Health and Safety Guide No. 66






    This is a companion volume to Environmental Health Criteria 132:

    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

    Trichlorfon : health and safety guide.

    (Health and safety guide ; no. 66)

    1.Trichlorfon - adverse effects
    2.Trichlorfon -poisoning
    3.Trichlorfon - standards
    4.Environmental exposure  I.Series

    ISBN 92 4 151066 8          (NLM Classification: WA 240)
    ISSN 0259-7268

    (c) World Health Organization 1991

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    proprietary products are distinguished by initial capital letters.



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

         2.1. Exposure
         2.2. Uptake, metabolism, and excretion
         2.3. Effects on organisms in the environment
         2.4. Effects on experimental animals and  in vitro test systems
         2.5. Effects on human beings


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



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




    The Environmental Health Criteria (EHC) documents produced by the
    International Programme on Chemical Safety include an assessment of
    the effects on the environment and on human health of exposure to a
    chemical or combination of chemicals, or physical or biological
    agents.  They also provide guidelines for setting exposure limits.

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

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

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

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



    1.1  Identity

    Common name:                  trichlorfon (ISO)

    Chemical structure:


    Chemical formula:             C4H8Cl3O4P

    Relative molecular mass:      257.44

    CAS chemical name:            dimethyl2,2,2-trichloro-1-hydroxyethyl-

    Synonyms:                     Chlorofos; DEP; DETF; dipterex; dimethyl
                                  phosphonate;  O,O-dimethyl
                                  phosphonate; metrifonate, foschlor;
                                  trichlorofon; trichlorphon

    Trade names:                  Agroforotox; Anthon; L 13/59; Bilarcil;
                                  Cekufon; Danex; Dipterex; Ditriphon;
                                  Dylox; Dyrex; Dyvon; Masoten;
                                  Metrifonate; Neguvon; Proxol; Tugon;

    CAS registry number:          52-68-6

    RTECS registry number:        TA0700000

    Conversion factors:           1 ppm = 11.4 mg/m3
                                  1 mg/m3 = 0.088 ppm, 
                                  at 25C and 101.3 kPa (760 mmHg)

    The purity of technical trichlorfon is reported to be more than 98%.
    It is a racemic mixture of two isomers. The main impurities are
    2,2-dichlorovinyl dimethyl phosphate, dichlorvos (0-0.2%),
    trichloroacetaldehyde (0-0.05%), dichloroacetaldehyde (0-0.03%),
    methyl hydrogen 2,2,2-trichloro-1-hydroxyethylphosphonate, demethyl
    trichlorfon (0-0.3%), and water (less than 0.3%).  The technical
    product also contains phosphoric acid, 2,2,2-trichloro-1-
    hydroxyethylphosphonic acid, and dimethyl phosphite.

    1.2  Physical and Chemical Properties

    Trichlorfon is a colourless crystalline powder that is stable at room
    temperature.  It is slowly hydrolysed in acid media; the half-life is
    526 days at pH 1-5 and 20C.  In alkaline media, at pH 8 and 37.5C,
    it hydrolyses initially to the more toxic compound dichlorvos, but is
    essentially 100% hydrolysed in 24 h to less toxic products, such as
    dimethyl hydrogen phosphate, dichloroacetaldehyde, and glyoxal. 
    Trichlorfon also decomposes under ultraviolet irradiation.

    Some physical properties are given in the Summary of Chemical Safety
    Information (section 6).

    1.3  Analytical Methods

    Trichlorfon residues can be determined using gas liquid
    chromatography.  The same method can be used for product analysis;
    alternative methods include thin layer chromatography and high
    performance liquid chromatography.

    1.4  Production and Uses

    Trichlorfon was introduced as a commercial chemical in 1952.  It is a
    broad spectrum insecticide that is particularly effective against
    Diptera.  It is used mainly against insect pests in field and fruit
    crops, but it is also used to control forest insects and in public
    health.  Further applications of trichlorfon include the control of
    endo- and ectoparasites in, or on, domestic animals and fish.  Under
    the generic name of metrifonate, trichlorfon is used as an
    antihelminthic, and in the treatment of schistosomiasis in humans.

    The global consumption of trichlorfon, which was more than 3000 tonnes
    in 1980, was reported to be approximately 850 tonnes in 1987.

    Formulations used in agriculture are: 50% emulsifiable concentrate,
    95, 80, and 50% soluble powders, 50% wettable powders, 5 and 4% dusts,
    5, 2.5, and 1% granules, and 75, 50, 40, and 25% ultra-low volume

    The following formulations are used in the treatment of animals: 90,
    80, and 50% soluble powders, 6% suspension, 11% solution, and 50%
    injectable solution tablets.  A 1% fly bait is also available and a
    0.1% preparation against house ants.

    Tablets containing 100 mg metrifonate are used in the treatment of
    schistosomiasis in humans.


    2.1  Exposure

    Trichlorfon is an organophosphorus insecticide that has been in use
    since the early 1950s.  It is considered to be a slow release
    reservoir of dichlorvos.

    The air concentration of trichlorfon insecticide may be as high as
    0.1 mg/m3, soon after spraying, but, within days, levels decrease to
    below 0.01 mg/m3.  Levels of trichlorfon in runoff water from
    sprayed areas may be as high as 50 g/litre, though levels in surface
    waters are usually much lower and decrease rapidly.

    Trichlorfon is relatively stable in water at pH values below 5.5.  At
    higher pH values, trichlorfon is transformed into dichlorvos.  While
    micro-organisms and plants may metabolize trichlorfon, the most
    important route of removal is abiotic hydrolysis.

    Trichlorfon degrades rapidly in the soil, and levels generally
    decrease to negligible amounts within one month of application.

    With a few exceptions, levels of trichlorfon on crops are below
    10 mg/kg, the day after application, and below 0.1 mg/kg, two weeks

    Milk from cows treated with trichlorfon for pest control may contain
    residues as high as 1.2 mg/litre, 2 h after application, but the
    levels decline to less than 0.1 mg/litre, 24 h after treatment. 
    Significant levels of trichlorfon have not been found in the meat from
    treated animals.  Eggs from treated hens have been found to contain
    0.05 mg trichlorfon/kg.

    2.2  Uptake, metabolism, and excretion

    Trichlorfon is readily absorbed via all routes of exposure (oral,
    dermal, inhalation) and is rapidly distributed to the tissues of the
    body.  Peak blood concentrations are detected within 12 h, with
    disappearance from the blood stream occurring in a matter of 1.5-4 h;
    only low levels are detected after 8-24 h.  The biological half-life
    of trichlorfon in the mammalian blood is estimated to be about 30 min.

    Trichlorfon undergoes transformation, via dehydrochlorination, to form
    dichlorvos (2,2-dichlorovinyl dimethyl phosphate) in water and all
    biological fluids and tissues, at pH values higher than 5.5. 
    Dichlorvos is a physiologically active anticholinesterase.  The main
    routes of degradation of trichlorfon are demethylation, P-C bond
    cleavage, and ester hydrolysis via dichlorvos.  The major metabolites
    of trichlorfon found  in vivo are demethyl trichlorfon, demethyl
    dichlorvos, dimethyl hydrogen phosphate, methyl hydrogen phosphate,
    phosphoric acid, and trichloroethanol.  The last of these metabolites
    is found in the urine as a glucuronide conjugate.

    The elimination of trichlorfon and its metabolic products occurs
    primarily via the urine.  Studies conducted with radiolabelled
    (14C-methyl and 32P-) trichlorfon revealed that the bulk of the
    chemical was excreted as water-soluble material, little being
    chloroform-soluble.  Some 66-70% of water-soluble products appeared in
    the urine within 12 h.  Twenty-four percent of the 14C-methyl
    labelled material was eliminated in the expired air as carbon dioxide. 
    Low levels of trichlorfon and its metabolites have been detected in
    the milk of cows treated with trichlorfon.

    2.3  Effects on organisms in the environment

    Trichlorfon is moderately toxic for fish (96-h LC50 values range
    between 0.45 mg/litre and 51 mg/litre), and moderately to highly toxic
    for aquatic arthropods (48-h/96-h LC50 values range between
    0.75 g/litre and 7800 g/litre).  However, the reported
    concentrations of trichlorfon found in surface waters, after
    application in forests at 6 kg/ha, fell short of these ranges.  Thus,
    normal use of trichlorfon will have little or no effect on populations
    of aquatic organisms, since other groups, such as molluscs and
    microorganisms, are less sensitive than arthropods.  Trichlorfon is
    moderately toxic for birds, LD50 values from laboratory studies
    ranging between 40 mg/kg and 180 mg/kg body weight.  However, field
    studies following aerial application of trichlorfon did not reveal any
    effects on the numbers, breeding pairs, nesting success, or mortality
    of forest songbirds.  A reduction observed in singing and an increase
    in feeding activity may have resulted from a reduction in food
    organisms.  There is no indication that trichlorfon will adversely
    affect organisms in the terrestrial environment other than arthropods. 
    There is no information on the effects on beneficial arthropods.

    2.4  Effects on experimental animals and in vitro test systems

    Trichlorfon is an insecticide that is moderately toxic for animals. 
    The oral LD50 values of technical trichlorfon in laboratory animals
    range from 400 to 800 mg/kg body weight; the dermal LD50 values for
    the rat exceed 2000 mg/kg body weight. Trichlorfon poisoning causes
    the usual organophosphate cholinergic signs attributed to the
    accumulation of acetylcholine at nerve endings.  Technical trichlorfon
    was shown to be moderately irritating to the eyes of rats, but was not
    irritating in skin tests on rabbits.  Skin sensitization potential was
    demonstrated in guinea-pigs.

    Short-term, oral toxicity studies were carried out on rats, dogs,
    monkeys, rabbits, and guinea-pigs.  In a 16-week study on rats, a
    4-year study on dogs, and a 26-week study on monkeys,
    no-observed-effect levels (NOELs) of 100 mg/kg diet, 50 mg/kg diet,
    and 0.2 mg/kg body weight (based on plasma, erythrocyte, or brain ChE
    activity) respectively, were determined.  Inhalation exposure of rats,
    over a 3-week period, indicated a NOEL of 12.7 mg/m3, based on the
    inhibition of plasma, erythrocyte, and brain ChE activity. Long-term
    toxicity/carcinogenicity studies were carried out on mice, rats,

    monkeys, and hamsters, after oral, intraperitoneal, or dermal
    administration.  An adverse effect on the gonads was demonstrated
    following the oral exposure of mice and rats at dose levels of
    30 mg/kg body weight and 400 mg/kg diet, respectively.  From a
    24-month study on rats and a 10-year study on monkeys,
    no-observed-adverse-effect levels (NOAELs) of 50 mg/kg diet and
    0.2 mg/kg body weight, respectively, were determined.  

    No evidence of carcinogenicity has been found following the long-term
    exposure of test animals using several routes of administration.

    Under physiological conditions, trichlorfon has been reported to have
    a DNA-alkylating property.  The trichlorfon mutagenicity results have
    been both positive and negative.  Dichlorvos may be either partly or
    fully responsible for the effects observed.  The results of most of
    the  in vitro mutagenicity studies on both bacterial and mammalian
    cells were positive, while few of the  in vivo studies produced
    positive results.

    Studies on mice, rats, and hamsters indicate that trichlorfon produces
    a teratogenic response in rats at doses high enough to produce
    maternal toxicity.  Exposure of rats to 145 mg/kg diet during
    gestation caused fetal malformations.  A dose of 400 mg/kg body
    weight, administered by gavage to hamsters, also produced both
    maternal toxicity and a teratogenic response.  The lowest dose by
    gavage that produced teratogenic effects in rats was 80 mg/kg body
    weight.  The effects appeared to be time specific in the gestation
    period.  The NOEL in this study was 8 mg/kg.  NOAELS of 8 mg/kg body
    weight for rats and 200 mg/kg body weight for hamsters were
    demonstrated.  Teratogenic responses involving the central nervous
    system have been reported for the pig and guinea-pig.  However, no
    teratogenic effects were observed in a 3-generation reproduction study
    on rats, in which high dose levels induced adverse reproductive
    effects.  The NOEL in this study was 300 mg/kg diet.

    Very high doses have produced neurotoxicity in animals.

    The active transformation product in mammals is dichlorvos, which is
    estimated to be at least 100 times more potent as an
    anticholinesterase than trichlorfon.

    2.5  Effects on Human Beings

    Several cases of acute poisoning from intentional (suicide) or
    accidental exposure have occurred.  Signs and symptoms of intoxication
    included characteristics of AChE inhibition, such as exhaustion,
    weakness, confusion, excessive sweating and salivation, abdominal
    pains, vomiting, pinpoint pupils, and muscle spasms.  In severe cases
    of poisoning, unconsciousness and convulsions developed and death
    usually resulted from respiratory failure.  In cases where victims
    survived because of medical intervention, a delayed polyneuropathy
    associated with weakness of the lower limbs occurred a few weeks after

    exposure.  In fatal cases, autopsy findings have shown ischaemic
    changes in the brain, spinal cord, and vegetative ganglia, damage to
    the myelin sheath in the spinal cord and brain peduncles, and
    structural changes in the axons of peripheral nerves.

    A few cases of occupational poisoning have occurred, mainly because
    safety precautions were neglected.  Occupational exposure at a
    workplace where air concentrations exceeded 0.5 mg/m3, resulted in
    decreased levels of plasma cholinesterase and changes in the EEG
    pattern.  However, these effects were completely reversible on
    cessation of exposure. No cases of skin sensitization have been

    Trichlorfon has been extensively used for the treatment of
    schistosomiasis in humans.  Administration of a single dose
    (7-12 mg/kg) resulted in 40-60% inhibition of cholinesterase in the
    plasma and erythrocytes, without the manifestation of any cholinergic
    symptoms.  However, mild symptoms were observed in cases with a
    repeated dose regimen.  A high dose level (24 mg/kg) caused severe
    cholinergic symptoms.


    3.1  Conclusions

    Trichlorfon is a moderately toxic organophosphorus ester insecticide. 
    Overexposure through handling during manufacture or use, or accidental
    or intentional ingestion may cause serious poisoning.

    The general population is exposed to trichlorfon mainly as a result of
    agricultural and veterinary practices, and in the treatment of
     Schistosoma haematobium.

    The reported trichlorfon intakes are far below the Acceptable Daily
    Intake established by FAO/WHO and should not constitute a health
    hazard for the general population.

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

    Despite its high toxicity for non-target arthropods, trichlorfon has
    been used with little or no adverse effect on populations of organisms
    in the environment.

    3.2  Recommendations

    For the health and welfare of workers and the general population, the
    handling and application of trichlorfon should only be entrusted to
    competently supervised and well-trained operators, who will follow
    adequate safety measures and apply trichlorfon according to good
    application practices.

    The manufacture, formulation, agricultural use, and disposal of
    trichlorfon should be carefully managed to minimize contamination of
    the environment, particularly surface waters.

    Regularly exposed workers and patients should undergo periodic health

    The rates of application of trichlorfon should be limited, to avoid
    effects on non-target arthropods.  The insecticide should never be
    sprayed over water bodies or streams.


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

    Trichlorfon is an organophosphorus insecticide.  Technical trichlorfon
    and concentrated formulations are slightly toxic (acute, oral LD50
    for the rat: 560 mg/kg), but can be hazardous for human beings if
    incorrectly handled.  Trichlorfon is hazardous through ingestion and
    skin contact, because of rapid absorption.  Typical signs and symptoms
    of organophosphorus poisoning may occur rapidly with overexposure.

    Cases of delayed neurotoxicity have been reported as well as sporadic
    cases of effects on spermatogenesis.

    The human health hazards associated with certain types of exposure to
    trichlorfon, together with preventive and protective measures and
    first aid recommendations are listed in the Summary of Chemical
    Information (section 6).

    4.1.1  Advice to physicians  Symptoms of poisoning

    Trichlorfon is an indirect inhibitor of cholinesterase, i.e., it is
    converted in the body into the active transformation product,
    dichlorvos.  As a result, signs and symptoms of overexposure develop
    after a latent period and may continue to increase after exposure has
    been discontinued.  Initially, there may be feelings of exhaustion,
    headache, weakness, and confusion.  Then, vomiting, abdominal pain,
    and excessive sweating and salivation may develop.  The pupils are
    small.  Difficulty in breathing may be experienced, due to either
    congestion of the lungs or weakness of the respiratory muscles.  In
    severe cases of poisoning, muscle spasms, unconsciousness, and
    convulsions may develop.  Death results from respiratory failure.

    For a more complete treatise on the effects of organophosphorus
    insecticides, especially their short- and long-term effects on the
    nervous system, refer to Environmental Health Criteria 63:
    Organophosphorus insecticides - a general introduction (WHO 1968).  Medical treatment

    Since trichlorfon formulations may contain petroleum distillates, it
    is preferable not to induce vomiting.  In the case of ingestion of
    liquid formulations containing hydrocarbon solvents, vomiting involves
    a risk of aspiration pneumonia.  Instead, the stomach should be
    emptied, as soon as possible, by careful gastric lavage using 5%
    sodium bicarbonate (with 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 intravenously and
    1000-2000 mg of pralidoxime chloride or 250 mg of obidoxime chloride

    (adult dose), intramuscularly or intravenously, to patients suffering
    from severe respiratory difficulties, convulsions, or 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.  For children, the doses are
    0.04-0.08 mg of atropine/kg body weight, 250 mg of pralidoxime
    chloride per child or 48 mg of obidoxime chloride/kg body weight.

    Diazepam 10 mg (adult dose) should be given, subcutaneously or
    intravenously, in all but the mildest cases.

    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 the determination of the cholinesterase activity (ChE) in venous

    For more information on the treatment of poisoning by organophosphorus
    insecticides see Environmental Health Criteria 63: Organophosphorus
    insecticides: - a general introduction (WHO 1986).  The section on
    therapy from this publication is attached as Annex 1 of this guide.

    4.1.2  Health surveillance advice

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

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

    4.2  Explosion and Fire Hazards

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

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

    4.3  Storage

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

    4.4  Transport

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

    4.5  Spillage and Disposal

    4.5.1  Spillage

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

    Prevent liquid from spreading and contaminating other cargo,
    vegetation, or waterways with a barrier of the most suitable material
    available, e.g., earth or sand.  If the spill occurs into a waterway
    and the trichlorfon-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 material.

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

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

    4.5.2  Disposal

    Contaminated absorbents, containers, surplus product, etc., should be
    burnt in a proper incinerator, at high temperatures, 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.


    Trichlorfon is moderately toxic for birds and fish, but highly toxic
    for arthropods. It does not bioaccumulate, and it breaks down rapidly
    in the environment.

    Avoid contamination of the soil, water, and atmosphere by proper
    methods of storage, transport, handling, and waste disposal.

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


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

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


    Chemical formula: C4H8Cl3O4P

    CAS chemical name: dimethyl 2,2,2-trichloro-1-hydroxyethylphosphonate

    CAS registry number: 52-68-6


    PHYSICAL PROPERTIES                                                   OTHER CHARACTERISTICS

    Appearance                         colourless crystals                Colourless crystalline powder; stable at room temperature;
    Melting point                      83-84C                            slowly hydrolysed in acid media, with half-life of 526 days at
    Boiling point                      100C (0.1 mmHg)                   pH 1-5 (20C); at pH 8 (37.5C) hydrolyses to dichlorvos,
    Vapour pressure                    7.8  10-6mmHg (20C)              but 100% transformed to less toxic products within 24 h;
    Volatility                         0.022 mg/m3(20C)                  decomposes under ultraviolet radiation

    Density                            d  1.73

    Solubility at 25C in g/100 ml
      water                            15.4
      benzene                          15.2
      chloroform                       75.0
      diethyl ether                    17.0
       n-hexane                         0.08
    Partition coefficient
      (octanol/water) log Pow          0.57
    Corrosiveness                      corrosive to metals


    HAZARDS/SYMPTOMS                        PREVENTION AND PROTECTION                    FIRST AID

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

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

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

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

    INGESTION: an unlikely                  Wash hands before eating, drinking,          Induce vomiting, if the subject is conscious,
    occupational hazard                     using the toilet, and after work             except in the case of an emulsifiable 
                                                                                         concentrate; obtain medical attention  

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


    HAZARDS/SYMPTOMS                        PREVENTION AND PROTECTION                    FIRST AID

    REPEATED EXPOSURE BY                    As above                                     As above
    OR THROUGH SKIN may gradually 
    lead to signs and symptoms associated
    with inhibition of cholinesterase 



    The information given in this section has been extracted from the
    International Register of Potentially Toxic Chemicals (IRPTC) legal
    file. A full reference to the original national document from which
    the information was extracted can be obtained from IRPTC.  When no
    effective date appears in the IRPTC legal file, the year of the
    reference from which the data are taken is indicated by (r).

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

    7.1  Previous Evaluations by International Bodies

    Trichlorfon was evaluated by the Joint FAO/WHO Meeting on Pesticide
    Residues (JMPR) in 1971, 1975, and 1978.  In 1978, the JMPR
    established an Acceptable Daily Intake (ADI) for humans of
    0-0.01 mg/kg body weight.

    The International Agency for Research on Cancer (IARC) evaluated
    trichlorfon in 1987, and concluded that the data were inadequate to
    evaluate its carcinogenicity for experimental animals, and that no
    data on its carcinogenicity for humans were available.  It was
    therefore classified in Group 3.

    The International Programme on Chemical Safety (WHO) classified
    technical trichlorfon as "slightly hazardous" (Class III).  WHO has
    issued a data sheet on trichlorfon (No. 27).

    7.2  Exposure Limit Values

    Some exposure limit values are given in the table on pp. 28-29.  When
    considering exposure limits, however, it is important also to include
    any residues of its major conversion product, dichlorvos (see HSG
    No. 18: Dichlorvos).

    7.3  Specific Restrictions

    Trichlorfon has been officially approved for use as a pesticide in
    most countries.  In some countries, specific uses as well as
    limitations and precautions are defined. In the USSR, it was banned
    for use in livestock farming in 1987.  In Norway, its use is not
    permitted for medical treatment.



    Medium     Specification     Country/          Exposure limit description                            Value               Effective
                                 organization                                                                                date

    AIR        Workplace         Hungary           Maximum allowable concentration (MAC)
                                                   - Ceiling value                                       0.5 mg/m3           1988

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

    AIR        Ambient           USSR              Maximum allowable concentration (MAC) 
                                                   (average per day)                                     0.04 mg/m3          1984
                                                   - Ceiling value                                       0.5 mg/m3

    FOOD       Intake from       FAO/WHO           Acceptable daily intake (ADI)                         0-0.01 mg/kg        1978
                                                                                                         body weight

    FOOD       Residue           FAO/WHO           Maximum residue limit (MRL)                           0.05-2 mg/kg        1986, 1988,
                                                   products specified as follows:                                            1989
                                                   -  Carrots, eggplants (aubergines), milk, parsley, 
                                                      sugar beets                                        0.05 mg/kg
                                                   -  Artichokes, beans (black-eyed, green, lima), 
                                                      cattle (carcass, meat, byproducts, fat), cereal 
                                                      grains, cherries, citrus fruits, cotton seed,
                                                      cow peas, linseed, mustard greens, peanuts
                                                      (shell-free), pigs (carcass meat, byproducts, 
                                                      fat), pumpkins, radishes, rapeseed, safflower
                                                      seed (plus cob), sheep (carcass meat), soya
                                                      beans, turnips                                     0.1 mg/kg
                                                   -  Bananas (pulp), beet root, brussels sprouts, 
                                                      cauliflower, celery, kale, peaches, sweet corn
                                                      (kernels + cob), tomatoes                          0.2 mg/kg
                                                   -  Cabbage, grapes, lettuce, spinach                  0.5 mg/kg
                                                   -  Banana, peppers, strawberries                      1.0 mg/kg
                                                   -  Apples                                             2.0 mg/kg


    Medium     Specification     Country/          Exposure limit description                            Value               Effective
                                 organization                                                                                date

    WATER      Surface           USSR              Maximum allowable concentration                       0.05 mg/kg          1983
               fishing           USSR              Maximum allowable concentration                       0.00 mg/kg          1983

    SOIL                         USSR              Maximum allowable concentration                       0.05 mg/kg          1976


    7.4  Labelling, Packaging, and Transport

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

         Hazard Class 6.1:        poisonous substance;

         Packing Group III:       a substance presenting a relatively low
                                  risk of poisoning in transport, for
                                  material containing 70% (solid) or 23%

    The label should be as follows:

    FIGURE 1

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

    FIGURE 2

    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 Economic Community legislation on the labelling of
    pesticide preparations classifies trichlorfon in Class IIB for the
    purpose of determining the labels for preparations containing
    trichlorfon and other active ingredients.

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

    "The material shall consist of trichlorfon together with related
    manufacturing compounds and shall be in the form of a white
    crystalline powder free from extraneous impurities or added modifying

    The material should contain at least 970 g trichlorfon per kg.  The
    acidity and water content are specified and analytical methods for
    checking are given.

    The specification continues:

    "The technical trichlorfon 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 trichlorfon to specification WHO/SIT/13.R3

         Batch or reference number, and date of test

         Net weight of contents

         Date of manufacture


   and the following minimum cautionary notice:

          "Trichlorfon is an organophosphorus compound that inhibits
          cholinesterase.  It is poisonous if swallowed or absorbed
          through the skin.  Avoid skin contact;  wear protective gloves
          and clean protective clothing while using 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."

    Similar specifications and instructions are given for trichlorfon
    emulsifiable concentrate and water-soluble powder.

    FAO gives similar product specifications for trichlorfon for its use
    in plant protection.  In this case, the technical material should
    contain at least 97% active material.  Containers must comply with
    pertinent national and international transport and safety regulations.

    7.5  Waste Disposal

    In the USA, any waste containing trichlorfon is considered a hazardous
    waste and permits are required for its handling, transport, treatment,
    storage, discharge, and disposal.


    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-present)  Evaluation of some pesticide residues in food.
    Rome, Food and Agriculture Organization of the United Nations.

    FAO/WHO (1986a)  Guide to Codex recommendations concerning pesticide
    residues.  Part 8. Recommendations for methods of analysis of
    pesticide residues. 3rd ed., Rome, Codex Committee on Pesticide

    FAO/WHO (1986b)  Codex maximum limits for pesticide residues.
    CAC/Vol.XIII - ed. 2, Rome, Codex Alimentarius Commission, Food and
    Agriculture Organization of the United Nations, - plus Supplement 1
    (1988) and Supplement 2 (1989).

    GIFAP (1982)  Guidelines for the safe handling of pesticides during
    their formulation, packing, storage and transport. Brussels,
    Groupement International des Associations Nationales des Fabricants de
    Produits Agrochimiques.

    GIFAP (1983) Guidelines for the safe and effective use of pesticides.
    Brussels, Groupement International des Associations Nationales des
    Fabricants de Produits Agrochimiques.

    GIFAP (1984)  Guidelines for emergency measures in cases of pesticide
    poisoning. Brussels, Groupement International des Associations
    Nationales des Fabricants de Produits Agrochimiques.

    GIFAP (1987)  Guidelines for the safe transport of pesticides.
    Brussels, Groupement International des Associations Nationales des
    Fabricants de Produits Agrochimiques.

    IARC (1972-present)  IARC monographs on the evaluation of carcinogenic
    risk of chemicals to man. Lyon, International Agency for Research on

    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. Geneva, International Register of
    Potentially Toxic Chemicals, United Nations Environment Programme.

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

    SAX, N.I. (1984)  Dangerous properties of industrial materials. New
    York, Van Nostrand Reinhold Company Inc.

    UNITED NATIONS (1986)  Recommendations on the transport of dangerous
    goods. 4th ed., New York, United Nations.

    US NIOSH/OSHA (1981)  Occupational health guidelines for chemical
    hazards. 3 Vols, Washington DC, US Department of Health and Human
    Services, US Department of Labor (Publication No. DHHS(NIOSH) 01-123).

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

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

    WHO (in preparation)  Environmental Health Criteria 132: Trichlorfon.
    Geneva, World Health Organization.

    WHO/FAO (1975-87)  Trichlorfon, Data sheets on pesticides, No. 27.
    Geneva, World Health Organization (Unpublished document).

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



    (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 water.  This treatment is, however,
    contraindicated in the case of pesticides dissolved in hydrocarbon
    solvents.  Gastric lavage (with addition of bicarbonate solution or
    activated charcoal) can also be performed, particularly in unconscious
    patients, taking care to prevent aspiration of fluids into the lungs
    (i.e., only after a tracheal tube has been put in place).

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

    I.2  General Supportive Treatment

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

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

    I.3  Specific Pharmacological Treatment

    I.3.1  Atropine

    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 of 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 on 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 I

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

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

    PLESTINA, R.  (1984) Prevention, diagnosis, and treatment of
    insecticide poisoning. Geneva, World Health Organization (Unpublished
    WHO document. VBC/84.889).

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

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


    See Also:
       Toxicological Abbreviations
       Trichlorfon (EHC 132, 1992)
       Trichlorfon (JECFA Food Additives Series 51)
       Trichlorfon (WHO Food Additives Series 45)
       TRICHLORFON (JECFA Evaluation)
       Trichlorfon (WHO Pesticide Residues Series 1)
       Trichlorfon (WHO Pesticide Residues Series 5)
       Trichlorfon (Pesticide residues in food: 1978 evaluations)
       Trichlorfon (IARC Summary & Evaluation, Volume 30, 1983)