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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/83.54

                                                      ORIGINAL: ENGLISH






    DATA SHEETS ON PESTICIDES No. 54

    1983

    OXAMYL






         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.

                                    CLASSIFICATION:

                                    Primary use: Insecticide

                                    Secondary use: Nematicide, Acaricide

                                    Chemical group: Carbamate

                                    Date issued: March 1983

    1.  GENERAL INFORMATION

    1.1  COMMON NAME:

         Oxamyl (BSI, ISO, ANSI, JMAF)

    1.1.1  Identity:

         IUPAC:    N, N-dimethyl-2-methyl-carbamoyloximino-2-
                   (dimethylthio) acetamide

         CAS#1:    methyl N', N'-dimethyl-N-((methylcarbamoyl)oxy)-1-
                   thiooxamimidate

         CAS Reg. No.: 23135-22-O

         Mol. Form.: C7H13N3O3S

         Mol Wt.:  219. 29

    CHEMICAL STRUCTURE

    1.1.2  Synonyms:

         D-1410; DPX-1410; Thioxamyl; VydateR

    1.2  SYNOPSIS

         Oxamyl is a broad spectrum, carbamate pesticide; a fast acting
    anti-cholinesterase agent with effective direct contact and stomach
    action. Highly toxic to mammals, it is rapidly metabolized and it is
    non-cumulative in animal tissues. Oxamyl is an effective plant

    systemic with excellent knockdown properties but poor residual
    action.

    1.3  SELECTED PROPERTIES

    1.3.1  Physical properties

         Oxamyl is a colourless crystalline solid with a melting point
    of 100-102°C changing to a dimorphic form with a melting point of
    108-110°C. It has a slightly sulfurous odour. Oxamyl is non-
    corrosive. It has a specific gravity of 0.97 (25°/4°).

    1.3.2  Solubility:

         (25°c)               280 g/kg water
                             1440 g/kg methanol
                             1080 g/kg DMF
                              670 g/kg acetone
                              330 g/kg ethanol
                              290 g/kg cyclohexanone
                              110 g/kg isopropanol
                               10 g/kg toluene
                             insoluble in hexane

    1.3.3  Stability

         Solid oxamyl is very stable, in neutral or acid solutions it is
    quite stable; in alkaline solution, natural waterbodies and soil
    oxamyl decomposes readily to carbon dioxide and organosoluble
    degradation products. In soil, the decomposition rate is inversely
    proportional to the organic content of the soil.  When in solution,
    aeration, sunlight and heat hasten the degradation process.

    1.3.4  Vapour pressure

         3.059 x 10-5 kPa (2.3 x 10-4 mmHg) at 25°C.

    1.4  AGRICULTURE, HORTICULTURE AND FORESTRY

    1.4.1  Common formulations

         Oxamyl is commercially available in a water soluble liquid
    formula (24% a.i.), as a granule formulation (10% a.i.) and as
    technical material in cyclohexanone/water (42% a.i.).

    1.4.2  Susceptible pests

         Oxamyl is used to control a wide variety of plant parasitic
    insects, mites and nematodes on fruit, vegetable and field crops
    and, ornamentals.

    1.4.3  Use pattern

         Used in soil applications between furrows at 1-30 kg/ha; in
    soil dressing at 4.5-16.8 kg/ha; and, as a foliar spray at 0.4
    kg/ha.

    1.4.4  Unintended effects

         Increased soil microbial population may follow soil treatment.
    Phytotoxicity is not a problem when recommended application rates
    are used.

    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 route

         Oxamyl may be absorbed from the gastrointestinal tract; through
    the intact skin; or, through inhalation of spray mist or fine
    residue of granular formulations.

    2.1.2  Mode of action

         Oxamyl acts through inhibition of cholinesterase activity, this
    inhibition is rapidly reversed spontaneously. The half-life of the
    inhibited enzyme is approximately 30 minutes.

    2.1.3  Excretion products

         Oxamyl is rapidly absorbed from the gastrointestinal tract and
    rapidly metabolized by liver microsome enzymes. In rats and mice the
    excretion rate is 70 and 95% respectively within 72 hours of
    administration, excretion is largely in the urine. The major
    excretion products are oxamyl and several organosoluble metabolites
    of which methyl N-hydroxy-N',N'-dimethyl-1-thiooxamimidate and N,N-
    dimethyloxamate are the most prominent. Glucoronide conjugation
    accompanies metabolism. The acute toxicity of these metabolites is
    lower than oxamyl.

    2.1.4  Toxicity, single dose

    Oral LD50:    Rat(M);       5.4 mg/kg bw  (technical material)
                               37.0 mg/kg bw  (24% liquid formulation)
                              110.0 mg/kg bw  (10% granular formulation)

    Dermal LD50:  Rabbit(M);  740 mg/kg bw    (27% liquid formulation)
                             2960 mg/kg bw    (24% liquid formulation)

    Dermal ALD*:  Rabbit(M); 2250-5000 mg/kg bw, in a hydrophilic
                                                ointment on intact skin
                               90-130 mg/kg bw, in a hydrophilic
                                                ointment on abraded skin
                                  130 mg/kg bw, in propylene glycol on
                                                intact skin
                                   60 mg/kg bw, in propylene glycol on
                                                abraded skin

    Inhalation LC50 (1 hour): Rat(M):    0.17 mg/l (oxamyl dust)
                              Rat(F):  0.12 mg/l (oxamyl dust)
                              Rat(M):  0.035 mg/l (27% liquid
                                       formulation)

         Eye irritation: Exposure of the rabbit eye to the solid, or
    to a propylene glycol suspension of oxamyl caused marked pupillary
    constriction, some iritic congestion but no corneal injury.
    Insufficient information in published form to select the most
    susceptible species.

    2.1.5  Toxicity, repeated doses

         Oral: Male rats (fed oxamyl for 2 weeks at 2.4 mg/kg bw
    showed no evidence of tissue accumulation, cumulation of effect nor
    lasting ill-effects.

         Dermal: Groups of male and female rabbits were given dermal
    applications of a 24% liquid formulation (193 mg/kg bw) or oxamyl
    (50 mg/kg bw) on intact or abraded skin for 15 days. No mortalities
    occurred during the 4 week study period. No treatment related
    changes in body weight, organ weight or histopathology were found.
    Mild erythema of the treated skin was observed on all animals. All
    oxamyl treated rabbits with abraded skin showed marked signs of
    cholinesterase inhibition but only slight signs were observed in
    those with intact skin.

                 

    * ALD: approximate lethal dose.

         Cumulation of compound: See above.  In vitro biodegradation
    of oxamyl by rumen fluids indicate that the rate of rumen floral
    activity would preclude the absorption of moderate amounts of
    dietary oxamyl into tissues of the ruminant organism.

    2.1.6  Dietary studies

         Short-term: In a 90-day study, groups of male and female rats
    were fed oxamyl at 0, 50, 100 and 500 mg/kg of diet, the highest
    dose level proved to be too toxic and was reduced to 150 mg/kg diet
    after 3 days on a normal diet. At the highest dose level only, food
    consumption was decreased and protein was found in the urine. At the
    two highest dose levels body weights and organ weights were
    decreased and, blood was observed in the urine. No treatment related
    changes in haematology, clinical chemistry or histopathology were
    observed at any dose level. Cholinesterase activity was not
    determined.

         In a 90-day dog study, males and females were fed oxamyl at 0,
    50, 100 and 150 mg/kg of diet. Only marginal clinical effects were
    observed at 150 mg/kg. No significant changes in body weight, organ
    weight, haematology, clinical chemistry or histopathology were
    observed in any animals.

         Long-term: In a two year study, groups of male and female
    rats were fed oxamyl at 0, 50, 100 or 150 mg/kg of diet. In the 50
    mg/kg diet group only the males showed a slight decrease in body
    weight at 4 weeks and continuing for the duration of the test
    period. A dose dependent decrease in body weight was observed in the
    100 and 150 mg/g diet group. At 150 mg/g, food consumption was
    significantly decreased; cholinesterase activity decreased in the
    females after 4 days of treatment, in the males after 8 days
    (returning to normal after one month); relative weights of brain,
    testes and adrenals increased in males and brain, heart, lungs,
    kidney and adrenal weight increased in the two highest dose female
    groups. No compound related changes in haematology, clinical
    chemistry or histopathology was observed at any dietary dose level.

         In a two year dog dietary study (0, 50, 100 and 150 mg/g of
    diet), haemoglobin levels, haematocrit and erythrocyte count were
    lower in the highest dose group while cholesterol levels and
    alkaline phosphatase activity were increased from week 4 to the end
    of the test period. No treatment related changes in organ weights,
    cholinesterase activity or histopathology were observed at any dose
    level.

    2.1.7  Supplementary studies

         Carcinogenicity: No tumours were found in the rat and dog
    dietary studies described above. Mouse dietary study results are not
    available at this time.

         Mutagenicity: Oxamyl was not mutagenically active in two
    microbial tests, or rec-assay test with  B. subtilis and a reverse
    mutation test with five strains of  S. typhimurium and one of  E.
     coli.; and, in a host mediated assay in mice using the  S.
     typhimurium G-46 strain.

         Teratogenicity: No teratogenic or embryotoxic effects were
    observed when groups of pregnant rats were fed oxamyl at 50, 100,
    150 or 300 mg/kg of diet from day 6-15 of the gestation period.

         Reproduction: Six male and female rats from each dosage group
    of a 90-day dietary study (described in 2.1.6) were used for a
    three-generation reproductive performance test. At weaning the body
    weight of all pups was significantly decreased. In the F1a and
    F1b generation, the fertility index and letter size were
    significantly decreased for the 100 and 150 mg/kg dietary dose
    groups.

         Neurotoxicity: Two groups of five adult hens received 20 or
    40 mg/kg bw of oxamyl followed by 0.5 mg/kg bw of atropine. No
    mortalities occurred in either group. All hens showed marked signs
    of cholinesterase inhibition, recovery was complete after 12 hours
    and there was no evidence of delayed neurotoxicity.

    2.2  TOXICOLOGY - MAN

    2.2.1  Absorption route

         Oxamyl may be absorbed through the gastrointestinal tract; the
    intact skin; and by inhalation of spray mist or fine residue of
    granular preparations.

    2.2.2  Dangerous doses

         No published information available.

    2.2.3  Observations on occupationally exposed
    workers

         No published information available.

    2.2.4  Observations on exposure of the general
    public

         No information available. The public should not be exposed to
    hazardous amounts of oxamyl due to its poor persistence in plant and
    animal tissues and provided proper treatment precautions are
    followed.

    2.2.5  Observations on volunteers

         No published information available.

    2.2.6  Reported mishaps

         No published information available.

    2.3  TOXICITY TO NON-MAMMALIAN SPECIES

    2.3.1  Fish

         Toxic to fish.

         LC50 (96 h):   Bluegill:            5.6 mg/l
                        Goldfish:           27.6 mg/l
                        Rainbow trout:       4.2 mg/l

    2.3.2  Birds

         Birds, oral LD50:  Japanese Quail:  4.2 mg/g bw (technical
                                                            cmpd.)
                            Bobwhite Quail: 39.2 mg/g bw (24% a.i.,
                                                            liquid)
                            Mallard Duck:   10.75 mg/kg bw (24% a.i.,
                                                            liquid)

         Birds, 8-day dietary: Bobwhite Quail: 225 ppm/l diet (24% a.i.,
                                                               liquid)
                            Mallard Duck:  1536 ppm/1 diet (24% a.i.,
                                                               liquid)

    2.3.3  Other species

         Toxic to earthworms.

         LC50:  Daphnia magna 1.95 mg/l (24% a.i., liquid)

    3.  FOR REGULATORY AUTHORITIES - RECOMMENDATIONS ON REGULATION OF
        COMPOUND

    3.1  RECOMMENDED RESTRICTIONS ON AVAILABILITY

         (For definitions of categories see the Introduction to Data Sheets)

         Liquid formulations of 24% only available, Category 2

         Solid (granular) formulations of 104 available, 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 paragraph
    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 the site of handling. Eating,
    drinking and smoking should be prohibited during handling and before
    washing after handling. A respirator should be worn at all times
    when spraying. Oxamyl 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, minimum cautionary statement:

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

         Oxamyl 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.
    Ensnare 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 is a specific
    antidote and repeated doses may be necessary. Artificial respiration
    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

         Oxamyl 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. - no information. 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 oxamyl 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 oxamyl.

    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 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. Decontaminated
    containers should not be used for other purposes.

         Spillage of oxamyl 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 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 oxamyl.

    5.  FOR MEDICAL AND LABORATORY PERSONNEL

    5.1  MEDICAL DIAGNOSIS AND TREATMENT IN CASES OF POISONING

    5.1.1  General information

         Oxamyl 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 and 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 oxamyl is a reversible inhibitor of cholinesterase,
    measurements of cholinesterase activity should be made by a method
    which minimizes the reactivation of inhibited 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 oxamyl 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 oxamyl 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

    secretion, maintenance of airways, intravenous fluids if needed, and
    bladder catheterization. Contraindications are barbiturates and
    central stimulants of all kinds. The chemical similarities between
    oxamyl and aldicarb suggest that pralidoxime chloride (25-50 mg/g
    bw) may be safely used in addition to atropine to counter the
    nicotinic symptoms of oxamyl poisoning when it is known for certain
    that contraindicating carbamates are not involved and if the
    severity of the symptoms warrant.

    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

         Few cases of oxamyl poisoning have been reported, very few
    fatalities, see Gehlbach, S.A. & Williams, W. A. (1975) Accidental
    ingestion, Arch. Environ. Contam., 30, 49.

    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 over-
    exposure. 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 and residues

         Chapman, R. A. & Harris, C. R. (1979) Journal of
              Chromatography, 171, 249-262

         Davis, P. L. et al. (1978) J. Agric. Food Chem., 26(3),
              777-778

         Holt, R. F. & Pease, H. (1976) J. Agric. Food Chem., 24(2),
              263-266

         Holt, R. F. & Leitch, P. E. (1978) Anal. Methods Pestic. Plant
              Growth Regul., 10, 111-119

         Kanazawa, J. (1978) Bunseki, 6, 389-394

         Krause, R. T. (1980) J. Assoc. Off. Anal. Chem., 63(5),
              1114-1124

         Singhal, J.P. et al. (1977) J. Agric, Food Chem., 25(2),
              377-380

         Singhal, J.P. et al. (1978) Analyst (London), 103, 872-875

         Thean, J. E. et al. (1978) J. Assoc. Off. Anal. Chem., 61(1),
              15-17

    5.3.2  Other tests in cases of poisoning

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

         Plasma cholinesterase activity; Ellman, G. L. et al. (1961)
              Biochem. Pharmacol, 7 88095

         Whole blood cholinesterase activity; Fleischer, J. et al.
              (1956) Arch. Indust. Hyg., 14, 510

         Bull. Wld Hlth Org., 48, 235-238 (1973)



    See Also:
       Toxicological Abbreviations
       Oxamyl (JMPR Evaluations 2002 Part II Toxicological)
       Oxamyl (Pesticide residues in food: 1980 evaluations)
       Oxamyl (Pesticide residues in food: 1983 evaluations)
       Oxamyl (Pesticide residues in food: 1984 evaluations)
       Oxamyl (Pesticide residues in food: 1985 evaluations Part II Toxicology)