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         It must be noted that the issue of a Data Sheet for a
    particular pesticide does not imply endorsement of the pesticide by
    WHO or FAO for any particular use, or exclude its use for other
    purposes not stated. While the information provided is believed to
    be accurate according to data available at the time when the sheet
    was compiled, neither WHO nor FAO are responsible for any errors or
    omissions, or any consequences therefrom.

    The issue of this document does    Ce document ne constitue pas une
    not constitute formal              publication. Il ne doit faire
    publication. It should not be      l'objet d'aucun compte rendu ou
    reviewed, abstracted or quoted     résumé ni d'aucune citation sans
    without the agreement of the       l'autorisation de l'Organisation
    Food and Agriculture               des Nations Unies pour
    Organization of the United         l'Alimentation et l'Agriculture
    Nations or of the World Health     ou de l'Organisation Mondiale de
    Organization.                      la Santé.


    Primary Use: Insecticide

    Secondary Uses: Acaricide, Anthelminthic 

    Chemical Group: Organophosphorous compound

    Date issued:


    1.1   COMMON NAME - Trichlorfon (ISO)

          Identity: Dimethyl (2,2,2-trichloro-1-hydroxyethyl)phosphonate


          Synonyms:  OMS-0800    
                     Dipterex, Dylox, Neguvon
                     Bay 15922,  Bayer 2349  
                     Tugon, Masoten, Anthon  
                     Dyvon,  L 13/59  
                     Metrifonate  (when used as a parasiticidal drug)

          Local synonyms:

    1.2   SYNOPSIS - An organophosphorous compound of 
          moderate mammalian toxicity, with a wide spectrum of usage.  It 
          is rapidly metabolised in man and animals and does not accumulate 
          in body tissues. 


    1.3.1 Characteristics - A white crystalline powder of m.p. 
          83-84°C; the technical material is trichlorfon 98% pure, with a 
          minimum m.p. of 77°C. 

    1.3.2  Solubility - Its solubility in water is good. 
          15.4 g/litre at 25°C.  It is also soluble in benzene, ethanol and 
          most chlorinated hydrocarbons, but insoluble in petroleum oils 
          and poorly soluble in diethyl ether and carbon tetrachloride. 

    1.3.3 Stability - It is stable at room temperature 
          and is converted to dichlorvos in alkaline medium. In acid medium 
          (pH 1-5) 50% is hydrolysed at 20°C in 526 days. 

    1.3.4 Vapour pressure (volatility) - 10-5 mbar at 20°C.


    1.4.1 Common formulations - Wettable powders 50%; soluble 
          powders 58, 80 and 95%; soluble concentrate 50%; ULV at 
          concentrations of 250, 500 and 750 g. A.I. per litre; dusts 5%, 
          granules 2-1/2 and 5%; Tugon fly mats; cardboard discs 
          impregnated with 0.1 g A.I.; Nevugon preparations for veterinary 

    1.4.2 Pests controlled - Lepidopterous larvae, 
          household pests, DDT resistant flies and chlordane resistant 
          cockroaches, ectoparasites on domestic animals. 

    1.4.3 Use pattern - Used in sugar based fly baits; as 
          dust against insects on vegetables, tobacco, and ornamentals; as 
          granules for control of stalk borers and leaf eating caterpillars 
          as maize and sugar cane; by ULV application in forestry, cotton 
          and cereal crops. 

    1.4.4 Unintended effects - It should not be applied 
          to wet cotton plants of sensitive varieties.  It should not be 
          applied on apple trees until 4 weeks after petal fall otherwise 
          damage to fruit and leaves may be caused. 


          No public health use for insecticide but extensive trials have 
          been carried out in its use orally as a schistosomicidal drug. 


          Marketed as a shampoo and powder formulation for control of fleas 
          and ticks in dogs and cats, and also for control of stable flies 
          as "Tugon fly mats". 



    2.1.1 Absorption route - Trichlorfon can be absorbed from 
          the gastrointestinal tract by inhalation or through the intact 

    2.1.2 Mode of action - Metabolised to dichlorvos 
          which inhibits cholinesterase. 

    2.1.3 Excretion products - Although studied 
          extensively, the metabolism is not fully understood.  Trichlorfon 
          can be rearranged by dehydrochlorination to form dichlorvos, 
          though only to a very minor extent in mammals.  As dichlorvos is 
          considerably more toxic than trichlorfon, this rearrangement is 
          important toxicologically.  Hydrolysis of the phosphonate bond
          can occur as well as hydrolysis of the methoxy moiety. 
          Trichloroethanol, which is subsequently conjugated, may be 
          formed.  Degradation and excretion is very rapid in mammals.
          In rats after an oral dose, 71% of the total was found in the 
          urine in 16 hours and in cows 66% in 12 hours.  Trichlorfon may
          be excreted in milk. 

    2.1.4 Toxicity, single dose

          Oral: LD50 Rat (M) 630 mg/kg
                     Rat (F) 560 mg/kg

          Dermal: LD50 Rats (M  &  F)  >2800  mg/kg
                     Rabbits (M & F) 5000 mg/kg

    2.1.5 Toxicity, repeated doses

          Oral: Rats were fed diets containings 0, 20, 100 and 300 ppm of 
          trichlorfon for 16 weeks.  Significant cholinesterase inhibition 
          was observed at 300 ppm.  No effects on growth, behaviour, food 
          consumption or gross and microscopic tissue examination were 
          observed at 100 ppm.  Two dogs were given trichlorfon at 45 mg/kg 
          orally six days a week for three months.  No mortality was 
          observed.  The serum cholinesterase level was 60% of normal at 
          the conclusion of the experiment. 

          Inhalation: Inhalation studies in a static chamber exposing rats 
          and guinea-pigs to concentrations of 22 mg/litre of air, caused 
          symptoms of cholinergic stimulation but no deaths.  At 8 
          mg/litre, no signs of poisoning were observed. 

          Cumulation of compound:  Trichlorfon is rapidly absorbed, 
          degraded and excreted. Dermal application of 300 and 100 ml of 
          labelled trichlorfon to cattle resulted in maximum blood 
          concentrations 10-16 hours after application, and the levels were 
          0.45-0.47 ppm with 300 ml and 0.1-0.2 ppm with 100 ml; 
          respectively.  Trace amounts were still detected after 60 hours. 

          Cumulation of effect: In spite of its low toxicity, continued 
          ingestion of trichlorfon can be expected to reduce cholinesterase 
          to hazardous levels. It has been shown that recovery of 
          cholinesterase activity in man may take 30-40 days after oral 

    2.1.6 Dietary studies

          Short-term: Dogs of both sex were fed trichlorfon in the diet at 
          levels of 0, 50, 250, 500 and 1000 ppm for one year. 

          Cholinesterase activity was reduced at 500 and 100 ppm and 
          increased spleen weight with congestion of apparent lymphoid 
          atrophy was noted. Males at 1000 ppm exhibited a decrease in 
          spermatogenesis and hyperplastic nodules in the adrenals.  No 
          effects were noted on mortality, growth, food consumption, 
          behaviour of gross and microscopic tissue examination apart from 
          those mentioned above. 

          Long-term: Several long-term studies on the toxicity of 
          trichlorfon have been carried out, both in rats and dogs. 

          In rats, survival time was decreased at doses of 1000 ppm in the 
          diet.  Reduction of serum cholinesterase activity have been 
          observed at dietary levels of 400 ppm and above.  Enhanced aging 
          of the reproductive tissues, aspermogenesis in males and an 
          absence of primary follicles and primitive ova in females, were 
          observed in one experiment at dietary levels of 500 and 1000 ppm.  
          In a second experiment, an increased incidence of cystic granular 
          ovaries was observed, that appeared to be dose related at dietary 
          levels of 100, 200 and 400 ppm.  A third and larger experiment 
          failed to confirm these findings on the reproductive tissues.  
          Decreased cholinesterase (values were observed at 1000 ppm and 
          increased liver size and SG-OT activity in female rats and SDH 
          activity in both sexes was observed. 

          Dogs of both sexes were maintained for four years on diets 
          containing 0, 50, 200, 800 and 3200 ppm.  One out of four male 
          dogs and two out of four female fed diet at 800 ppm survived the 
          four year period.  Cholinesterase activity was reduced at 200 ppm 
          and this reduction was greatest at the beginning of the 
          experiment and tended to decrease as the experiment progressed.  
          At 3200 ppm, levels of serum transaminases SGOT and SGPT were 
          increased.  At 800 ppm male dogs had enlarged spleens and smaller 
          adrenals and testis, and females at 3200 ppm had enlarged liver, 
          spleen and adrenals and reduced ovary size. 

    2.1.7 Supplementary studies of toxicity

          Reproductive study: A three generation rat reproduction study at 
          levels of 0, 100, 300, 1000 and 3000 ppm in the diet resulted in 
          adverse effects on reproduction at 1000 ppm and above.  At 1000 
          ppm there was evidence of reduced fertility, smaller litters and 
          reduced body weight of pups. At 3000 ppm the pregnancy rate was 
          markedly reduced and the pups were smaller and lighter in weight 
          with none surviving to weaning.  No effects were noted at 300 ppm 
          or below. Microscopic examination of the F3b generation indicated 
          no adverse effects. 

          Carcinogenicity: In two experiments in rats fed diets containing 
          200 ppm and above, an increased incidence of benign mammary 
          tumours was observed, which appeared to be dose related.  In 
          another experiment a higher incidence of forestomach papilloma 
          was observed when mice were administered trichlorfon three times 
          per week for five months. 

          Teratogenicity: No foetal abnomalities or embryo-toxic effects 
          were observed when trichlorfon was administered orally at 100 
          mg/kg to pregnant rats from day 6 to day 15 of 
          gestation.  However, when pregnant rats were subjected to 
          continuous inhalation exposure to trichlorfon for 20 days at 
          0.0005, 0.02 and 9 mg/m3, at all dose levels, there were external 
          and internal abnormalities in the development of the embryos. 

          Mutagenicity: Dominant lethal tests run  with  male  mice  
          injected  with  a  single  dose of 0.50 or 100 mg/kg and mated to 
          untreated females, resulted in no adverse effects on reproduction 
          or on the young. 

          Acute oral and subcutaneous dosing of hens at doses of 100 mg/kg 
          and 90 mg/kg respectively, have not resulted in any delayed 
          ataxia.  Dietary levels of trichlorfon fed to hens at 5000 ppm 
          for 30 days did not result in ataxia.  However, delayed 
          neurotoxicity has been reported in men exposed to certain 
          formulations (see 2.2.3 and 2.2.6 below). 

          Other studies: A single acute oral dose of trichlorfon (500 
          mg/kg) when given to rats caused immunological depression; the 
          phagocytic activity of the reticuloendothelial system was 
          decreased for 60 days.  Chronic dosing at 25 mg/kg, insufficient 
          to produce symptoms of toxicity, caused a similar depression from 
          the second week of dosing and lasting for two months after the 
          termination of treatment. The most sensitive parameters appeared 
          to be the bactericidal activity of the skin, serum lysozyme and 
          ß-lysine levels, and the phagocytic activity of the 
          reticuloendothelial system. 

    2.2   TOXICOLOGY - MAN

    2.2.1 Absorption - Trichlorfon may be absorbed from the 
          gastrointestinal tract, by inhalation, or through the intact 

    2.2.2 Dangerous doses

          Single: 75 mg/kg caused severe vomiting, colic and weakness for 
          three days. 35 mg/kg caused vomiting, colic and weakness that 
          were evident for three hours. 

          Repeated: 3 doses of 7.5 mg/kg on consecutive days caused a 50% 
          reduction in plasma cholinesterase. 12 daily doses of 5 mg/kg 
          caused colic and blurring of vision. 

    2.2.3 Observations of occupationally exposed workers 
          - A group of workers were poisoned while working in a field 
          treated on day previously with chlorofos (trichlorfon).  Symptoms 
          included headaches, dizziness, nausea, weakness, hand tremor and 
          pain in the limbs, burning sensations in the tongue and eyes and 
          a feeling of permanent noise in the ears.  Two of these workers 
          lost consciousness and some had psychic disturbances such as 
          depression and apathy.  Peripheral nervous system disturbances 
          developed 7-10 days following this incident, focused mainly on 
          the lower limbs. 

    2.2.4 Observations of the general population - 
          Trichlorfon is of low persistency; under normal conditions of use 
          the general population should not be exposed to levels of 
          toxicological significance.  Residues found in food usually 
          disappear during processing or cooking.  The estimate of the 
          temporary acceptable daily intake for man is from 0-0.01 mg/kg 
          per day. 

    2.2.5 Observations of volunteers and people receiving the 
          compound as antiparasitic drug - Over 12 000 people have 
          been treated with trichlorfon under the name of metrifonate over 
          the last few years for various intestinal and body parasites.  
          The dosage has varied from 5 mg/kg up to 70 mg/kg.  Repeated dose 
          over periods of 12 days have been given, at 5 mg/kg. 7.5 mg/kg 
          given 2-4 times at two week intervals has caused cholinesterase 
          inhibition, weakness, nausea, diarrhoea, and abdominal pain.  
          Higher doses, 24 mg/kg, caused more severe symptoms, including 
          tachycardia, salivation, colic pain, vomiting, nausea, fatigue 
          trends and sweating. Spontaneous recovery in all cases was rapid. 

    2.2.6 Reported mishaps - There have been several 
          reports of accidental or suicidal poisonings with trichlorfon.  
          Most of these reports involve the chlorofos formulation of 
          trichlorfon.  A 37-year old man who intentionally ingested 100 ml 
          of a 30% formulation of chlorofos was admitted to hospital with 
          miosis, bronchorrhea and bradycardia.  Cholinesterase activity 
          was severely reduced.  Acute relapses, including bronchospasm and 
          cardiac arrest were seen and pneumonia was also evident.  
          Recovery took 47 days and in the course of treatment 200 ml of 
          atropine solution and 120 ml of oxime reactivator were used.  
          Some cases of neurological disorders have resulted from ingestion 
          of chlorofos, these are typified by the case of a woman who had 
          drunk about 200 ml of this compound.  She was in a comatose state 
          for 11 hours and subsequently there was exhausting vomiting, 
          severe headache, stomach pains, frequent liquid stools and 
          general weakness. She was considerably improved and discharged 
          after 10 days.  Later she noticed increased general 
          fatiguability, especially "tiredness" of the muscles of the lower 
          extremities.  Seven to 10 days after discharge, paresthesia 
          appeared in the form of burning and stabbing pains in the region 
          of the foot.  This slowly increased to affect the hands, intense 
          pain occurred in the arms and legs.  There was increased tendency 
          to sweat and discolouration of the hands and feet appeared.  By 
          this time the patient could no longer walk or hold a spoon.  Two 
          months after the initial poisoning her condition was diagnosed as 
          toxic polyneuritis with severe motor sensory and vegetative-
          trophic disorders.  Three months after ingestion the patient 
          still walked with difficulty because of deep foot paresis, her 
          Achilles reflexes could not be stimulated. 

          No cases of this type of syndrome have occurred either in man or 
          animals with any other formulation of trichlorfon. 


    2.3.1 Fish - Toxic to carp (6 ppm/48 hours)

    2.3.2 Birds - Toxic (chickens 110 mgm/kilo)

    2.3.3 Other species - Very low order of toxicity to 
          bees.  No danger once spray has dried. 



          (for definition of categories, see introduction)

          Formulations of 2% and above, category 4.

          Formulations below 2%, category 5


          Formulations in category 4 - Should be transported or stored in 
          clearly labelled rigid and leakproof containers under lock and 
          key, safe from access by unauthorized persons and children.  No 
          food or drink should be stored in the same compartment. 

          Fomulations in category 5 - Should be stored in clearly labelled 
          leakproof containers out of reach of children and away from food 
          and drink. 

    3.3   HANDLING

          Formulations in category 4 - Protective clothing (see 4.1.3 on 
          part 4) should be provided for all handling of the compound.  
          Adequate washing facilities should be available at all times 
          during handling and should be close to the site of handling.  
          Eating, drinking and smoking should be prohibited during handling 
          and before washing after handling. 

          Formulations in category 5 - No facilities other than those 
          needed for the handling of any chemical need be required. 

          All formulations - Container may be decontaminated (for method 
          see paragraph 4.3, part 4).  Decontaminated containers should not 
          be used for food and drink.  Containers that are not 
          decontaminated should be burned or crushed and buried below the 
          topsoil and care must be taken to avoid subsequent contamination 
          of water sources. 


          Formulations in category 4 - Pre-employment medical examination 
          for workers desirable.  Workers suffering from active hepatic or 
          renal disease should be excluded from contact.  Pre-employment 
          and periodic cholinesterase test for workers desirable.  Special 
          account should be taken of the workers mental ability to 
          comprehend and follow instructions.  Training of workers in 
          techniques to avoid contact essential. 
          Formulations in category 5 - Cholinesterase test for workers not 
          required. Warning of workers to minimize contact essential. 

          All formulations - Pilot and loaders should have special training 
          in application methods and early symptoms of poisoning and must 
          wear a suitable respirator.  Flagmen, if used, should wear 
          overalls and be located well away from the dropping zone. 
    3.7   LABELLING

          Formulations in category 4 - Minimum cautionary statement

          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 reach 
          of children and well away from foodstuffs, animal feed and their 
          containers.  If poisoning occurs, call a physician.  Atropine and 
          pralidoxime are specific antidotes and artificial respiration may 
          be needed. 

          Formulations in category 5 - Minimum cautionary statement
          This formulation contains trichlorfon, an organophosphorus 
          compound which inhibits cholinesterase.  It is poisonous if 
          swallowed.  Keep the material out of reach of children and well 
          away from foodstuffs, animal feed and their containers. 
    3.8   RESIDUES IN FOOD - Maximum residue limits for 
          trichlorfon have been recommended by the Joint FAO/WHO Meeting on 
          Pesticide Residues. 



    4.1.1 General - Trichlorfon is an organophosphorous 
          pesticide of moderate toxicity.  It is readily absorbed from the 
          gastrointestinal tract and may also be absorbed by the intact 
          skin and by inhalation. 

    4.1.2 Manufacture and formulation - TLV: (ACGIH) 
          (USSR) 0.5 mg/m3. Closed systems and forced ventilation may be 
          required to reduce as much as possible the exposure of workers to
          the chemical. 

    4.1.3 Mixers and applicators - When opening the 
          container and when mixing, protective impermeable boots, clean 
          overalls, gloves and respirator should be worn.  Mixing if not 
          mechanical, should always be carried out with a paddle of 
          appropriate length. When spraying tall crops or during aerial 
          application, a face mask should be worn as well as an impermeable 
          hood, clothing, boots and gloves.  The applicator should avoid 
          working in spray mists 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 the gloves.  Splashes must be 
          washed immediately from the skin and eyes, with large quantities 
          of water.  Before eating, drinking or smoking, hands and other 
          exposed skin should be washed. 

    4.1.4 Other associated workers (including flamen in aerial 
          operations) - Persons exposed to trichlorfon and associated 
          with its application should wear protective clothing and observe 
          the precautions described above in 4.1.3 under "mixers and 

    4.1.5 Other populations likely to be affected - With 
          good use, practice subject to 4.2 below, other persons should not 
          be exposed to hazardous amounts of trichlorfon. 

          Unprotected persons should be kept out of treated areas for two 

          Residues in containers should be emptied in a diluted form into a 
          deep pit, taking care to avoid ground waters.  The emptied 
          containers may be decontaminated by rinsing two or three times 
          with water and scrubbing the sides.  An additional rinse should 
          be carried out with 5% sodium hydroxide solution which should 
          remain in the container overnight.  Impermeable gauntlets should 
          be worn during this work and a soakage pit should be provided for 
          the rinsings.  Decontaminated containers should not be used for 
          food and drink. 

          Spillage of trichlorfon and its formulations should be removed by 
          washing with 5% sodium hydroxide solution and then rinsing with 
          large quantities of water. 

    4.4.1 Early symptoms of poisoning - Early symptoms of 
          poisoning may include excessive sweating, headache, weakness, 
          giddiness, nausea, vomiting, stomach pains, blurred vision, 
          slurred speech and muscle twitching.  Later there may be 
          convulsions, coma, loss of reflexes and loss of sphincter 

    4.4.2  Treatment before person is seen by a physician, if 
          these symptoms appear following exposure - The person should 
          stop work immediately, remove contaminated clothing and wash the 
          affected skin with water and soap, if available, and flush the 
          area with large quantities of water.  If swallowed, vomiting 
          should be induced if the person is conscious.  In the event of 
          collapse, artificial respiration should be given, bearing in mind 
          that if mouth to mouth respiration, vomit may contain toxic 
          amounts of trichlorfon. 



    5.1.1 General information - Trichlorfon is an 
          organophosphorus pesticide of moderate toxicity.  It is readily 
          absorbed from the gastrointestinal tract, by inhalation and to 
          lesser extent by the intact skin.  It acts by inhibiting 
          acetylcholinesterase.  It is rapidly degraded and excreted mainly 
          in the urine. 

    5.1.2 Symptoms and signs - Symptoms of poisoning are 
          mainly cholinergic and include headache, excessive sweating, 
          weakness, giddiness, nausea and vomiting, stomach pains, blurred 
          vision, slurred speech and muscle twitching.  More advanced 
          symptoms of poisoning may be convulsions, coma, loss of reflexes 
          and loss of sphincter control.  Delayed ataxia has been recorded 
          in cases involving the chlorofos formulation. 

    5.1.3 Laboratory - The most important laboratory 
          finding is reduction in activity of blood cholinesterases.  
          Urinary levels of phosphate metabolites can also be used to 
          monitor exposure. 

    5.1.4 Treatment - If the pesticide has been ingested, 
          unless the patient is vomiting, rapid gastric lavage should be 
          performed using 5% sodium bicarbonate, if available.  For skin 
          contact, the skin should be washed with soap and water.  If the 
          compound has entered the eyes, they should be washed with 
          isotonic saline or water. 

          Persons without signs of respiratory inefficiency but with 
          manifest peripheral symptoms should be treated with 2-4 mg of 
          atropine sulfate and 1000-2000 mg of pralidoxime chloride or 250 
          mg of toxogonin (adult dose) by slow intravenous injection.  More 
          atropine may be given as needed.  Persons with severe 
          intoxication, with respiratory difficulties, convulsions and 
          unconsciousness should immediately be given atropine and a 
          reactivator.  In such severe cases 4-6 mg of atropine sulfate 
          should be given initially followed by repeated doses of 2 mg at 
          5-10 minute intervals.  The patients' condition including 
          respiration, blood pressure, pulse frequency, salivation and 
          convulsions should be carefully observed as a guide to further 
          administration of atropine.  If the patient is cyanotic, 
          artificial respiration should be given at the same time as 

          The airways should be kept free and artificial respiration should 
          be applied, if required, preferably by mechanical means.  If 
          necessary, intubation should be performed. 
          Contraindications are morphine, barbiturates, phenothiazine 
          tranquillizers and central stimulants of all kinds. 

    5.1.5 Prognosis - If the acute toxic effect is 
          survived and adequate artificial respiration has been given, if 
          needed, the chances of complete recovery are good.  However, in 
          very severe cases, particularly if artificial respiration has 
          been inadequate, prolonged anoxia may give rise to pemanent brain 
          damage.  There has been report of delayed ataxia with the 
          chlorofos formulation. 

    5.1.6 References of previously reported cases

          Stutev, A. A. & Varenkina, T. T. (1969) KLINIK Med., 47, 9, 140-
          142 abstracted in Health Aspects of Pesticides (1970), 3 (3), 70-

          Luzhrikov, Ye.  A. & Kosarev, V. A. (1971) TER ARKH, 43, 106-108 
          abstracted in Health Aspects of Pesticides (1972), 5, (7), 72-


          Test            Normal level*  Action level*  Symptomatic level*

    Plasma cholinesterase     100%           50%             Variable

    Erythrocyte               100%           70%           Usually <40%

                 *Expressed as a percentage of pre-exposure activity.

          Urinary levels of organophosphorus metabolites can also be used 
          to determine exposure. 


    5.3.1  Detection and assay of compound - References are 
          given only. 

          Trichlorfon can be extracted from animal tissues with 
          acetonitrile and be determined by gas liquid chromatography 
          (Anderson et al., 1966) or by thin layer chromatography (Beck 
          et al., 1968).  A colorimetric total phosphorus method is 
          also applicable for plant material and milk, though non-
          specific. The lower limit of determination is 0.1-0.2 ppm. 
          (Sissons, 1970 and Leaky, 1964). 

    5.3.2 Other tests in cases of poisoning - Levels of cholinesterase in 
          the blood, particularly plasma, provide the most useful 
          diagnosis of poisoning. 

          Michel, N. O. (1949), J. Lab. Clin. Med., 34, 1564-1568

          Ellman, G. L., Courtney, K. D., Andres, Y. jr & Featherstone, 
          R. M. (1961) Biochem. Pharmacol., I, 88-95 

See Also:
        Trichlorfon (EHC 132, 1992)
        Trichlorfon (IARC Summary & Evaluation, Volume 30, 1983)
        Trichlorfon (PIM 539)