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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/82.55
                                          ORIGINAL:   ENGLISH


    DATA SHEET ON PESTICIDES No. 55

    METHOMYL


    CLASSIFICATION:
    Primary use:  Insecticide
    Secondary use :  Nematicide
    Chemical group:  Carbamate

    Date issued:  January 1983


         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: Methomyl (BSI, ISO, ANSI, JMAF)

    1.1.1 Identity: IUPAC: S-methyl N-(methylcarbamoyloxy) 
                    thioacetimidate 

                    CAS No. 1: Acetimidic acid, thio-N-
                    ((methylcarbamoyl)oxy)-,methyl ester 

                    CAS Reg. No.: 16752-77-5

                    Mol. Form.: C5H10N2O2S

                    Str. Form.:

    Chemical Structure

                    Mol. Wt.: 162.23

    1.1.2 Synonyms: Insecticide 1179; LannateR: Mesomile; NudrinR:
          SD 14999;   WL 18236 

    1.2  SYNOPSIS: Methomyl is a broad spectrum carbamate insecticide; a 
         fast acting anti-cholinesterase agent; and, a direct contact and 
         stomach action poison.  A plant systemic of high acute toxicity to 
         mammals, it is non-cumulative and rapidly metabolized in both 
         plants and animals to substances of lower toxicity.  Methomyl is 
         particularly effective against organophosphorus resistant pests. 

    1.3  SELECTED PROPERTIES

    1.3.1 Physical characteristics - The pure compound is a colourless 
          crystalline solid with melting point of 78-79°C and a density d24 
          of 1.2946.  Methomyl has a slightly sulfurous odour.           4
          The aqueous solution is non-corrosive.

    1.3.2 Solubility - (25°C)   58  g/kg  water
                              1000  g/kg  methanol
                               730  g/kg  acetone
                               420  g/kg  ethanol
                               220  g/kg isopropanol
                                30  g/kg toluene
          Completely soluble in most other organic solvents.

    1.3.3 Stability - Methomyl is stable in the solid form and in aqueous 
          solutions at pH 7.0 or less, it rapidly decomposes in alkaline
          solutions and in moist soils.

    1.4  AGRICULTURE, HORTICULTURE AND FORESTRY

    1.4.1 Common formulations - Water soluble powders (40 and 900 g 
          a.i./kg); wettable powder (250 g a.i./kg); water soluble liquid 
          (200-360 g a.i./kg). 

    1.4.2 Susceptible pests - Methmyl is effective against a wide range of 
          plant parasitic insects and stored product pests, especially 
          those which are resistant to organophosphorus pesticides. 

    1.4.3 Use pattern - Methomyl is used most effectively as a foliar 
          treatment of certain vegetable and fruit crops, field crops and 

          commercial plantings of ornamentals. 

    1.4.4 Unintended effects - Methomyl is toxic to many beneficial insects 
          and other arthropods 

    1.5  PUBLIC HEALTH PROGRAMMES - No recommended usage reported.

    1.6  HOUSEHOLD USE - No recommended usage reported.

    2.   TOXICOLOGY AND RISKS

    2.1  TOXICOLOGY - MAMMALS

    2.1.1 Absorption routes - Methomyl may be absorbed from the 
          gastrointestinal tract; through the intact skin; and through 
          inhalation of fine spray mist or dust. 

    2.1.2 Mode of action - Methomyl acts through inhibition of 
          cholinesterase activity which is rapidly and spontaneously 
          reversed within minutes. 

    2.1.3 Excretion products - In animals methomyl is metabolized by 
          hydrolysis.  Metabolism and excretion is very rapid in 
          rats, the degradation products are carbon dioxide, acetonitrile, 
          and urinary polar metabolites in a ratio of 1:2:1.  Methomyl, its 
          oxidation products and their glucuronide conjugates have not been 
          found in rat urine. 

    2.1.4 Toxicity, single dose

          Oral LD50:    Rat (M)    14.3-20.2 mg a.i./kg b.w.
                        Rat (F)    21.8-25.4 mg a.i./kg b.w.
                        Mouse           10.0 mg a.i./kg b.w
                        Mule deer  11.0-22.0 mg a.i./kg b.w.
        
          Oral LD50:    Beagle          30   mg a.i./kg b.w.
                        Hamster         30   mg a.i./kg b.w.
                        Monkey          40   mg a.i./kg b.w.
                        Guinea-pig      15   mg a.i./kg b.w.

          Dermal LD50:  Rat (M)       1000   mg a.i./kg b.w.
                        Rabbit        5880   mg a.i./kg b.w.

          Subcutaneous LD50:  Rat        9.0 mg a.i./kg b.w.

          Inhalation LC50:    Rat       77.0 mg a.i./l

          During the inhalation test the rats exhibited dose related 
          clinical signs of toxicity which rapidly disappeared in the 
          survivors during the post-exposure observation period. 

          Most susceptible species: Mice appear to be the most susceptible 
          among the animals tested, fish are the most susceptible among all 
          animals tested. 

    2.1.5 Toxicity, repeated doses

          Oral: Six male rates given 5.1 (mg/kg b.w.)/day by incubation in 
          10 doses over two weeks showed only mild signs of toxicity; no 
          cumulation of effects; and, no depression of cholinesterase 
          function.  There were no mortalities. 

          Dermal: a 5% aqueous solution of methomyl applied to the intact 
          skin of male and female rabbits in 15 daily doses at 200 mg/kg 
          b.w. for six hour intervals produced no cumulative effects; no 
          mortalities; and, only mild clinical signs of toxicity.  In a 
          similar application to abraided skin the signs were more severe 
          and only eight of 10 rabbits survived the treatment.  No 
          histopathologic effects were produced in either group. 

          Dermal irritation and sensitization: Methomyl is a mild, 
          nonsensitizing skin irritant in guinea-pigs, a mild eye irritant 
          in guinea-pigs and rabbits. 

    2.1.6 Dietary studies

          Short-term: Rats of both sexes were fed on diets containing 
          methomyl at 0, 10, 50, 125 and 250 mg/kg of diet for 90 days.  
          After six weeks the 125 mg diet was raised to 500 mg/kg of diet.  
          All the test animals survived the treatment.  Rats on the two 
          highest level diets had significantly lower body weight gains 
          than the control rats. No treatment related clinical, 
          haematological, biochemical, urinary or histopathologic signs of 
          toxicity were observed. 

          One-year-old beagles of both sexes were fed methomyl containing 
          diets at 0, 50 100, and 400 mg/kg levels for 90 days.  No 
          treatment related adverse effects were observed. 

          Long-term: Rats of both sexes were placed on diets containing 
          methomyl at 0, 50, 100, 200 and 400 mg/kg levels for two years.  
          Males on the 400 mg diet and females on the 200 and 400 mg diet 
          had significantly reduced body weights.  All animals survived the 
          treatment, histopathologic alterations of kidneys occurred in 
          males and females at the 400 and 200 mg diet levels respectively, 
          spleen histopathologic alterations occurred in females at the two 
          highest treatment levels.  There were no treatment related 
          increases in neoplastic lesions. 

          In a two-year study, year-old beagles were placed on diets 

          containing methomyl at 0, 50, 100, 400 and 1000 mg/kg levels.  No 
          treatment related adverse effects were observed in the 50-100 mg 
          diet groups. Anaemia and histopathologic changes in the kidney 
          and the spleen were observed in the dogs fed the two highest 
          level diets.  Mild clinical signs of toxicity and histopathologic 
          changes in the liver and bone marrow were observed only in the 
          1000 mg diet group.  Two mortalities occurred among the females 
          in the 1000 mg diet group, an original animal and its 
          replacement.  No treatment related increase in neoplastic lesions 
          was observed.  The no-adverse-effect levels for rats and dogs 
          were calculated from the 100 mg/kg diet to be 5.0 and 2.5 (mg/kg 
          b.w.)/day respectively. 

    2.1.7 Supplementary studies of toxicity

          Carcinogenicity: No evidence of methomyl-treatment related 
          carcinogenicity was reported in the dietary and subacute toxicity 
          studies described in sections 2.1.5 and 2.1.6 above.  Methomyl 
          was found to be carcinogenically inactive in a transplacental, 
          host-mediated hamster cell culture assay.  Nitrosomethomyl was 
          carcinogenically active in six- to eight-week-old rats given 50 
          mg/kg b.w. once a week for 10 weeks. There were no survivors by 
          the 120th week of observation.  Fourteen of 16 males and eight of 
          16 females developed tumours in the nonglandular stomach tissue, 
          five males and four females had carcinomas. 

          Nitrosation of ingested methomyl by dietary nitrites in the 
          acidic gastric environment is unlikely to be carcinogenically 
          threatening since the reaction yield under the best of conditions 
          is very low.  Under simulated stomach conditions, over a 
          three-hour period no significant amount of nitrosomethomyl was 
          produced in an in vitro attempt. 

          Teratogenicity: No evidence of teratogenetic effects was found in 
          29-day and full term foetuses of pregnant rabbits fed methomyl at 
          50 and 100 mg/kg diet levels on days 8-16 of gestation.  A study 
          in rats at levels of 0, 50, 100 and 400 mg/kg of diet showed no 
          evidence of teratogenic or embryotonic effects.1

          1 Information provided by the manufacturer.

          Mutagenicity: No evidence of cellular alteration was observed in 
          circulating erythrocytes in rabbits following a single injection 
          of a low dose of methomyl.  No evidence of mutagenic potential 
          was found in a number of microbial assay systems; histidine 
          autotrophs of S. typhimurium, diploid S. cerevisiae, E. coli and 
          R. subtilis.  Liver microsomal enzyme activation of methomyl did 
          not change its potential but nitrosomethomyl was found to be very 
          positively mutagenic in the microbial assay systems and in human 
          skin cell cultures, producing irreversibly DNA alterations in the 

          latter test. 

          Reproduction: No adverse effects in reproduction and lactation 
          performance occurred in a three-generation study of rats fed 
          methomyl at 50 and 100 mg/kg diet levels.  No pathological 
          changes were observed in the F-3b generation animals. 

          Neurotoxicity: A 28 mg/kg b.w. dose of 5% methomyl in acetone was 
          administered orally to one-year-old hens, neither paralysis of 
          the limbs, nor sciatic nerve degeneration were observed. 

    2.1.8 Modifications of toxicity - The response in rats, to the combined 
          administration of methomyl (200 mg/kg diet) and caffeine (30 mg % 
          aqueous solution) or ethanol (10% aqueous solution) produced 
          evidence of interaction resulting in decreased growth rates and 
          elevated relative-weights of adrenals in animals of both sexes.  
          In males hepatic lipid levels increased, in females the relative-
          weights of kidneys and fasting blood glucose levels increased. 

    2.2  TOXICOLOGY - MAN

    2.2.1 Absorption route - Methomyl may be absorbed from the 
          gastrointestinal tract; through the intact skin; and, by 
          inhalation of spray mist and dust. 

    2.2.2 Dangerous doses

          Single: The accepted range of the maximum lethal dose is 5-50 
          mg/kg b.w. In a report of an accidental poisoning, the fatal dose 
          was found to be 12-15 mg/kg b.w. (see 2.2.6). 

          Repeated: No information.  Because methomyl is rapidly degraded 
          in organisms and the environment, chronic toxicity is not 
          expected to be a major problem. 

    2.2.3 Observations among occupationally exposed workers - There have 
          been several reports of poisoning among agricultural workers, 
          pilots, spraymen and pesticide manufacturing workers.  Fatalities 
          are rare and hospitalization is infrequent.  Lack of proper 
          precaution in handling the pesticide is the most frequent cause 
          of poisoning.  Agricultural workers have become ill while using 
          manual ULV sprayers and during manual dusting of vegetables.  The 
          symptoms are usually mild and often persist for several days.  In 
          one pesticide manufacturing plant, short-term hospitalization of 
          employees for methomyl related illnesses was a common occurrence 
          until housekeeping practices and physical conditions were 
          improved. 

    2.2.4 Observations on exposure of the general public - No information.
          With good agriculture practice the general public should not be 

          exposed to hazardous amounts of methomyl. 

    2.2.5 Observations of volunteers - In an allergy screening programme 
          one out of 29 agricultural workers with a history of exposure to 
          methomyl showed a positive reaction to a methomyl patch test. 

    2.2.6 Reported mishaps - There have been many reports of accidental and 
          suicidal poisonings but few fatalities from ingestion of 
          methomyl. In one episode in the West Indies, methomyl from an 
          unlabelled container was used in the preparation of food. Three 
          fatalities occurred within minutes of eating, death was preceded 
          by severe clinical signs of toxicity;  perfuse sweating, 
          involuntary defecation, vomiting and convulsions. A dog died 
          following ingestion of vomitus.  Two persons who ate sparingly 
          (only one showed clinical signs of a mild sort) were treated with 
          intravenous atropine. The symptomatic patient recovered within 
          two hours.  The lethal doses were estimated to be 12-15 mg/kg 
          b.w. 

    2.3  TOXICITY - NON MAMMALIAN SPECIES

    2.3.1 Fish

            LC50 (96 hr.):  Bluegill sunfish   0.87 mg a.i./l
                            Goldfish           0.1  mg a.i./l
                            Carp               0.5-10.0 mg a.i./l
                            Rainbow trout      3.4  mg a.i./l
                            Channel  catfish   0.94 mg a.i./l

            Residue studies in fish have shown that methomyl is not 
            accumulated in body tissues. 

    2.3.2 Birds

           LC50 (8 days):   Pekin duck         1890 mg a.i./kg diet
                           Bobwhite quail     3680 mg a.i./kg diet

           LC50 (5 days):  Mallard duck       2883 mg a.i./kg diet

           Oral LD50       Domestic hens        28 mg a.i./kg b.w.
                           Mallard duck       15.9 mg a.i./kg b.w
                           Pekin  duck        15.0 mg a.i./kg b.w.
                           Pheasant           15.4 mg a.i./kg b.w.
                           Bobwhite quail     15.0 mg a.i./kg b.w.
                           Japanese quail     34.0 mg a.i./kg b.w.

             No compound related adverse effects were observed in field-
             caged bobwhite quail subjected to methomyl spray (1 kg a.i. in 
             280 l of water/ha) six times at five day intervals.  There 
             were no compound related adverse effects observed in Japanese 

             quail fed diets containing up to 210 mg/kg every third day of 
             a 30 day feeding study. 

    2.3.3 Beneficial insects - Freshly applied methomyl is toxic to honey 
          bees by direct contact and ingestion, it is relatively nontoxic 
          when dry. 

    2.3.4 Other species

          LC50 (96 hr.):  Grass shrimp  0.49 mg a.i./l
                          Pink shrimp   0.02 mg a.i./l
                          Mud crab      0.41 mg a.i./l
                          Fiddler crab  2.38 mg a.i./l

    3.   FOR REGULATORY AUTHORITIES - RECOMMENDATIONS ON REGULATION OF 
         COMPOUND

    3.1  RECOMMENDED RESTRICTIONS ON AVAILABILITY - (For definition of 
         categories see the Introduction to data sheets)

         Liquid formulations of 8.5% and over, Category 2

         Other liquid formulations, Category 3

         Solid formulations of 35% and over, Category 2

         Other solid formulations of 3.5% and over, Category 3

    3.2  TRANSPORTATION AND STORAGE

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

    3.3  HANDLING

         All formulations - Full protective clothing (see 4.3 part 4) 
         should be used by those handling the compound.  Adequate washing 
         facilities should be available at all times during the handling 
         and should be close to site of handling.  Eating, drinking and 
         smoking should be prohibited during handling and before washing 
         after handling.  A Methomyl respirator should be worn at all
         times when spraying.  Methomyl formulations should not be
         applied by hand-held ULV applicators.

    3.4  DISPOSAL AND/OR DECONTAMINATION OF CONTAINERS

         All formulations - Container must be either burned or crushed and 
         buried below topsoil.  Care must be taken to avoid subsequent 

         contamination of water sources.  Decontamination of containers in 
         order to use them for other purposes should not be permitted. 

    3.5  SELECTION, TRAINING AND MEDICAL SUPERVISION OF WORKERS

         All formulations - Pre-employment medical examination of workers 
         necessary.  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. 

    3.6  ADDITIONAL REGULATIONS RECOMMENDED IF DISTRIBUTED BY AIRCRAFT

         All formulations - Pilots and loaders should have special training 
         in application methods and early symptoms of poisoning, and must 
         wear a suitable respirator.  Use of flagmen not recommended.  
         Flagmen, if used, should wear protective clothing and be located 
         well away from the dropping zone. 

    3.7  LABELLING

         All formulations

                               "DANGER - POISON"
                       (skull and cross bones insignia)

         Methomyl is a carbamate compound which inhibits cholinesterase.  
         It is of very high toxicity.  Contact with the skin, inhalation of 
         dust or spray, or swallowing may be fatal.  Wear protective 
         gloves, clean protective clothing, and a respirator of the 
         organic-vapour type when handling this material.  Bathe 
         immediately after work.  Ensure that containers are stored under 
         lock and key.  Empty containers must be disposed of in such a way 
         as to prevent all possibility of 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 sulfate is a 
         specific antidote, repeated doses may be necessary.  
         Artificial respiration also may be needed. 

    3.8  RESIDUES IN FOOD

         Maximum residue levels

         Maximum residue levels have been recommended by the Joint 
         FAO/WHO Meeting on Pesticides Residues. 

    4.   PREVENTION OF POISONING IN MAN AND EMERGENCY AID

    4.1  PRECAUTIONS IN USE

    4.1.1 General - Methomyl is a carbamate pesticide of very high 
          toxicity.  It penetrates the intact skin and is also 
          absorbed by inhalation and from the gastrointestinal tract.  Most 
          formulations should be handled by trained personnel wearing 
          protective clothing. 

    4.1.2 Manufacture and formulation - T.L.V. - (A.C.G.I.H.) 2.5 mg/m3. 
          Formulation should not be attempted without advice from the 
          manufacturer. 

          Although volatility is low, vapour and dusts should be controlled 
          preferably by mechanical means. Protective equipment for the skin 
          and respiratory protection is usually necessary. 

    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 respirator 
          should be worn as well as an impermeable hood, clothing, boots 
          and gloves.  The applicator should avoid working in spray mist 
          and avoid contact with the mouth.  Particular care is needed when 
          equipment is being washed after use.  All protective clothing 
          should be washed immediately after use, including the insides of 
          the 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 methomyl 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 - With good agricultural 
           practice subject to 4.2 below, other populations should not be 
           exposed to hazardous amounts of methomyl. 

    4.2  ENTRY OF PERSONS INTO TREATED AREAS - Unprotected persons should 
         be kept out of treated areas for at least one day. 

    4.3  SAFE DISPOSAL OF CONTAINERS AND SPILLAGE - 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 a 
         container overnight. Impermeable gauntlets should be worn 
         during this work and a soakage pit should be provided for the 
         rinsings.  Decontamination of containers in order to use them for 
         other purposes should not be pemitted. 

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

    4.4  EMERGENCY AID

    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 control. 

    4.4.2 Treatment before a 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 is used, vomit may contain toxic
          amounts of methomyl. 

    5.   FOR MEDICAL LABORATORY PERSONNEL

    5.1  MEDICAL DIAGNOSIS AND TREATMENT IN CASES OF POISONING

    5.1.1 General information - Methomyl is a carbamate insecticide of very 
          high toxicity.  It is absorbed from the gastrointestinal tract 
          and by inhalation, and only to a limited extent through the 
          intact skin.  Its mode of action is by reversibly inhibiting 
          acetyl cholinesterase.  Erythrocyte cholinesterase is more 
          inhibited than plasma cholinesterase.  Symptoms of poisoning are 
          short lasting and in case of occupational overexposure occur 
          without delay and at doses well below the fatal dose.  Because of 
          its rapid metabolism and excretion it does not accumulate in the 
          tissues. 

    5.1.2 Symptoms and signs - Symptoms of poisoning include excessive 
          sweating, headache, chest tightness, weakness, giddiness, nausea, 
          vomiting, stomach pains, salivation, blurred vision, slurred 
          speech and muscle twitching. Paraesthesia and mild skin reactions 

          have also been reported. 

    5.1.3 Laboratory - Because methomyl is a reversible inhibitor of 
          cholinesterase, measurements of cholinesterase activity should be 
          made by a method which minimizes the reactivation of inhibted 
          enzyme.  Erythrocyte cholinesterase determination is more 
          informative than measuring either plasma or whole blood 
          cholinesterase, but the enzyme will only be inhibited for a short 
          time (few hours) after exposure.  The presence of metabolites of 
          methomyl in urine is also indicative of 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.  Since the symptoms of poisoning with methomyl are of 
          short duration, atropine treatment is usually not necessary by 
          the time the patient reaches a place where this antidote is 
          available.  Where there are manifest symptoms 1-2 mg of atropine 
          sulfate (adult dose) may be given intramuscularly or even 
          intravenously and repeated as necessary.  Care should be taken to 
          avoid overdosage of atropine, especially when treating children.  
          In extreme cases, if the patient is unconscious or is in 
          respiratory distress, oxygen may be required.  Provide patient 
          support as required, including; suction of secretions, 
          maintenance of airways, i.v. fluids p.r.n. and, bladder 
          catheterization.  Contraindications include barbiturates and 
          central stimulants of all kinds.  The chemical similarities 
          between methomyl and aldicarb suggest that pralidoxime chloride 
          (25-50 mg/kg b.w.) may be safely used, in addition to atropine, 
          to counter nicotinic symptoms of methomyl poisoning when it is 
          known for certain that contraindicating carbamates are not 
          involved and, if the severity of the symptoms warrants. 

    5.1.5 Prognosis - If the acute toxic effect is survived, the chances of 
          complete recovery are very good. 

    5.1.6 References of previously reported cases

          Morse, D. L. & Baker, E. L. (1979), Clinical Toxicology, 15 (1), 
          13; intoxication 
          Simpson, G. R. & Bermingham, S. (1977)  Medical Journal of 
          Australia, 4, 148, intoxication 
          Liddle, J. A. et al. (1979) Clinical Toxicology, 15 (2), 159; 
          fatalities 

    5.2  SURVEILLANCE TESTS - Due to rapid reactivation of inhibited 
         enzyme, determination of blood cholinesterase levels is of little, 
         if any, practical value in determining when workers should be 

         withdrawn to prevent overexposure.  Minor complaints, such as 
         headache and nausea, cause the worker to stop work and thus 
         prevent further exposure.  The worker quickly recovers, 
         particularly if appropriate decontamination procedures are 
         followed. 

    5.3  LABORATORY METHODS

    5.3.1 Detection and assay of compound

          Leitch, R. L. & Pease, H. L. (1973) Anal. Methods Pestic. Plant 
          Growth Regul., 7, 331 
          Pease, H. C. & Kirkland, J. J. (1968) J. Agric. Food Chem., 16,
          554
          Rangaswamy, J. R. et al. (1977) J. Assoc. Off. Anal. Chem., 60
          (5), 1043 
          Sundaram, K. M. S. et al. (1979) Jour. Chromatog., 177, 29
          Szeto, S. Y. & Sundaram, K. M. S. (1980) Jour. Chromatog., 172,
          528
          Thean, J. E. et al. (1978) Jour. Assoc. Off. Anal. Chem., 61,
          15
          Thewari, S. N. & Singh, R. (1979) Jour. Chromatog., 172, 528
          Williams, J. H. (1972) Pestic. Sci., 3, 179

    5.3.2 Other tests in cases of poisoning - Cholinesterase levels in 
          blood are unreliable as a routine test to detect poisoning by 
          methomyl.  However, shortly after absorption, inhibition of 
          erythrocyte cholinesterase may be demonstrated by an appropriate 
          method. 

          In plasma; Ellman, G. et al. (1961) Biochem. Pharmacol., 7, 88 
          In whole blood; Fleischer, J. et al. (1956) Arch. Indust. Hyg., 
                          14, 510 
                          Wilhelm, K. et al. (1973) Bull. Wld Hlth Org.,
                          48, 235 

          Note: This data sheet was drafted in the Bureau of Chemical 
                Standards, Envirormental Health Directorate, Health and 
                Welfare, Canada, and subsequently underwent medical, 
                scientific, and industrial review. 







    See Also:
       Toxicological Abbreviations
       Methomyl (EHC 178, 1996)
       Methomyl (HSG 97, 1995)
       Methomyl (ICSC)
       Methomyl (WHO Pesticide Residues Series 5)
       Methomyl (Pesticide residues in food: 1976 evaluations)
       Methomyl (Pesticide residues in food: 1977 evaluations)
       Methomyl (Pesticide residues in food: 1978 evaluations)
       Methomyl (Pesticide residues in food: 1986 evaluations Part II Toxicology)
       Methomyl (Pesticide residues in food: 1989 evaluations Part II Toxicology)
       Methomyl (JMPR Evaluations 2001 Part II Toxicological)