IPCS INCHEM Home

    IPCS INTERNATIONAL PROGRAMME ON CHEMICAL SAFETY
    Health and Safety Guide No. 48

    BENTAZONE
    HEALTH AND SAFETY GUIDE






    UNITED NATIONS ENVIRONMENT PROGRAMME

    INTERNATIONAL LABOUR ORGANISATION

    WORLD HEALTH ORGANIZATION




    WORLD HEALTH ORGANIZATION, GENEVA 1990

    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

    WHO Library Cataloguing in Publication Data

    Bentazone: health and safety guide

         (Health and safety guide ; no. 48)

         1.Benzothiadiazines - standards  I.Series

         ISBN 92 4 151048 X          (NLM Classification: WA 240)
         ISSN 0259-7268

    The World Health Organization welcomes requests for permission to
    reproduce or translate its publications, in part or in full. 
    Applications and enquiries should be addressed to the Office of
    Publications, World Health Organization, Geneva, Switzerland, which
    will be glad to provide the latest information on any changes made to
    the text, plans for new editions, and reprints and translations
    already available.

    (c) World Health Organization 1990

    Publications of the World Health Organization enjoy copyright
    protection in accordance with the provisions of Protocol 2 of the
    Universal Copyright Convention.  All rights reserved.

    The designations employed and the presentation of the material in this
    publication do not imply the expression of any opinion whatsoever on
    the part of the Secretariat of the World Health Organization
    concerning the legal status of any country, territory, city or area or
    of its authorities, or concerning the delimitation of its frontiers or
    boundaries.

    The mention of specific companies or of certain manufacturers'
    products does not imply that they are endorsed or recommended by the
    World Health Organization in preference to others of a similar nature
    that are not mentioned.  Errors and omissions excepted, the names of
    proprietary products are distinguished by initial capital letters.

    CONTENTS

    INTRODUCTION

    1. PRODUCT IDENTITY AND USES

         1.1. Identity
         1.2. Physical and chemical properties
         1.3. Analytical methods
         1.4. Production and uses

    2. SUMMARY AND EVALUATION

         2.1. Human exposure to bentazone
         2.2. Uptake, metabolism, and excretion
         2.3. Effects on animals
         2.4. Effects on human beings
         2.5. Effects on the environment

    3. CONCLUSIONS AND RECOMMENDATIONS

    4. HUMAN HEALTH HAZARDS, PREVENTION AND PROTECTION, EMERGENCY
         ACTION

         4.1. Main human health hazards, prevention and protection,
               first aid
               4.1.1. Prevention and protection
               4.1.2. First aid
         4.2. Advice to physicians
         4.3. Explosion and fire hazards
         4.4. Storage and transport
         4.5. Spillage and disposal

    5. HAZARDS FOR THE ENVIRONMENT AND THEIR PREVENTION

    6. CURRENT REGULATIONS, GUIDELINES, AND STANDARDS

         6.1. Exposure limit values
         6.2. Specific restrictions
         6.3. Transport and labelling
    

    INTRODUCTION

    This Health and Safety Guide is not based on an existing Environmental
    Health Criteria document, but on critical national reviews. The hazard
    evaluation in the Health and Safety Guide was made on the basis of
    carefully selected studies, after scrutiny of the original
    publications.

    In order to assist the peer-review process of the present Health and
    Safety Guide, a background companion document was prepared by the IPCS
    and can be obtained from the Manager on request; the IPCS does not
    intend that the background document should be published.

    The first three sections of this Health and Safety Guide present
    essential technical information and the hazard evaluation. 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.
    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.

    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
    Switzerland

    THE INFORMATION IN THIS GUIDE SHOULD BE CONSIDERED AS A STARTING POINT
    TO A COMPREHENSIVE HEALTH AND SAFETY PROGRAMME

    1.  PRODUCT IDENTITY AND USES

    1.1  Identity

    Common name              Bentazone

    Chemical formula:        C10H12N2O3S

    Chemical structure:

    CHEMICAL STRUCTURE 1

    Common trade             Bas 351-H; Basagran; Bendioxide;
    names (including         Bentazon
    formulations):

    CAS chemical name:       3-(1-methylethyl)-1H-2,1,3-benzothiadiazin-
                             4(3H)-one, 2,2-dioxide

    Synonyms:                1H-2,1,3-benzothiadiazin-4(3H)-one-2,2-
                             dioxide, 3-isopropyl-; 3-isopropyl-
                             2,1,3-benzothiadiazinon-(4)-2,2-dioxide;
                             3-isopropyl-1H-2,1,3-benzothiadiazin-
                             4(3H)-one-2,2-

    CAS registry             25057-89-0
    number:                  50723-80-3 (bentazone, sodium)

    RTECS registry
    number:                  DK 9900000

    The technical product is about 93-96% pure. Main impurities are
    anthranilic acid,  N-isopropylsulfamoyl anthranilic acid, and sodium
    chloride.

    Almost all end-use products contain sodium bentazone as the active
    ingredient.

    The usual carrier is water, but, under certain conditions, an oil
    concentrate is used.

    1.2  Physical and Chemical Properties

    Technical bentazone is a yellow-white crystalline powder without a
    noticeable odour (vapour pressure < 10 nPa). A melting point range of
    137-139C has been reported for the technical product. It is slightly
    soluble in water (0.5 g/litre), moderately soluble in benzene
    (33 g/litre) and chloroform (180 g/litre), and readily soluble in
    acetone (1.51 kg/litre) and ethanol (861 g/litre). Sodium bentazone is
    considerably more soluble in water than the parent compound, with a
    solubility of 2300 g/litre. Bentazone is stable in acid as well as
    basic solutions; it decomposes at about 200C.

    The relative molecular mass is 240.3.

    1.3  Analytical Methods

    Residues are determined using gas chromatography with an  N-specific
    detector, after conversion to the 1-methyl derivatives. The minimum
    detection limit varies according to the substrate.

    1.4  Production and Uses

    In 1982, 5 kilotonnes of bentazone/year were sold in the USA. It is
    used as a contact herbicide for the control of broadleaf weeds and
    sedges in crops, such as corn, rice, sorghum, soybeans, peanuts, corn,
    peas, and established ornamental turf. It is applied, from the ground
    or from the air, as a broadcast foliar spray, after crop and weeds
    have emerged from the soil.

    2.  SUMMARY AND EVALUATION

    2.1  Human Exposure to Bentazone

    No investigations dealing with the quantification of human exposure to
    bentazone have been found.

    2.2  Uptake, Metabolism, and Excretion

    The uptake, metabolism, and excretion of bentazone have been studied
    in rats and rabbits. The substance is rapidly absorbed from the
    gastrointestinal tract and distributed to various organs and tissues.
    Penetration across the blood-brain barrier does not occur. Bentazone
    is rapidly eliminated from the mammalian organism, mainly via the
    urine as unchanged bentazone.

    2.3  Effects on Animals

    Bentazone has a moderate to low oral acute toxicity (oral LD50,
    1100 mg/kg in the rat). Inhalation toxicity appears to be low.

    After repeated administration of high doses, bentazone has
    demonstrated a potential for inducing toxicity involving the kidneys
    and liver of experimental animals. Under these conditions, it also
    seems to interfere with blood coagulation.

    Although there was no apparent indication of carcinogenicity in rats,
    a slight increase in proliferative lesions was observed in female
    mice. The biological significance of this is not clear. No indications
    of genotoxicity were found in several  in vivo and  in vitro assays.
    Bentazone does not appear to be tetratogenic.

    2.4  Effects on Human Beings

    No information is available.

    2.5  Effects on the Environment

    Based on acute and short-term dietary tests, bentazone is practically
    non-toxic to birds. Avian reproduction testing did not reveal any
    significant effects up to the highest dietary levels tested.
    Furthermore, technical bentazone is practically non-toxic for
    freshwater fish, and only slightly toxic for aquatic invertebrates.

    Bentazone appears to be stable to hydrolysis, but photodegrades in
    water with a half-life of < 24 h. It is also photochemically degraded
    in soil. Under aerobic conditions, bentazone degrades with a half-life
    ranging from < 7 days to 14 weeks, depending on soil types and
    conditions.

    Bentazone is very mobile in soil and, therefore, has the potential to
    contaminate surface water.

    Although degradation is relatively rapid, bentazone, or its major
    metabolite, could contaminate ground water.

    Bentazone has a low potential for bioaccumulation, with a measured
    bioconcentration factor of < 10 in crayfish.

    3.  CONCLUSIONS AND RECOMMENDATIONS

    The acute toxicity of bentazone in animals is low to moderate. After
    long-term administration of high doses, various manifestations of
    toxicity were observed in rodents and dogs, including hepatic and
    renal toxicity. Although there was no apparent indication of
    oncogenicity in rats, a slight increase in proliferative lesions was
    observed in the liver in female mice. The biological significance of
    this increase is not clear. No indications of genotoxicity were found
    in several  in vivo and  in vitro assays. Although bentazone does
    not appear to present a teratogenic hazard for human beings,
    additional reproductive toxicity testing is needed.

    There is no indication that bentazone poses a health hazard for the
    general population or exposed workers.

    Bentazone is practically non-toxic for birds and fish and is slightly
    toxic for aquatic invertebrates. Bentazone is highly mobile in soils
    and may not be readily degradable, depending on soil type and
    conditions. Thus, adequate precautions must be taken to avoid
    contamination of surface and ground water.

    4.  HUMAN HEALTH HAZARDS, PREVENTION AND PROTECTION, EMERGENCY ACTION

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

    The toxicity of technical bentazone for human beings is thought to be
    low, and no adverse health effects from exposure to this herbicide
    have been reported. Nevertheless, proper care should be taken during
    occupational use to avoid excessive inhalation of dust or spray
    particles and to prevent accidental contamination of food products and
    water.

    4.1.1  Prevention and Protection

    The following precautions should be observed during handling and use,
    in order to reduce the risk of accidental contamination:

    (a) Avoid contact with the skin and eyes.

    (b) Do not smoke, drink, or eat in the workplace. Wash hands and any
    exposed skin before eating, drinking, smoking, and after work.

    (c) Avoid raising a dust cloud when handling wettable powder
    formulations.

    (d) Avoid breathing dust from powder products.

    (e) When unloading and handling containers, wear protective PVC or
    neoprene gloves.

    (f) When handling leaking containers, or when dealing with leaks and
    spills, wear overalls, PVC or neoprene gloves, boots and eye/face
    protection. If overalls become contaminated, change and wash them
    thoroughly before re-use.

    (g) Store products in closed original containers, out of reach of
    children, and away from food, drink, and animal feed.

    4.1.2  First Aid

    Acute poisoning by bentazone is unlikely unless large amounts have
    been ingested. In case of over-exposure, apply routine first-aid
    measures. If material has been spilled on the skin, immediately remove
    the patient from the source of contamination, remove all contaminated
    clothing, and wash affected areas with soap and running water. If the
    material is in the eyes, flush with clean water for at least 15
    minutes. In case of ingestion of significant quantities, if the
    patient is conscious, give several glasses of water. Do not induce
    vomiting. In serious cases, medical attention should be sought.

    4.2  Advice to Physicians

    The acute toxicity of bentazone for human beings is believed to be
    low. There is no specific antidote. Treat symptomatically when
    required. In cases of ingestion of large amounts, gastric lavage may
    be indicated.

    4.3  Explosion and Fire Hazards

    Bentazone as such is not flammable, but on heating may produce toxic
    fumes, such as sulfur dioxide and oxides of nitrogen.

    Extinguish small fires with carbon dioxide, dry powder, or alcohol-
    resistant foam. Water spray can be used for larger fires and for the
    cooling of unaffected stock, but avoid the accumulation of polluted
    run-off from the site.

    Beware: Some liquid formulations may be highly flammable and require
    alcohol-resistant foam as an extinguishing agent.

    4.4  Storage and Transport

    All products should be stored in secure buildings, out of reach of
    children and animals, and local regulations should be complied with.
    Containers should be sound and adequately labelled.

    4.5  Spillage and Disposal

    Avoid contact with solid or dust. Keep spectators away from any
    leakage. Prevent contamination of other goods or cargo, or nearby
    vegetation and waterways.

    Absorb spilled liquid products with earth or sand. If available,
    sawdust, peat moss, and straw are also suitable absorbents. Sweep up
    and place in a separate container. Empty any product remaining in
    damaged or leaking containers into a clean empty container, which
    should be suitably labelled. Sweep up any spilled powder with damp
    sawdust taking care not to raise a dust cloud (use a vacuum cleaner).
    Remove trapped material with suction hoses. Place in separate
    container for subsequent disposal.

    Bentazone is characterized by high mobility in soil and should not be
    buried in dump sites. Incineration seems to offer the most acceptable
    method for disposal of bentazone. Contaminated absorbents, used
    containers, and surplus product should be burnt in an incinerator,
    preferably designed for pesticide disposal. Comply with any local
    legislation applying to waste disposal.

    5.  HAZARDS FOR THE ENVIRONMENT AND THEIR PREVENTION

    Bentazone is highly mobile in soil and may contaminate ground water.

    Technical bentazone is practically non-toxic for birds, fish, and
     Daphnia and no adverse environmental effects have been reported.

    Contamination of ponds, waterways, and ditches with bentazone should
    be avoided.

    6.  CURRENT REGULATIONS, GUIDELINES, AND STANDARDS

    The information given in this section has been extracted from the
    International Register of Potentially Toxic Chemicals (IRPTC) legal
    file. A full reference to the original national document from which
    the information was extracted can be obtained from IRPTC. When no
    effective date appears in the IRPTC legal file, the year of the
    reference from which the data are taken is indicated by (r).

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

    6.1  Exposure Limit Values

    Exposure limit values are presented in the table on page 18.

    6.2  Specific Restrictions

    In the USA (1985), no new uses of bentazone will be permitted until a
    data base adequate to complete a hazard assessment has been obtained.

    6.3  Transport and Labelling

     Supply and use labelling

    European Economic Community legislation requires labelling as a
    dangerous substance using the symbol:

    FIGURE 1

    The label must read:

    R20        Harmful by inhalation

    R21        Harmful in contact with skin

    R22        Harmful if swallowed

    S2         Keep out of reach of children

    S13        Keep away from food, drink, and animal feed.


        CURRENT REGULATIONS, GUIDELINES, AND STANDARDS

    EXPOSURE LIMIT VALUESa
                                                                                                                                  
    Medium    Specification          Country/              Exposure limit description              Value                Effective
                                     organization                                                                         date
                                                                                                                                  

    WATER     Drinking-              USA                   Long-term maximum concentration:        0.06 mg/litre          1987
                                                           for a 10-kg child                       0.25 mg/litre
                                                           for a 70-kg adult                       0.875 mg/litre
                                                           Life-time health advisory value         87.5 g/litre          1987

    WATER     Oral intake            WHO/                  WHO-EURO/guideline value                2.0 g/litre           1987
                                     EURO                  ADI                                     0.0075 mg/kg           1987

    FOOD      Plant (specified)      Germany, Federal      Tolerance                               0.1 mg/kg              1984
                                     Republic of

    FOOD      Animal feed            USA                   Tolerance                               4 mg/kg

    FOOD      Raw specified          USA                   Tolerance                               0.05-3.0 mg/kg         1984
              plants

              Raw specified          USA                   Tolerance                               0.02-0.05 mg/kg        1984
              animal products
                                                                                                                                  

    a  For further details of other regulatory data, see IRPTC legal file.
        


    See Also:
       Toxicological Abbreviations
       Bentazone (ICSC)
       Bentazone (Pesticide residues in food: 1991 evaluations Part II Toxicology)