Health and Safety Guide No. 52






    This is a companion volume to Environmental Health Criteria 39:
    Paraquat and Diquat

    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

    Diquat : health and safety guide.

    (Health and safety guide ; no. 52)

    1. Diquat - standards  I. Series

    ISBN 92 4 151052 8          (NLM Classification: WA 240)
    ISSN 0259-7268

    (c) World Health Organization 1991

    Publications of the World Health Organization enjoy copyright
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    Universal Copyright Convention.  For rights of reproduction or
    translation of WHO publications, in part or  in toto, application
    should be made to the Office of Publications, World Health
    Organization, Geneva, Switzerland.  The World Health Organization
    welcomes such applications.

    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

    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.



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

         2.1. Environmental distribution and transformation
         2.2. Kinetics and metabolism
         2.3. Effects of experimental animals
         2.4. Effects on human beings
              2.4.1. Occupational exposure
              2.4.1. General population exposure and cases of poisoning
         2.5. Effects on the environment

         3.1. Conclusions
              3.1.1. General population exposure
              3.1.2. Occupational exposure
              3.1.3. Environment
         3.2. Recommendations
              3.2.1. Environment
              3.2.2. Prevention and treatment

         4.1. Main human health hazards, prevention and protection,
              first aid
              4.1.1. Advice to physicians
              4.1.2. Health surveillance advice
              4.1.3. Personal protection and hygienic measures
         4.2. Explosion and fire hazards
         4.3. Storage
         4.4. Transport
              4.4.1. Accident procedures
         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 a Summary of Chemical Safety
    Information 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

    Common name:                  Diquat

    Molecular formula:            C12H12N2Br2

    Chemical structure:


    CAS chemical name:            6,7-dihydrodipyrido[1,2-a:2'1'-c]-
                                  pyrazinediium (9CI)

    Trade names (inter alia):     Reglone; Aquacide; Pathclear

    CAS registry number:          2764-72-9 (ion)
                                  85-00-7 (dibromide)
                                  4032-26-2 (dichloride)

    RTECS registry number:        JM5685000 (ion)
                                  JM5690000 (dibromide)
                                  JM5750000 (dichloride)
                                  JM5755000 (diodide)

    Relative molecular mass:      184.2 (ion)

    1.2  Physical and Chemical Properties

    The commonly available analytical standard is diquat dibromide
    monohydrate, which is an odourless, pale yellow, crystalline powder. 
    Some of the physical properties of diquat dibromide are listed in the
    Summary of Chemical Safety Information (section 6).

    The herbicide is supplied mainly as an aqueous solution of the

    It is slightly soluble in alcohol, and practically insoluble in
    non-polar organic solvents.  Diquat is non-explosive and non-flammable
    in aqueous formulations.

    Diquat is stable in neutral or acid solutions, but is hydrolysed by
    alkali.  It is inactivated by inert clay and by anionic surfactants.

    1.3  Analytical Methods

    Product analysis is by ultraviolet (UV) spectroscopy and residue
    analysis, by colorimetry.  Impurities can be determined by gas-liquid
    chromatography (GLC).

    1.4  Uses

    Diquat is a non-selective contact herbicide that is used for:  the
    control of both broad-leaved weeds among crops, and submerged and
    floating weeds in water bodies; the destruction of potato haulms; and
    seed crop desiccation (rice, sunflower, etc.).

    It is sold primarily as a 20% w/v solution of the dibromide salt, and
    is usually formulated to contain wetters.


    2.1  Environmental Distribution and Transformation

    Photochemical degradation takes place when diquat-treated plants are
    exposed to normal daylight and continues after the plants have died. 
    The products formed are of lower toxicity than diquat.  The rapidity
    of photochemical degradation on plant and soil surfaces minimizes the
    hazards of diquat for the environment.

    (a)  Soil

    Diquat rapidly becomes tightly bound to clay particles in the soil,
    and is then inert.  Toxic breakdown products are not expected to occur
    in the soil under normal conditions of agricultural use.  Total diquat
    residues in the soil, after repeated spraying, ranged from 0.2 to
    3.9 mg/kg.  In field studies, on the 15th day after a single
    application of diquat, residues were less than 0.1 mg/kg.  No adverse
    effects were found on soil microorganisms, fungi, or invertebrates,
    and no phytotoxic effects on crops have been reported from these bound

    (b)  Water

    Following its use as an aquatic herbicide at normal application rates,
    diquat residues in water have been found to decrease rapidly to
    essentially undetectable levels within 7-14 days.

    (c)  Air

    Diquat is not volatile.  However, during spraying applications,
    droplets of diquat solution may be present in the air, as an aerosol.

    2.2  Kinetics and Metabolism

    Diquat is poorly absorbed from the intestinal tract and skin.  Diquat
    monopyridone is the major metabolite of diquat in the body; of lesser
    importance is diquat dipyridone.  Both metabolites are considerably
    less toxic than diquat itself.  Less than 20% of an oral dose is
    metabolized.  Diquat is primarily metabolized in the gastrointestinal

    Diquat accumulates in the kidneys, but not in the lungs.  The kidneys
    are the major route of excretion, but a considerable amount of diquat
    can also be excreted in the bile, varying according to the animal

    2.3  Effects on Experimental Animals

    Diquat is less toxic than paraquat and does not cause the specific
    lung lesion associated with paraquat poisoning.  The toxic effects of
    diquat depend on its ability to undergo a single electron addition, to
    form a radical. This reacts with molecular oxygen to reform diquat, at
    the same time producing a superoxide anion. This oxygen radical may
    directly or indirectly cause cell death.

    The initial toxic effect of diquat in animals is gastrointestinal
    damage, resulting in diarrhoea, with consequent dehydration.  High
    doses of diquat have produced toxic effects in the liver, kidney, and
    the nervous and endocrine systems.  High concentrations are also
    irritating to the skin.  Development of eye cataracts has been
    reported in rats and dogs following long-term treatment with diquat. 
    This observation has not been reported in human beings.  Diquat is
    embryotoxic, but it has not been found to be teratogenic in rats and
    mice. Carcinogenic effects were not induced in long-term studies on
    rats given diquat at levels of up to 720 mg/kg diet.  The results of
    in vitro mutagenicity studies have been inconclusive, but have
    generally suggested weak activity; the results of in vivo studies have
    been negative.  Thus, on the basis of animal studies, low-level
    exposure to diquat is unlikely to induce toxic effects in man.  The
    no-observed-effect level in rats has been estimated to be 0.75 mg
    diquat ion/kg body weight per day.

    2.4  Effects on Human Beings

    2.4.1  Occupational exposure

    There may be inhalation, dermal, and, to some extent, oral
    occupational exposure.  Spray aerosols and dust particles settle in
    the upper respiratory tract.  Diquat aerosol concentrations ranged
    from 0.06 to 0.56 mg/m3, according to the spraying method.  At
    distances of 200 and 400 m from the treated field, they decreased to
    0.09 mg/m3 and less than 0.01 mg/m3, respectively.  Inhalation
    exposure to diquat was found to be very low in comparison with dermal
    (0.17-1.82 mg/h) exposure, during application for aquatic weed
    control.  Skin irritation, epistaxis, nail damage, and delayed wound
    healing have been reported.  However, no data have been found in the
    literature on severe or fatal cases of occupational intoxication,
    acute ocular damage, or occupational contact dermatitis caused by

    2.4.2  General population exposure and cases of poisoning

    Inhalation exposure of the general population to diquat may occur from
    spray drift off treated fields, but this is thought to be
    insignificant.  There are no published data on total diquat intake
    among the general population but, on the basis of residue data, this
    is expected to be insignificant.

    Few cases of diquat poisoning have been reported.  Most have been due
    to the intentional ingestion of concentrated formulations, but
    accidental ingestion has occurred, for example, as a result of
    decanting liquid concentrates into a beverage bottle.  Diquat
    poisoning involves severe ill-effects similar to those caused by
    paraquat, with two notable differences:  (a) diarrhoea is a prominent
    feature, and (b) pulmonary fibrosis has not been described.

    The acute lethal dose of diquat dibromide is considered to be 6-12 g
    for human beings.  Recovery from diquat poisoning depends on the cause
    of ingestion, the dose absorbed, the renal damage, and prompt
    initiation of therapy.  No long-term adverse effects have been
    reported in those who have survived acute diquat poisoning.

    2.5  Effects on the Environment

    The fact that diquat is used as a herbicide indicates that it is toxic
    for aquatic and terrestrial vegetation.

    Diquat undergoes rapid photochemical degradation in aqueous solution
    and on surfaces.  The major degradation products produced have been
    identified and are of lower acute oral toxicity for rats than diquat

    Diquat reaching the soil becomes rapidly and strongly adsorbed on clay
    minerals in the soil.  This process inactivates the herbicidal
    activity of diquat.  Strongly-bound diquat has no adverse effects on
    soil microfauna or soil microbial processes.

    Diquat residues disappear rapidly from water by adsorption on aquatic
    weeds and by strong adsorption on bottom mud.  The toxicity of diquat
    for fish is low and it does not accumulate in them.  Normal
    applications of diquat for aquatic weed control are not harmful for
    aquatic animal life.  However, in applying diquat to water containing
    heavy weed growth, care should be taken to treat only a part of the
    weed growth, since oxygen consumed by subsequent weed decay may
    decrease dissolved oxygen levels to an extent that may be dangerous
    for fish.  Treated water should not be used for overhead irrigation
    until a period of 10 days has elapsed following treatment.


    3.1  Conclusions

    3.1.1  General population exposure

    Residue levels of diquat in food and drinking-water, resulting from
    its normal use, are unlikely to present a health hazard for the
    general population.

    Diquat has caused some fatalities following suicidal ingestion. 
    Occasional accidental fatalities have followed ingestion of decanted
    diquat.  Ill effects similar to those caused by paraquat occur, but
    the characteristic fibrosis of the lungs is not a feature.

    3.1.2  Occupational exposure

    With reasonable work practices, including safety precautions, hygiene
    measures, and proper supervision, occupational exposure during the
    manufacture, formulation, and application of diquat will not cause a
    hazard.  However, the undiluted concentrate must be handled with great
    care, because contamination of the eyes and skin (with possible
    consequent dermal absorption) can result from improper work practices.

    3.1.3  Environment

    Diquat in soil binds rapidly and tightly to clay particles, and
    residual phytotoxicity from freely available diquat is unlikely. 
    Under normal conditions of use, the toxicity of diquat for aquatic
    animal life is low, though resulting depletion of water oxygen, due to
    weed decay, may pose a problem.  Diquat does not seem to present an
    environmental hazard.

    3.2  Recommendations

    3.2.1  General

    Where practical and reasonable, the availability and use of the 20%
    liquid product should be limited to  bona fide agriculturalists,
    horticulturalists, and professional users, who work with trained
    personnel, properly maintained equipment, and adequate supervision.

    Every effort should be made to prevent the practice of decanting, or
    rebottling, of the product into containers that have not been properly

    3.2.2  Prevention and treatment

    Attention should be drawn to the fact that persons with skin lesions
    (either pre-existing or following contamination with diquat) should
    not be permitted to take any part in spraying procedures, until the
    skin condition has resolved.

    It must be stressed that treatment of persons with diquat poisoning
    should be instituted as early as possible.  The likelihood of recovery
    from a potentially fatal dose is greatest when therapy begins within
    5-6 h of poisoning.


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

    Diquat is toxic and can be fatal, if swallowed.  Contact with
    undiluted liquid products can cause damage to the skin or eyes, and
    the utmost care must be taken to avoid exposure during handling
    operations and application in the field.  Where inhalation exposure to
    aerosols containing diquat is likely, proper respiratory protection
    equipment should be used.

    The human health hazards, preventive and protective measures, and
    first-aid recommendations are listed in the Summary of Chemical Safety
    Information (section 6).

    4.1.1  Advice to physicians

    The most important measures are the immediate neutralization of
    ingested diquat by 15% Fuller's earth, bentonite, or activated
    charcoal, and urgent removal of the poison by vomiting or, when
    possible, gastric lavage.  The urgency of these measures is such that,
    where transfer to hospital may involve a delay of an hour or more,
    this emergency treatment may have to be given by a paramedical person,
    e.g., a nurse or a medical assistant.  The delay should not be more
    than 4-5 h. Furthermore, Fuller's earth should be given together with
    a strong purgative, such as magnesium sulfate or mannitol.

    Admission to a hospital (preferably a specialized intensive care unit)
    either directly, or after emergency treatment elsewhere, is essential.

    When a person has swallowed a lethal dose, the most important single
    determinant of survival is the early commencement of treatment.

    Depending on local facilities, patients who reach hospital after the
    initial treatment will have further treatment aimed at neutralizing
    diquat in the gastrointestinal tract (Fuller's earth, bentonite,
    activated charcoal) or its excretion in the faeces (purgatives, 10%
    mannitol, gut lavage).  In addition, attempts to remove absorbed
    diquat from the circulation (haemoperfusion, haemodialysis) or aid its
    excretion by the kidney (forced diuresis) can be instituted.

    Care must be exercised in the administration of most of these
    treatments, as the following serious complications may occur:
    perforation of the oesophagus during gastric intubation; serious blood
    chemistry disturbance when severe diarrhoea is induced; fluid overload
    during forced diuresis.

    In centres where facilities for analytical procedures are available,
    measurement of urinary or, ideally, plasma levels of diquat may give
    guidelines for the required intensity of treatment, and likely

    It should be noted that, as with the great majority of chemicals,
    there is no specific antidote.

    In cases of skin and eye contamination, irrigation with water
    (preferably running-water) should be commenced urgently and must be
    continued uninterrupted for at least 15 minutes (timed by the clock). 
    Eye cases should always be taken for medical treatment.  In cases of
    skin contamination by the concentrate, or extensive and/or prolonged
    contamination by the diluted material (particularly where signs of
    skin irritation are present), the patient must be assessed at hospital
    for systemic poisoning.

    4.1.2  Health surveillance advice

    Pre-employment and annual medical examinations should be made
    available to all persons who are regularly exposed to diquat at
    potentially hazardous levels.  Special attention should be paid to the
    condition of the skin, kidney function, urinalysis, and liver function

    4.1.3  Personal protection and hygienic measures

    *    Avoid all contact with the skin, eyes, nose, and mouth, when
         handling concentrated diquat.  Wear PVC, neoprene, or butyl
         rubber gloves (preferably gauntlet form), neoprene apron, rubber
         boots, and face-shield;

    *    Take off heavily contaminated clothing immediately, and wash
         underlying skin;

    *    Wash clothes before re-use;

    *    When using diquat, do not eat, drink, or smoke;

    *    Wash concentrate from skin or eyes, immediately;

    *    Do not inhale spray;

    *    Wash hands and exposed skin before meals and after work;

    *    Keep away from food, drink, and animal feed;

    *    Diquat for spraying should be adequately diluted;

    *    It should not be used by people suffering from dermatitis, or by
         people with wounds, notably on the hands, until these have

    4.2  Explosion and Fire Hazards

    Diquat products are generally not flammable.  If involved in a fire,
    control with dry powder or alcohol-resistant foam.  Advise the fire
    service that protective clothing and self-contained breathing
    apparatus should be worn, to avoid skin contamination and the
    breathing of toxic fumes.  Confine the use of water spray 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 in an area designated for pesticide storage,
    preferably without drains.  Store away from foodstuffs and animal

    4.4  Transport

    Before dispatch, ensure that containers are sound and that labels are
    securely fixed and undamaged.  Comply with local transport
    regulations.  Do not load together with foodstuffs or animal feed.

    4.4.1  Accident procedures

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

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

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

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

    4.5  Spillage and Disposal

    4.5.1  Spillage

    Avoid exposure by using appropriate protective clothing and

    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 below).  If spillage is large, contain it by building a
    barrier of 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 or crush containers to prevent re-use.

    4.5.2  Disposal

    Waste containing diquat 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.  A 5%
    sodium hydroxide (caustic soda) solution, or saturated (7-10%) sodium
    carbonate (washing soda) solution, can be used.  Before disposal of
    the resultant waste, the material must be analysed to ensure that the
    active ingredient has been degraded to a safe level.

    Diquat is rapidly inactivated by clay soil.  If the above mentioned
    methods are not possible, it can be buried in an approved landfill.

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


    Diquat is toxic for aquatic and terrestrial vegetation.

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

    When using diquat for aquatic weed control, follow instructions on the


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

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


    C12H12N2Br2, 1,1'-ethylene-2,2'-bipyridylium dibromide

    CAS registry no. 85-00-7

    RTECS registry no. JM5690000


    PHYSICAL PROPERTIES                                                   OTHER CHARACTERISTICS

    Physical state                     crystalline powder                 A non-selective contact herbicide and desiccant
    Colour                             yellow                             for terrestrial and aquatic applications; slightly
    Odour                              odourless                          soluble in alcohol and practically insoluble
    Relative molecular mass            184.2 (ion)                        in non-polar organic solvents; stable in neutral 
    Specific gravity (20C)            1.200                              and acidic solutions, but hydrolysed by alkali;
    Melting point                      180C                              inactivated by inert clay and by anionic surfactants
    Boiling point                      approximately 300C
                                       with decomposition
    Solubility in water (20C)         700 g/litre
    pH of liquid formulation           6.0-7.0
    Vapour pressure                    not measurable


    HAZARDS/SYMPTOMS                        PREVENTION AND PROTECTION                    FIRST AID

    SKIN: Irritating to skin;               Proper application technique, proper         Remove contaminated clothing; wash skin with
    concentrated material may cause         skin protection, including impervious        soap and water; launder clothes before re-use
    blisters, re-use and affect nails       clothing and gloves 

    EYES: Severe irritant                   Wear face-shield or goggles                  Flush immediately with clean water for at least
                                                                                         15 minutes; seek medical advice and observe for
                                                                                         delayed effects

    INHALATION: Irritant to                 Avoid inhalation of fine dust                Fresh air
    respiratory system                      and mist; use proper
                                            respiratory protection

    INGESTION: Unlikely                     Do not eat, drink, or smoke
    occupational hazard                     during work; wash hands

    Accidental or deliberate ingestion                                                   Obtain medical attention immediately; transport
    may cause vomiting, abdominal pain,                                                  to hospital urgently; induce vomiting;
    and diarrhoea, followed by burns in                                                  do not delay
    mouth and throat; kidney damage and
    shock may occur, but no lung damage


    SPILLAGE                                STORAGE                                      FIRE AND EXPLOSION

    Absorb spillage with lime, damp         Store in locked, well-ventilated             Non-flammable and non-explosive
    sawdust, sand, or earth; sweep up,      storeroom, away from foodstuffs 
    place in closed container, and          and animal feed, children,
    dispose of safely; avoid                and unauthorized personnel
    contamination of personnel,
    ponds, and waterways



    Burn in high-temperature                National Occupational Exposure               UN No. 2782, 3015, 3016
    incinerator with effluent scrubbing;    Limit:
    alternatively, treat with 5%
    caustic soda as a hydrolysing agent;    National Poison Control Centre:
    comply with local regulations
                                            Local trade names:



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

    7.1  Previous Evaluations by International Bodies

    The Joint FAO/WHO Meeting on Pesticide Residues (JMPR) reviewed
    residues and toxicity data on diquat in 1970, 1972, 1976, 1977, and
    1978.  In 1977, it estimated that the acceptable daily intake (ADI)
    for man was 0-0.008 mg/kg body weight, expressed as diquat ion.

    The JMPR has also recommended maximum residue levels (tolerances) for
    diquat in food commodities of plant and animal origin.

    A data sheet on diquat has been prepared by WHO/FAO (1979) in a series
    of "Data sheets on chemical pesticides" (No. 44).  Technical diquat is
    qualified as moderately hazardous in normal use (WHO, 1990).

    7.2  Exposure Limit Values

    Some exposure limit values are given in the table on pages 26-27.

    7.3  Specific Restrictions

    In some countries, diquat is only registered for certain specified
    applications, or for use under certain specified conditions, e.g., in
    the Federal Republic of Germany, Sweden, the United Kingdom, the USA,
    and the USSR.  For example, in the United Kingdom and the USA, the use
    of the 20% liquid is restricted to bona fide certified professionals.

    In the Federal Republic of Germany, diquat may not be handled by
    adolescents and pregnant or nursing women.



    Medium      Specification       Country/            Exposure limit descriptiona                  Value                Effective
                                    organization                                                                          date

    AIR         Work-place          Australia           Threshold limit value (TLV)
                                                        - Time-weighted average (TWA)                0.5 mg/m3            1983
                                                        - Short-term exposure limit (STEL)           1 mg/m3

                                    Belgium             Tolerable limit value (TLV)
                                                        - Time-weighted average (TWA)                0.5 mg/m3            1988
                                                        - Short-term exposure level (STEL)           1 mg/m3

                                    Bulgaria            Maximum permissible concentration
                                                        - Time-weighted average (TWA)                0.5 mg/m3            1987

                                    Finland             Maximum permissible concentration
                                                        - Time-weighted average (TWA)                0.5 mg/m3            1988
                                                        - Short-term exposure limit (STEL)           1.5 mg/m3

                                    Netherlands         Maximum permissible limit
                                                        - Time-weighted average (TWA)                0.5 mg/m3            1986

                                    Switzerland         Maximum work-site concentration (MAK)
                                                        - Time-weighted average (TWA)                0.5 mg/m3            1987

                                    United Kingdom      Recommended limit (RECL)
                                                        - 8-h time-weighted average (TWA)            0.5 mg/m3            1987
                                                        - Short-term exposure level (STEL)           1 mg/m3
                                                          (10-min time-weighted average)

                                    USA (OSHA)          Permissible exposure limit (PEL)
                                                        - Time-weighted average (TWA)                0.5 mg/m3            1989

                                    USA (ACGIH)         Threshold limit value (TLV)
                                                        - Time-weighted average (TWA)                0.5 mg/m3            1987


    Medium      Specification       Country/            Exposure limit descriptiona                  Value                Effective
                                    organization                                                                          date

                                    USSR                Preliminary safety level (vapour
                                                        and aerosol)
                                                        - Ceiling value (CLV)                        0.2 mg/m3            1978

    FOOD        Intake from         FAO/WHO             Acceptable daily intake (ADI)                0-0.008 mg/kg        1977
                                                        (diquat ion)                                 body weight

    FOOD        General             FAO/WHO             Maximum residue limit (MRL)                  0.01-5 mg/kg         1982
                                                        for specified products
                                                        (diquat ion)

                                    European            Maximum levels in fruit and
                                    Community           vegetables (expressed as diquat
                                                        - vegetables                                 0.1 mg/kg            1989
                                                        - other products                             0.05 mg/kg           1989

    a TWA=time-weighted average over one working day (usually 8h).

    7.4  Labelling, Packaging, and Transport

    The United Nations Committee of Experts on the Transportation of
    Dangerous Goods classifies diquat (at liquid concentrations of
    45-100%) in:

         -    Hazard Class 6.1: poisonous substance;

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

    The label should be as follows:

    FIGURE 1

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

    FIGURE 2

    The label must read:

          Toxic in contact with skin and if swallowed; irritating to eyes,
          respiratory system and skin.

    The European Economic Community legislation on labelling of pesticide
    preparations classifies diquat in Class 2B, for the purpose of
    determining the label for preparations containing diquat and other
    active ingredients.

    The chemical name must be stated on the label.

    The FAO specifications for plant protection products containing diquat
    specify the composition and purity of its formulations and the methods
    for checking this.  They also specify the quality of the containers.

    7.5  Waste Disposal

    In the USA, diquat is regarded as a hazardous waste and permits are
    required for its discharge from any point source into USA national
    waters.  This requirement contains detailed instructions.


    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

    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 Agrochimiques.

    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. Lyon, International Agency
    for Research on Cancer.

    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 1986. 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 WHO/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.

    US 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  (1984)  Environmental Health Criteria 39: Paraquat and diquat.
    Geneva, World Health Organization.

    WHO  (1990)  The WHO recommended classification of pesticides by
     hazard and guidelines to classification 1990/91. Geneva, World
    Health Organization (unpublished document WHO/PCS/90.1).

    WHO/FAO  (1979)  Data sheets on pesticides, No. 44: Diquat, Geneva,
    World Health Organization (unpublished WHO documents).

    WORTHING, C.R. & WALKER, S.B. (1987)   The  pesticide  manual. 8th
    ed. Lavenham, Lavenham Press Limited, British Crop Protection Council.


    See Also:
       Toxicological Abbreviations
       Diquat (PIM 580F, French)
       Diquat (AGP:1970/M/12/1)
       Diquat (WHO Pesticide Residues Series 2)
       Diquat (Pesticide residues in food: 1976 evaluations)
       Diquat (Pesticide residues in food: 1977 evaluations)
       Diquat (Pesticide residues in food: 1978 evaluations)
       Diquat (Pesticide residues in food: 1993 evaluations Part II Toxicology)