en el agua superficial (semivida de 1-2 días),
    los sedimentos aerobios (1-3 días) y los sistemas marinos y de
    estuarios (5-10 días).

        Durante el tratamiento primario de las aguas residuales se adsorbe
    alrededor del 25% (intervalo, 10-40%) de los ASL en los fangos
    residuales y se elimina con ellos. No se eliminan durante la digestión
    anaerobia de los fangos, sino durante su tratamiento aerobio, con una
    semivida de unos 10 días. Tras la aplicación de fangos al suelo, en
    general se degrada el 90% de los ASL en tres meses, con una semivida
    de 5-30 días.

        Los factores de concentración en el organismo completo para los
    ASL oscilan entre 100 y 300 para la suma de los ASL-14C y los
    metabolitos de 14C. Los peces los absorben sobre todo por las
    branquias, distribuyéndose después al hígado y la vesículas biliar
    tras la biotransformación. Los ASL se excretan con rapidez, por lo que
    no hay pruebas de que se produzca bioampliación.

    1.4.2  alpha-Olefinsulfonatos

        Los datos disponibles sobre el transporte, distribución y
    transformación en el medio ambiente para los AOS son más escasos que
    para los ASL. Cabe suponer que los AOS llegan al medio ambiente de
    manera análoga a la establecida para los ASL, los AS y otras
    sustancias tensioactivas detergentes, y su destino en él es semejante
    al de los ASL y los AS. En condiciones aerobias se biodegradan
    fácilmente y la biodegradación primaria se completa en 2-10 días, en
    función de la temperatura. Son limitados los datos disponibles sobre
    la bioacumulación de los AOS; en peces no se observó ninguna. No hay
    datos relativos a la degradación abiótica.

    1.4.3  Alkilsulfatos

        Los AS llegan al medio ambiente por mecanismos análogos a los de
    los ASL y los AOS.Son fácilmente biodegradables en condiciones
    aerobias y anaerobias en el laboratorio y en el medio ambiente; la
    biodegradación primaria se termina en 2-5 días. El factor de
    bioconcentración en el organismo entero oscila entre 2 y 73 y varía
    con la longitud de la cadena de los homólogos de los AS. Los peces
    absorben, distribuyen, biotransforman y excretan los AS de la misma
    manera que los ASL y no se produce bioconcentración en los organismos
    acuáticos.

    1.5  Cinética

        Los ASL, los AOS y los AS se absorben fácilmente en el aparato
    digestivo y se distribuyen ampliamente por todo el organismo, con una
    metabolización extensa. En los ASL se produce omega- y ß-oxidación.
    Las sustancias originales y los metabolitos se excretan sobre todo a
    través de los riñones, aunque una parte de la cantidad absorbida se
    puede excretar en forma de metabolitos en las heces por excreción
    biliar. Parece que por la piel intacta solamente se absorben
    cantidades mínimas de ASL, AOS y AS, aunque el contacto prolongado
    puede poner en peligro la integridad de la barrera cutánea,
    permitiendo así una mayor absorción; las concentraciones elevadas
    pueden reducir el tiempo necesario para la penetración.

    1.6  Efectos en los animales de laboratorio y en los sistemas
         de prueba  in vitro

        Los valores de la DL50 por vía oral para las sales sódicas de
    los ASL fueron de 404-1470 mg/kg de peso corporal en ratas y de
    1259-2300 mg/kg en ratones, lo cual parece indicar que las ratas son
    más sensibles que los ratones a la toxicidad de los ASL. En ratones se
    midió para una sal sódica de AOS una DL50 por vía oral de
    3000 mg/kg de peso corporal. Los valores de la DL50 de AS por vía
    oral en ratas fueron de 1000-4120 mg/kg de peso corporal. Los ASL, AOS
    y AS irritan la piel y los ojos.

        Se han descrito efectos mínimos, entre ellos alteraciones
    bioquímicas y cambios histopatológicos en el hígado, en estudios de
    toxicidad subcrónica en los que se administraron ASL a ratas con los
    alimentos o el agua de beber en concentraciones equivalentes a dosis
    superiores a 120 mg/kg de peso corporal al día. Aunque en un estudio
    se observaron cambios estructurales de las células hepáticas a dosis
    menores, al parecer eran reversibles. En otros estudios no se
    detectaron efectos con dosis análogas, pero tal vez el examen de los
    órganos fuera más detenido en el primer estudio. Se han notificado
    efectos en la reproducción, por ejemplo menor tasa de gestación y
    pérdida de crías, en animales que recibieron dosis > 300 mg/kg al
    día. Se observaron cambios histopatológicos y bioquímicos tras la
    aplicación cutánea de larga duración a ratas de soluciones > 5% de
    ASL y después de la aplicación durante 30 días de 60 mg/kg de peso
    vivo en la piel de cobayas. La aplicación cutánea repetida de
    soluciones > 0,3% de ASL indujo efectos fetotóxicos y en la
    reproducción, pero también se observó toxicidad materna.

        Son escasos los datos disponibles de estudios en animales
    experimentales que permitan evaluar los posibles efectos de los AOS en
    el ser humano. No se observó ningún efecto en ratas que recibieron por
    vía oral dosis de 250 mg/kg de peso corporal al día en aplicación
    crónica, pero se apreció fetotoxicidad en conejas a las que se
    administró una dosis tóxica para la madre de 300 mg/kg de peso
    corporal al día. La aplicación de AOS a la piel y los ojos de animales
    experimentales indujo efectos locales.

        Aunque se han investigado en varios estudios los efectos de la
    exposición de corta y larga duración de animales a los AS, en la
    mayoría de los casos el examen histopatológico fue inadecuado o el
    tamaño de los grupos pequeño; por otra parte, las dosis más altas
    utilizadas en los estudios de larga duración no produjeron ningún
    efecto tóxico, de manera que no se pudo establecer un NOAEL. Sin
    embargo, se han descrito habitualmente efectos en ratas que recibían
    AS en los alimentos o el agua de beber a concentraciones equivalentes
    a 200 mg/kg de peso corporal al día o más. Se han observado efectos
    locales en la piel y los ojos tras la aplicación tópica de
    concentraciones aproximadas del 0,5% de AS o más. A concentraciones
    más elevadas se han registrado efectos de toxicidad materna y
    fetotóxicos.

        La mayoría de los estudios de larga duración son inadecuados para
    evaluar el potencial carcinogénico de los ASL, los AOS y los AS en
    animales experimentales, debido a factores como el pequeño número de
    animales, el número limitado de dosis, la ausencia de una dosis
    tolerada máxima y la limitación del examen histopatológico en la
    mayoría de los estudios. En los casos en que se describieron de manera
    apropiada los hallazgos patológicos no se utilizaron dosis toleradas
    máximas y las dosis no produjeron efectos tóxicos. Teniendo presentes
    estas limitaciones, sin embargo, en los estudios en los que se
    administraron por vía oral ASL, AOS y AS no se obtuvo ninguna prueba
    de carcinogenicidad; en estudios de larga duración de aplicación de
    AOS en la piel con un pincel no se observó ningún efecto.

        Según los limitados datos disponibles, no parece que estas
    sustancias tengan efectos genotóxicos  in vivo o  in vitro.

    1.7  Efectos en el ser humano

        Los resultados obtenidos en pruebas de parche demuestran que la
    piel humana puede tolerar el contacto con soluciones de ASL, AOS o AS
    de hasta un 1% durante 24 horas con la única reacción de una
    irritación leve. Estas sustancias tensioactivas provocaron la pérdida
    de lípidos de la superficie de la piel, la elución del factor
    hidratante natural y la desnaturalización de las proteínas de la capa
    epidérmica externa y aumentaron la permeabilidad y la hinchazón de
    esta capa. Los ASL, los AOS y los AS no indujeron sensibilización
    cutánea en voluntarios y no se ha encontrado ninguna prueba definitiva
    de que induzcan la formación de eczemas. No se han comunicado lesiones
    graves ni muertes tras la ingestión accidental de estas sustancias
    tensioactivas por personas.

    1.8  Efectos en el medio ambiente

    1.8.1  Alkilsulfonatos lineales

    1.8.1.1  Medio acuático

        Los ASL han sido objeto de amplios estudios tanto en el
    laboratorio (estudios de corta y larga duración) como en condiciones
    más naturales (microcosmos y mesocosmos y estudios sobre el terreno).
    En general, la disminución de la cadena alkilo o la posición más
    interna del grupo fenilo van acompañadas de una menor toxicidad. Las
    observaciones en peces y en  Daphnia indican que al disminuir la
    longitud de la cadena en una unidad (por ejemplo de C12 a C11) la
    toxicidad se reduce prácticamente a la mitad.

        Los resultados de las pruebas de laboratorio han sido los
    siguientes:

        --  Microorganismos: Los resultados son muy variables debido al
    uso de diversos sistemas de prueba (Por ejemplo, inhibición de fango
    activado; cultivos mixtos y especies individuales). Los valores de la
    CE50 oscilan entre 0,5 mg/litro (especie única) y > 1000 mg/litro.
    Para los microorganismos no hay relación lineal entre la longitud de
    la cadena y la toxicidad.

        --  Plantas acuáticas: Los resultados dependen mucho de las
    especies. Para los organismos de agua dulce, los valores de la
    CE50 son de 10-235 mg/litro (C10-C14) en las algas verdes, de
    5-56 mg/litro (C11,1-C13) en las algas cianofíceas, de
    1,4-50 mg/litro (C11,6-C13) en las diatomeas y de
    2,7-4,9 mg/litro (C11,8) en las macrofitas; al parecer las algas
    marinas son aún más sensibles. En las algas es probable que no haya
    relación lineal entre la longitud de la cadena y la toxicidad.

        --  Invertebrados: Los valores de la CL(E)50 aguda por lo menos
    en 22 especies de agua dulce son de 4,6-200 mg/litro (longitud de la
    cadena sin especificar; C13) para los moluscos; 0,12-27 mg/litro
    (sin especificar; C11,2-C18) para los crustáceos; 1,7-16 mg/litro
    (sin especificar; C11,8) para los gusanos; y 1,4-270 mg/litro
    (C10-C15) para los insectos. Los valores de la CL(E)50 crónica
    son de 2,2 mg/litro (C11,8) para los insectos y 1,1-2,3 mg/litro
    (C11,8-C13) para los crustáceos. La concentración crónica sin
    efectos observados (NOEC; basada en la letalidad o los efectos en la
    reproducción) es de 0,2-10 mg/litro (sin especificar; C11,8) para
    los crustáceos. Parece que los invertebrados marinos son más
    sensibles, con valores de la CL50 de 1 a > 100 mg/litro (casi
    siempre C12) para 13 especies y NOEC de 0,025-0,4 mg/litro (sin
    especificar en todas las pruebas) para siete especies ensayadas.

        --  Peces: Los valores de la CL50 aguda son de 0,1-125 mg/litro
    (C8-C15) para 21 especies de agua dulce; los valores de la
    CL(E)50 crónica son de 2,4 y 11 mg/litro (sin especificar; C11,7)
    para dos especies; y las NOEC de 0,11-8,4 y 1,8 mg/litro (sin
    especificar; C11,2-C13) para dos especies. También en este caso
    los peces marinos parecen ser más sensibles, con valores de la CL50
    aguda de 0,05-7 mg/litro (sin especificar; C11,7) para seis especies
    y de la CL50 crónica de 0,01-1 mg/litro (sin especificar) para
    dos especies. En la mayoría de los informes no se indicaba la
    longitud de la cadena. Para especies marinas se señaló una NOEC de <
    0,02 mg/litro (C12).

        La longitud media de la cadena de los productos utilizados
    habitualmente en el comercio es C12. Se han probado compuestos de
    numerosas longitudes de cadena en  Daphnia magna y en peces, pero la
    longitud utilizada en otros organismos de agua dulce ha solido ser la
    de C11,8. Los valores típicos de la CL(E)50 para el ASL C12 son
    de 3-6 mg/litro en  Daphnia magna y de 2-15 mg/litro en peces de agua
    dulce, y las NOEC crónicas típicas son de 1,2-3,2 mg/litro para
     Daphnia y de 0,48-0,9 mg/litro para los peces de agua dulce. Los
    valores típicos de la CL50 de los ASL con cadenas de esta longitud
    son en los peces marinos < 1-6,7 mg/litro.

        Los organismos de agua salada, en particular los invertebrados,
    parecen ser más sensibles que los de agua dulce a los ASL. En los
    invertebrados, la acción inhibidora de los ASL sobre el calcio puede
    afectar a la disponibilidad de este ión para la morfogénesis. Los ASL
    tienen un efecto general sobre el transporte iónico. Los productos de
    la biodegradación y los subproductos de los ASL son 10-100 veces menos
    tóxicos que las sustancias de las que proceden.

        Los resultados obtenidos en condiciones más reales son los
    siguientes: Se han utilizado ASL en todas las pruebas de agua dulce a
    varios niveles tróficos, como recintos cerrados en lagos (organismos
    inferiores), modelos de ecosistemas (sistemas de sedimentos y agua),
    ríos por debajo y por encima del desagüe de depuradoras de aguas
    residuales y corrientes experimentales. En casi todos los casos se
    emplearon ASL C12. Al parecer las algas son más sensibles en verano
    que en invierno, puesto que los valores de la CE50 en tres horas
    fueron de 0,2-8,1 mg/litro después de la fotosíntesis, mientras que en
    los modelos de ecosistemas no se observó ningún efecto en la
    abundancia relativa de las comunidades de algas con 0,35 mg/litro. Los
    niveles sin efecto en estos estudios fueron de 0,24-5 mg/litro, en
    función del organismo y del parámetro ensayado. Estos resultados
    prácticamente coinciden con los de las pruebas de laboratorio.

    1.8.1.2  Medio terrestre

        Se dispone de información acerca de las plantas y las lombrices de
    tierra. Las NOEC para siete especies de plantas en pruebas realizadas
    con soluciones de nutrientes son < 10-20 mg/litro; la correspondiente
    a tres especies en suelo, mediante pruebas basadas en el crecimiento
    fue de 100 mg/litro (C10-C13). La CL50 en 14 días fue para las
    lombrices de tierra > 1000 mg/kg.

    1.8.1.3  Aves

        En un estudio con pollos tratados en la alimentación se obtuvo una
    NOEC (basada en la calidad de los huevos) > 200 mg/kg.

    1.8.2  alpha-Olefinsulfonatos

        Los datos acerca de los efectos de los AOS en los organismos
    acuáticos y terrestres son limitados.

    1.8.2.1  Medio acuático

        Solamente se dispone de datos de pruebas de laboratorio:

        --  Algas: Los valores de la CE50 que se han descrito para las
    algas verdes son > 20-65 mg/litro (C16-C18).

        --  Invertebrados: Para  Daphnia se han notificado valores de la
    CL50 de 19 y 26 mg/litro (C16-C18).

        --  Peces: Los valores de la CL50 son de 0,3-6,8 mg/litro
    (C12-C18) para nueve especies de peces. De los estudios de corta
    duración realizados en la trucha común  (Salmo trutta), Idus
     melanotus y  Rasbora heteromorpha, cabe concluir que la toxicidad
    de los compuestos C14-C16 es unas cinco veces inferior a la de los
    C16-C18, con valores de la CL50 (todas las concentraciones
    medidas) de 0,5-3,1 (C16-C18) y 2,5-5,0 mg/litro (C14-C16). En
    dos estudios de larga duración en la trucha arcoiris se comprobó que
    el crecimiento era el parámetro más sensible, con una CE50 de
    0,35 mg/litro. En un pez marino, el pardete  (Mugal cephalus), el
    valor de la CL50 en 96 horas fue de 0,70 mg/litro.

    1.8.2.2  Medio terrestre

        En un estudio de plantas con soluciones de nutrientes, la NOEC fue
    de 32-56 mg/litro. En un estudio con pollos tratados en la
    alimentación, se notificó una NOEC (basada en la calidad de los
    huevos) > 200 mg/kg.

    1.8.3  Alkilsulfatos

    1.8.3.1  Organismos acuáticos

        Se han realizado estudios de los AS de corta y larga duración y
    uno en condiciones más reales. Su toxicidad también depende de la
    longitud de la cadena alkilo; no se disponía de información sobre
    diferencias de toxicidad entre los AS lineales y ramificados.

        Los resultados de las pruebas de laboratorio son los siguientes:

        --  Microorganismos: Los valores de la CE50 en un conjunto de
    microorganismos marinos fueron de 2,1-4,1 mg/litro (C12). Las NOEC
    en  Pseudomonas putida fueron de 35-550 mg/litro (C16-C18).

        --  Plantas acuáticas: Los valores de la CE50 fueron >
    20-65 mg/litro (C12-C13) en algas verdes y de 18-43 mg/litro
    (C12) en macrofitas. Las NOEC fueron de 14-26 mg/litro
    (C12-C16/C18) en algas verdes.

        --  Invertebrados: Los valores de la CL(E)50 fueron de
    4-140 mg/litro (C12/C15-C16/C18) en especies de agua dulce y
    de 1,7-56 mg/litro (todos C12) en especies marinas. La NOEC crónica
    en  Daphnia magna fue de 16,5 mg/litro (C16/C18) y en especies
    marinas de 0,29-0,73 mg/litro (longitud de la cadena sin especificar).

        --  Peces: Los valores de la CL50 fueron de 0,5-5,1 mg/litro
    (longitud de la cadena sin especificar o C12-C16) en especies de
    agua dulce y de 6,4-16 mg/litro (todos C12) en especies marinas. No
    había estudios de larga duración.

        Hay que señalar que muchos de estos estudios se llevaron a cabo en
    condiciones estáticas. Los AS son fácilmente biodegradables, por lo
    que se puede haber infravalorado su toxicidad. En un estudio de 48
    horas con Oryzias latipes, los valores de la CL50 fueron de 46, 2,5
    y 0,61 mg/litro (concentraciones medidas) para los compuestos C12,
    C14 y C16 respectivamente. Este y otros estudios indican que la
    toxicidad difiere en un factor de cinco por cada dos unidades de
    longitud de la cadena. En un estudio de biocenosis de paso de
    corriente con compuestos de C16-C18 se observó una NOEC de
    0,55 mg/litro.

    1.8.3.2  Organismos terrestres

        Se han notificado valores de la NOEC > 1000 mg/kg (C16-C18)
    en lombrices de tierra y en nabos.

    1.9  Evaluación del riesgo para la salud humana

        Los ASL son los agentes tensioactivos más utilizados en
    detergentes y productos de limpieza. También se utilizan AOS y AS en
    detergentes y en productos de aseo personal. Por consiguiente, la
    principal vía de exposición humana es el contacto cutáneo. Pueden
    ingerirse pequeñas cantidades de ASL, AOS y AS con el agua potable y
    debido a la presencia de residuos en utensilios y alimentos. Aunque la
    información de que se dispone es limitada, la ingesta diaria de ASL
    por esos medios se puede estimar en unos 5 mg/persona. Puede
    producirse exposición en el trabajo a los ASL, AOS y AS durante la
    formulación de diversos productos, pero no hay datos acerca de los
    efectos de una exposición crónica a estas sustancias en el ser humano.

        Los ASL, AOS y AS pueden irritar la piel después de un contacto
    cutáneo repetido o prolongado con concentraciones análogas a las
    presentes en los productos sin diluir. En los cobayas los AOS pueden
    inducir sensibilización cutánea cuando el nivel de sulfona g
    insaturada es superior a unas 10 ppm.

        Los estudios disponibles de larga duración en animales
    experimentales son insuficientes para evaluar el potencial
    carcinogénico de los ASL, AOS y AS, debido a factores como el diseño
    del estudio, el uso de un número pequeño de animales, el ensayo de
    dosis insuficientes y lo limitado del examen histopatológico. En los
    escasos estudios en los que se administró ASL, AOS o AS a animales por
    vía oral no se observaron signos de carcinogenicidad; también fueron
    negativos los resultados de los estudios de larga duración en los que
    se administraron AOS mediante aplicación cutánea. Estas sustancias no
    parecen ser genotóxicas  in vivo o  in vitro, aunque se tienen
    noticias de pocos estudios.

        Se han descrito efectos mínimos, entre ellos alteraciones
    bioquímicas y cambios histopatológicos hepáticos, en estudios
    subcrónicos en los que se administraron ASL a ratas en la alimentación
    o el agua de beber a concentraciones equivalentes a una dosis
    aproximada de 120 mg/kg de peso corporal al día, aunque no se observó
    ningún efecto en estudios en los que los animales estuvieron expuestos
    a dosis más elevadas durante períodos más largos. La aplicación
    cutánea de ASL ocasionó tanto toxicidad sistémica como efectos
    locales.

        La ingesta diaria media de ASL de la población general, con
    arreglo a estimaciones limitadas de la exposición por medio del agua
    potable, utensilios y alimentos probablemente sea muy inferior (unas
    tres veces menor) a los niveles con los que se ha observado que
    inducen efectos leves en los animales experimentales.

        Los efectos de los AOS observados en el ser humano en los escasos
    estudios disponibles son parecidos a los descritos en los animales
    expuestos a los ASL. Debido a que son insuficientes los datos para
    estimar la ingesta diaria media de AOS de la población general y los
    relativos a los niveles que inducen efectos en el ser humano y en los
    animales, no es posible evaluar con suficiente confianza si la
    exposición a los AOS en el medio ambiente representa un riesgo para la
    salud humana. Sin embargo, los niveles de AOS en medios a los que
    puede estar expuesto el ser humano probablemente sean inferiores a los
    de ASL, puesto que se utilizan menos.

        Se han descrito repetidamente efectos en un pequeño número de
    estudios limitados en ratas que recibieron AS en la alimentación o en
    el agua de beber en concentraciones equivalentes a dosis de
    200 mg/kg de peso corporal al día o más. Se han observado efectos
    locales en la piel y en los ojos tras una aplicación tópica repetida
    o prolongada. Los datos disponibles son insuficientes para estimar la
    ingesta diaria media de AS de la población general. Sin embargo, dado
    que no se utilizan tanto agentes tensioactivos con AS como los que
    contienen ASL, la ingesta de AS será probablemente como mínimo tres
    veces inferior a las dosis que se ha demostrado que inducen efectos en
    los animales.

    1.10  Evaluación de los efectos en el medio ambiente

        Los ASL, los AOS y los AS se utilizan en grandes cantidades y se
    liberan en el medio ambiente por medio de las aguas residuales. Para
    evaluar el riesgo es preciso comparar las concentraciones de
    exposición con las que no producen efectos adversos, y esto se puede
    hacer para varios compartimentos del medio ambiente. Para los agentes
    tensioactivos aniónicos en general, los compartimentos más importantes
    son las depuradoras de aguas residuales, las aguas superficiales, los
    suelos tratados con sedimentos y fangos y los medios estuarinos y
    marinos. Se produce tanto biodegradación (primaria y final) como
    adsorción, por lo que disminuyen las concentraciones y la
    biodisponibilidad en el medio ambiente. Con la reducción de la
    longitud de la cadena y la pérdida de la estructura original se forman
    sustancias menos tóxicas que la primera. Es importante tener en cuenta
    estos aspectos a la hora de interpretar los resultados de laboratorio
    con los posibles efectos en el medio ambiente. Por otra parte, al
    evaluar el riesgo asociado con la exposición del medio ambiente a
    estos tres compuestos aniónicos se debe establecer una comparación con
    los resultados de las pruebas de toxicidad de sustancias cuya cadena
    tenga la misma longitud.

        Se han realizado abundantes pruebas de los efectos de los ASL en
    los organismos acuáticos. En las pruebas de laboratorio con agua dulce
    parece que los peces eran las especies más sensibles; la NOEC para
    Pimephales promelas fue de unos 0,5 mg/litro (C12), y estos
    resultados se confirmaron en pruebas realizadas en condiciones más
    reales. en el fitoplancton se han observado diferencias: en ensayos

    de toxicidad agua de tres horas los valores de la CE50 fueron de
    0,2-0,1 mg/litro (C12-C13), mientras que no se detectaron efectos
    en la abundancia relativa en otras pruebas con 0,24 mg/litro
    (C11,8). Parece que las especies marinas eran ligeramente más
    sensibles que la mayoría de los otros grupos taxonómicos.

        En el medio ambiente hay una amplia gama de concentraciones de las
    tres sustancias aniónicas, como se ha puesto de manifiesto en las
    numerosas mediciones de los ASL. Debido a esta amplia gama, no se
    puede hacer una evaluación del riesgo de estas sustancias para el
    medio ambiente de aplicación general. Para evaluar el riesgo se deben
    conocer de manera apropiada las concentraciones de exposición y las
    que tienen efectos en el ecosistema que interesa.

        Se necesitan datos precisos sobre la exposición a los AS y los AOS
    si se quiere hacer una evaluación del riesgo para el medio ambiente.
    Por consiguiente se están utilizando modelos a fin de evaluar las
    concentraciones de exposición en los compartimentos del medio ambiente
    que los reciben. Los datos sobre la toxicidad de los AS y los AOS para
    los organismos acuáticos, especialmente después de una exposición
    crónica a concentraciones estables, son relativamente escasos. Los
    datos disponibles indican que la toxicidad de estos productos es
    análoga a la de otras sustancias tensioactivas aniónicas.

        Los organismos de agua salada parecen ser más sensibles que los de
    agua dulce a estos compuestos; sin embargo, su concentración es menor
    en el agua del mar, excepto cerca de los desagües de alcantarillados.
    No se han investigado con detalle su destino y sus efectos en las
    aguas residuales vertidas en el mar.

        Si se desea evaluar la inocuidad para el medio ambiente de agentes
    tensioactivos como los ASL, los AOS y los AS hay que comparar las
    concentraciones reales en el medio ambiente con las que no tienen
    ningún efecto. Las necesidades de investigación se determinan no sólo
    por las propiedades intrínsecas de un producto químico, sino también
    por sus características o la tendencia del consumo. Estos varían
    considerablemente entre las distintas zonas geográficas, por lo que la
    evaluación debe ser de ámbito regional.

    1.11  Recomendaciones para la protección de la salud humana y
          el medio ambiente

    1.  Puesto que en el lugar de trabajo se puede producir exposición al
    polvo (durante la elaboración y formulación), deben utilizarse
    prácticas normalizadas de higiene del trabajo a fin de asegurar la
    protección de la salud de los trabajadores.

    2.  La composición de las formulaciones para uso privado e industrial
    se debe diseñar de manera que se evite el riesgo, especialmente en las
    formulaciones utilizadas para la limpieza o el lavado a mano.

    3.  La exposición y los efectos en el medio ambiente se deben vigilar
    de manera apropiada con objeto de tener una indicación pronta de
    cualquier acumulación excesiva en los compartimentos pertinentes del
    medio ambiente.

    1.12  Recomendaciones de nuevas investigaciones

     Salud humana

    1.  Debido a que la piel es la principal vía de exposición humana a
    los ASL, los AOS y los AS y a que no se dispone de estudios adecuados
    de larga duración acerca de la toxicidad cutánea o la carcinogenicidad
    en animales experimentales, se recomienda la realización de estudios
    de larga duración debidamente diseñados de aplicación cutánea de estas
    sustancias.

    2.  Ante la falta de datos definitivos sobre la genotoxicidad de los
    AOS y los AS, deben llevarse a cabo nuevos estudios  in vivo e  in
     vitro.

    3.  A la vista de la insuficiencia de los estudios disponibles sobre
    la toxicidad en la reproducción y el desarrollo, se han de realizar
    estudios definitivos en animales de laboratorio a fin de obtener datos
    relativos a los efectos de los ASL, los AOS y los AS y los niveles con
    efectos y sin ellos.

    4.  Puesto que la exposición a los ASL, los AOS y los AS no está
    debidamente definida, se debe vigilar la exposición de la población
    general, en particular cuando estas sustancias tensioactivas se
    utilizan en la limpieza y el lavado a mano.

    5.  Debido a que los ASL, los AOS y los AS pueden potenciar el
    transporte de otras sustancias químicas y regular su biodisponibilidad
    y toxicidad en las aguas superficiales, los sedimentos fluviales y los
    suelos a los que puede estar expuesto el ser humano, deben
    investigarse las interacciones con otras sustancias químicas del medio
    ambiente y las consecuencias para las personas.

     Inocuidad para el medio ambiente

    6.  Deben realizarse nuevos estudios sobre los mecanismos de adsorción
    y desorción de los AOS y los AS. También se debe estudiar el reparto
    de los ASL, los AOS y los AS entre las partículas coloidales disueltas
    y suspendidas en el agua. Hay que elaborar modelos matemáticos de los
    coeficientes de sorción y validarlos con arreglo a parámetros
    fisicoquímicos.

    7.  Se han de realizar estudios de la biodegradación de los AOS y los
    AS en suelos tratados con fangos y en sedimentos fluviales (zonas
    aerobias y anaerobias) corriente abajo de los vertidos de aguas
    residuales tratadas y sin tratar.

    8.  Se deben vigilar en los ámbitos regional y nacional las
    concentraciones de ASL, AOS y AS en el medio ambiente, a fin de
    obtener información acerca de la exposición. Se han de preparar
    métodos analíticos para la detección de niveles bajos de AOS y AS en
    los compartimentos pertinentes del medio ambiente.

    9.  Hay que organizar bases de datos nacionales sobre las
    concentraciones de ASL, AOS y AS en las aguas residuales y en los ríos
    y sobre los tipos, la eficacia y el lugar de las depuradoras de aguas
    residuales, con objeto de facilitar la evaluación de los efectos de
    los vertidos de estas sustancias tensioactivas en el medio ambiente.

    10.  Deben realizarse estudios de la toxicidad de los AOS y los AS en
    los peces (de agua dulce y marinos) y los invertebrados acuáticos para
    establecer la sensibilidad relativa de estas especies.
    


    See Also:
       Toxicological Abbreviations