Health and Safety Guide No. 18






    This is a companion volume to Environmental Health Criteria 79:

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

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

    ISBN 92 4 154337 X
    ISSN 0259-7268

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

    (c) World Health Organization 1988

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

    The designations employed and the presentation of the material in this
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    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. Production and uses


         2.1. Evaluation of effects on animals and human health
         2.2. Evaluation of effects on the environment


         3.1. Conclusions
         3.2. Recommendations


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




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


    ANNEX I.   Treatment of organophosphate insecticide poisoning in man


    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 chemical's, or physical or biological
    agents. They also provide guidelines for setting exposure limits.

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

    The target readership includes occupational health services, those in
    ministries, governmental agencies, industry, and trade unions, who are
    involved in the safe use of chemicals and the avoidance of
    environmental health hazards and those wanting more information on
    this topic. An attempt has been made to use only terms that will be
    familiar to the intended user. However, it is inevitable that sections
    1 and 2 contain 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:             Dichlorvos

     Primary constiment

    Chemical structure:      CHEMICAL STRUCTURE 1

    Chemical formula:        C4H7Cl2O4P

    Relative molecular
    mass:                    221

    Chemical name:           2,2-dichloroethenyl dimethylphosphate
                             2,2-dichlorovinyl dimethylphosphate

    Common synonyms:         Bayer-19149, DDVF, DDVP,
                             ENT-20738, OMS-14, SD 1750, C-177

    CAS registry             62-73-7

     Technical product

    Common trade             Dedevap, Nogos, Nuvan, Phosvit,
    names:                   Vapona a

    Purity:                  Not less than 97%

    Impurities:              Depends on the manufacturing process


    a  The Shell trademark Vapona was formerly used exclusively for
       dichlorvos and dichlorvos-containing formulations. Now, this
       trademark is used more widely to include formulations containing
       other active ingredients.

    Additives:               On standing, in the presence of traces of
                             moisture, dichlorvos breaks down with the
                             formation of acidic products that catalyse
                             further decomposition of the compound. In the
                             past, 2-4% epichlorohydrin was added to
                             stabilize the technical grade product. Other
                             stabilizers may now be used in some products,
                             but improved technology and purity has
                             largely eliminated the need for them.

    1.2  Physical and Chemical Properties

    Technical dichlorvos is a colourless to amber liquid with a mild
    chemical odour. It is hydrolysed by water at a rate of 3% per day at
    room temperature. It is corrosive to iron and mild steel.

    For some physical properties see the International Chemical Safety

    1.3  Analytical Methods

    Dichlorvos residues can be determined by gas liquid chromatography.
    The same method can be used for product analysis; alternative methods
    include infrared spectrometry, or reaction with an excess of iodine,
    which is estimated by titration.

    1.4  Production and Uses

    Dichlorvos, an organophosphate, is a direct-acting cholinesterase
    (ChE) inhibitor. Since 1961, it has been commercially manufactured and
    used throughout the world as a contact and stomach insecticide.

    At present, the global production of dichlorvos is of the order of
    4 million kg per year. It is used to protect stored products, to
    protect crops (mainly in greenhouses), to control internal and external
    parasites in livestock (granules of impregnated resin), and to control
    insects in houses, buildings, and outdoor areas (as aerosols or liquid
    sprays or as impregnated cellulose, ceramic, or resin strips).


    2.1  Evaluation of Effects on Animals and Human Health

    Dichlorvos is readily absorbed by the body of mammals via all routes
    of exposure, and readily metabolized in the liver. Within 1 h of oral
    administration, dichlorvos is found in the liver, kidneys, and other
    organs of experimental animals. The substance is rapidly eliminated
    via the kidneys, with a half-life of 14 min.

    The metabolism of dichlorvos in various species, including man,
    follows similar pathways and differences between species relate only
    to the rate of metabolism, but this is always rapid.

    Dichlorvos is moderately to highly toxic in mammals (oral LD50 for
    the rat is 30-110 mg/kg body weight). The classification of dichlorvos
    by WHO (1986b) is based on an oral LD50 for the rat of 56 mg/kg body
    weight. Signs of intoxication usually occur shortly after exposure and
    are typical of an organophosphorus pesticide. A sensitive criterion of
    exposure is inhibition of cholinesterase (ChE) activity. In short-term
    toxicity studies on mammals, it has been shown that ChE activity is
    not decreased at oral doses below about 0.5 mg/kg body weight. In
    long-term oral studies on rats at dose levels of 2.5 mg/kg body weight
    or more, hepatocellular fatty vacuolization was seen. A dose level of
    0.25 mg/kg body weight did not induce ChE inhibition or any other

    The results of reproduction and teratogenicity studies, over a wide
    range of dose levels (6.25-500 mg/kg body weight), were negative.
    Dichlorvos showed alkylating properties in  in vitro studies, but not
    in  in vivo studies. The results of many  in vitro mutagenicity
    studies with bacteria and yeast were positive, while those of
     in vivo studies were mainly negative.

    On the basis of available mutagenicity studies, it is unlikely that
    dichlorvos constitutes a mutagenic hazard for man.

    Negative results were obtained in carcinogenicity studies on mice and
    rats administered dichlorvos via the oral route (dose levels up to
    234 mg/kg diet). Two recent carcinogenicity studies were carried out
    on mice and rats in which dichlorvos was administered by intubation at
    dose levels of between 10 and 40 mg/kg body weight (mice) and 4 and
    8 mg/kg body weight (rats) for up to 2 years. Only preliminary
    information is available. The evidence for carcinogenicity in these

    new studies is difficult to interpret at this time. Only when complete
    and final reports become available will it be possible to draw more
    definite conclusions.a

    The results of studies on hens have neither established nor refuted
    the suspicion of delayed neurotoxicity arising from exposure to
    dichlorvos. Furthermore, there have been two clinical reports of four
    patients suffering from severe poisoning after oral ingestion of
    dichlorvos who survived following treatment and who then displayed
    neurotoxic effects. Thus, the possibility of delayed neurotoxicity in
    man cannot be entirely discounted, but it is likely to occur only
    following excessive oral doses.

    Human volunteers given single or repeated oral doses of 2 mg
    dichlorvos/kg body weight or more showed significant inhibition of
    erythrocyte-ChE activity. No inhibition was found at 1 mg/kg body

    Application of dichlorvos to crops and animals results in residues
    that rapidly disappear through volatilization and hydrolysis. In
    general, residues of dichlorvos and its break-down product,
    dichloroacetaldehyde, in food commodities are low and will be further
    reduced during processing. The exposure of the general population to
    dichlorvos through food and drinking-water is negligible, as has been
    confirmed in total diet studies.

    In short-term inhalation studies on mammals, 1 or 2 mg dichlorvos/m3
    did not inhibit ChE activity.

    In a 2-year inhalation study on rats, whole-body exposure to 0.48 mg
    dichlorvos/m3 for 23 h/day caused inhibition of plasma- and red
    cell-ChE activity, but AchE activity in the brain was not inhibited
    and there were no clinical signs. An unquantified, but considerable,
    increase in exposure resulting from the grooming of contaminated fur,


    a  The US National Toxicology Program Peer Review Panel reviewed
       these studies and came to the following conclusions:
         "Under the conditions of these 2-year gavage studies, there was
         some evidence of carcinogenic activity of dichlorvos for male
         F344/N rats, as shown by increased incidences of adenomas of the
         exocrine pancreas and mononuclear cell leukemia. There was
         equivocal evidence of carcinogenic activity of dichlorvos for
         female F344/N rats, as shown by increased incidence of adenomas
         of the exocrine pancreas and mammary gland fibroadenomas. There
         was some evidence of carcinogenic activity of dichlorvos for male
         B6C3F1 mice and clear evidence for female B6C3F1 mice, as shown
         by increased incidences of forestomach squamous cell papillomas".

    and the contamination of food and drinking-water, had contributed to
    this effect. The no-observed-adverse-effect level was 0.05 mg/m3.
    There was no evidence of carcinogenicity.

    After 6-7-h exposure of human volunteers to concentrations of
    approximately 1 mg/m3, only inhibition of plasma-ChE activity was
    found. This is generally considered as an indication of exposure. The
    red cell-AChE activity, taken to be representative of the AChE
    activity in the nervous tissue, was not affected.

    Residents exposed to an average air concentration of dichlorvos of
    0.1 mg/m3, arising from slow-release strips for over one year, did
    not show any inhibition of plasma- or erythrocyte-ChE activity, or any
    deleterious effects on health.

    The main exposure of the general population is through the inhalation
    of dichlorvos, when used indoors to control insects. The recommended
    use (one slow-release strip/ 30 m3) will give concentrations in the
    air of up to 0.1-0.3 mg/m within the first few days, decreasing
    thereafter to below 0.1 mg/m3. The air concentration depends on
    temperature, humidity, and ventilation.

    As long as approved slow-release strips are used according to the
    instructions on the label, no health hazard can be expected for man.
    However, special care may need to be taken with young children and
    sick or elderly people, who are especially vulnerable when
    continuously exposed (24 h a day) in poorly ventilated rooms. Other
    methods of indoor application should be safe, if the instructions on
    the label are followed.

    There is some indication that dichlorvos may induce dermatitis and
    cross-sensitization in workers also handling other types of

    Under occupational conditions, the main route of exposure to
    organophosphorus pesticides is, generally, the dermal route. In the
    case of dichlorvos, with its high vapour pressure, exposure through
    inhalation is also important. In such occupational situations, the
    dichlorvos concentrations in air are generally below 1 mg/m3 but,
    under certain circumstances, they may rise considerably above this
    level. This stresses the need for adequate protection measures to be
    taken during occupational exposure and regular monitoring of ChE

    2.2  Evaluation of Effects on the Environment

    The presence of dichlorvos as a result of accidental loss or direct
    application on soil or in water will not lead to long-term effects,
    because of its fast breakdown and evaporation. Furthermore, dichlorvos
    will be converted by microorganisms to a number of compounds including
    dichloroacetic acid. Certain bacteria can use dichlorvos as a sole
    source of carbon. Other strains cannot and are inhibited in their
    growth. Thus, the influence of dichlorvos on microorganisms is rather

    Dichlorvos is moderately to highly toxic (range, 0.2-10 mg/litre) for
    fresh-water and estuarine species of fish and invertebrates. In
    certain fish, concentrations of 0.25-1.25 mg/litre cause inhibition of
    brain-and liver-ChE activity. Concentrations of 0.05 mg/litre may
    already have deleterious effects, particularly in invertebrates.
    Dichlorvos is highly toxic for birds and bees. Caution is advised in
    the use and handling of dichlorvos where these species might be

    No bioaccumulation occurs in the different compartments and organisms.


    3.1  Conclusions

    (a)  Exposure of the general population to dichlorvos through food and
         drinking-water is negligible and does not constitute a health

    (b)  The in-house use of dichlorvos as an insecticide in the form of
         sprays or slow-release strips, at recommended levels of use, does
         not constitute a short- or a long-term hazard for the general
         population. However, continuous (24 h per day) exposure of young
         children and sick or elderly people in non- or poorly-ventilated
         rooms should be avoided.

    (c)  Notwithstanding their toxicity, dichlorvos and its formulations
         do not present an undue hazard for those occupationally exposed,
         when adequate ventilation and skin protection are used.

    (d)  Except inthe case of gross spillage, the recommended use of
         dichlorvos as an insecticide does not pose any acute or long-term
         hazards for aquatic and terrestrial organisms, though there may
         be an acute hazard for birds and bees.

    3.2  Recommendations

    (a)  Continuous (24 h/day) exposure of young children and sick or
         elderly people to dichlorvos in non- or poorly-ventilated rooms
         should be avoided.

    (b)  As dichlorvos from various sources may differ in purity and
         impurities, attention should be paid to its composition. This
         should conform to FAO and WHO specifications. In the case of
         formulations, other components, such as solvents and stabilizers,
         should also be considered.


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

    Dichlorvos is an organophosphorus insecticide. Technical dichlorvos
    and concentrated formulations are moderately to highly toxic and can
    be hazardous for human beings, if incorrectly handled. Dichlorvos has
    a relatively high vapour pressure and is therefore hazardous through
    inhalation; it is also hazardous through ingestion and skin contact,
    because of fast absorption. Typical signs and symptoms of
    organophosphorus poisoning may occur rapidly with overexposure.

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

    4.1.1  Advice to physicians  Symptoms of poisoning

    Dichlorvos is a direct inhibitor of cholinesterase. Initially, there
    may be feelings of exhaustion, headache, weakness, and confusion.
    Then, vomiting, abdominal pain, excessive sweating, and salivation may
    develop. The pupils are small. Difficulty in breathing may be
    experienced, due to either congestion of the lungs or weakness of the
    respiratory muscles. In severe cases of poisoning, muscle spasms,
    unconsciousness, and convulsions may develop. Respiration may stop.
    For a more complete treatise on the effects of organo-phosphorus
    insecticides, especially their short- and long-term effects on the
    nervous system, refer to EHC 63:  Organophosphorus insecticides - a
     general introduction (WHO, 1986a).  Medical treatment

    If ingested and the formulation does not contain petroleum
    distillates, induce vomiting, or preferably perform gastric lavage
    using 5% sodium bicarbonate. In the case of ingestion of liquid
    formulations containing hydrocarbon solvents, vomiting involves a risk
    of aspiration pneumonia. Instead, the stomach should be emptied as
    soon as possible by careful gastric lavage (using a cuffed
    endotracheal tube). If possible, identify the solvents present in the
    formulation and observe the victim for additional toxic effects. As
    early as possible, administer 2 mg of atropine surfate i.v. and
    1000-2000 mg of pralidoxime chloride or 250 mg of obidoxime chloride
    (adult dose) intramuscularly or intravenously to patients suffering
    from severe respiratory difficulties, convulsions, and unconsciousness.
    Repeated doses of 2 mg of attopine surfate should be given, as required,

    based on the respiration, blood pressure, pulse frequency, salivation,
    and convulsion conditions. For children, the doses are 0.04-0.08 mg of
    atropine/kg body weight, 250 mg of pralidoxime chloride per child or
    4-8 mg of obidoxime chloride kg body weight.

    Artificial respiration should be applied if required.

    Morphine, barbiturates, phenothiazine derivatives, tranquillizers, and
    all killds of central stimulants are contraindicated.

    The diagnosis of intoxication should be confirmed as soon as possible
    by determination of the cholinesterase activity in venous blood.

    For more information on the treatment of organophosphorus insecticides
    see EHC No. 63:  Organophosphorus insecticides: - a general
     introduction (WHO 1986a). The section on therapy from this
    publication is attached as Annex 1 of this guide.

    4.1.2  Health surveillance advice

    Occupational exposure to organophosphorus insecticides can be
    monitored by measurement of erythrocyte- and whole blood-ChE activity.
    Physiological variations in erythrocyte- and blood-ChE values occur in
    healthy persons.

    Inhibition of AChE or ChE activity of less than 20-25% is considered
    diagnostic of exposure but not necessarily indicative of hazard.
    However, work procedures and hygiene should be checked. Inhibition of
    30-50% or more is considered an indication that an exposed individual
    should be removed from further contact with ChE-inhibiting pesticides,
    until values return to normal. Work procedures and hygiene should also
    be checked.

    4.2  Explosion and fire hazards

    Liquid formulations may be flammable. Inform the fire service that
    skin contamination and the breathing of fumes must be avoided.
    Protective clothing and self-contained breathing apparatus must be

    Extinguish fires with alcohol-resistant foam or powder. The use of
    water spray should be confined to the cooling of unaffected stock, to
    avoid polluted run-off from the site.

    4.3  Storage

    Technical dichlorvos and its formulations should be stored in locked,
    well ventilated buildings preferably specifically used for insecticide
    storage. Do not expose to direct sunlight. Keep products out of reach
    of children and unauthorized personnel. Do not store near feed or

    4.4  Transport

    Comply with any local regulations regarding movement of hazardous
    goods. Do not load with feed or foodstuffs. Check that containers are
    sound and labels undamaged before despatch.

    4.5  Spillage and Disposal

    4.5.1  Spillage

    Stay upwind, avoid skin contamination and inhalation of vapour. Absorb
    spilled liquid and cover contaminated areas with 1:3 mixture of sodium
    carbonate crystals and damp sawdust, lime, sand, or earth. Sweep up
    and place in a closeable impervious container. Ensure that container
    is tightly closed and suitably labelled before transfer to a safe
    place for disposal.

    Prevent liquid from spreading and contaminating other cargo,
    vegetation, or waterways with a barrier of the most suitable material
    available, e.g., earth or sand. If the spill occurs into a waterway
    and the dichlorvos-containing material is immiscible in water and
    sinks, dam the waterway to stop flow and to retard dissipation by
    water movement. Use a bottom pump, dredging, or underwater vacuum
    equipment to remove undissolved material.

    Empty any of the product remaining in the damaged/leaking container
    into a clean empty container, which should then be tightly closed and
    suitably labelled.

    Decontaminate emptied leaking containers with a 10% sodium carbonate
    solution added at the rate of at least 1 litre per 20-litre drum.
    Swirl round to rinse walls, empty, and add rinsings to sawdust, etc.
    Puncture empty containers to prevent re-use.

    4.5.2  Disposal

    Contaminated absorbents, containers, surplus product, etc., should be
    burnt in a proper incinerator at high temperatures in a unit with
    effluent gas scrubbing. When no incinerator is available, bury in an
    approved dump, or in an area where there is no risk of contamination
    of surface or ground water. Before burying, liberally mix with sodium
    carbonate (washing soda) crystals to help neutralize the product and
    with soil rich in organic matter. Comply with any local legislation.


    Dichlorvos is highly toxic for honey bees, birds, and fish. It does
    not bioaccumulate and it breaks down rapidly in the environment.

    Avoid contamination of soil, water, and the atmosphere by proper
    methods of storage, transport, handling, and waste disposal. Caution
    is advised in the use and handling of dichlorvos where sensitive non-
    target animal species might be exposed.

    In case of spillage, use the methods advised in section 4.5.1.


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

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



    Chemical formula: C4H7Cl2O4P
    CAS chemical name: (2,2-Dichloroethenyl dimethylphosphate)
    CAS: registry number: 62-73-7
    PHYSICAL PROPERTIES                                                                   OTHER CHARACTERISTICS
    Boiling point (C)                           35C (0.05 mmHg)                         Colourless to amber liquid with a mild chemical
                                                 74C (1 mm Hg)                           odour; stable to heat, but is hydrolysed by
    Vapour pressure                              1.6 Pa at 20C                           water at a rate of 3% per day at room
    Density (25C) g/ml                          1.415                                    temperature; corrosive to iron and mild steel
    Relative molecular mass                      221
      in water (20C)                            10 g/litre
      in kerosine                                2-3 g/litre
      miscible with most organic solvents
    Log n-octanol/water partition
    coefficient                                  1.47
    HAZARD/SYMPTOM                               PREVENTION AND PROTECTION                FIRST AID

    GENERAL: readily absorbed via skin,
    ingestion, and inhalation; may cause
    organophosphate poisoning: weakness,
    headache, vomiting, excessive sweating
    and salivation, pinpoint pupils; in
    severe cases: convulsions, unconsciousness,
    and death due to respiratory paralysis

    PHYSICAL PROPERTIES                                                                   OTHER CHARACTERISTICS

    SKIN: irritation; redness; extensive         Wear PVC or neoprene gloves and          Remove and wash contaminated
    contamination may cause poisoning            apron; rubber boots                      clothing; wash contaminated skin with
                                                                                          water and soap; obtain medical
                                                                                          attention immediately

    EYES: irritation; redness                    Wear safety goggles or face shield       Flush eyes with clean water for at
                                                                                          least 15 min; if irritation persists,
                                                                                          obtain medical attention immediately

    INHALATION: overexposure may                 Avoid inhaling the vapour; use           In case of signs and symptoms, remove
    cause poisoning                              proper (exhaust) ventilation or          from contaminated area and obtain
                                                 suitable respiratory protection          medical attention immediately

    INGESTION: an unlikely                       Wash hands before eating, drinking,
    occupational hazard                          using the toilet, and after work

    Accidental or intentional ingestion                                                   Obtain medical attention immediately;
    may rapidly lead to severe poisoning                                                  if breathing has stopped, apply
                                                                                          artificial respiration.

    REPEATED EXPOSURE BY                         As above                                 As above
    OR THROUGH SKIN may gradually
    lead to signs and symptoms
    of inhibition of cholinesterase
    SPILLAGE                                     STORAGE                                  FIRE AND EXPLOSION

    Absorb spilled liquid and cover              Store in locked, well-ventilated         Use alcohol-resistant foam or powder;
    contaminated area with 1:3 mixture           storeroom, away from feed and            cool unaffected stock; wear protective
    of sodium carbonate crystals and             foodstuffs, children, and unauthorized   clothing and self-contained
    damp sawdust, lime, sand, or earth;          personnel                                breathing apparatus
    sweep up and place in closed and
    suitably labelled container

    Burn at high temperature in incinerator      National Occupational Exposure Limit:    UN: 2783, 2784, 3017, 3018
    with effluent scrubbing;
    comply with local legislation; when          National Poison Control Centre:
    allowed, treat with washing soda
    mixed with soil rich in organic              Local trade names:
    matter and bury in an approved

    FIGURE 1

    The information given in this section has been extracted from the
    International Register of Potentially Toxic Chemicals (IRPTC) legal
    file and other UN sources. Its intention is to give the reader a
    representative but non-exhaustive overview of current regulations,
    guidelines, and standards.a

    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.

    7.1  Previous Evaluations by International Bodies

    Dichlorvos was evaluated by the Joint FAO/WHO Expert Committee on
    Pesticide Residues (JMPR) in 1965, 1966, 1967, 1969, 1970, 1974, and
    1977. In 1966, the JMPR established an Acceptable Daily Intake (ADI)
    for man of 0-0.004 mg/kg body weight, a level still maintained as

    The Pesticide Development and Safe Use Unit, Division of Vector
    Biology and Control, WHO, classified technical dichlorvos as "highly
    hazardous" (Class IB) (Plestina, 1984; WHO, 1986a). This division has
    also issued a data sheet on dichlorvos (WHO/FAO, 1975).

    In 1979, IARC came to the following conclusion in considering the
    carcinogenicity of dichlorvos:

    -    Dichlorvos was tested in different animal species via different
         routes; no conclusive evaluation on the basis of these studies
         could be made;

    -    Dichlorvos is an alkylating agent and binds to bacterial and
         mammalian nucleic acids;

    -    It is a mutagen in a number of microbial systems, but there is no
         evidence of its mutagenicity in mammals, in which it is rapidly

    IRPTC has published a volume on Dichlorvos, in its series "Scientific
    Reviews of Soviet Literature on Toxicity and Hazards of Chemicals".


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

    7.2  Exposure Limit Values

    Some exposure limit values are given in the following table.

    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).

    7.3  Specific Restrictions

    Dichlorvos has been officially approved for use as a pesticide in many
    countries, in each of which specific uses are defined as well as
    limitations and precautions. Absorption through the skin is indicated
    as a potentially hazardous route in the regulatory documents in
    Argentina, the countries of the European Community, the USA, and the

    In Brazil, the maximum concentration of the active substance
    authorized for use as an insecticide is 1-5% (weight/weight).

    In the USSR, the presence of dichlorvos in fishing waters is not
    allowed, but a level of 0.1 mg/litre is allowed in other surface
    waters. The preliminary safety limit for soil is 0.1 mg/kg.

    7.4  Labelling, Packaging, and Transport

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

    -    Hazard Class 6.1: poisonous substance;

    -    Packing Group II: a substance presenting a serious risk of
         poisoning in transport, for material containing 35-100%

    -    Packing Group III: a substance presenting a relatively low risk
         of poisoning in transport, for material containing 7-35%

    Medium    Specification    Country                Exposure limit description                      Value             Effective
                               organization                                                                               Date

    AIR       Work-place       Argentina              Maximum permissible concentration                                   1979
                                                      - Time-weighted average (TWA)                   1 mg/m3
                                                      - Short-term exposure limit (STEL)              3 mg/m3

                               Germany,               Maximum work-site concentration (MAK)           1 mg/m3
                                 Federal              - Time-weighted average (TWA)
                                 Republic of          - 30-min short-term exposure
                                                        limit (STEL)                                  10 mg/m3

                               United Kingdom         Recommended limit (RECL)                        1 mg/m3
                                                      - Short-term exposure limit (STEL)              3 mg/m3

                               USA                    Permissible exposure limit
                                                      - Time-weighted average (TWA)                   1 mg/m3

                               USSR                   Maximum allowable concentration (MAC)
                                                      - Ceiling value                                 0.2 mg/m3           1977

    AIR       Ambient          USSR                   Maximum allowable concentration (MAC)
                                                      (average per day)                               0.002 mg/m3

    FOOD      General          FAO/WHO                Acceptable daily intake (ADI)                   0-0.004 mg/kg       1966
                                                                                                      body weight

    FOOD      Plant            Brazil                 Acceptable limit (AL)                           0.1-5 mg/kg         1981
                                                      - Safety interval                               30 days

                               Czechoslovakia         Maximum residue limit (MRL)                     0.02-2 mg/kg        1978

                               European Community     Maximum residue limit (MRL)                     0.1 mg/kg           1984

    Medium    Specification    Country                Exposure limit description                      Value             Effective
                               organization                                                                               Date

    FOOD      Plant            FAO/WHO                Maximum residue limit (MRL)                     0.02-5 mg/kg        1978

                               India                  Maximum tolerable concentration (MTC)           0.1-1 mg/kg         1976

                               Japan                  Acceptable residue limit (ARL)                  0.1 mg/kg

                               Sweden                 Maximum tolerable concentration (MTC)           0.1-2 mg/kg         1985

                               USSR                   Maximum residue limit (MRL) for
                                                      specific food items                             0-0.3mg/kg          1983

                                                      Acceptable daily intake (ADI)                   0.04 mg/kg

    FOOD      Animal           Kenya                  Maximum limit                                   0.02-5 mg/kg

                               Sweden                 Maximum tolerable concentration (MTC)           0.02-0.1 mg/kg      1983

                               USA                    Acceptable residue limit (ARL)                  0.05-10 mg/kg
        The label should be as follows:

    In Packing Group II

    FIGURE 2

    In Packing Group III

    FIGURE 3

    The European Community Legislation requires labelling as dangerous
    substance using the symbol:

    FIGURE 4

    The label must read:

          Toxic by inhalation, in contact with skin and if swallowed; keep
          out of reach of children; keep away from food, drink and animal
          feeding stuffs - if you feel unwell, seek medical advice (show
          the label where possible).

    The European Community legislation on labelling of pesticide
    preparations classifies dichlorvos in Class lc for the purpose of
    determining the label for preparations containing dichlorvos and other
    active ingredients.

    WHO gives the following product specification for dichlorvos for use
    in public health:

     Technical dichlorvs: the material shall consist of dichlorvos
    togethex with related manufacturing compounds and shall be a pale
    amber-coloured liquid free from extraneous impurities or added
    modifying agents. It shall contain at least 970 g of dichlorvos
    per kg. Acidity and water content are specified and analytical methods
    for checking are given.

     Technical dichlorvos shall be packed in suitable clean containers,
     and all packages shall bear; durably and legibly marked on the
     container, the following:

    -    Manufacturer's name

    -    Technical dichlorvos to specification WHO/SIT/16.R2

    -    Batch or reference number, and date of test

    -    Net weight of contents

    -    Date of manufacture

    and the following minimum cautionary notice:

     "POISON (skull-and-crossbones emblem): dichlorvos is an
     organophosphorus compound that inhibits cholinesterase. It is
     poisonous if swallowed, inhaled, or absorbed through the skin. Wear
     protective gloves, clean protective clothing goggles, and a
     respirator of the organic-vapour type when handling this material.
     Avoid prolonged exposure to fumes. Wash hands and exposed skin after
     handling and before eating and bathe immediately after work.

     Keep the material out of the reach of children and well away from
     foodstuffs, animal feed and theircontainers. Ensure that containers
     are tightly sealed, and stored and disposed of in such a way as to
     prevent accidental contact.

     In case of contact, immediately remove cotstansinated clothing and
     wash the skin thoroughly with soap and water; for eyes, flush with
     water for 15 minutes.

     If poisoning occurs, call a physician. Atropine and pralidoxime are
     specific antidotes and artificial respiration may be needed."

    Similar specifications and instructions are given for dichlorvos
    emulsifiable concentrate. FAO gives similar product specifications for
    dichlorvos for its use in plant protection. In this case, the
    technical material should contain at least 95% active material.

    Containers must comply with pertinent national and international
    transport and safety regulations.


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

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

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

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

    FAO/WHO (1986b)  Guide to Codex recommendations concerning pesticitle
     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)  LARC Monographs on the Evaluation of Carcinogenic
     Risk of Chelnicals to Man. Lyons, International Agency for Research
    on Cancer.

    IRPTC (1985)  IRPTC file on treatment and disposal methods for waste
     chemicals. Geneva, International Register of 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 treatntent of
     insecticide poisoning. Geneva, World Health Organization
    (Unpublished report No. 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 Vols. Washington DC, US Department of Health and Human
    Services, US Department of Labor (Publication No. DHHS(NIOSH) 01-123).

    WHO (1986a)  EHC No. 63. Organophosphorus Insecticides : a general
     introduction. Geneva, World Health Organiyation, 181 pp.

    WHO (1986b) The  WHO recommended classification of pesticides by
     hazard. Guidelines to classification 1986-87. Geneva, World Health
    Organization (Unpublished report VBC/86.1).

    WHO (1988)  EHC No. 79: Dichlorvos. Geneva, World Health

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

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

    ANNEX 1


    (From EHC 63: Organophosphorus Insecticides - A General Introduction)

    All cases of organophosphorus poisoning should be dealt with as an
    emergency and the patient sent to hospital as quickly as possible.
    Although symptoms may develop rapidly, delay in onset or a steady
    increase in severity may be seen up to 48 h after ingestion of some
    formulated organophosphorus insecticides.

    Extensive descriptions of treatment of poisoning by organophosphorus
    insecticides are given in several major references (Kagan, 1977;
    Taylor, 1980; UK DHSS, 1983; Plestina, 1984) and will also be included
    in the IPCS Health and Safety Guides to be prepared for selected
    organophosphorus insecticides.

    The treatment is based on:

    (a) minimizing the absorption;

    (b) general supportive treatment; and

    (c) specific pharmacological treatment.

    I.1  Minimizing the Absorption

    When dermal exposure occurs, decontamination procedures include
    removal of contaminated clothes and washing of the skin with alkaline
    soap or with a sodium bicarbonate solution. Particular care should be
    taken in cleaning the skin area where venupuncture is performed. Blood
    might be contaminated with direct-acting organophosphorus esters and,
    therefore, inaccurate measures of ChE inhibition might result.
    Extensive eye irrigation with water or saline should also be
    performed. In the case of ingestion, vomiting might be induced, if the
    patient is conscious, by the administration of ipecacuanha syrup
    (10-30 ml) followed by 200 ml water. This treatment is, however,
    contraindicated in the case of pesticides dissolved in hydrocarbon
    solvents. Gastric lavage (with addition of bicarbonate solution or
    activated charcoal) can also be performed, particularly in unconscious
    patients, taking care to prevent aspiration of fluids into the lungs
    (i.e., only after a tracheal tube has been put in place).

    The volume of fluid introduced into the stomach should be recorded and
    samples of gastric lavage frozen and stored for subsequent chemical
    analysis. If the formulation of the pesticide involved is available,
    it should also be stored for further analysis (i.e., detection of
    toxicologically relevant impurities). A purgative can be administered
    to remove the ingested compound.

    I.2  General Supportive Treatment

    Artificial respiration (via a tracheal tube) should be started at the
    first sign of respiratory failure and maintained for as long as

    Cautious administration of fluids is advised, as well as general
    supportive and symptomatic pharmacological treatment and absolute

    I.3  Specific Pharmacological Treatment

    I.3.1  Atropine

    Attopine should be given, beginning with 2 mg i.v. and given at
    15-30-min intervals. The dose and the frequency of attopine treatment
    varies from case to case, but should maintain the patient fully
    atropinized (dilated pupils, dry mouth, skin flushing, etc.).
    Continuous infusion of atropine may be necessary in extreme cases and
    total daily doses up to several hundred mg may be necessary during the
    first few days of treatment.

    I.3.2  Oxime reactivators

    Cholinesterase reactivators (e.g., pralidoxime, obidoxime)
    specifically restore AChE activity inhibited by organophosphates. This
    is not the case with enzymes inhibited by carbamates. The treatment
    should begin as soon as possible, because oximes are not effective on
    "aged" phosphorylated ChEs. However, if absorption, distribution, and
    metabolism are thought to be delayed for any reasons, oximes can be
    administered for several days after intoxication. Effective treatment
    with oximes reduces the required dose of attopine. Pralidoxime is the
    most widely available oxime. A dose of 1 g pralidoxime can be given
    either i.m. or i.v. and repeated 2-3 times per day or, in extreme
    cases, more often. If possible, blood samples should be taken for AChE
    determinations before and during treatment. Skin should be carefully
    cleansed before sampling. Results of the assays should influence the
    decision whether to continue oxime therapy after the first 2 days.

    There are indications that oxime therapy may possibly have beneficial
    effects on CNS-derived symptoms.

    I.3.3  Diazepam

    Diazepam should be included in the therapy of all but the mildest
    cases. Besides relieving anxiety, it appears to counteract some
    aspects of CNS-derived symptoms, which are not affected by atropine.
    Doses of 10 mg s.c. or i.v. are appropriate and may be repeated as

    required (Vale & Scott, 1974). Other centrally acting drugs and drugs
    that may depress respiration are not recommended in the absence of
    artificial respiration procedures.

    I.3.4  Notes on the recommended treatment

    I.3.4.1  Effects of atropine and oxime

    The combined effect far exceeds the benefit of either drug singly.

    I.3.4.2  Response to atropine

    The response of the eye pupil may be unreliable in cases of
    organophosphorus poisoning. A flushed skin and drying of secretions
    are the best guide to the effectiveness of atropinization. Although
    repeated dosing may well be necessary, excessive doses at any one time
    may cause toxic side-effects. Pulse-rate should not exceed 120/min.

    I.3.4.3  Persistence of treatment

    Some organophosphorus pesticides are very lipophilic and may be taken
    into, and then released from, fat depots over a period of many days.
    It is therefore quite incorrect to abandon oxime treatment after
    1-2 days on the supposition that all inhibited enzyme will be aged.
    Ecobichon et al. (1977) noted prompt improvement in both condition and
    blood-ChEs in response to pralidoxime given on the 11th-15th days
    after major symptoms of poisoning appeared due to extended exposure to
    fenitrothion (a dimethyl phosphate with a short half-life for aging of
    inhibited ACHE).

    I.3.4.4  Dosage of atropine and oxime

    The recommended doses above pertain to exposures, usually for an
    occupational setting, but, in the case of very severe exposure or
    massive ingestion (accidental or deliberate), the therapeutic doses
    may be extended considerably. Warriner et al. (1977) reported the case
    of a patient who drank a large quantity of dicrotophos, in error,
    while drunk. Therapeutic dosages were progressively increased up to
    6 mg attopine i.v. every 15 min together with continuous i.v. infusion
    of pralidoxime chloride at 0.5 g/h for 72 h, from days 3 to 6 after
    intoxication. After considerable improvement, the patient relapsed and
    further aggressive therapy was given at a declining rate from days 10
    to 16 (atropine) and to day 23 (oxime), respectively. In total, 92 g
    of pralidoxime chloride and 3912 mg of atropine were given and the
    patient was discharged on the thirty-third day with no apparent

    References to Annex I

    ECOBICHON, D.J., OZERE, R.L., REID, E., & CROCKER, J.F.S (1977) Acute
    fenitrothion poisoning.  Can. Med. Assoc. J.,116: 377-379.

    KAGAN, JU.S. (1977)  [Toxicology of organophosphorus pesticides.]
    Moscow, Meditsina, pp. 111-121, 219-233, 260-269 (in Russian).

    PLESTINA, R. (1984)  Prevention, diagnosis, and treatment of
     insecticide poisoning. Geneva, World Health Organization
    (Unpublished report No. VBC/84.889).

    TAYLOR, P. (1980) Anticholinesterase agents. In: Goodman, L.S. &
    Gilman, A., ed.  The pharmacological basis of therapeutics. 6th ed.
    New York, Macmillan Publishing Company, pp. 100-119.

    UK DHSS (1983)  Pesticide poisoning: notes fof the guidance of medical
     practitioners, London, United Kingdom Department of Health and
    Social Security, pp. 41-47.

    VALE, J.A. & SCOTT, G.W. (1974) Organophosphorus poisoning.  Guy's
     Hosp. Rep., 123: 13-25.

    WARRINER, R.A., III, NIES, A.S., & HAYES, W.J., Jr (1977) Severe
    organophosphate poisoning complicated by alcohol and terpentine
    ingestion.  Arch. environ. Health, 32: 203-205.

    See Also:
       Toxicological Abbreviations
       Dichlorvos (EHC 79, 1988)
       Dichlorvos (ICSC)
       Dichlorvos (FAO Meeting Report PL/1965/10/1)
       Dichlorvos (FAO/PL:CP/15)
       Dichlorvos (FAO/PL:1967/M/11/1)
       Dichlorvos (FAO/PL:1969/M/17/1)
       Dichlorvos (AGP:1970/M/12/1)
       Dichlorvos (WHO Pesticide Residues Series 4)
       Dichlorvos (Pesticide residues in food: 1977 evaluations)
       Dichlorvos (Pesticide residues in food: 1993 evaluations Part II Toxicology)
       Dichlorvos (IARC Summary & Evaluation, Volume 53, 1991)