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    WORLD HEALTH ORGANIZATION             FOOD AND AGRICULTURE
                                          ORGANIZATION
    ORGANISATION MONDIALE DE LA SANTE     ORGANISATION POUR L'ALIMENTATION
                                          ET L'AGRICULTURE

                                           VBC/DS/75.2  (Rev.1) 
                                           ORIGINAL : ENGLISH 


   DATA SHEETS ON PESTICIDES  No. 2  (Rev.1) 


   DICHLORVOS


                                      CLASSIFICATION: 

                                      Primary use: Insecticide 

                                      Secondary use: Acaricide, nematocide 

                                      Chemical group: Organophosphorus 
                                      compound 

                                      Data sheet No. 2 (Rev.1) August 1978 


         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.

    1.    GENERAL INFORMATION 

    1.1   COMMON NAME: Dichlorvos (ISO)                              O " 
    1.1.1 Identity: 2,2-dichloroethenyl dimethyl phosphate

    Chemical Structure

     Chemical structure;pest2.bmp

    <A NAME = 1.1.2 Synonyms: DDVP OMS 14 
            
          Local synonyms: 

    1.2   SYNOPSIS: A volatile organophosphorus insecticide.  It is of high 
          acute toxicity but its rapid metabolism renders it safe under 
          correct conditions of use.  It is directly active without having 
          to be metabolized first. 

    1.3   SELECTED PROPERTIES 

    1.3.1 Physical characteristics - When pure a colourless liquid, b.p. 
          35°C at 0.05 Torr, density 1.415 at 25°C.  Corrosive to mild 
          steel and other metals. 

    1.3.2 Solubility - Water at 20°C, 0.9%, kerosine 2-3%.  Miscible with 
          aromatic hydrocarbon solvents, chlorinated hydrocarbon solvents 
          and alcohols.       

    1.3.3 Stability - Stable to heat, hydrolyses in aqueous solutions.  The 
          saturated aqueous solution is decomposed at the rate of 3% per 
          day (half life 23 days).  Decomposition occurs more rapidly in 
          alkali and in strongly acid solutions.  At pH 1 complete 
          hydrolysis occurs within 50 minutes at room temperature.  The 
          vapour is rapidly hydrolysed in air.  Compatible with most 
          technical pesticides. 

    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 not constitute formal publication.   
    It should not be reviewed, abstracted or quoted without the     
    agreement of the Food and Agriculture Organization of the     
    United Nations or of the World Health Organization.      

    Ce document ne constitue pas une publication. Il ne dolt faire l'objet
    d'aucun compte rendu ou résumé ni d'aucune citation sans l'autorisation
    de l'Organisation des Nations Unies pour l'Alimentation et 
    l'Agriculture ou de l'Organisation Mondiale de la Santé. 

    R 683 

    1.3.4 Vapour pressure (volatility) 1.2 x 10-2 Torr at 20°C.

           
    1.4 AGRICULTURE, HORTICULTURE AND FORESTRY 

    1.4.1 Common formulations - Oil-soluble concentrate, 1000 g/l; 
    emulsifiable concentrates, 14-1000 g/l; aerosols, 4-10 g/l; bait, 1-5 
    g/l liquid, 5 g/kg dry; impregnated resin strip, giving slow release of 
    vapour, 200 g/kg. 

    1.4.2 Pests mainly controlled - Used against a wide range of mite and 
    insect pests of plants, farm animals and man, and as an anthelmintic. 

    1.4.3 Use pattern - On plants as a pre-harvest treatment for fruit, 
    vegetable, rice and field crops. on stored products and in food 
    processing premises and similar locations in the form of aerosols, 
    impregnated resin strips and in automatic dispensers.  In some 
    countries it is added to stored grain as a dust, spray or emulsion. 

    On livestock generally as sprays and aerosols and in pellets for oral 
    dosing of poultry, pigs and horses as an anthelmintic. In agricultural 
    premises as a spray or aerosol. 

    1.4.4 Unintended effects - None under normal conditions of use.  Non 
    persistant.  Danger of phytotoxicity to certain sensitive plants such 
    as ornamentals. 

        
    1.5   PUBLIC HEALTH PROGRAMMES - Used extensively in hospitals, food in 
    store and transport and food processing establishments, and in aircraft 
    for disinsection during flight. 

            
    1.6    HOUSEHOLD USE 

    1.6.1 Common formulations - Impregnated plastic strips, aerosols and 
    dilute solutions mixed with other pesticides. 

    1.6.2 Pests mainly controlled - Flies, mosquitos and crawling insects. 

    1.6.3 Use pattern - Strips are suspended in air and dichlorvos slowly 
    released for an effective period of about 3 months, depending on 
    ventilation. 

    1.6.4 Unintended effects - None known. 

            
    2.    TOXICOLOGY AND RISKS 

    2.1   TOXICOLOGY - MAMMALS 

    2.1.1 Absorption route - Absorbed by the intact skin as well as by 
    inhalation and from the gastrointestinal tract. 

    2.1.2 Mode of action - Cholinesterase inhibition. 

    2.1.3 Excretion products - Dichlorvos is rapidly metabolized in 
    mammals; hydrolytic metabolism occurs in all species and leads 
    presumably to dichloroacetaldehyde which is further metabolized by (i)
    reduction to dichloroethanol and excretion in the urine as the 
    glucuronide and (ii) dechlorination followed by incorporation of the 
    carbon atoms into endogenous biosyntheses and excretion as carbon 
    dioxide and hippuric acid in the urine.  This may form the basis of a 
    method of monitoring the exposure of humans to high concentrations of 
    dichlorvos. 

    2.1.4 Toxicity, single dose 

          Oral: LD50 rat (M): 80 mg/kg rat (F): 56 mg/kg 

          Dermal: LD50 rabbit: 107 mg/kg 

          Dermal: rat (M): 107 mg/kg rat (F):  75 mg/kg 

          Most susceptible species: Rat, oral LD50 56-80 mg/kg. 
          The mouse appears to be more susceptible than the rat to
          inhalation. 

    2.1.5 Toxicity, repeated doses: 

          Oral: See dietary studies. 

          Dermal:  A dermal dose at 50 mg/kg produced cholinergic signs
          in a monkey 20 minutes after administration; after 8 daily doses
          at this level, the animal died. 

          Inhalation: Dogs, cats and rabbits were continuously exposed
          for 8 weeks to dichlorvos atmospheres generated from impregnated 
          polyvinyl chloride strips.  Concentrations of dichlorvos in air 
          were produced in the range of 0.05-0.3 mg/m3.  No effects were 
          found on the general health, behaviour, plasma and erythrocyte 
          cholinesterase activities and electroencephalographic patterns of 
          the animals. 

          Cumulation of compound: Due to its rapid metabolism there is no
          accumulation of the compound. 

          Cumulation of effect: Repeated exposure to sub-lethal amounts
          may reduce cholinesterase activity to hazard levels. 

    2.1.6 Dietary studies 

          Short-term: A dietary concentration of only 50 mg/kg soon 
          produced detectable inhibition of plasma and erythrocyte 
          cholinesterase in rats but a dietary level of 1000 mg/kg (about 
          50 (mg/kg)/day) was tolerated for 90 days without any diminution 
          of growth or sign of intoxication. 

          Long-term: In a 2-year study in rats there was slight plasma and 
          erythrocyte cholinesterase inhibition at about 50 mg/kg (2.5 
          (mg)/day) diet but not at about 5 mg/kg (0.25 (mg/kg)/day).  No 
          visible signs of toxicity were evident at the maximum level fed 
          (about 230 mg/kg on 11.5 (mg/kg)/day).  Some hepatocellular 
          changes were however evident at about 50 mg/kg (2.5 (mg/kg)/day) 
          and above. 

    2.1.7 Supplementary studies of toxicity 

          Carcinogenicity 

          Rat: There was no increase in tumour incidence from dietary 
          levels up to 500 mg/kg, an in inhalatory concentrations of up to 
          5 mg/m3 for up to 2 years. 

          Teratogenicity 

          Rat: No terata were observed in a 3-generation reproduction 
          study with dietary levels up to 500 mg,/kg (25 mg/kg/day). 

          Rabbit: Daily doses of 31 mg/kg on days 6-11 of gestation did 
          not produce skeletal malformations in the offspring. 

          The teratogenic potential of inhaled dichlorvos vapour for 
          rabbits and rats was investigated.  The animals were exposed 
          throughout pregnancy at concentrations of 0.25 1.25 and 6.25 
          mg/m3 of dichlorvos.  The results gave no indication that 
          dichlorvos vapour is teratogenic in rabbits or rats even at 
          exposure concentrations resulting in maternal deaths in rabbits
          and causing reduction of plasma, erythrocyte and brain
          cholinesterase activities in pregnant animals of both species. 

          Mutagenicity 

          Mouse - There was no increase in incidence of aberrations of 
          bone marrow cells in mice administered a single dose of up to 20 
          mg/kg of dichlorvos.  Mice were exposed to atmospheres containing 
          vapour concentrations of 64-72 mg/m3 of dichlorvos for 16 hours, 
          or to 5 mg/m3 for 21 days.  Chinese hamsters were exposed by 
          the inhalation and oral routes to high concentrations of 
          dichlorvos.  In chromosome preparations made from bone marrow and 
          spermatocytes following exposure, the incidence of chromosome 
          abnormalities did not differ from the control values. 

          Male CFI mice were exposed to atmospheres containing dichlorvos 
          at concentrations of 30 and 55 mg/m3 for 16 hours or to 2.1 and
          5.8 mg/m3 for 23 hours daily for 4 weeks.  These exposures to
          dichlorvos produced no mutagenic effects as expressed by 
          increased pre-implantation losses or early foetal deaths in
          subsequent test mating.  No impairment of male fertility was 
          detected following the exposures to dichlorvos vapour. 

          Host-mediated assays, using saccharomyces cerevisiae D4 as the 
          test organism, were carried out on male mice dosed orally with 
          dichlorvos or exposed to dichlorvos vapour.  No enhancement of 
          mitotic gene conversion was recorded in yeast cells harvested 
          from mice which had been dosed orally with 50 or 100 mg/kg 
          dichlorvos or exposed for 5 hours to atmospheres containing 60 or 
          99 mg/m3 of dichlorvos vapour.  In stationary phase cultures of
          the yeast treated with dichlorvos, the rate of conversion
          increased after 5 hours at a concentration of 4 g/l, but no
          effect was evident with 2 g/l dichlorvos. 

          In vitro - Dichlorvos, when added at specific intervals to 
          cultures of human lymphocytes at concentrations ranging from 1 to 
          40 g/l, was cytotoxic to cells at concentrations of 5-40 g/l; the 
          cytotoxicity was not accompanied by significant cytogenetic 
          changes. 

          Man - No increase in chromosome aberrations occurred in a human 
          subject after exposure to 1 mg/m3 of dichlorvos for 6 hours. 

          Delayed neurotoxicity 

          Fowl - There was no histological evidence of demyelination of 
          the peripheral nerves when atropinized fowls were treated with 
          sufficient dichlorvos to produce 70% inhibition of 
          cholinesterase.  No paresis or paralysis was observed. 

    2.1.8 Modifications of toxicity 

          Potentiation - The acute oral toxicity of rats to dichlorvos
          was markedly potentiated by malathion and slightly potentiated by 
          mevinphos, phosphamidon and trichlorfon.  No potentiation was 
          observed when administered in combination with 23 other 
          pesticides. 

            
    2.2   TOXICOLOGY - MAN 

    2.2.1 Absorption - See 2.1.1. 

    2.2.2 Dangerous doses

          Single - Serious poisoning occurred in a man who spilled about
          120 ml of a 3% oil formulation on his lap (see 2.2.6).

          Repeated - See "observations on volunteers".

    2.2.3 Observations of occupationally exposed workers - No information 
          available. 

    2.2.4 Observations on exposure of the general population - From 
          observations on hospital patients it is necessary to inhale 
          dichlorvos at concentrations in the range 0.1-0.2 mg/m3 for 24 
          hours a day for several days before any plasma cholinesterase 
          reduction is observed.  There were no symptoms at this level. 
                                                                            
          There have been at least four studies of the value of dichlorvos 
          for malaria control. In three of them, the concentration of the 
          insecticide in the air of treated dwellings was measured, ranging 
          from 0.007 to 0.840 mg/m3, 0.004 to 0.56 mg/m3 and 0.09 to 
          0.17 mg/m3.  People of all ages and conditions were represented
          in all the studies. In no instance was there a complaint or 
          observed illness referable to dichlorvos. In two of the studies,
          it was possible to measure cholinesterase activity, but no 
          abnormality was found, even in the plasma enzyme. 

    2.2.5 Observations of volunteers 

          Oral - Dichlorvos given to a group of 5 men in daily doses of 
          2.5 mg reduced after 20 days feeding plasma cholinesterase 
          activity to 70% of pre-exposure level. 

          Symptoms of poisoning became evident when human subjects reached 
          a dose level of 8 mg/kg after receiving daily doubling doses 
          starting at 1 mg/kg.  At this dosage the erythrocyte 
          cholinesterase activity was found 20-55% of normal. 

          In studies designed to test the safety of using dichlorvos for 
          the disinsection of aircraft, a group of 15 volunteers underwent 
          intermittent exposure totalling 5 hours per night, 4 nights per 
          week, for 2 weeks, at a concentration of 0.5 mg/m3 of air; this 
          produced a gradual, moderate reduction of plasma cholinesterase 
          activity, but no illness, no impairment of visual performance, no 
          increase in airway resistance of complex reaction time, and no 
          change in physical condition or neurological function.  There was 
          no inhibition of erythrocyte cholinesterase activity, and the 
          lowest single plasma value observed was 34% of normal.  Exposure 
          to half that concentration for 10 half-hour periods each night 
          for 10 weeks was tolerated without any effect, even on plasma 
          cholinesterase. 

          Inhalation - Volunteers were exposed to an average dichlorvos
          concentration of 5.8 mg/m3 20 hours a day for up to 20 days.  
          Plasma cholinesterase activity was reduced to 80%, 70% and 60% of 
          normal after 12, 24 and 48 hours respectively. 

    2.2.6 Reported mishaps - After a man spilled about 120 ml of a 3% oil 
          solution of dichlorvos on his lap, he developed slurred speech, 
          drowsiness and finally collapsed.  Use of oxygen, treatment with 
          atropine sulfate (mostly intravenously) and supportive treatment 
          was life-saving.  Periodic hallucinations and violent 
          combativeness occurred during the course of recovery. 

          An unspecified amount (less than 120 ml) of a 3% oil solution of 
          dichlorvos was spilled on a man's arm.  The man washed with soap 
          and water 15 minutes later.  The only symptoms were dizziness and 
          nausea. 


    2.3   TOXICITY TO NON-MAMMALIAN SPECIES - The entries in these sections 
          are intended to draw attention to special risks and to give 
          warnings of any needs for special precautions. 

    2.3.1 Fish - The toxicity to some species of fish is high (LC50 
          0.5-1 mg/l) but, unless the water is sprayed directly, the hazard
          is low in practice owing to relatively rapid hydrolysis. 

    2.3.2 Birds - No evidence of hazard, but high toxicity to chicks, 
          starlings, and redwings was found in laboratory studies. 

    2.3.3 Beneficial insects - Toxic to bees.

           
     3.    FOR REGULATORY AUTHORITIES - RECOMMENDATIONS ON REGULATION OF 
          COMPOUND

    3.1   RECOMMENDED RESTRICTIONS ON AVAILABILITY - (For definition of 
          categories see introduction Liquid formulations over 30% Category 
          3 and over 3% Category 4. Solid formulations over 12% except slow 
          release strips, Category 4. All other formulations Category 5. 
                
        
    3.2   TRANSPORTATION AND STORAGE 

          All formulations - Should be transported or stored in clearly 
          labelled rigid and leakproof containers.  No food or drink should 
          be transported in the same compartment.  Storage should be under 
          lock and key and secure from access by unauthorized persons and 
          children. 

        
    3.3   HANDLING 

          All formulations in Categories 3 and 4 - Full protective 
          clothing (see part 4) should be used by all those handling 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. 

          All formulations in Category 5 - No facilities other than those
          needed for handling of any chemical need be required. 

        
    3.4   DISPOSAL AND/OR DECONTAMINATION OF CONTAINERS 

          All formulations - Container may be decontaminated (for method 
          see paragraph 4.3 on part 4). 

          Decontaminated containers should not be used for food and drink. 
          Containers that are not decontaminated should be burned or should 
          be crushed and buried below topsoil.  Care must be taken to avoid 
          subsequent contamination of water sources. 


        
    3.5   SELECTION, TRAINING AND MEDICAL SUPERVISION OF WORKERS 

          All formulations in Categories 3 and 4 - Pre-employment medical 
          examination including cholinesterase test for workers desirable. 
          Workers suffering from active hepatic or renal disease should be 
          excluded from contact.  Pre-employment and periodic 
          cholinesterase tests 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 - No special cholinesterase test for 
          workers necessary.  Warning of workers to avoid contact 
          essential. 

        
    3.6   ADDITIONAL REGULATIONS RECOMMENDED IF DISTRIBUTED BY AIRCRAFT 

          All formulations - Pilot and loaders should have special 
          training in application methods and recognition of 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 

          All formulations in Categories 3 and 4 - Minimum cautionary 
          statement -


                                      "POISON" 
                          (Skull and crossbones insignia) 

          "Dichlorvos is an organophosphorus compound-which inhibits 
          cholinesterase.  It is poisonous if inhaled, swallowed or 
          absorbed through the skin.  Wear protective gloves, clean 
          protective clothing, goggles and, when working in enclosed 
          spaces, a respirator of the organic-vapour type when handling 
          this material. Avoid prolonged exposure to vapour.  Wash hands 
          and exposed skin after handling and before eating, drinking or 
          smoking and bathe immediately after work. 

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

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

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

          Aerosols and strips in Category 5 - Minimum cautionary 
          statement: 

          "The vapour from this strip (aerosol) may be toxic if discharged 
          into unventilated space.  Use strictly according to manufacturers 
          instructions.  Keep away from children." 


    3.8   RESIDUES IN FOOD 

    3.8.1 Maximum residue limits - Maximum residue limits for dichlorvos 
          have been recommended by the Joint FAO/WHO Meeting on Pesticide 
          Residues. 

            
    4.    PREVENTION OF POISONING IN MAN AND EMERGENCY AID 

    4.1   PRECAUTIONS IN USE 

    4.1.1 General - Dichlorvos is a volatile organophosphorus insecticide 
          and acaricide of high toxicity which is easily absorbed by 
          inhalation as well as by the gastrointestinal tract and which 
          penetrates the intact skin.  Formulations of liquid concentrates 
          should be handled by trained personnel wearing protective 
          clothing. 

    4.1.2 Manufacture and formulation 

          T.L.V.:  (ACGIH) 1 mg/m3; (USSR) 0.2 mg/m3.  Formulation should
          not be attempted without advice from the manufacturer.

    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 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. 

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

    4.1.5 Other populations likely to be affected - Due to its rapid 
          metabolism and breakdown, with correct use in agriculture and 
          public health, the general population should not be exposed to 
          hazardous amounts of dichlorvos. 


           
    4.2   ENTRY OF PERSON INTO TREATED AREAS - It is advisable that 
          unprotected persons stay out of areas treated with formulations 
          in Category 3 for 12 hours. 
                                                                 

    4.3   DECONTAMINATION OF SPILLAGE AND CONTAINERS - Residues in 
          containers should be emptied in a diluted form into a deep pit 
          taking care to avoid contamination of ground waters.  The empty 
          container 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 dichlorvos and its formulations should be removed by 
          washing with 5% sodium hydroxide solution and then rinsing with 
          large quantities of water.  Alternatively, sand or sawdust (which 
          must be burnt in a proper incinerator) may be used to absorb 
          spillage. 

            
    4.4   EMERGENCY AID 

    4.4.1 Early symptoms of poisoning - As a result of local exposure to 
          the vapours, the following signs and symptoms may occur: miosis,
          frontal headache, rhinorrhea, tightness in chest, 
          bronchoconstriction or increased secretion, cough. Following 
          systemic absorption, 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 control. 

    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 soap and water 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. 

            
    5.    FOR MEDICAL AND LABORATORY PERSONNEL 

    5.1   MEDICAL DIAGNOSIS AND TREATMENT OF CASES OF POISONING 

    5.1.1 General information - A volatile organophosphorus pesticide of 
          moderately high acute toxicity which is easily absorbed through 
          the intact skin as well as by inhalation and via the 
          gastrointestinal tract.  Its mode of action is related to the 
          inhibition of cholinesterase. It is very rapidly metabolized and 
          excreted.  Sub-toxic doses can be ingested at frequent intervals 
          without resulting in hazardous build-up. 

    5.1.2 Symptoms and signs - As a result of local exposure to the 
          vapours, the following signs and symptoms may occur: miosis, 
          frontal headache, rhinorrhea, tightness in chest, 
          bronchoconstriction or increased secretion, cough.  Following 
          systemic absorption, initial symptoms of poisoning may include 
          excessive sweating, headache, weakness, giddiness, nausea, 
          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. 

    5.1.3 Laboratory - The most important laboratory finding is reduction 
          in activity of blood cholinesterase.  However, there is some 
          indication that plasma cholinesterase will recover very quickly 
          and thus the levels may not give a true indication of the 
          seriousness of the case of poisoning. 

    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 large quantities of 
          water.  Local symptoms upon inhalation should be treated with 
          atropine sulfate.  Persons with manifest peripheral symptoms 
          should be treated with 2 mg of atropine sulfate and 1000-2000 g 
          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 2 mg 
          of atropine sulfate should be given initially followed by 
          repeated doses of 2 mg as required.  The patient's 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 atropine sulfate. 

          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 - Due to the rapid detoxification of dichlorvos, if 
          the acute toxic effect is survived, the chances of complete
          recovery are good.  However, in very severe cases prolonged
          hypoxia may give rise to permanent brain damage. 

    5.1.6 References of previously reported cases - Case histories and 
          general methods for treatment are given in: 

          Hayes, W. J. jr, Clinical Handbook on Economic Poisons, U.S. 
          Public Health Ser., No. 476, revised 1963.

          See also "Safe use of Pesticides in Public Health" (1967) Wld 
          Hlth Org. techn. Rep. Ser., No. 356, pp. 58-59. 

            
    5.2   SURVEILLANCE TESTS 

          Test                Normal     Action    Symptomatic
                                level     level      level

    Plasma cholinesterase         100%*      50%        variable 
    Erythrocyte cholinesterase    100%         70%        usually  < 40% 


    5.3   LABORATORY METHODS - References only are given. 
          
    5.3.1 Detection and assay of compound - Because of its rapid metabolism 
          it is unlikely that measurable amounts of dichlorvos will be 
          found in human tissues.  For determination in grain, the 
          collaboratively tested gas-chromatographic method of the 
          Committee for Analytical Methods for Residues of Pesticides and 
          Veterinary Products in Foodstuffs (1973) is recommended. For 
          other foodstuffs the methods of Elgar et al. (1970) and Abbott et 
          al. (1970) are suitable.  Both are gas-chromatographic.  Methods 
          of residue analysis by cholinesterase inhibition, bioassay and 
          gas chromatography are also given by Ciba-Geigy Ltd. (1971). 

    5.3.2 Other tests in cases of poisoning 

          Levels of cholinesterase in the blood, particularly plasma, 
          provide the most useful diagnosis of poisoning.  See: Michel, N. 
          0. (1949) J. Lab. Clin. Med., 34, 1564-1568.  Ellmen, G. L., 
          Courtney, K. D., Andres, V., Jr & Featherstone, R. M. (1961-) 
          Biochem. Pharmacol., 7, 88-95 

    ------------
    * Percentage of pre-exposure activity by any test. 
          
          
                                     REFERENCES

    Committee for Analytical Methods for Residues of Pesticides and 
          Veterinary Products in Foodstuffs, Panel on Malathion and 
          Dichlorvos Residues in Grain (1973) The determination of 
          malathion and dichlorvos residues in grain, Analyst., 98, 19 

    Elgar, K. E., Marlow, R. G. & Mathews, B. L. (1970) The determination 
          of residues of dichlorvos in crops and tissues, Analyst., 95, 
          875 

    Abbott, D. C., Crisp, S., Tarrant, K. R. & Tatton, J. O'G. (1970) 
          Pesticide residues in the total diet in England and Wales, 1966-
          1967.  III.  Organophosphorus pesticide residues in the total 
          diet, Pestic. Sci., 1, 10 

    Ciba-Geigy Limited (1971) "Nogos Nuvan", Basel, pp. 28-29 




    See Also:
       Toxicological Abbreviations
       Dichlorvos (EHC 79, 1988)
       Dichlorvos (HSG 18, 1988)
       Dichlorvos (ICSC)
       Dichlorvos (FAO Meeting Report PL/1965/10/1)
       Dichlorvos (FAO/PL:CP/15)
       Dichlorvos (FAO/PL:1967/M/11/1)
       Dichlorvos (FAO/PL:1969/M/17/1)
       Dichlorvos (AGP:1970/M/12/1)
       Dichlorvos (WHO Pesticide Residues Series 4)
       Dichlorvos (Pesticide residues in food: 1977 evaluations)
       Dichlorvos (Pesticide residues in food: 1993 evaluations Part II Toxicology)
       Dichlorvos (IARC Summary & Evaluation, Volume 53, 1991)