PESTICIDE RESIDUES IN FOOD - 1979


    Sponsored jointly by FAO and WHO






    EVALUATIONS 1979





    Joint meeting of the
    FAO Panel of Experts on Pesticide Residues
    in Food and the Environment
    and the
    WHO Expert Group on Pesticide Residues
    Geneva, 3-12 December 1979



    PARATHION METHYL

    Explanation

    Parathion methyl was evaluated by the meeting in 1968 and reviewed in
    1972 and 1975.  Studies on teratogenesis and on reproduction in
    species appropriate to such tests were required by the 1975 Meeting.
    In addition, long-term studies in at least one mammalian species were
    indicated to be desirable.

    New data on teratogenicity were available to the Meeting, and are
    reviewed in this monograph addendum.

    EVALUATION FOR ACCEPTABLE DAILY INTAKE

    TOXICOLOGICAL STUDIES

    Special Studies on Teratogenicity

    Parathion methyl (in 10 percent DMSO) was used in a chick embryo
    screening test.  Single doses of 3, 30 and 100 µg were administered
    subgerminally on day 2 and intraamniotically on days 3 and 4.  These
    treatments induced no specific malformations.  Embryotoxicity was
    noted only in the two high doses (30 and 100 µg) (Benes and Jelinek,
    1979).

    Parathion methyl was orally administered by gavage to groups of female
    rats (20-24 rats/group) during pregnancy from day 6 to day 15 of
    gestation at dosage levels of 0, 0.1, 0.3 and 1 mg/kg.  On day 20 of
    pregnancy, the animals were sacrificed, the foetuses removed, and the
    following parameters examined: number and weight of litters, number
    and mean weight of foetuses, fetal sex, weight of placenta, number of
    implantations, resorptions and dead embryos, and external and internal
    defects including skeletal abnormalities.  A modified Wilson procedure
    was used for determining visceral malformations.  Skeletal defects
    were assessed by Alizarin red staining.  Weight gain in mothers and a
    slight retardation of growth in foetuses was noted at the highest dose
    level.  This maternally toxic effect was attributed to the fact that
    the high dose of 1 mg/kg is close to the acutely toxic dose for rats.
    Parathion methyl was not toxic to the embryo or foetus and there was
    no apparent teratogenic effect noted (Machemer, 1977a).

    Groups of female rats (24-26 rats/group) were injected intravenously
    with parathion methyl from day 6 to day 15 of pregnancy at dosage
    levels of 0, 0.03, 0.1 and 0.3 mg/kg body weight.  The methods
    employed and parameters examined were the same as previously reported
    in the oral application study.  None of the doses were toxic for dams
    and parathion methyl did not affect the development of the embryo
    (Machemer, 1977b).  With both oral and intravenous administration,
    parathion methyl was not teratogenic.

    COMMENTS

    Some of the studies required by the 1975 Meeting became available and
    were evaluated.  Teratogenicity studies in rats indicated neither
    teratogenic nor embryo-toxic effects of oral and intravenous exposure.
    The meeting was informed that the previously-requested studies were in
    progress, and decided to extend the temporary acceptable daily intake.

    TOXICOLOGICAL EVALUATION

    Level Causing No Toxicological Effect

    Man:  0.3 mg/kg body weight

    ESTIMATE OF TEMPORARY DAILY INTAKE FOR MAN

    0-0.001 mg/kg body weight

    FURTHER WORK OR INFORMATION

    Required by June 1982:

    1.  Reproduction study in species appropriate to such test;
    2.  Adequate long-term study reported to be in progress.

    REFERENCES

    Benes, V. and Jelinek, R.  Embryotoxicity of Parathion Methyl with the
    Chick Embryo-toxicity Screening Test (CHEST).  (1979) Unpublished
    report from Institute of Hygiene and Epidemiology, Prague.

    Machemer, L.  Parathion Methyl.  Untersuchungen auf Embrotoxische und
    Teratogene Wirkungen an Ratten Nach Oraler Verabreichung.  (Parathion
    Methyl.  Evaluation for Embryotoxic and Teratogenic Effects on Rats
    following Oral Administration).  (1977a) Unpublished report from
    Institut für Toxikologie, submitted by Bayer AG.

    Machemer, L.  Parathion Methyl.  Untersuchungen auf Embrotoxicische
    und Teratogene Wirkungen an Ratten Nach Intravenöser Injection. 
    (Parathion Methyl.  Evaluation for Embryotoxic and Teratogenic Effects
    on Rats Following Intravenous Injection).  (1977b) Unpublished report
    from Institut für Toxikologice, submitted by Bayer AG.
    

    See Also:
       Toxicological Abbreviations
       Parathion-methyl (FAO/PL:1968/M/9/1)
       Parathion-methyl (WHO Pesticide Residues Series 2)
       Parathion-methyl (WHO Pesticide Residues Series 5)
       Parathion-methyl (Pesticide residues in food: 1978 evaluations)
       Parathion-methyl (Pesticide residues in food: 1980 evaluations)
       Parathion-methyl (Pesticide residues in food: 1984 evaluations)
       Parathion-methyl (Pesticide residues in food: 1995 evaluations Part II Toxicological & Environmental)