IPCS INCHEM Home

    IPCS INTERNATIONAL PROGRAMME ON CHEMICAL SAFETY
    Health and Safety Guide No. 51

    PARAQUAT
    HEALTH AND SAFETY GUIDE






    UNITED NATIONS ENVIRONMENT PROGRAMME

    INTERNATIONAL LABOUR ORGANISATION

    WORLD HEALTH ORGANIZATION




    WORLD HEALTH ORGANIZATION, GENEVA 1991

    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

    Paraquat : health and safety guide.

    (Health and safety guide ; no. 51)

    1. Paraquat - standards  I. Series

    ISBN 92 4 151051 X          (NLM Classification: WA 240)
    ISSN 0259-7268

    (c) World Health Organization 1991

    Publications of the World Health Organization enjoy copyright
    protection in accordance with the provisions of Protocol 2 of the
    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
    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. Uses

    2. SUMMARY AND EVALUATION
         2.1. Environmental distribution and transformation
         2.2. Kinetics and metabolism
         2.3. Effects on experimental animals
         2.4. Effects on human beings
              2.4.1. Occupational exposure
              2.4.2. Poisoning by paraquat
         2.5. Effects on the environment

    3. CONCLUSIONS AND RECOMMENDATIONS
         3.1. Conclusions
              3.1.1. General population exposure
              3.1.2. Occupational exposure
              3.1.3. General
         3.2. Recommendations
              3.2.1. General
              3.2.2. Prevention and treatment

    4. HUMAN HEALTH HAZARDS, PREVENTION AND PROTECTION, EMERGENCY ACTION
         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
                     when handling concentrated paraquat
              4.1.2. Health surveillance advice
              4.1.3. Personal protection and hygienic measures
                     when handling concentrated paraquat
         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

    5. HAZARDS FOR THE ENVIRONMENT AND THEIR PREVENTION

    6. SUMMARY OF CHEMICAL SAFETY INFORMATION

    7. CURRENT REGULATIONS, GUIDELINES, AND STANDARDS
         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

    BIBLIOGRAPHY
    

    INTRODUCTION

    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
    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                   paraquat

    Molecular formula:                 C12H14N2Cl2
                                  1,1'-dimethyl-4,4'-
                                  bipyridyliumdichloride (paraquat
                                  dichloride)

                                  C12H14N2(CH3SO4)2

                                  1,1'-dimethyl-4,4'-bipyridylium
                                  dimethylsulfate sulfate (paraquat
                                  dimethylsulfate)

    Chemical structure  of 1,1'-dimethyl-4,4'-bipyridylium-dichloride:

    CHEMICAL STRUCTURE 1

    CAS chemical name:            1,1'-dimethyl-4,4'-bipyridylium (9 Cl)

    Trade names:                  Gramoxone; Dextrone X; Esgram; and
                                  others

    CAS registry number:          4685-14-7  (ion)
                                  1910-42-5  (dichloride)
                                  4032-26-2  (diiodide)
                                  2074-50-2  (dimethylsulfate)

    RTECS registry number:        DW1960000  (ion)
                                  DW2275000  (dichloride)
                                  DW2280000  (diiodide)
                                  DW2010000  (dimethylsulfate)

    Relative molecular mass:      186.2 (ion)

    1.2  Physical and Chemical Properties

    Pure paraquat salts are white and the technical products, yellow. 
    They are crystalline, odourless, hygroscopic powders.

    Some of the physical properties of paraquat dichloride, the salt most
    used for herbicide formulations, are listed in the Summary of Chemical
    Safety Information (section 6).

    Paraquat is slightly soluble in alcohol and practically insoluble in
    organic solvents.

    Paraquat is non-explosive and non-flammable in aqueous formulations. 
    It is corrosive to metals and incompatible with alkylarylsulfonate
    wetting agents.  It is stable in acid or neutral solutions, but is
    readily hydrolysed by alkali.

    1.3  Analytical Methods

    Product analysis and determination of residues can be carried out
    colorimetrically after reduction; impurities can be determined by
    gas-liquid chromatography (GLC).

    1.4  Uses

    Paraquat is a total contact herbicide, applied around trees in
    orchards and between crop rows, to control broad-leaved and grassy
    weeds.  It kills all green tissues, but does not harm mature bark. 
    Paraquat is used for plantation crops (banana, cocoa-palm, coffee,
    oil-palm, rubber, etc.) and for citrus fruits, apples, plums, vines,
    and tea.  On certain crops (potato, pineapple, sugar-cane, sunflower),
    it is used as a desiccant; it is also used as a cotton defoliant.

    Uncropped land on industrial sites, railways, roadsides, etc. can be
    cleared of weeds by applying high concentrations of paraquat.

    2.  SUMMARY AND EVALUATION

    2.1  Environmental Distribution and Transformation

    Photochemical degradation takes place when paraquat-treated plants are
    exposed to normal daylight and continues after the plants die.  The
    products formed have been identified and found to be of a lower order
    of toxicity than the parent compounds.  Ultraviolet degradation on
    soil surfaces also occurs, but photodecomposition of paraquat in the
    soil is insignificant in comparison with adsorption on clay particles. 
    Microorganisms can degrade free paraquat rapidly, but chemical
    degradation of adsorbed paraquat is relatively slow.

    (a)   Soil

    Paraquat is rapidly and tightly bound to clay materials in soils.  
    The adsorbed paraquat is biologically inactive and, in normal
    agricultural use, no harmful metabolic or breakdown products are to be
    expected.  In multiple spray trials, paraquat residues in soil varied
    from 22 to 58 mg/kg.  Under field conditions, the residual paraquat is
    slowly redistributed.  Long-term field studies have shown degradation
    rates of 5-10% per annum, which is usually sufficient to prevent
    saturation of the deactivation capacity of the soil.  Thus, no adverse
    effects are expected on the soil microflora and other soil organisms,
    or on crop growth, at normal and high rates of application.

    Paraquat is similarly strongly bound to humus and other organic
    material in soils containing little clay.  However, in sandy soils
    with a low organic content, paraquat may be more readily released into
    soil water and be more bioavailable to organisms.  While it is still
    unlikely to pose any hazard to the organisms in the soil, its
    bioavailability to higher animals feeding on soil biota may be
    increased.

    (b)   Water

    When paraquat was applied as an aquatic herbicide, at a normal
    application rate of 1 mg/litre, the concentration was found to
    decrease to about one half of the initial level within 36 h and to
    below 0.01 mg/litre in less than 2 weeks.  Phytotoxic damage to crops
    irrigated with treated water is unlikely to occur, if an interval of
    10days is observed between treatment of the water and its use, because
    of the rapid decrease of paraquat residues in the water.

    Normal application of paraquat for aquatic weed control is not harmful
    for aquatic organisms.  However, care should be taken in the
    application of paraquat to water containing heavy weed growth, since
    oxygen consumed by subsequent weed decay may decrease oxygen levels in
    the water to an extent that is dangerous for fish or other aquatic
    organisms.

    (c)   Air

    Paraquat is not volatile; thus, inhalation of paraquat vapour is not a
    problem. The amount of respirable airborne paraquat was found to be
    negligible under normal conditions of use.

    The amount of paraquat present in airborne dust was found to range
    from 0.0004 to 0.001 mg/m3.  The paraquat was so strongly bound to
    the dust particles that it did not exert any toxicological effect on
    rats that were exposed via inhalation.

    2.2  Kinetics and Metabolism

    Although toxic amounts of paraquat may be absorbed after oral
    ingestion, the greater part of ingested paraquat is eliminated
    unchanged in the faeces.  Paraquat is poorly absorbed through normal
    human skin, but the extent of absorption may increase significantly in
    cases of severe skin damage.  The toxic effects of paraquat are
    largely the result of a metabolically catalysed, single-electron,
    reduction-oxidation reaction, resulting in depletion of cellular NADPH
    and the generation of potentially toxic forms of oxygen, such as the
    superoxide radical.

    Absorbed paraquat is distributed via the bloodstream to practically
    all organs and tissues of the body, but storage is not prolonged in
    any tissue.  The lung selectively accumulates paraquat from the plasma
    by an energy-dependent process.  Consequently, this organ contains
    higher concentrations than other tissues.  Since the removal of
    absorbed paraquat occurs mainly via the kidneys, an early onset of
    renal failure following uptake of toxic doses will have a marked
    effect on paraquat elimination and distribution, and on its
    accumulation in the lungs.

    2.3  Effects on Experimental Animals

    Paraquat induces a characteristic dose-related lung injury in the rat,
    mouse, dog, and monkey, but not in the rabbit, guinea-pig, or hamster. 
    Pulmonary toxicity is characterized by the initial development of
    pulmonary oedema and damage to the alveolar epithelium, which may
    progress to fibrosis.  Exposure to high doses of paraquat may also
    cause less severe toxic effects in other organs, primarily the liver
    and kidney.  Minor toxic effects have been noted in the nervous,
    cardiovascular, blood, adrenal, and male reproductive systems, but
    only at high doses.  Toxic effects have not been reported at low doses
    of paraquat.

    Paraquat has not been found to be teratogenic or carcinogenic in
    long-term studies on rats and mice. The results of in vitro
    mutagenicity studies were  inconclusive, but generally suggested a
    weak potential activity; the results of  in vivo studies were
    negative.

    Concentrated solutions of paraquat have been found to irritate both
    the skin and the eyes.

    The FAO/WHO (1986) determined no-observed-effect levels of paraquat
    dichloride of: 17 and 52 mg/kg diet, equivalent to 1.9 and 5.9 mg/kg
    body weight, per day, for male and female mice, respectively; 30 mg/kg
    diet, equivalent to 1.1 and 1.2 mg/kg body weight, per day, for male
    and female rats, respectively; and 20 mg/kg diet, equivalent to 0.62
    and 0.66 mg/kg body weight, per day, for male and female dogs,
    respectively.

    2.4  Effects on Human Beings

    2.4.1  Occupational exposure

    There are several studies on paraquat exposure during normal
    agricultural use.  The main route of occupational exposure of
    agricultural workers is via the skin.  The spray aerosol and dust
    particles are relatively large and are mostly deposited in the upper
    respiratory tract.  Paraquat aerosol concentrations (total airborne)
    ranged up to 0.55 mg/m3 in the work situation, depending on the
    method of spraying.  Under normal conditions of use, the amount of
    respirable airborne paraquat was found to be insignificant.

    The potential dermal exposure of field workers is closely related to
    working conditions.  Workers on tractors were found to have a paraquat
    exposure of 12-168 mg/h, while spraying between tomatoes or citrus. 
    In other studies, field workers were dermally exposed to paraquat at
    approximately 0.40 mg/h, and individuals spraying the garden, to
    0.29 mg/h.  In all trials, respiratory exposure was not higher than
    0.01 mg/h.  Urine concentrations in occupationally-exposed workers
    were often lower than 0.01 mg/litre, but concentrations of up to
    0.73 mg/litre were determined, after improper paraquat application in
    tropical agriculture use.

    2.4.2  Poisoning by paraquat

    A large number of cases of poisoning have been reported, following the
    drinking of concentrated paraquat, overwhelmingly with suicidal
    intent.  A few unusual cases, in which the liquid concentrate was used
    improperly to treat body lice, have also been reported.

    The possibility of patient recovery clearly depends on the dose of
    paraquat taken and the time interval between ingestion and the
    commencement of emergency treatment.  Speed is imperative, and it
    should be noted that emergency treatment can start before the patient
    arrives at hospital.

    In less severe cases, without lung damage, recovery has always been
    complete.

    (a)   Suicidal ingestion

    The majority of paraquat poisonings are due to swallowing liquid
    concentrates. The response to treatment is disappointing and the
    mortality rate is high.  Ingestion of granular paraquat is less common
    and usually causes milder poisoning, though fatalities have occurred. 

    (b)   Accidental poisoning

    Poisoning by accidental swallowing is less common than intentional
    swallowing and is usually the result of storing liquid concentrates in
    inappropriate containers, particularly beer or soft drink bottles. 
    The mortality rate is lower than in suicidal cases.  Childhood
    poisoning is usually accidental.  In some countries, legislation on
    the control of the sale of liquid concentrates has reduced accidental
    ingestion.

    A small number of fatal cases of accidental paraquat poisoning via the
    skin have been reported following the intentional application of
    liquid concentrates (200 g/litre) to kill body lice.

    (c)   Occupational poisoning

    A number of cases of severe poisoning following inappropriate
    behaviour have occurred.  Fatal poisoning through dermal soaking with
    insufficiently diluted paraquat, associated with severe skin lesions,
    has been reported.  This may result from continuous contact with
    paraquat-soaked clothing, e.g., as a result of using a leaking
    sprayer. 

    Splashes of liquid concentrate may lead to severe ocular and skin
    damage.  Spraying with inadequately diluted paraquat (e.g., with
    ultra-low-volume application) may result in similar problems.

    Local skin effects (contact, irritative, or photoallergic dermatitis),
    delayed wound healing, and nail damage have been observed among
    formulation workers and among individuals handling the herbicide
    improperly.  Blepharitis and epistaxis may result through the delayed
    irritative action of paraquat.  Such incidents illustrate the need for
    strict personal hygiene and rigorous adherence to safe handling
    procedures (see section 4).

    2.5  Effects on the Environment

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

    On reaching the soil, paraquat becomes rapidly and strongly adsorbed
    on the clay minerals present.  This process inactivates the herbicidal
    activity of the compound.  Strongly-bound paraquat does not have any
    adverse effects on soil microfauna or soil microbial processes.

    Paraquat residues disappear rapidly from water by adsorption on
    aquatic weeds and by strong adsorption on the bottom mud.  The
    toxicity of paraquat for fish is low, and the compound is not
    cumulative.  Normal applications of paraquat for aquatic weed control
    are not harmful for aquatic organisms.  However, when applying
    paraquat to water containing heavy weed growth, care should be taken
    to treat only a part of the growth, since oxygen consumption by
    subsequent weed decay may result in a reduction in dissolved oxygen
    levels to an extent that may be dangerous for fish.

    Treated water should not be used for overhead irrigation for 10 days
    following treatment.

    Normal use of paraquat has been shown not to have any harmful effects
    on birds.

    Paraquat is not subject to bioconcentration and has not been found to
    accumulate in food chains.

    3.  CONCLUSIONS AND RECOMMENDATIONS

    3.1  Conclusions

    3.1.1  General population exposure

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

    This likely lack of hazard with normal usage of dilute paraquat
    contrasts strongly with the potentially serious hazard that may result
    from handling concentrated paraquat.

    Accidental paraquat poisoning usually results from swallowing liquid
    concentrate that has been decanted into unlabelled bottles or other
    containers, and stored inappropriately.

    The number of suicides by means of paraquat is of great concern, but
    the total number of such suicides is unknown.  The reasons for suicide
    may be manifold and complex, and paraquat is only one among many means
    towards this goal. However, because of the prolonged and painful way
    of dying from paraquat poisoning, every effort should be made to
    diminish its attractiveness and availability for this purpose.

    3.2.1  Occupational exposure

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

    Spray concentrations should not exceed 5 g paraquat ion/litre, in
    order to avoid skin damage and absorption of the herbicide through the
    skin.  Hand-held, ultra-low-volume application should be discouraged.

    3.1.3  Environment

    Paraquat in soil binds rapidly and strongly to clay particles, and
    residual phytotoxicity from freely-available paraquat is unlikely. 
    The toxicity of paraquat for birds has been shown to be of little
    significance.  Under normal conditions of use, paraquat toxicity for
    aquatic animal life is low, though the resulting depletion of
    water-oxygen, because of weed decay, may pose a problem.  Paraquat
    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 into,
    or rebottling of the product in, improperly labelled containers.

    Further research should be carried out, to achieve a safer commercial
    product and a reduced incidence of fatalities.

    National Registers of cases of poisoning should be maintained for all
    classes of chemicals, including paraquat.  The information obtained
    should be made available to international bodies, such as the World
    Health Organization.

    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 paraquat) 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 paraquat 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.  HUMAN HEALTH HAZARDS, PREVENTION AND PROTECTION, EMERGENCY ACTION

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

    Paraquat is highly toxic and often fatal, if swallowed. Contact with
    liquid products can cause severe damage to the skin or eyes.  Utmost
    care must be taken to avoid exposure during handling operations and
    application in the field.  In applications where inhalation exposure
    to aerosols containing paraquat is likely, proper respiratory
    protective equipment should be used.

    The human health hazards, together with 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 paraquat 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, the
    emergency treatment may need to be given by a paramedical person,
    e.g., a nurse or a medical assistant, without any delay.  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.

    Where 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
    paraquat 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
    paraquat 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 paraquat may
    give guidelines for the required intensity of treatment or likely
    prognosis.  Determination of paraquat levels in stomach washings,
    serum, and urine is useful for the management of poisoning.  The
    urinary levels decline rapidly during the 24 h following exposure and
    may remain low for some weeks.

    Many other therapies including corticosteroids, immunosuppressive
    treatment, vitamins, beta-blocking and alkylating agents,
    alpha-tocopherol, superoxide dismutase and/or glutathione peroxides
    proved to be of no significant importance in human paraquat poisoning. 
    The administration of oxygen should be avoided, unless vital for the
    patient's comfort.

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

    Despite such an array of both simple and sophisticated measures, the
    response to therapy in paraquat poisoning is disappointing and the
    mortality rate remains high.

    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 paraquat  at
    potentially hazardous levels.  Attention should be given to all normal
    parameters of overall health status, with particular attention to the
    state of the skin and of pulmonary function.

    4.1.3  Personal protection and hygienic measures

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

    *    Wear a face-shield when handling and applying the diluted
         formulation.

    *    Immediately remove heavily contaminated clothing and wash
         underlying skin.



    *    Wash clothes before re-use.

    *    Do not eat, drink, or smoke, when using paraquat.

    *    Wash splashes 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. 

    *    Paraquat should not be sprayed with inadequate dilution, e.g., by
         hand-held, ultra-low-volume application.

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

    4.2  Explosion and Fire Hazards

    Paraquat 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 feed.

    4.4  Transport

    Ensure that containers are sound and that labels are securely fixed
    and undamaged before dispatch.  Comply with local transport
    regulations.

    Do not load together with foodstuffs or animal feed.

     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; sweep up and place in a secure
    container for subsequent safe disposal.

    4.5  Spillage and Disposal

    4.5.1  Spillage

    Avoid exposure by the use of appropriate protective clothing and
    face-shield.

    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 paraquat should be burnt in a proper high temperature
    incinerator with effluent gas 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.

    Paraquat 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.

    5.  HAZARDS FOR THE ENVIRONMENT AND THEIR PREVENTION

    Paraquat is highly toxic for aquatic and terrestrial vegetation. 
    Under normal conditions of use, the toxicity of paraquat for aquatic
    animal life is low, though resulting depletion of water-oxygen,
    because of weed decay, may pose a problem.

    Do not contaminate ponds, waterways, or ditches with the product or
    used containers.

    6.  SUMMARY OF CHEMICAL SAFETY INFORMATION

     This summary should be easily available to all health workers
     concerned with, and users of, paraquat. It should be displayed at, or
     near, entrances to areas where there is potential exposure to
     paraquat, 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.


        PARAQUAT

    (C12H14N2Cl2) 1,1'-dimethyl-4,4'-bipyridylium dichloride (paraquat dichloride)

    CAS registry no. 1910-42-5

    RTECS registry no. DW2275000
                                                                                                                                         

    PHYSICAL PROPERTIES                                                   OTHER CHARACTERISTICS
                                                                                                                                         

    Physical state                     crystalline powder                 Total contact herbicide, used to control broad-leaved 
    Colour                             yellow                             and grassy weeds; corrosive to metals, and incompatible
    Odour                              odourless                          with alkylarylsulfonate wetting agents; stable in acid 
    Relative molecular mass            186.2 (ion)                        or neutral solutions, but readily hydrolysed by alkali; 
    Specific gravity (20C)            1.240-1.260                        slightly soluble in alcohol and practically insoluble in
    Melting point (C)                 175-180                            organic solvents
    Boiling point (C)                 approximately 300
                                       with decomposition
    Solubility in water (20C)         700 g/litre
    pH of liquid formulation           6.5-7.5
    Vapour pressure                    not measurable

                                                                                                                                         

    HAZARDS/SYMPTOMS                        PREVENTION AND PROTECTION                    FIRST AID
                                                                                                                                         

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

    EYES: Severe irritant                   Wear face-shield; 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 working hours; wash
                                            hands

    Accidental or deliberate ingestion                                                   Obtain medical attention immediately;
    may cause vomiting, abdominal                                                        transport to hospital urgently; induce vomiting;
    discomfort, and soreness of mouth                                                    do not delay
    and throat; signs of liver and kidney
    damage may appear in 1-3 days;
    signs of lung damage may gradually 
    develop after a few days; paraquat
    can kill

                                                                                                                                         

    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
    place in closed container, and          foodstuffs and animal feed, 
    dispose of safely; avoid                children, and unauthorized
    contamination of personnel, ponds,      personnel
    and waterways

                                                                                                                                         

    WASTE DISPOSAL
                                                                                                                                         

    Burn in high-temperature                National Occupational Exposure               UN No. 2781, 2782, 3015, 3016
    incinerator with effluent scrubbing;    Limit:
    alternatively treat with 5% caustic 
    soda as a hydrolysing agent; comply     National Poison Control Centre:
    comply with local regulations
                                            Local trade names:

                                                                                                                                         
    
    7.  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.  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 FAO/WHO Joint Meeting on Pesticide Residues (JMPR) has reviewed
    residues and toxicity data on paraquat on several occasions (1970,
    1972, 1976, 1978, 1981, 1982, 1985, and 1986).  In 1986, it estimated
    the acceptable daily intake (ADI) for man to be 0-0.006 mg paraquat
    dichloride/kg body weight (or 0.004 mg paraquat ion/kg body weight).

    The same JMPR recommended maximum residue levels (tolerances) for
    paraquat in food commodities of plant and animal origin.

    The WHO/FAO (1979), in its series of "Data sheets on chemical
    pesticides", issued one on paraquat (No. 4).  It classified technical
    paraquat as moderately hazardous in normal use (WHO, 1990).

    7.2  Exposure Limit Values

    Some exposure limit values are given in the table on pages 30-32.

    7.3  Specific Restrictions

    Paraquat is prohibited for use in, amongst other countries, Finland
    and Sweden.

    In some other countries, e.g., the Federal Republic of Germany,
    Hungary, the United Kingdom, and the USA, the use of paraquat is only
    registered for certain specified applications or for use under certain
    specified conditions. For instance, 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, paraquat may not
    be handled by adolescents or pregnant or nursing women.


        EXPOSURE LIMIT VALUES

                                                                                                                                         

    Medium      Specification       Country/            Exposure limit descriptiona                  Value                Effective
                                    organization                                                                          date
                                                                                                                                         

    AIR         Work-place          Argentina           Maximum permissible concentrationb
                                                        - Time-weighted average (TWA)                0.1 mg/m3            1979

                                    Australia           Threshold limit value (TLV)b
                                                        - Time-weighted average (TWA)                0.5 mg/m3            1983
                                                          of respirable dust (provisional)

                                    Belgium             Tolerable limit value (TLV)
                                                        - Time-weighted average (TWA)                0.1 mg/m3            1988

                                    Bulgaria            Maximum permissible concentrationb
                                                        - Time-weighted average (TWA)                0.1 mg/m3            1987

                                    Germany, Federal    Maximum work-site concentration (MAK)b
                                    Republic of         - Time-weighted average (TWA)                0.1 mg/m3            1988
                                                        - Short-term exposure level (STEL)           0.2 mg/m3
                                                          (5min) (8  per shift)
                                                          (ceiling value)

                                    Hungary             Maximum permissible concentration
                                                        - Time-weighted average (TWA)                0.02 mg/m3           1978
                                                        - short-term exposure level (STEL)           0.02 mg/m3
                                                          (30 min)

                                    Netherlands         Maximum permissible concentration
                                                        - Time-weighted average (TWA)                0.1 mg/m3            1986

                                    Switzerland         Maximum work-site concentration (MAK)b
                                                        - Time-weighted average (TWA)                0.1 mg/m3            1987

                                                                                                                                         

    Medium      Specification       Country/            Exposure limit descriptiona                  Value                Effective
                                    organization                                                                          date
                                                                                                                                         

    AIR         Work-place          United Kingdom      Recommended limit
                                                        - 8-h Time-weighted average (TWA)            0.1 mg/m3            1987
                                                          (of respirable dust)

                                    USA (OSHA)          Permissible exposure limit (PEL)b
                                                        - Time-weighted average (TWA)                0.1 mg/m3            1989
                                                          (respirable dust)

                                    USA (ACGIH)         Threshold limit value (TLV)
                                                        - Time-weighted average (TWA)                0.1 mg/m3            1987
                                                          (respirable sizes)

    FOOD        Intake from         FAO/WHO             Acceptable daily intake (ADI)                0-0.004 mg/kg        1986
                                                        (paraquat ion)                               body weight

    FOOD        General             FAO/WHO             Maximum residue limit (MRL)                  0.01-10 mg/kg        1983
                                                        for specified products

                                    European            Maximum levels in and on fruit
                                    Community           and vegetables                               0.05 mg/kg           1989
                                                        (expressed as paraquat cation)

                                                                                                                                         

    a TWA=time-weighted average over one working day (usually 8h).
    b Skin absorption.
        7.4  Labelling, Packaging, and Transport

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

    *    Hazard Class 6.1: poisonous substance.

    *    Packing Group II: substances and preparations presenting a
         serious risk of poisoning, when the active ingredient is within
         the range of 40-100%.

    *    Packing Group III: substance presenting a relatively low risk of
         poisoning in transport, when the active ingredient is in the
         range of 8-40%.

    The labels should be as follows:

    FIGURE 1

    FIGURE 2

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

    FIGURE 3

    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 the labelling of
    pesticide preparations classifies paraquat in Class 1A, for the
    purpose of determining the label for preparations containing paraquat
    and other active ingredients.

    The chemical name must be stated on the label.

    The FAO specifications for plant protection products containing
    paraquat 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, paraquat 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.

    BIBLIOGRAPHY

    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
    Nations.

    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 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. 4: Paraquat. 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
       Paraquat (PIM 399)
       Paraquat (JMPR Evaluations 2003 Part II Toxicological)
       Paraquat (AGP:1970/M/12/1)
       Paraquat (WHO Pesticide Residues Series 2)
       Paraquat (Pesticide residues in food: 1976 evaluations)
       Paraquat (Pesticide residues in food: 1978 evaluations)
       Paraquat (Pesticide residues in food: 1981 evaluations)
       Paraquat (Pesticide residues in food: 1982 evaluations)
       Paraquat (Pesticide residues in food: 1986 evaluations Part II Toxicology)