FAO, PL:CP/15
    WHO/Food Add./67.32


    The content of this document is the result of the deliberations of the
    Joint Meeting of the FAO Working Party and the WHO Expert Committee on
    Pesticide Residues, which met in Geneva, 14-21 November 1966.1

    1 Report of a Joint Meeting of the FAO Working Party and the WHO
    Expert Committee on Pesticide Residues, FAO Agricultural Studies, in
    press; Wld Hlth Org. techn. Rep. Ser., 1967, in press


    This pesticide was evaluated by the Joint Meeting of the FAO Committee
    on Pesticides in Agriculture and the WHO Expert Committee on Pesticide
    Residues in its 1965 report (FAO Meeting Report No. PL/1965/10/1;
    WHO/food Add./27.65). Since its publication some new experimental work
    has been reported on this compound. This new work is presented and
    discussed in the following monograph addendum.


    Short-term studies

    Monkey. Groups, each of 3 male and 3 female monkeys (species
    unstated) were given daily oral doses of 0.05, 0.5 and 5.0 mg diazinon
    per kg body-weight for 2 years. The control animals generally showed a
    slightly greater weight gain than the treated animals and the signs
    noted were periodic soft stools, seen noticeably in the middle and
    high dosage levels, and hyperaesthesia, recorded for one low level and
    one high level monkey. Cholinesterase determinations showed no
    significant inhibition of erythrocyte or plasma cholinesterase
    activity at the 0.05 mg/kg/day level, though this did occur at the
    higher levels of feeding and there was a dose-response relationship
    (Geigy, 1966).

    Man. When 2 adult males were given daily doses of approximately
    0.025 mg/kg diazinon for 5 days, the plasma cholinesterase, but not
    the erythrocyte cholinesterase, showed a marked reduction as compared
    with pre-test levels. Then, 4 adult males were given daily doses of
    about 0.025-0.030 mg/kg diazinon for 32-34 days. There was no
    significant change in either plasma or erythrocyte cholinesterase
    levels, nor in the serum phosphatases, blood picture, clot elasticity,
    recalcification times, sedimentation rate or in the urine (Geigy,

    Three adult males were given daily doses of 0.05 mg/kg diazinon for 5
    days, allowed to recover for 23 days and then the same dosing regime
    was resumed for 5 days. Plasma cholinesterase activity was depressed
    to about 60-65 per cent of pre-test levels. Then groups of 3 adult
    males were given daily doses of 0 and 0.025 mg/kg diazinon for 43
    days. Plasma cholinesterase activity in the test group was about 80-85
    per cent of the control, but there was no depression in that of the
    erythrocytes. Finally, 3 adult males were given 0.020 mg/kg diazinon
    daily for 37 days. By the second week, plasma cholinesterase activity
    was about 86 per cent of the pre-test level without any change in that
    of the erythrocytes. During none of these tests was there any
    alteration in blood haemoglobin levels, haematocrit, blood cell
    counts, prothrombin and clotting times, serum alkaline phosphatase and
    glutamic pyruvic transaminase activities, blood urea, urinary
    constituents or body-weight. Nor were any symptoms experienced (Ind.
    Biotest. Lab., 1966)


    More information is desirable about the metabolism and fate of
    diazinon in the body, especially in man.

    The studies made on man to ascertain the minimum dose for
    cholinesterase depression are valuable, but it would be helpful if
    they could be extended to more subjects, especially females.

    Reproduction and long-term experiments with diazinon in animals would
    be desirable.


    Levels causing no toxicological effect

    Rat            2 ppm in the diet, equivalent to 0.10 mg/kg/day

    Dog            0.02 mg/kg/day

    Monkey         0.05 mg/kg/day

    Man            0.02 mg/kg/day

    Estimate of acceptable daily intake for man

    0.002 mg/kg body-weight


    Geigy, J. R., S. A. (1966) Unpubl. report submitted to WHO

    Industrial Biotest Laboratories, Inc. (1966) Unpubl. report submitted
    to Geigy.

    See Also:
       Toxicological Abbreviations
       Diazinon (EHC 198, 1998)
       Diazinon (ICSC)
       Diazinon (FAO Meeting Report PL/1965/10/1)
       Diazinon (FAO/PL:1967/M/11/1)
       Diazinon (FAO/PL:1968/M/9/1)
       Diazinon (AGP:1970/M/12/1)
       Diazinon (WHO Pesticide Residues Series 5)
       Diazinon (Pesticide residues in food: 1979 evaluations)
       Diazinon (Pesticide residues in food: 1993 evaluations Part II Toxicology)
       Diazinon (JMPR Evaluations 2001 Part II Toxicological)