Health and Safety Guide No. 20






    This is a companion volume to Environmental Health Criteria 90:

    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)

    ISBN 92 4 154342 6
    ISSN 0259 - 7268

    (c) World Health Organization 1988

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    Universal Copyright Convention.  For rights of reproduction or
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    should be made to the Office of Publications, World Health
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    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

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



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

         2.1. Human exposure
         2.2. Evaluation of human health risks
         2.3. 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. Waste disposal



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


    ANNEX 1.  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 chemicals, or physical or biological
    agents.  They also provide guidelines for setting exposure limits.

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

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

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

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



    1.1  Identity

    Common name:             dimethoate (accepted by BSI, ISO, ANSI, and
                             JMAF); fosfamid (used in USSR)

    Chemical structure:

                             CH3O  S
                                 \ "
                                   P - SCH2CONHCH3

    Molecular formula:       C5H12NO3PS2

    IUPAC name:               O,O-dimethyl  S-methyl-carbamoylmethyl

    CAS chemical name:       Phosphorodithioic acid,  O,O-dimethyl
                              S-[2-(methylamino)-2-oxoethyl] ester (9CI)

    CAS registry number:     60-51-5

    RTECS RN:                TE1750000

    Technical dimethoate is about 93-95% pure.  The major impurities are
     O,O-dimethyl  S-methylphosphorodithioate and  O,O,S-trimethyl

    1.2  Physical and Chemical Properties

    Pure dimethoate is a colourless crystalline solid with an odour of
    mercaptan.  Technical dimethoate (about 93% pure) varies from
    off-white crystals to a grey semi-crystalline material.  Some physical
    and chemical properties of dimethoate are given in the International
    Chemical Safety Card (pages 18-21).

    Dimethoate is highly soluble in chloroform, methylene chloride,
    benzene, toluene, alcohols, esters, and ketones, slightly soluble in
    xylene, carbon tetrachloride, and aliphatic hydrocarbons, and partly
    soluble in water.

    Dimethoate is fairly stable in water and acid solution at room
    temperature, and unstable in alkaline solution.  On heating, it is
    converted to  O,S-dimethyl phosphorodithioate.

    1.3  Analytical Methods

    The method of choice for the determination of dimethoate is gas
    chromatography with flame photometric detection.

    1.4  Uses

    Dimethoate is an organophosphorus insecticide with contact and
    systemic action that is used against a broad range of insects in
    agriculture and also for fly control.  It was introduced in 1956 and
    is produced in many countries.

    Demethoxon, an oxygen analogue metabolite of dimethoate, appears to
    play a dominant role in the toxicity for insects and mammals. 
    Dimethoxon is also used as an insecticide known as omethoate.

    Formulations of dimethoate include emulsifiable concentrates, wettable
    powders, and granules.  There is also a formulation for
    ultra-low-volume application.


    2.1  Human Exposure

    The general population is not normally exposed to dimethoate from air
    or water.  Residues in food are mostly below 1 mg/kg.  Dimethoate was
    detected only infrequently in the latest reported total-diet studies

    Occupational exposure to dimethoate may occur during manufacture,
    formulation, and application.  This exposure is mainly through
    inhalation and dermal absorption.  Higher occupational exposures may
    be observed in the case of accident or as a result of incorrect

    2.2  Evaluation of Human Health Risks

    Dimethoate is moderately toxic.  Most oral LD50s in rats have ranged
    from 150 to 400 mg/kg body weight.  The dermal LD50 in rats is
    greater than 600mg/kg.  It is not irritating to the skin, but may be
    slightly irritating to the eye.

    Dimethoate can be absorbed following ingestion, inhalation, and skin
    contact.  It is readily metabolized and eliminated and does not
    accumulate in the body.  Dimethoxon (omethoate), the oxygen analogue
    found in plants, insects, and mammals, is about 10 times more toxic
    and is a more potent inhibitor of cholinesterase activity than

    Signs of intoxication from exposure to dimethoate are those typical of
    organophosphorus pesticides.  Inhibition of cholinesterases is the
    most sensitive indicator of exposure to dimethoate and may indicate
    toxicity.  A dietary level of 5mg/kg equivalent to 0.25 mg of
    dimethoate per kg body weight is considered to be a no-observed-
    adverse-effect level in the rat.

    A five-generation reproduction study on mice given drinking-water
    containing dimethoate at 60 mg/litre showed decreased mating success
    and increased reproduction time in all generations.  On the basis of
    available data on experimental animals, dimethoate is not considered
    to be a teratogen.

    Dimethoate is considered mutagenic in a variety of  in vitro and  in
     vivo test systems.a  Although long-term studies have been
    conducted on rats and mice administered dimethoate orally and rats
    administered the compound by i.m. injection, the available data are
    considered to be inadequate to assess the carcinogenic potential of

    In man, several cases of suicidal or accidental poisoning with
    dimethoate have been reported.  Some cases of occupational poisoning
    have been reported, which were the result of accidents or neglect of
    safety precautions.  The lethal oral dose for human beings has been
    estimated to be in the range of 50-500mg/kg body weight.

    Skin sensitization due to dimethoate has been reported.

    2.3  Evaluation of the Effects on the Environment

    Dimethoate does not persist in the environment; hydrolytic degradation
    is rapid and is the main inactivating pathway.  In moist air, it is
    degraded photochemically into hydrolytic and oxidation products.  The 
    half-life of dimethoate in different plants is between 2 and 5 days. 
    Degradation in soil is dependent on the type of soil, temperature,
    moisture, and pH level.  The toxicity of dimethoate for aquatic
    organisms and birds is moderate to high. It is more toxic for honey


    a    New adequate mutagenicity and carcinogenicity studies have
         become available since  these conclusions were reached.  The
         FAO/WHO Joint Meeting on Pesticide Residues (JMPR) evaluated the
         new data in 1987 and concluded that dimethoate is mutagenic in
         bacterial tests, but negative in mammalian cells in  in vivo
         tests.  Moreover, no indications for carcinogenicity were found
         in rats and mice.


    3.1  Conclusions

    (a)  Under proper conditions of use, exposure of the general
         population to dimethoate is negligible.

    (b)  When appropriate safety precautions are taken, exposure to
         dimethoate during manufacture, formulation, use, and disposal
         should not pose an unacceptable human health hazard.

    (c)  Dimethoate is rapidly degraded and does not persist in the
         environment.  Care should be taken not to expose honey bees, fish
         and aquatic organisms, and birds.

    3.2 Recommendations

    (a)  Workers should be monitored for exposure to dimethoate and for
         potential adverse health effects.

    (b)  Cleaning and disposal of contaminated equipment, clothing, and
         containers should be in accordance with recommended procedures.


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

    Dimethoate is an indirect acting organophosphorus insecticide, i.e.,
    it is converted in the body into the active metabolite, dimethoxon. 
    As a result, signs and symptoms of overexposure develop after a latent
    period and may continue to increase after exposure has been
    discontinued.  The acute oral toxicity of dimethoate is moderate and
    it can be hazardous for human beings if incorrectly handled.  On
    overexposure, typical signs and symptoms of organophosphorus poisoning
    may occur rapidly.  For details, see the International Chemical Safety
    Card on pages 18-21.

    4.1.1  Advice to Physicians

    For a more complete treatise on the effects of organophosphorus
    insecticides, especially their short- and long-term effects on the
    nervous system, please refer to EHC 63: Organophosphorus insecticides
    -  a general introduction (WHO, 1986).  The section on "Treatment of
    organophosphate insecticide poisoning in man" is included in this
    publication as Annex 1.  Symptoms of poisoning

    Signs and symptoms may include a feeling of exhaustion, headache,
    blurred vision, weakness, and confusion.  Vomiting, abdominal pain,
    excessive sweating, and salivation may develop.  The pupils are
    constricted.  Difficulty in breathing may be experienced, owing to
    congestion of the lungs and weakness of the respiratory muscles. 
    Arrhythmia and cardiac failure have been reported.  In severe
    poisoning, there will be muscle spasms, unconsciousness, and
    convulsions.  Breathing may stop, followed by death.  Medical treatment

    Induce vomiting if dimethoate has been ingested. It should be noted
    that dimethoate may be dissolved in one or more solvents (e.g., a
    petroleum distillate) and that inducing vomiting then involves a risk
    of aspiration pneumonitis. Alternatively, perform rapid gastric lavage
    using 5% sodium bicarbonate.  Persons without signs of respiratory
    inefficiency, but with manifest peripheral symptoms, should be treated
    with 2-4 mg of atropine sulfate by intravenous injection.  More
    atropine may be given as needed.  Severely intoxicated persons
    suffering from respiratory difficulties or convulsions, or becoming
    unconscious, should be given atropine and a reactivator immediately. 
    In such severe cases, 4-6 mg of atropine sulfate should be given
    initially followed by repeated doses of 2 mg at 5-10-min intervals.

    In all cases of clinical poisoning with dimethoate and other
    organophosphorus insecticides, it is essential to maintain general
    surveillance and cholinesterase and cardiac monitoring for at least 4
    days, or more if necessary, and to adapt general supportive and
    specific therapy in accordance with the findings.

    If the patient is cyanotic, artificial respiration should be given at
    the same time as atropine sulfate.  Haemoperfusion may be effective in
    the early stages of poisoning.  The airway should be kept free and
    artificial respiration should be applied.  If necessary, intubation
    should be performed.

     The following drugs are contraindicated: morphine, barbiturates,
     phenothiazine, tranquillizers, and central stimulants of all kinds.

    Data on the effects of oxime reactivators in dimethoate poisoning are
    contradictory, some showing that they may have a negative effect on
    cholinesterase inhibition.  It is therefore suggested that, if oxime
    reactivators are indicated, they should be used with caution and under
    close supervision.

    4.1.2  Health Surveillance Advice

    Human beings potentially exposed to dimethoate should undergo periodic
    health monitoring and monitoring of cholinesterase activity in the

    Measurement of whole blood-AChE is the most widely adopted method for
    monitoring occupational exposure to organophosphorus insecticides. 
    However, physiological variations in blood-ChE levels occur in healthy

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

    4.2  Explosion and Fire Hazards

    Liquid formulations may be flammable.  With sufficient burning or
    external heat, dimethoate will decompose emitting toxic fumes. 
    Fire-fighters should be equipped with protective clothing and
    self-contained breathing apparatus.

    Fires should be extinguished with alcohol-resistant foam or powder. 
    The use of water spray should be confined to the cooling of unaffected
    stock, thus avoiding polluted run-off from the site.

    4.3  Storage

    Technical dimethoate and its formulations must be stored in locked,
    well-ventilated buildings, preferably dedicated to insecticides.  They
    should not be exposed to direct sunlight.  Products must be kept out
    of reach of children and unauthorized personnel.  They should not be
    stored near feed or foodstuffs.

    4.4  Transport

    Any local regulations regarding movement of hazardous goods must be
    complied with.  Products must not be transported with feed or
    foodstuffs.  Containers should be checked before despatch to ensure
    that they are in good condition and that the labels are undamaged. 

    4.5  Spillage and Disposal

    4.5.1  Spillage

    Skin contamination and inhalation of vapour should be avoided. 
    Spilled liquid  should  be absorbed  and  contaminated areas  covered
    with a 1:3 mixture of sodium carbonate crystals and damp sawdust,
    lime, sand, or earth.  After sweeping up, it should be transferred to
    a safe place for disposal in a tightly closed and labelled container. 

    It is important to prevent liquid from spreading and contaminating
    other cargo, vegetation, or waterways by making a barrier of the most
    suitable available material, e.g., earth or sand.

    Any of the product remaining in the damaged/leaking container should
    be emptied into a clean empty container, which should then be tightly
    closed and suitably labelled.  The emptied leaking containers can be
    decontaminated with a 10% sodium carbonate (washing soda) solution,
    added at a rate of at least 1litre per 20-litre drum, and swirled
    round to rinse the walls. The rinsings should be added to sawdust.
    Containers should be punctured so that they cannot be re-used.

    4.5.2  Waste disposal

    Large amounts should be incinerated at high temperatures in a unit
    with effluent gas scrubbing, or adsorbed on vermiculite and placed in
    a landfill if incineration is impossible (IRPTC, 1985).  The waste
    should be buried in an approved dump, or in an area where there is no
    risk of contamination of surface or ground water.  Before burying,
    liberal mixing with sodium carbonate (washing soda) crystals and soil
    rich in organic matter will to help neutralize the product.  Local
    legislation must be complied with.


    Dimethoate is rapidly hydrolysed and does not persist in the
    environment. The toxicity of dimethoate for aquatic organisms and
    birds is moderate to high. It is more toxic for honey bees.

    Avoid contamination of soil, water, and the atmosphere by proper
    methods of use, storage, transport, handling, and waste disposal.  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, dimethoate. It should be displayed at, or near,
     entrances to areas where there is potential exposure to dimethoate,
     and on processing equipment and containers.  The card should be
     translated into the appropriate language(s).  All persons potentially
     exposed to the chemical should also have the instructions on the
     chemical safety card clearly explained.

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


    CAS chemical name: Phosphorodithioic acid,  O,O-dimethyl
     S-[2-(methylamino)-2-oxoethyl] ester (9CI)
    RTECS RN: TE1750000;   CAS No. 60-51-5
    Molecular formula: C5H12NO3PS2


    PHYSICAL PROPERTIES                                                   OTHER CHARACTERISTICS

    Relative molecular mass            229.2                              Pure dimethoate is a colourless crystalline solid
    Odour threshold (mg/m3)            0.010                              with an odour of mercaptan; technical dimethoate varies
    Melting point (C)                 45-52.5                            from off-white crystals to a grey semi-crystalline
    Boiling point (C)                 107 at 0.05 mmHg                   material; dimethoate is soluble in organic
                                       86 at 0.01 mmHg                    solvents; it is fairly stable in water and acid
    Vapour pressure (25C)             8.5 x 10-6 mmHg                    solutions at room temperature, and unstable
    Water solubility (21C)            up to  39 g/litre                  in alkaline solutions; it is readily absorbed via
    Half-life in aqueous media:                                           the skin, ingestion, and inhalation.
      at pH 2- 7                       relatively stable
      at pH 9                          50% loss in 12 days
    n-octanol/water partition          5.9


    HAZARDS/SYMPTOMS                        PREVENTION AND PROTECTION                    FIRST AID

    GENERAL: Cholinesterase inhibition      Avoid exposure

    SKIN: Contamination may cause           Wear PVC or neoprene gloves, apron           Remove and wash contaminated clothing;
    organophosphorus poisoning: weakness,   and rubber boots                             wash contaminated skin with water and
    headache, vomiting, excessive                                                        soap
    sweating and salivation, pin-point
    pupils; in severe cases: convulsions,
    unconsciousness, and death due to
    respiratory paralysis.

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

    INHALATION: Excessive inhalation        Avoid breathing dust; use proper             In case of signs and symptoms, remove
    may cause poisoning                     (exhaust) ventilation or suitable            from contaminated area and obtain medical
                                            mask                                         attention immediately

    INGESTION: Unlikely occupational        Wash hands before eating, drinking,
    hazard                                  using the toilet, and after work;
                                            do not keep food in areas with 
                                            potential exposure

    Accidental or intentional                                                            Obtain medical attention immediately;a
    ingestion may rapidly lead to                                                        induce vomiting if subject is conscious;
    severe poisoning (see skin)                                                          if breathing has stopped, apply artificial


    HAZARDS/SYMPTOMS                        PREVENTION AND PROTECTION                    FIRST AID

    REPEATED EXPOSURE                       As above                                     In case of poisoning, same as abovea
    gradually lead to signs, symptoms,-
    and poisoning; sensitization 
    may occur

    ENVIRONMENT: Toxic for fish,            Avoid contamination of soil,
    birds, and bees                         water, and atmosphere


    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 of   storeroom, away from feed and                cool unaffected stock; wear protective
    of sodium carbonate crystals and damp   foodstuffs, children, and unauthorized       clothing and self-contained breathing
    sawdust, lime, sand, or earth; sweep    personnel                                    apparatus
    up and place in closed container


    WASTE DISPOSAL                          NATIONAL INFORMATION

    Burn at high temperature in             National occupational exposure limit:        UN: 2783, 2784, 3017, 3018
    incinerator with effluent scrubbing;
    comply with local legislation;          National Poison Control Centre:
    when allowed, treat with washing
    soda mixed with soil rich in organic    Local Trade Names:
    matter and bury in approved dump

    FIGURE 1


    a Caution: if dimethoate is dissolved in solvents, e.g., petroleum solvents, vomiting may cause aspiration pneumonitis.


    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.

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

    7.1  Previous Evaluations by International Bodies

    Dimethoate was evaluated by the Joint Meeting on Pesticide Residues
    (JMPR) in 1963, 1965, 1966, 1967, 1970, 1973 (evaluation of the
    related compound formathion), 1977, 1978, 1984, and 1987.

    An acceptable daily intake (ADI) for man for dimethoate was estimated
    at 0-0.01 mg/kg body weight per day in 1987.

    A data sheet on dimethoate (No. 42) is available from the WHO Division
    of Vector Biology and Control in their series "Data sheets on
    pesticides" (WHO/FAO 1975-87).

    In the WHO Recommended Classification of Pesticides by Hazard,
    technical dimethoate has been classified as moderately hazardous, when
    handled in accordance with instructions.

    IRPTC has issued a review on dimethoate (No. 5) in its series
    "Scientific reviews of Soviet literature on toxicity and hazards of

    7.2  Exposure Limit Values

    Some exposure limit values are given in the table on pages 24-26.

    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).


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

    7.3  Specific Restrictions

    Dimethoate is approved as a pesticide in many countries.  Specific
    uses, limitations, and precautions are listed in national regulatory
    documents.  Since 1986, the use of dimethoate in greenhouses and on
    cherries and cabbage has been forbidden in the USSR.

    7.4  Labelling, Packaging, and Transport

    The United Nations Committee of Experts on the Transportation of
    Dangerous Goods classified dimethoate (solid >73%; liquid >29%) in:

         -    Hazard Class 6.1: poisonous substance

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

    The symbol on the label should be as follows:

    FIGURE 2

    The International Maritime Organization lists dimethoate as a
    pesticide of high hazard and as a poisonous substance at
    concentrations above 5% (Hazard Class 6.1).



    Medium      Specification       Country/            Exposure limit description                   Value                Effective
                                    organization                                                                          date

    AIR         Work-place          Bulgaria            Maximum permissible concentration (MPC)                           1971
                                                        - Time-weighted average (TWA)                1 mg/m3

                                    Romania             Maximum permissible concentration (MPC)
                                                        - Time-weighted average (TWA)                7 mg/m3
                                                        - Ceiling value                              10 mg/m3

                                    USSR                Maximum allowable concentration (MAC)
                                                        - Ceiling value                              0.5 mg/m3            1977

                                    Yugoslavia          Maximum allowable concentration (MAC)
                                                        - Time-weighted average (TWA)                0.5 mg/m3

    AIR         Ambient             USSR                Maximum allowable concentration (MAC)                             1984
                                                        - 1 time per day                             0.003 mg/m3
                                                        - Average per day                            0.003 mg/m3

                                                        Preliminary safety limit
                                                        - 1 time per day                             0.003 mg/m3

    WATER       Surface             USSR                Maximum allowable concentration (MAC)        0.03 mg/litre

    SOIL                            USSR                Permissible limit                            0.3 mg/kg

    FOOD        Intake from         FAO/WHO             Acceptable daily intake (ADI)                0-0.01 mg/kg         1987
                                                        body weight

                                    USSR                Acceptable daily intake (ADI)                0.02 mg/kg
                                                        body weight


    Medium      Specification       Country/            Exposure limit description                   Value                Effective
                                    organization                                                                          date

    FOOD        Plant               Brazil              Acceptable limit (safety                     0.02-2 mg/kg 
                                                          interval: 1 - 28 days)

                                    Czechoslovakia      Maximum residue limit (MRL)                  1-2 mg/kg            1978

                                    European            Maximum residue limit (MRL)                  1 mg/kg              1982

                                    India               Maximum tolerable concentration              2 mg/kg              1976

                                    Japan               Acceptable residue limit (ARL)               1 mg/kg

                                    Kenya               Maximum limit                                1-2 mg/kg

                                    Sweden              Maximum tolerable concentration              0.22 mg/kg           1983

                                    USSR                Maximum residue limit (MRL)                  0.1-0.4 mg/kg        1983

    FOOD        Plant               Exports and         Maximum residue limit (MRL)                  0.5 mg/kg
                                    imports by

    FOOD        Raw                 USA                 Acceptable residue limit (ARL)               0.002-2 mg/kg

    FOOD        Animal              USA                 Acceptable residue limit (ARL)               5 mg/kg

                                    USSR                Maximum residue limit (MRL)                  2 mg/kg              1981


    The WHO specifications for pesticides used in public health, in an
    interim specification on dimethoate technical and emulsifiable
    concentrate, require that the technical material shall consist of
    dimethoate together with related manufacturing compounds and shall be
    in the form of white/grey crystals free from extraneous impurities or
    added modifying agents.

    The emulsifiable concentrate shall consist of technical dimethoate
    dissolved in suitable solvents with other necessary formulants added. 
    It shall be in the form of a stable liquid, free from suspended matter
    and sediment.  The technical dimethoate used in the manufacture of the
    concentrate shall comply with the requirements of specification

    Chemical and physical requirements and the methods for checking them
    are specified.

    The material shall be packed in suitable, clean containers, as
    specified in the order.

    All packages shall bear, durably and legibly marked on the container,
    the following: 

         Manufacturer's name
         Technical dimethoate to Interim Specification WHO/IS/1.0094-1
         Batch or reference number, and date of test
         Net weight of contents
         Date of manufacture

    and, in the case of the emulsifiable concentrate: 

         Manufacturer's name
         Dimethoate emulsifiable concentrate to Interim Specification
         Dimethoate ... g/kg
         Batch or reference number, and date of test
         Net weight of contents
         Instructions for dilution
         Date of formulation

    and the following minimum cautionary notice:

          Dimethoate is an organophosphorus compound that inhibits
          cholinesterase.  It is poisonous if swallowed or inhaled.  It
          may be absorbed through the skin.  Avoid skin contact: wear
          protective gloves, clean protective clothing, and a respirator
          when handling the material.  Wash thoroughly with soap and water
          after using.

          Keep the material out of the reach of children and well away
          from foodstuffs and animal feed and their containers.

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

    The FAO specifications for plant protection products give similar
    specifications and the methods for checking them.

    The dimethoate content shall be declared (minimum 95% for the
    technical product) and shall not differ from the declared percentage
    by more than 2% for the technical product and 5-10% for its

    Containers shall be suitable, clean, dry, and as specified in the
    order, and shall not adversely affect, or be affected by, the product,
    but shall adequately protect it from external conditions. They shall
    comply with pertinent national and international transport and safety

    Specifications for storage stability are given.

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

    FIGURE 3

    The label must read:

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

    The European Community legislation on labelling of pesticide
    preparations classifies dimethoate in Class II/b for the purpose of
    determining the label for preparations containing dimethoate and other
    active ingredients.

    7.5  Waste Disposal

    In the USA, any non-domestic waste containing dimethoate is considered
    a hazardous waste and permits are required for its handling,
    transport, treatment, storage, or disposal.  Waste incinerators must
    achieve 99.99% destruction and removal of this substance.


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

    FAO/WHO  (1986b) 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. 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 and diagnosis of pesticide 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. 14th 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)

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

    WHO  (In press) EHC No. 90:  Dimethoate. Geneva, World Health

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

    WORTHING, C.R. & WALKER, S.B.  (1983)  The pesticide 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 venepuncture 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 of 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 purge to remove the ingested
    compound can be administered.

    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

    Atropine should be given, beginning with 2 mg i.v. and given at
    15-30-min intervals.  The dose and the frequency of atropine 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 atropine.  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 atropine 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 1

    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.

    DHSS  (1983)  Pesticide poisoning: notes for 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 turpentine
    ingestion.  Arch. environ. Health, 32: 203-205.


    See Also:
       Toxicological Abbreviations
       Dimethoate (EHC 90, 1989)
       Dimethoate (ICSC)
       Dimethoate (FAO Meeting Report PL/1965/10/1)
       Dimethoate (FAO/PL:CP/15)
       Dimethoate (FAO/PL:1967/M/11/1)
       Dimethoate (JMPR Evaluations 2003 Part II Toxicological)
       Dimethoate (AGP:1970/M/12/1)
       Dimethoate (Pesticide residues in food: 1983 evaluations)
       Dimethoate (Pesticide residues in food: 1984 evaluations)
       Dimethoate (Pesticide residues in food: 1984 evaluations)
       Dimethoate (Pesticide residues in food: 1987 evaluations Part II Toxicology)
       Dimethoate (Pesticide residues in food: 1996 evaluations Part II Toxicological)