Health and Safety Guide No. 24






    This is a companion volume to Environmental Health Criteria
    87: Allethrins

    Published by the World Health Organization for the International
    Programme on Chemical Safety (a collaborative programme of the United
    Nations Environment Programme, the International Labour Organisation,
    and the World Health Organization)

    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

    ISBN 92 4 154345 0
    ISSN 0259-7268

    The World Health Organization welcomes requests for permission to
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    (c) World Health Organization 1989

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    that are not mentioned. Errors and omissions excepted, the names of
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         1.1. Identity
         1.2. Physical and chemical properties
         1.3. Analytical methods
         1.4. Production and uses

         2.1. Human exposure to allethrins
         2.2. Decomposition and metabolism
         2.3. Evaluation of effects on the environment
         2.4. Evaluation of human health risks

         3.1. Conclusions
         3.2. Recommendations

         4.1. Main human health hazards, prevention and protection,
               first aid
               4.1.1. Advice to physicians
               4.1.2. Health surveillance advice
         4.2. Explosion and fire hazards
         4.3. Storage
         4.4. Transport
         4.5. Spillage and disposal
               4.5.1. Spillage
               4.5.2. Disposal



         7.1. Previous evaluations by international bodies
         7.2. Exposure limit values
         7.3. Specific restrictions
         7.4. Labelling, packaging, and transport
         7.5. Waste disposal




    The Environmental Health Criteria (EHC) documents produced by the
    International Programme on Chemical Safety include an assessment of
    the effects on the environment and on human health of exposure to a
    chemical or combination of chemicals, or physical or biological
    agents. They also provide guidelines for setting exposure limits.

    The purpose of a Health and Safety Guide is to facilitate the
    application of these guidelines in national chemical safety
    programmes. The first three sections of a Health and Safety Guide
    highlight the relevant technical information in the corresponding EHC.
    Section 4 includes advice on preventive and protective measures and
    emergency action; health workers should be thoroughly familiar with
    the medical information to ensure that they can act efficiently in an
    emergency. Within the Guide is an International Chemical Safety Card
    which should be readily available, and should be clearly explained, to
    all who could come into contact with the chemical. The section on
    regulatory information has been extracted from the legal file of the
    International Register of Potentially Toxic Chemicals (IRPTC) and from
    other United Nations sources.

    The target readership includes occupational health services, those in
    ministries, governmental agencies, industry, and trade unions who are
    involved in the safe use of chemicals and the avoidance of
    environmental health hazards, and those wanting more information on
    this topic. An attempt has been made to use only terms that will be
    familiar to the intended user. However, sections 1 and 2 inevitably
    contain some technical terms. A bibliography has been included for
    readers who require further background information.

    Revision of the information in this Guide will take place in due
    course, and the eventual aim is to use standardized terminology.
    Comments on any difficulties encountered in using the Guide would be
    very helpful and should be addressed to:

    The Manager
    International Programme on Chemical Safety
    Division of Environmental Health
    World Health Organization
    1211 Geneva 27



    1.1  Identity

    Allethrin is an ester of chrysanthemic acid with allethrolone. It is a
    racemic mixture of 8 stereoisomers, which are present in the technical
    material roughly in the proportion of 1:1:1:1:1:1:1:1. d-Allethrin,
    bioallethrin, esbiothrin, and  S-bioallethrin are also available as
    selected stereoisomers or in mixtures.

    Molecular formula:       C19H26O3

    Chemical structure:      CHEMICAL STRUCTURE

    1.2  Physical and Chemical Properties

    The physical and chemical properties of allethrin and its selected
    isomers are given in the International Chemical Safety Card.

    1.3  Analytical Methods

    Determination of residues and analyses of environmental samples are
    carried out using dual-wavelength densitometry (370 or 230 nm), or
    derivatization and colorimetric measurement of levels as low as
    0.1 mg/kg. Gas chromatography with a flame-ionization detector is used
    for the analysis of the technical product.

    1.4  Production and Uses

    It is estimated that several hundred tonnes of allethrin, d-allethrin,
    bioallethrin, esbiothrin, and  S-bioallethrin are manufactured and
    used each year throughout the world, mainly for the control of
    household insects. Formulations include aerosols, sprays, smoke coils,
    electric mats, and emulsifiable concentrates, with or without
    synergists and other insecticides.


    2.1  Human Exposure to Allethrins

    It is thought that human exposure occurs mainly through the inhalation
    of mists from aerosol sprays, and from other household applications,
    such as the electric mat and mosquito coil. Air levels arising from
    the conventional household application of allethrin in the form of an
    aerosol are not expected to exceed 0.5 mg/m3. In the case of
    individual isomers, the air levels are probably lower under the same
    conditions of use.

    Although the levels of allethrins in food have not been determined,
    current use patterns indicate that it is unlikely that such dietary
    exposure levels would be significant.

    No data are available on occupational exposure to the allethrins.

    2.2  Decomposition and Metabolism

    Allethrin is fairly rapidly decomposed under normal environmental
    conditions. Metabolism and excretion from the mammalian body are also
    known to take place quite rapidly. There are no indications of
    bio-accumulation under normal conditions of use.

    2.3  Evaluation of Effects on the Environment

    Allethrins are primarily used indoors. No information is available on
    levels in the environment. Allethrins are rapidly decomposed when
    exposed to sunlight and at temperatures exceeding 400C, but are
    vaporized by slow heating at 150C.

    Allethrins are toxic for fish with LC50 values ranging from 9 to
    90 g/litre. However, they are less toxic for  Daphnia and aquatic
    insect larvae (150-50 000 g/litre). The toxicity of allethrin is low
    for birds (LD50 2000 mg/kg), but high for honeybees (LD50 3-9 g/bee).

    2.4  Evaluation of Human Health Risks

    Although the allethrins have been used for many years, no data have
    been reported on their toxicity for human beings. Thus, this has to be
    determined by the extrapolation of data from  in vitro studies and
    studies on experimental animals.

    The results of short-term studies on experimental animals suggest that
    allethrins are weakly to moderately toxic (oral and dermal LD50 values
    ranging from 210 to 4290 mg/kg, inhalation LC50s > 1500 mg/m3).

    On the basis of several inhalation studies on mice and rats (using
    mosquito coils and mats), at a range of dose levels (10 , 20 , 25 
    normal use concentration), the short-term toxicities of S-Bioallethrin
    and d-allethrin appear to be low.

    Allethrins have shown mild primary eye and skin irritation in rabbits,
    but no skin sensitization.

    The allethrins were not mutagenic in a variety of test systems
    including gene mutations, DNA damage, DNA repair, and chromosomal

    d-Allethrin was not carcinogenic in rats fed diets containing
    2000 mg/kg diet over 2 years.

    Relatively high doses of allethrin, bioallethrin, or S-Bioallethrin
    were not embryotoxic or teratogenic in rabbits, rats, or mice. No
    adequate reproduction studies have been reported.

    Allethrins at near lethal doses are likely to cause hyperactivity,
    tremors, and convulsions and have been classified as Type I

    No-observed-adverse-effect levels for bioallethrin were established in
    a 90-day rat study and a 6-month dog study (1500 mg/kg of diet and
    200 mg/kg of diet, respectively, corresponding to 135 mg/kg body
    weight per day and 5 mg/kg body weight per day, respectively). In a
    2-year dog study, the no-observed-adverse-effect level for allethrin
    in the diet was greater than 50 mg/kg body weight (highest dose


    3.1  Conclusions

     General population. Under recommended conditions of use, the
    exposure of the general population to allethrins is negligible and is
    unlikely to present a hazard.

     Occupational exposure. With reasonable work practices, hygiene
    measures, and safety precautions, the use of allethrins is unlikely to
    present a hazard to those occupationally exposed to it.

     Environment: With recommended application rates and conditions of
    use, it is unlikely that allethrins or their degradation products will
    attain levels of environmental significance. In spite of their
    toxicity for fish and honeybees, a problem is only likely to arise in
    the case of spillage or misuse.

    3.2  Recommendations

    Labels for the household use of allethrins should include adequate
    instructions for use and storage and, where appropriate, warn of


    4.1  Main Human Health Hazards, Prevention and Protection, First Aid

    Allethrins are synthetic pyrethroid insecticides. No cases of
    poisoning have been reported either in the general population or
    through occupational exposure. The results of experimental animal
    studies suggest that, following massive overexposure or accidental
    ingestion, neurological symptoms, such as tremors and convulsions,
    could occur.

    The human health hazards associated with certain types of exposure to
    allethrins together with preventive and protective measures and first
    aid recommendations are listed on the International Chemical Safety

    4.1.1  Advice to physicians

    No specific antidote is known. Treat symptomatically. The main hazard
    with liquid formulations is aspiration of the solvent into the lungs,
    resulting in chemical pneumonitis.

    4.1.2  Health surveillance advice

    Pre-exposure and annual general medical examinations should be carried
    out on workers regularly exposed to allethrins.

    4.2 Explosion and Fire Hazards

    Some solvents in pyrethroid formulations are highly flammable. Use dry
    powder, carbon dioxide, or alcohol-resistant foam, sand, or earth for
    dealing with fires. DO NOT use water. Cool nearby drums with water

    If pyrethroid products are involved in a major fire or in a fire
    involving other products, advise the fire service that protective
    clothing and breathing apparatus should be worn. Also, warn the
    authorities that pyrethroids are highly toxic for fish, and that the
    use of water should be confined to the cooling of unaffected stock,
    thus avoiding the accumulation of polluted run-off from the site.

    4.3  Storage

    Store technical material and formulations away from heat, under lock
    and key, and out of reach of children, animals, and unauthorized
    personnel. Store away from foodstuffs and animal feed in an area
    designated for insecticide storage, preferably without drains.

    4.4  Transport

    Pyrethroids are classified as "harmful" or "low hazard" for transport
    purposes. Formulations based on flammable solvents may be subject to
    local transport controls. Before dispatch, ensure that containers are
    sound and that labels are securely fixed and undamaged. Comply with
    local transport regulations.

     Accident procedures:

    Avoid exposure, if possible by using appropriate protective clothing
    and masks. Keep spectators away from the leaking or spilled product
    and prevent smoking or the use of naked flames in the immediate

    Extinguish fires with dry powder, carbon dioxide, alcohol-resistant
    foam, sand, or earth.

    Prevent liquid from spreading to other cargo, vegetation, or waterways
    by making a barrier with the most readily available material, e.g.,
    earth or sand.

    Absorb spilled liquid and cover contaminated areas with earth, lime,
    sand, or other absorbent material and place in a secure container for
    subsequent safe disposal.

    4.5  Spillage and Disposal

    4.5.1  Spillage

    Avoid exposure, if possible by using appropriate protective clothing
    and masks.

    Empty any product remaining in damaged or leaking containers into a
    clean, empty drum and label.

    Absorb spillage with lime, damp sawdust, sand, or earth and dispose of
    safely (see section 4.5.2). If spillage is large, contain it by
    building a barrier using earth or sandbags.

    Decontaminate empty, damaged, or leaking containers with a 10% sodium
    carbonate solution added at the rate of at least 1 litre per 20-litre
    drum. Puncture containers to prevent re-use.

    4.5.2  Disposal

    Waste containing allethrins should be burnt in a proper high
    temperature incinerator with effluent scrubbing. Where no incinerator
    is available, contaminated absorbents or surplus products should be
    decomposed by hydrolysis at pH 12 or above. Contact with a suitable
    hydrolysing agent is required to ensure degradation of the active
    ingredient to a safe level.

     For emulsifiable material: 5% sodium hydroxide (caustic soda)
    solution or saturated (7-10%) sodium carbonate (washing soda) solution
    can be used.

     For non-emulsifiable material: use a 1:1 mixture (by volume) of
    either of the above solutions and a water/oil-soluble solvent, such as
    denatured alcohol, monoethylene glycol, hexylene glycol, or isopropyl

    Cover the material with the hydrolysing agent and put aside to stand
    for 7 days. Before disposal of the resultant waste, the material
    should be analysed to ensure that the active ingredient has been
    degraded to a safe level.

    Never pour untreated waste or surplus products into public sewers or
    where there is any danger of run-off or seepage into streams,
    watercourses, open waterways, ditches, fields with drainage systems,
    or the catchment areas of boreholes, wells, springs, or ponds.


    With recommended techniques and rates of application, it is unlikely
    that allethrin and its degradation products will attain levels of
    environmental significance. Allethrins are very toxic for fish and
    honeybees but, because the exposure levels that normally occur are
    very low, this will only cause a problem in the case of spillage.

    Avoid spraying over bodies of water. Do not contaminate ponds,
    waterways, or ditches with the product or with used containers.


     This card should be easily available to all health workers concerned
     with, and users of, allethrins. It should be displayed at, or near,
     entrances to areas where there is potential exposure to allethrins,
     and on processing equipment and containers. The card should be
     translated into the appropriate language(s). All persons potentially
     exposed to the chemical should also have the instructions on the
     chemical safety card clearly explained.

     Space is available on the card for insertion of the National
     Occupational Exposure Limit, the address and telephone number of the
     National Poison Control Centre, and for local trade names.



    CAS chemical name: Cyclopropanecarboxylic acid,
    2,2-dimethyl-3-(2-methyl-1-propenyl)-,2-methyl-4-oxo-3-(2-propenyl)-2-cyclopentene-1-yl ester
    Molecular formula: C19H26O3
    CAS registry no. 584-79-2
    RTECS registry no. GZ1476000

    Physical properties     Allethrin    d-Allethrin    Bioallethrin    Esbiothrin    S-Bioallethrin     Other characteristics

    Physical state          oil          oily           viscous         viscous       liquid             Technical allethrin contains 75-95%
                                         liquid         liquid          liquid                           allethrin, which is a mixture
                                                                                                         of 8 stereoisomers; d-allethrin,
    Colour                  pale         --             amber           yellow        yellow             bioallethrin, and S-bioallethrin
                            yellow                                                                       differ from allethrin in
                                                                                                         stereoisomeric composition; all
                                                                                                         four are unstable to light, air,
    Odour                   --           --             aromatic        --            --                 alkaline conditions, and heat, and
                                                                                                         decompose at temperatures above
    Relative molecular      302.45       302.45         302.45          302.45        302.45             400C; at 150C, they are
    mass                                                                                                 vaporized without decomposition

    Boiling point           140C        130C          65.6C          --            --                 Allethrin is a synthetic pyrethroid
                            (0.1 mmHg)   (flash)        (flash)                                          mainly used for the control of flies
                                                                                                         and mosquitos in homes, flying and
    Water solubility        insoluble    insoluble      insoluble       insoluble     insoluble          crawling insects in stables and on
                                                                                                         livestock, and fleas and ticks on
    Solubility in organic   solublea     soluble        solubleb        soluble       soluble            dogs and cats


    Physical properties     Allethrin    d-Allethrin    Bioallethrin    Esbiothrin    S-Bioallethrin     Other characteristics

                             25           20             20                            20
    Density                 d 4 1.005    d 4 1.005-     d 4 0.997       --            d 4 0.980

    Vapour pressure         1.2  10-4   --             3.3  10-4      --            --
                            mmhg                        mmHg
                            (30C)                      (25C)

    n-Octanol/water         --           --             4.8  104       --            --
    partition                                           (25C)

    a   Methanol ( > 1 kg/kg), hexane ( > 1 kg/kg), xylene ( > 1 kg/kg), acetone, carbon tetrachloride, kerosene, petroleum.
    b   Acetone, ethanol, hexa c, methylene chloride, kerosene.


    Hazards/symptoms                           Prevention and protection                 First aid

    SKIN: irritating to skin                   Proper application technique,             Remove contaminated clothing, wash skin
                                               proper skin protection                    with water and soap

    EYES: irritating to eyes                   Face shield; goggles                      Flush immediately with clean water for at
                                                                                         least 15 minutes

    INHALATION: irritant to respiratory        Avoid inhalation of fine dust             Fresh air
    system                                     and mist

    INGESTION: unlikely occupational           Do not eat, drink or smoke during         --
    hazard                                     working hours; wash hands before

    Accidental or deliberate ingestion                                                   Obtain medical attention immediately; if
    could lead to neurological symptoms                                                  breathing has stopped, apply artificial
    such as tremor and convulsions;                                                      respiration; do not induce vomiting
    main hazard of ingested liquid
    formulations is aspiration into lungs

    ENVIRONMENT: very toxic for fish           Do not contaminate ponds,                 --
    and honeybees                              waterways, or ditches with
                                               product or used containers

    Spillage                                   Storage                                   Fire and Explosion

    Absorb spillage with lime, damp            Store in locked, well ventilated          Some liquid formulations may be highly
    sawdust, sand, or earth; sweep up,         storeroom, away from feed                 flammable; DO NOT use water; use dry
    place in closed container, and             and foodstuffs, children and              powder, carbon dioxide, or alcohol-resistant
    dispose of safely; avoid contamination     unauthorized personnel                    foam; cool nearby drums with water spray
    of personnel, ponds, and waterways


    Waste disposal

    Burn in high temperature incinerator       National Occupational
    with effluent scrubbing; alternatively,
    treat with 5% caustic soda as a            Exposure Limit:
    hydrolysing agent; comply with
    local regulations                          National Poison Control Centre:

                                               Local trade names:
    FIGURE 1

    FIGURE 2

    The information given in this paragraph has been extracted from the
    International Register of Potentially Toxic Chemicals (IRPTC) legal
    file and other United Nations sources. The intention is to give the
    reader a representative but not exhaustive overview of current
    regulations, guidelines, and standards.

    The reader should be aware that regulatory decisions about chemicals
    taken in a certain country can only be fully understood in the
    framework of the legislation of that country.a

    7.1  Previous Evaluations by International Bodies

    The FAO/WHO Joint Meeting on Pesticide Residues (JMPR) discussed and
    evaluated allethrin at its meeting in 1965, but did not establish an

    WHO classified the acute hazard for health of technical allethrin and
    technical bioallethrin as slight and moderate, respectively (WHO,

    7.2  Exposure Limit Values

    In the USA (1983), the maximum residue limit in, or on, specified raw
    plant products was 2-4 mg/kg. An exemption from residue tolerance
    requirements was made for this insecticide when used before harvest on
    certain specified plant products.

    In the Federal Republic of Germany, the maximum residue limit on
    specified plant products ranges from 0.5 to 3 mg/kg.

    7.3  Specific Restrictions

    No information available.

    7.4  Labelling, Packaging, and Transport

    The United Nations Committee of Experts on the Transportation of
    Dangerous Goods classifies pyrethroids in:

    Hazard Class 6.1: poisonous substance

    Packing Group III: a substance presenting a relatively low risk of
    poisoning in transport.


    a   The regulations and guidelines of all countries are subject to
        change and should always be verified with the appropriate
        regulatory authorities before application.

    The label should be as follows:

    FIGURE 3

    The bottom half of the label should bear the inscription:

     Harmful, stow away from foodstuffs.

    The FAO specifications for plant protection products for
    d- trans-allethrin (technical product and formulations) advise on
    methods for the checking of the composition and purity of the product.
    The d- trans-allethrin content shall be declared and may not deviate
    more than 2% from this.

    Where necessary, containers should be lined with a suitable material
    or the interior surfaces treated to prevent corrosion and/or
    deterioration of the contents. They should comply with pertinent
    national and international transport and safety regulations.

    In the countries of the European Community, pyrethroids are classified
    as harmful for labelling and packaging purposes. The label must read:

     Harmful by inhalation, in contact with skin and if swallowed; keep out
     of reach of children; keep away from food, drink; and animal feeding

    The following symbol should be used:

    FIGURE 4

    7.5  Waste Disposal

    In the USA, permits are required for the discharge of pyrethroids from
    any point source into USA waters; detailed instructions are provided.


    FAO (1985a)  Guidelines for the packaging and storage of pesticides.
    Rome, Food and Agriculture Organization of the United Nations.

    FAO (1985b)  Guidelines for the disposal of waste pesticides and
     pesticide containers on the farm. Rome, Food and Agriculture
    Organization of the United Nations.

    FAO (1985c)  Guidelines on good labelling practice for pesticides.
    Rome, Food and Agriculture Organization of the United Nations.

    FAO (1986)  International code of conduct on the distribution and use
     of pesticides. Rome, Food and Agriculture Organization of the United

    FAO/WHO (1986)  Guide to Codex recommendations concerning pesticide
     residues. Part 8.  Recommendations for methods of analysis of pesticide
     residues. 3rd ed. Rome, Codex Committee on Pesticide Residues.

    GIFAP (1982)  Guidelines for the safe handling of pesticides during
     their formulation, packing storage and transport. Brussels, Groupement
    International des Associations Nationales des Fabricants de Produits

    GIFAP (1983)  Guidelines for the safe and effective use of pesticides.
    Brussels, Groupement International des Associations Nationales des
    Fabricants de Produits Agrochimiques.

    GIFAP (1984) Guidelines for emergency measures in cases of pesticide
    poisoning. Brussels, Groupement International des Associations
    Nationales des Fabricants de Produits Agrochimiques.

    GIFAP (1987)  Guidelines for the safe transport of pesticides.
    Brussels, Groupement International des Associations Nationales des
    Fabricants de Produits Agrochimiques.

    IARC (1972-present)  IARC monographs on the evaluation of carcinogenic
     risk of chemicals to man. Lyons, International Agency for Research on

    IRPTC (1985)  IRPTC file on treatment and disposal methods for waste
     chemicals. Geneva, International Register for Potentially Toxic
    Chemicals, United Nations Environment Programme.

    IRPTC (1987)  IRPTC legal file 1983. Geneva, International Register
    of Potentially Toxic Chemicals, United Nations Environment Programme.

    PLESTINA, R. (1984)  Prevention, diagnosis, and treatment of
     insecticide poisoning. Geneva, World Health Organization (unpublished
    document VBC/84.889).

    SAX, N.I. (1984)  Dangerous properties of industrial materials. New
    York, Van Nostrand Reinhold Company, Inc.

    UNITED NATIONS (1986) Recommendations on the transport of dangerous
    goods. 4th ed. New York, United Nations.

    NIOSH/OSHA (1981)  Occupational health guidelines for chemical hazards.
    3 Vol. Washington DC, US Department of Health and Human Services, US
    Department of Labor (Publication No. DHSS(NIOSH) 01-123).

    WHO (in press) Environmental Health Criteria 87:  Allethrins --
     allethrin, d-allethrin, bioallethrin, S-bioallethrin. Geneva, World
    Health Organization.

    WHO (1986)  The WHO recommended classification of pesticides by hazard
     and guidelines to classification 1986-87. Geneva, World Health
    Organization (unpublished document VBC/86.1).

    WHO/FAO (1975-87) Data sheets on pesticides. Geneva, World Health
    Organization (unpublished documents).

    WORTHING, C.R. & WALKER, S.B. (1983)  The pesticide manual. 7th ed.
    Lavenham, Lavenham Press Limited, British Crop Protection Council.

    See Also:
       Toxicological Abbreviations
       Allethrins (EHC 87, 1989)