Health and Safety Guide No. 74






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

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

    WHO Library Cataloguing in Publication Data

    Parathion : health and safety guide.

    (Health and safety guide ; no. 74)

    1. Parathion - poisoning  2. Parathion - standards
    3. Parathion - toxicity   4. Environmental exposure I.Series

    ISBN 92 4 151074 9          (NLM Classification: WA 240)
    ISSN 0259-7268

    The World Health Organization welcomes requests for permission to
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    (c) World Health Organization 1992

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    names of proprietary products are distinguished by initial capital



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

          2.1. Exposure
          2.2. Poisoning cases in humans
          2.3. Evaluation of human health risks
          2.4. Effects on the environment

          3.1. Conclusions
          3.2. Recommendations


          4.1. 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. Safety in use
          4.3. Explosion and fire hazards
          4.4. Storage
          4.5. Transport
          4.6. Spillage and disposal
               4.6.1. Spillage
               4.6.2. Disposal


          6.1. Previous evaluations by international bodies
          6.2. Exposure limit values
          6.3. Specific restrictions
          6.4. Labelling, packaging, and transport
          6.5. Waste disposal
          6.6. Other measures


    ANNEX 1


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

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

    The first three sections of this Health and Safety Guide present
    essential technical information and the hazard evaluation. Section 4
    includes advice on preventive and protective measures and emergency
    action; health workers should be thoroughly familiar with the
    medical information to ensure that they can act efficiently in an
    emergency. The section on regulatory information has been extracted
    from the legal file of the International Register of Potentially
    Toxic Chemicals (IRPTC) and from other United Nations sources.

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

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

    The Director
    International Programme on Chemical Safety
    World Health Organization
    1211 Geneva 27



    1.1  Identity

    Chemical structure:


    Molecular formula:                C10H14NO5PS

    Common name:                      Parathion (BSI, E-ISO, F-ISO, JMAF);

                                      parathion ethyl (some countries);

                                      thiophos (USSR)

    CAS chemical name:                 O,O-diethyl  O-(4-nitrophenyl)
                                      phosphorothioate (9CI)

    CAS registry number:              [56-38-2]

    OMS number:                       19

    RTECS registry number:            TF4550000

    Technical parathion is at least 95% pure.

    1.2  Physical and chemical properties

    Pure parathion is a pale yellow liquid. The technical material is a
    brown liquid with garlic-like odour. It is slightly soluble in
    water, heptane, and in petroleum oils, but readily soluble in most
    organic solvents, such as acetone, benzene, chloroform, ethanol, and

    Parathion is hydrolysed very slowly at pH 1-7, but undergoes rapid
    decomposition at higher pH. On heating, parathion readily isomerizes
    to the  O,S-diethyl analogue. It is generally considered to be a
    non-persistent compound.

    Some physical properties of parathion are given in Table 1.

    Table 1. Physical properties


    Relative molecular mass:             291.3
    Boiling point                        157-162 C at 0.6 mmHg
    Density d4                           1.265

    Vapour pressure (20 C)              5.0 mPa
    Water solubility (25 C)             24 mg/litre
                       (40 C)           77 mg/litre
    Flash point (open cup)(C)           200
    Hydrolysis in aqueous solution
      at pH 5.0-6.0 (25 C)              1% in 62 d
    Log Pow                              3.15

    1.3  Analytical methods

    The active ingredient content of formulated products has been
    determined using gas chromatography, high pressure liquid
    chromatography, or hydrolysis to 4-nitrophenol for colorimetric
    determination. Gas chromatographic and thin-layer chromatographic
    methods are available for residue determination.

    Recommendations for the methods of determining parathion residues
    have been given by the Codex Alimentarious Commission (FAO/WHO,

    1.4  Uses

    Parathion is a non-systemic insecticide that controls numerous
    insects by contact and stomach action. It is used in many countries
    throughout the world. It has some fumigant as well as acaricidal
    activity. Parathion is used as a pre-harvest soil and foliage
    treatment on a wide variety of crops, both outdoors and in
    glasshouses. The usual application rate is 0.2-1 kg/ha. Parathion is
    non-phytotoxic, except to some sensitive ornamentals, apples, and

    Parathion is available as 15 and 25% wettable powders, 2, 4, 6, and
    8% emulsifiable concentrates, 0.5, 1, and 2% dust, 10% granules and
    10% aerosols.


    2.1  Exposure

    In the environment, parathion is degraded quite rapidly, mainly by
    hydrolysis, but to a certain extent also by reduction of the nitro
    group as well as conversion to the oxon. The half-life of the oxon
    is much shorter than that of parathion itself, and it does not

    The general population is not usually exposed to parathion from air
    or water, parathion residues in food being the main source of
    exposure. Dermal exposure may also occur through accidental contact
    with foliar residues in sprayed fields or in areas adjacent to
    spraying operations, as a consequence of off-target loss of
    parathion. With correct usage, however, persons not occupationally
    involved should not be exposed to hazardous amounts.

    The data on levels of parathion reported so far by the Joint FAO/WHO
    Food Contamination Monitoring Programme indicate that parathion does
    not occur substantially above detection limits in most cases.
    However, sporadic instances of higher levels in fruit and vegetables
    indicate that contamination of crops can occur under certain
    conditions of use (GEMS, 1986).

    Analysis of fruit and vegetables entering commerce in Germany showed
    that only 14 out of 228 samples contained measurable amounts of
    parathion (more than 0.01 mg/kg). In most of these cases, the
    residue was less than 0.1 mg/kg, but 2 samples of lettuce contained
    residue levels of 0.15 and 1.5 mg/kg, respectively. One sample of
    parsley contained 0.4 mg parathion/kg.

    Total-diet studies in the USA in 1965-66 showed that only very low
    residues (0-0.001 mg/kg) were present in vegetables and fruits, as
    consumed. In 1963-64, parathion residues in food in commerce were
    0.03-0.83 mg/kg.

    Occupational exposure to parathion may occur during manufacturing,
    formulation, application, and storage. This exposure is mainly
    through dermal absorption and inhalation. Higher occupational
    exposures may be observed in cases of accident, or as a result of
    incorrect handling.

    2.2  Poisoning cases in humans

    There are more reported cases of poisoning with parathion than with
    any other pesticide currently in use. There have been a number of
    cases where intoxication and death have resulted from ingestion of
    foodstuffs that have been grossly contaminated with parathion.

    In one Asian country, there were 828 cases of poisoning with 106
    deaths caused by flour, sugar, and other foodstuffs becoming
    contaminated because parathion was transported in the same ship's
    hold as the food. In another Asian country, barley became
    contaminated with parathion. There were 38 cases of poisoning with
    nine deaths.

    In a country in the Americas, there were 559 cases of poisoning and
    16 deaths when sacks of sugar, and possibly flour, absorbed
    parathion from the floor of a truck. In another country in the
    Americas, there were 165 known, and 445 more suspected, cases of
    poisoning with 63 deaths, when parathion from broken containers
    contaminated sacks of flour during transportation in a truck. In a
    European country, there were 26 cases of poisoning, but no deaths,
    when flour became contaminated because of transportation in a wagon
    that was previously used for the transportation of parathion.

    Several operators have died after rather extensive skin contact with
    diluted agricultural sprays or dusts.

    2.3  Evaluation of human health risks

    Parathion is highly toxic and extremely hazardous (WHO, 1990), the
    oral LD50 in the rat being of the order of 13 mg/kg. In man, an
    oral dose of 3-5 mg/kg is usually fatal.

    Parathion is easily absorbed through the intact skin, as well as by
    inhalation and via the gastrointestinal tract. It is converted  in
     vivo to the more toxic oxygen analogue paraoxon, which inhibits
    acetylcholinesterase. In the mouse, the LD50 of paraoxon by the
    oral route is 12.8 mg/kg body weight. It is rapidly distributed to
    all organs and tissues in the body. The presence of the metabolite
     p-nitrophenol in the urine is used to monitor worker exposure to

    Parathion is not irritating to the eyes, but a single drop in the
    eye could be fatal. It is also not irritating to the nose and
    throat, but it is highly poisonous when inhaled. It is not
    irritating to the skin but is rapidly absorbed through the intact

    The acute and short-term studies on parathion are comprehensive and
    cover a wide range of animal species. Long-term studies have been
    carried out on the rat. The results of studies on the dog, though
    limited, suggest that this species is more sensitive than the rat to
    the anticholinesterase activity of parathion. Several short-term
    studies have been conducted on groups of human volunteers. Man and
    the rat are equally sensitive to the anticholinesterase action of
    parathion. Erythrocyte cholinesterase activity is the most sensitive
    indicator of this action of parathion and a wide margin exists
    between the highest dose without action on cholinesterase activity
    and the lowest dose needed to cause a clinical effect.

    Parathion was not mutagenic to a wide range of microorganisms in the
    presence or absence of rat liver microsomal preparations. It did not
    induce unscheduled DNA synthesis in cultured mammalian cells,
    recessive lethal mutations in  Drosophila melanogaster, or dominant
    lethal mutations in mice. Thus, no evidence has been found that
    parathion is mutagenic.

    Parathion was tested for carcinogenicity in one strain of mice and
    in three strains of rats by administration in the diet. Although a
    dose-related increase in the incidence of adrenal cortical adenomas
    was observed in male and female rats of one strain, the significance
    of the occurrence of these lesions in aged rats is not well
    understood. A low incidence of carcinomas at this site was observed
    in each of the treated groups in animals of both sexes.

    Evidence is inadequate to evaluate the carcinogenicity of parathion
    in experimental animals, and the available data are insufficient to
    evaluate the carcinogenicity of parathion for humans (IARC, 1983).

    Parathion produced embryocidal effects and fetal growth retardation,
    but no malformations, in mice and rats at doses that were generally
    below the level that was toxic for the mother.

    Maximum levels causing no significant toxicological effects in
    long-term studies (FAO/WHO, 1968) are as follows:

    *     Rat: the maximum level having no effect on cholinesterase
          activity in the rat was 1 mg/kg in the diet, equivalent to 0.05
          mg/kg body weight.

    *     Man: 0.05 mg/kg body weight per day.

    The estimated acceptable daily intake for man (FAO/WHO, 1968) is
    0-0.005 mg/kg body weight.

    2.4  Effects on the environment

    Parathion is degraded in soil, plants, and other substrates at a
    moderate rate, though such conversion may be initially to the more
    toxic metabolite paraoxon. Such conversion is especially true under
    dry, hot conditions. The other degradation products are
     p-nitrophenol,  p-aminophenol, diethyl thiophosphoric acid, and
    diethylphosphoric acid.

    Parathion is highly toxic for fish, lower aquatic organisms, birds,
    wild mammals, and soil organisms. There is no build up of this
    insecticide in food-chains.


    3.1  Conclusions

    Parathion is a highly toxic organophosphorus ester insecticide.
    Overexposure through handling during manufacture or use, and/or
    accidental or intentional ingestion may cause severe or fatal
    poisoning. Parathion formulations may, or may not, be irritating to
    the eyes or to the skin, but they are absorbed readily. As a
    consequence, hazardous exposures may occur without warning.

    Exposure of the general population to parathion residues occurs
    predominantly via food. If good agricultural practice is followed,
    the Acceptable Daily Intake (0-0.005 mg/kg body weight), established
    by FAO/WHO, will not be exceeded. Dermal exposure may also occur
    through accidental contact with foliar residues in sprayed fields or
    in areas adjacent to spraying operations as a result of off-target
    loss of the chemical.

    With good work practices, hygienic measures, and safety precautions,
    parathion is unlikely to present a hazard for those occupationally

    Parathion is degraded in the environment at a moderate rate. It is
    highly toxic for fish, lower aquatic organisms, birds, wild mammals,
    and soil organisms. There is no build up of this insecticide in

    3.2  Recommendations

    The existing uses of parathion in each country should be evaluated
    in terms of risk-benefit, and serious consideration should be given
    to replacing parathion with less hazardous chemicals.

    For the health and welfare of workers and the general population,
    the handling and application of parathion should be entrusted only
    to competently supervised and well-trained applicators, who must
    follow adequate safety measures and use the chemical according to
    good application practices.

    The manufacture, formulation, agricultural use, and disposal of
    parathion should be carefully managed to minimize contamination of
    the environment.

    Regularly exposed workers should receive appropriate monitoring and
    health evaluation.

    To minimize risk to all individuals, a 48-h interval between
    spraying and re-entry into any sprayed area is recommended.

    Pre-harvest intervals should be established and enforced by national

    In view of the high toxicity of parathion, this agent should not be
    considered for use in hand-applied, ultra-low-volume (ULV) spraying

    Do not overspray water bodies. Time spraying to avoid killing
    pollinating insects.


    4.1  Human health hazards, prevention and protection, first aid

    The acute oral and dermal toxicities of parathion are high and it is
    extremely hazardous for human beings, if incorrectly handled. With
    excessive exposure, typical signs and symptoms of organophosphorus
    poisoning may occur rapidly. For details see Table 2.

    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, refer to EHC 63:  Organophosphorus insecticides - a
     general introduction (WHO, 1986).  Symptoms of poisoning

    Parathion is an indirect inhibitor of cholinesterase, i.e., it is
    converted in the body into the active transformation product
    paraoxon. As a result, signs and symptoms of poisoning develop after
    a latent period and may continue to increase after exposure has been

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

        Table 2. Human health hazards, preventive and protective measures, and first aid


    HAZARD/SYMPTOM                                PREVENTION AND PROTECTION                    FIRST AID

    GENERAL Cholinesterase inhibition             Avoid exposure


    SKIN Contamination may cause                  PVC or neoprene gloves, apron,               Remove contaminated clothing;
    poisoning                                     and rubber boots                             wash contaminated skin with water
                                                                                               and soap; obtain medical attention
                                                                                               immediately; launder contaminated
                                                                                               clothing separately before reuse

    EYES Redness, irritation                      Goggles or face shield                       Flush immediately with clean water for
                                                                                               at least 15 min; if irritation
                                                                                               persists, obtain medical attention

    INHALATION Excessive inhalation               Avoid breathing mist or                      In case of signs and symptoms of
    may cause poisoning                           dust; use proper (exhaust)                   organophosphorus poisoning, remove
                                                  ventilation or proper mask                   from contaminated area and obtain
                                                  or ventilator                                medical 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;
    swallowing may rapidly cause                                                               induce vomitinga if subject is 
    typical organophosphorus                                                                   conscious; if breathing has stopped
    poisoning leading to respiratory                                                           apply artificial respiration
    arrest and death


    HAZARD/SYMPTOM                                PREVENTION AND PROTECTION                    FIRST AID


    SKIN: May gradually lead to                   Wash hands before eating,                    Obtain medical attention
    signs, symptoms and poisoning;                drinking, using the toilet, and              immediately; induce vomiting
    sensitization may occur                       after work                                   if subject is consciousa; if
                                                                                               breathing has stopped, apply
                                                                                               artificial respiration


    a   Caution: if parathion is dissolved in solvents, e.g., petroleum solvents, vomiting may cause pulmonary

    Instead, the stomach should be emptied as soon as possible by
    careful gastric lavage (using a cuffed endotracheal tube already in
    place). 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 sulfate i.v. and
    1000-2000 mg of pralidoxime chloride or 250 mg of obidoxime chloride
    (adult dose) i.v. to patients suffering from severe respiratory
    difficulties, convulsions, and unconsciousness. Repeated doses of
    2 mg of atropine sulfate should be given, as required, based on the
    respiration, blood pressure, pulse frequency, salivation, and
    convulsion conditions. Diazepam should be given in all but the
    mildest cases in doses of 10 mg, s.c. or i.v., which may be repeated
    as required.

    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 kinds of central stimulants
    are contraindicated.

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

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

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

    4.1.2  Health surveillance advice

    Human beings potentially exposed to parathion should undergo
    periodic health monitoring and monitoring of cholinesterase activity
    in the blood. Measurement of whole blood-AChE is the most widely
    adopted method for monitoring occupational exposure to
    organophosphorus insecticides. However, physiological variations of
    blood-ChE levels occur in healthy persons and are seen in

    Depressions of AChE or ChE of 20-25% are considered diagnostic of
    exposure, but not necessarily indicative of hazard. Depressions of
    30-50% or more are considered indicators for the removal of an
    exposed individual from further contact with pesticides until levels
    return to normal. Work procedures and hygiene should also be
    checked. Exposure can also be monitored by measuring the urinary
    excretion of  p-nitrophenol.

    4.2  Safety in use

    Parathion and its formulations should only be handled by
    well-trained, competent and supervised personnel wearing protective
    clothing. When opening a container or mixing, protective impermeable
    boots, clean overalls, gloves, and respirators should be worn.
    Mixing, if not mechanical, should be carried out with a paddle of
    appropriate length. When spraying tall crops or during aerial
    application, a respirator should be worn as well as an impermeable
    hood, clothing, boots, and gloves. The applicator should avoid
    working in spray mist and avoid contact with the mouth.

    Particular care is needed when equipment is being washed after use.
    All protective clothing should be washed immediately after use,
    including the insides of gloves. Splashes must be washed immediately
    from the skin or eyes with large quantities of water. Before eating,
    drinking, or smoking, hands and other exposed skin should be washed.

    Puncture and crush empty containers to prevent reuse.

    4.3  Explosion and fire hazards

    Liquid formulations may be flammable. With sufficient burning or
    external heat, parathion will decompose, emitting toxic fumes.
    Firefighters must wear protective clothing and self-contained
    breathing apparatus. Extinguish fires with alcohol-resistant foam or
    powder. Confine the use of water spray to the cooling of unaffected
    stock, thus avoiding polluted run-off from the site.

    4.4  Storage

    Technical parathion and its formulations should be stored in
    original, labelled containers in locked, well-ventilated storage
    areas, preferably dedicated to insecticides. Do not expose parathion
    formulations to direct sunlight. Keep products out of reach of
    children and unauthorized personnel. Do not store near food or
    animal feed.

    4.5  Transport

    Comply with any local regulations regarding the movement of
    hazardous goods. Do not transport with food or animal feed. Food and
    animal feed should not be transported in vehicles that have been
    used for the transport of pesticides. Make sure that containers are
    in good condition and labels undamaged before dispatch.

    4.6  Spillage and disposal

    4.6.1  Spillage

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

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

    Empty any of the product remaining in damaged/leaking containers
    into clean empty containers, 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 for
    proper disposal.

    4.6.2  Disposal

    Contaminated absorbents, containers, surplus product, etc., should
    be burnt in a proper incinerator at high temperature 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 mix with soil rich in organic matter. Comply with any
    local legislation.


    With normal usage, parathion does not accumulate in organisms. It is
    highly toxic for aquatic invertebrates, birds, bees, wild mammals,
    fish, and soil organisms.

    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 4.6.1.


    The information given in this section has been extracted from the
    International Register of Potentially Toxic Chemicals (IRPTC) legal
    file and other United Nations sources. A full reference to the
    original national document from which the information was extracted
    can be obtained from IRPTC.

    The reader should be aware that regulatory decisions about chemicals
    taken in a certain country can only be fully understood in the
    framework of the legislation of that country. Furthermore, the
    regulations and guidelines of all countries are subject to change
    and should always be verified with the appropriate regulatory
    authorities before application.

    6.1  Previous evaluations by international bodies

    Parathion was evaluated by the Joint FAO/WHO Expert Committee on
    Pesticide Residues (JMPR) in 1963, 1965, and 1967. In 1967, the JMPR
    established an Acceptable Daily Intake (ADI) for man of 0-0.005
    mg/kg body weight.

    The International Agency for Research on Cancer (IARC) evaluated
    parathion in 1983, and concluded that there was inadequate evidence
    to evaluate the carcinogenicity of parathion for experimental
    animals and that the available data were insufficient to evaluate
    the carcinogenicity of parathion for humans.

    WHO classified technical parathion as extremely hazardous (Class
    la). WHO has issued a data sheet on parathion (No. 6).

    6.2  Exposure limit values

    Some exposure limit values are given in the following table.


    Exposure limit values


    Medium     Specification        Country/            Exposurel limit description                   Value                     Effective
                                    organization                                                      date

    AIR        Workplace            Argentina           Maximum permissible concentration
                                                        - time-weighted average (TWA)                 0.1 mg/m3 a                 1979
                                                        - short-term exposure limit (STEL)            0.3 mg/m3

                                    Germany             Maximum worksite concentration (MAK)
                                                        - time-weighted average (TWA)                 0.1 mg/m3 a                 1986

                                    Japan               Maximum acceptable concentration              0.1 mg/m3 a                 1986

                                    United Kingdom      Recommended limit (RECL)
                                                        - time-weighted average (TWA)                 0.1 mg/m3 a                 1985
                                                        - short-term exposure level (STEL)            0.3 mg/m3
                                                                                                      (10-min TWA)

                                    USA-OSHA            Permissible exposure limit (PEL)
                                                        - time-weighted average (TWA)                 0.1 mg/m3 a                 1989

                                    USA-ACGIH           Threshold limit value (TVL)
                                                        - time-weighted average (TWA)                 0.1 mg/m3 a                 1990

                                    USSR                Maximum acceptable concentration
                                                          (ceiling)                                   0.05 mg/m3 a                1977

    GENERAL    Urine of             Germany             Maximum content of  p-nitrophenol              500 g/litre                1986


    Medium     Specification        Country/            Exposurel limit description                   Value                     Effective
                                    organization                                                      date

    FOOD       Intake from          FAO/WHO             Acceptable daily intake (ADI)                 0-0.005 mg/kg             1967
                                                                                                      body weight

               Residue              FAO/WHO             Maximum residue limit (MRL)                   0.5-1 mg/kg               1986
                                                        products specified as follows:
                                                        - apricots, citrus fruit, peaches             1 mg/kg
                                                        - other fruit                                 0.5 mg/kg
                                                        - vegetables (except carrots)                 0.7 mg/kg

    WATER      Ambient              EEC                 Maximum acceptable concentration for
                                                        total pesticides
                                                        - for drinking-water purification             0.001-0.005 mg/litre      1977

                                    Japan               Environmental water quality standard          Not detectable            1970

                                    Mexico              Maximum permissible concentration
                                                        (coastal)                                     0.001 mg/litre            1973
                                                        (estuarine)                                   0.01 mg/litre             1973

                                    USSR                Maximum acceptable concentration
                                                        (in surface water)                            0.003 mg/litre            1983

    a Skin absorption.

    6.3  Specific restrictions

    Because of its high toxicity, the use and/or sale of parathion is
    non-registered, banned, or has been phased out in many countries or
    territories, e.g., Belize, Bulgaria, China, Ecuador, El Salvador,
    Guatemala, Hong Kong, Hungary, India, Ireland, Japan, Malaysia, New
    Zealand, Philippines, Santa Lucia, Sri Lanka, Sweden, Thailand,
    Turkey, the United Kingdom, and the Russian Federation. Its use has
    been severely restricted in several other countries, including
    Brazil, Denmark, Finland, and Norway.

    In Canada, Israel, and the USA, the use, sale and application of
    parathion is restricted to those licensed to do so. In Germany,
    parathion may not be handled by adolescents or by pregnant women and
    nursing mothers.

    In the USA, field workers may not enter sprayed fields without
    protective clothing until at least 48 hours after spraying.

    Pre-harvest intervals have been set in many countries. These are
    generally in the range of 7-15 days, but, for greenhouse use, they
    may be double this time, and, for certain fruits, may last up to 5

    6.4  Labelling, packaging, and transport

    Depending on the content of the active ingredient, the United
    Nations Committee of Experts on the Transportation of Dangerous
    Goods classifies parathion in:

    Hazard Class 6.1:           poisonous substance;

    Packing Group I:            substances and preparations presenting a
                                very severe risk of poisoning, when the
                                content of the active ingredient is

    Packing Group II:           substances and preparations presenting a
                                serious risk of poisoning, when the content
                                of active incredient is 4-40%;

    Packing Group III:          a substance presenting a relatively low
                                risk of poisoning in transport, when the
                                content of active ingredient is 1-4%
                                (solid) or 0.4-4% (liquid).

    The label should be as follows:

    Packaging Groups I and II

    FIGURE 1

    Packaging Group III

    FIGURE 2

    Parathion has been identified as a severe marine pollutant in the
    International Maritime Dangerous Goods (IMDG) Code and a MARINE
    POLLUTANT mark (see below) is required for transport by sea.

    FIGURE 3

    The following specifications for technical material and some
    formulations (powders, dusts, concentrates, and solutions) have been
    agreed between FAO and the parathion manufacturers.

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

          manufacturer's name
          technical parathion to specification
          batch or reference number, and date of test
          net weight of contents
          date of manufacture
          and, in the case of the formulated products:
          manufacturer's name
          parathion to specification
          parathion ... 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:

           Parathion 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 needed.

    The parathion 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 regulations.

    Specifications for storage stability are given.

    The European Community legislation on labelling of pesticide
    preparations classified parathion in Class I/a for the purpose of
    determining the label for preparations containing parathion and
    other active ingredients.

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

    FIGURE 4

    The label must read:

           Very toxic by inhalation, in contact with skin and if
           swallowed; keep locked up; keep away from food, drink and
           animal feeding stuffs; after contact with skin, wash
           immediately with plenty of ..... (to be specified by the
           manufacturer); in case of accident or if you feel unwell, seek
           medical advice immediately (show the label where possible)

    6.5  Waste disposal

    In the USA, any non-domestic waste containing parathion and its
    metabolites must be treated as hazardous waste. Specific
    instructions are given for handling, transport, treatment, storage,
    and incineration, as well as notification and permit requirements.
    Owners/operators of vessels or onshore or offshore facilities must
    notify the USA Government (National Response Center) for any release
    of parathion in, or on, navigable waters, adjoining shorelines, in
    the contiguous zone, or beyond the contiguous zone in an amount
    equal to, or greater than, one pound (0.454 kg), in any 24-hour

    An owner or operator of a hazardous waste incinerator must achieve
    99.99% destruction and removal efficiency for this substance.

    6.6  Other measures

    In the countries of the European Economic Community, parathion is
    listed as a dangerous substance at quantities >100 kg in the
    directive on the major accident hazards of certain industrial
    activities. Any person in charge of an industrial activity
    involving, or possibly involving, one or more dangerous substances
    is obliged to take all the measures necessary to prevent major
    accidents, to limit their consequences for man and the environment,
    and to notify the competent authority about the industrial activity.


    CEC (1987) Legislation on dangerous substances - classification and
    labelling in the European Communities. Vol. 1 & 2. Commission of the
    European Communities, London, Graham & Trotman, Ltd.

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

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

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

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

    FAO/WHO (1964) Evaluation of the toxicity of pesticide residues in
    food. Report of a Joint Meeting of the FAO Committee on Pesticides
    in Agriculture and the WHO Expert Committee on Pesticide Residues.
    Geneva, World Health Organization (FAO Meeting Report. No.
    PL:1963/13; WHO/Food Add./23 (1964)).

    FAO/WHO (1965) Evaluation of the toxicity of pesticide residues in
    food. Geneva, World Health Organization (FAO Meeting Report, No.
    PL:1965/ 19/1; WHO Food Add./27.65).

    FAO/WHO (1968) 1967 Evaluation of the toxicity of some pesticide
    residues in food. Geneva, World Health Organization (FAO Meeting
    Report, No. PL:1967/M/11/1; WHO Food Add./68.30).

    FAO/WHO (1986) Codex Maximum Limits for pesticide residues. Codex
    Alimentarius Commission CAC/Vol. XIII, 3rd ed. Rome, Food and
    Agriculture Organization of the United Nations.

    FAO/WHO (1989) Guide to Codex recommendations concerning pesticide
    residues. Part 8. Recommendations for methods of analysis of
    pesticide residues. 4th ed. Rome, Codex Committee on Pesticide

    GEMS (1986) Chemical contaminants in food: 1980-1983. Global
    Environment Monitoring System (UNEP/FAO/WHO), World Health
    Organization, Geneva, (Unpublished document WHO/EHE/FOS/86.5).

    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.

    Hayes WJJ Jr & Laws, ER Jr (1991) Handbook of pesticide toxicology.
    3 Vol. New York, Academic Press.

    IARC (1983) IARC monographs on the evaluation of carcinogenic risk
    of chemicals to man. Vol. 30. Miscellaneous chemicals. Lyon,
    International Agency for Research on Cancer.

    ILO (1991) Safety and health in the use of agro-chemicals - a guide.
    Geneva, International Labour Office.

    IPCS/CEC (1990) International Chemical Safety Card No. 6: Parathion.
    Luxembourg, Commission of the European Communities.

    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

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

    Sax NI (1984) Dangerous properties of industrial materials. New
    York, Van Nostrand Reinhold Company, Inc.

    UNEP/IEO (1990) Storage of hazardous materials: a technical guide
    for safe warehousing of hazardous materials. Paris, United Nations
    Environment Programme, Industry and Environment Office, 80 pp.

    UNITED NATIONS (1989) Consolidated list or products whose
    consumption and/or sale have been banned, withdrawn, severely
    restricted or not approved by governments. 2nd ed. New York, United

    UNITED NATIONS (1989) Recommendations on the transport of dangerous
    goods. 6th ed. New York, United Nations.

    US NIOSH/OSHA (1981) Occupational health guidelines for chemical
    hazards. 3 Vol. Washington DC, US Department of Health and Human
    Services, US Department of Labor (Publication No. DHHS(NIOSH)

    WHO (1986) EHC 63: Organophosphorus insecticides - a general
    introduction. Geneva, World Health Organization, 181 pp.

    WHO (1992) The WHO recommended classification of pesticides by
    hazard and guidelines to classification, 1992-93. Geneva, World
    Health Organization, 66 pp. (Unpublished document, WHO/PCS/92.14).

    WHO/FAO (1975-87) Parathion: Data sheets on pesticides, No. 6.
    Geneva, World Health Organization (Unpublished documents).

    Worthing CR & Hance, RJ (1991) The pesticide manual. 9th ed. Unwin
    Brothers Ltd., Surrey, United Kingdom, British Crop Protection

    IN MANa

    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 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 into place).

    a  From EHC 63: Organophosphorus insecticides - a general
       introduction. Geneva, World Heralth Organization, 1986.

    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

    Atropine should be given, beginning with 2 mg iv 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 im or iv 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 that are not affected by atropine.
    Doses of 10 mg sc or iv 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

    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 iv every 15 min together with continuous iv
    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 sequelae.

    References to Annex 1

    Ecobichon DJ, Ozere RL, Reid E, & Crocker JFS (1977) Acute
    fenitrothion poisoning. Can Med Assoc J, 116: 377-379.
    Kagan JuS (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 document VBC/84.889).

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

    UK 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 RA III, Nies AS, & Hayes WJ Jr (1977) Severe
    organophosphate poisoning complicated by alcohol and turpentine
    ingestion. Arch environ Health, 32: 203-205.

    See Also:
       Toxicological Abbreviations
       Parathion (ICSC)
       Parathion (FAO Meeting Report PL/1965/10/1)
       Parathion (FAO/PL:1967/M/11/1)
       Parathion (FAO/PL:1969/M/17/1)
       Parathion (AGP:1970/M/12/1)
       Parathion (Pesticide residues in food: 1984 evaluations)
       Parathion (Pesticide residues in food: 1995 evaluations Part II Toxicological & Environmental)
       Parathion (IARC Summary & Evaluation, Volume 30, 1983)