WHO/FOOD ADD/71.42



    Issued jointly by FAO and WHO

    The content of this document is the result of the deliberations of the
    Joint Meeting of the FAO Working Party of Experts and the WHO Expert
    Group on Pesticide Residues, which met in Rome, 9-16 November, 1970.



    Rome, 1971


    This pesticide was evaluated toxicologically in 1965 (FAO/WHO, 1966b)
    when an acceptable daily intake was established. Following a review in
    1967 (FAO/WHO, 1968b) some temporary tolerances were recommended and
    the Meeting asked for further information by 30 June 1970.

    With a view to a removal of the 'temporary' qualification to the
    recommendation, data were required on: (a) residues resulting from
    pre-harvest treatment of cereals and the fate of parathion in storage
    and processing, (b) residues in cottonseed oil and cotton cake, (c)
    residues found in total diet studies.

    Further work was considered desirable, on: (a) the occurrence of the
    oxygen analogue in plants, (b) the metabolism of the amino analogue,
    e.g. in ruminants, (c) the presence of residues in food commodities
    moving in commerce.



    Parathion was found in only one sample in a twelve-month study of
    whole diets in England and Wales (Abbott et al., 1970); this was
    present in the fats group at 0.01 ppm and therefore at a much lower
    level in the total diet.

    It is clear from the degradation curves for parathion and paraoxon on
    lettuce published by Möllhoff (1968a) that the half-life of the oxon
    is much shorter than that of the thion, and that the oxon, if formed,
    will not tend to accumulate. This author also reports studies on field
    lettuce sprayed with parathion, analysing with a GLC method using a
    phosphorous-sensitive detector with-limits of 0.01 ppm for parathion
    and 0.02 ppm for paraoxon. The residue of parathion fell from 1.74 ppm
    to 0.02 ppm in 14 days. Paraoxon was present only at the limit of
    detection on the day of spraying, but was not detectable thereafter.
    Later reports by Möllhoff (1968b) concerning spinach show that
    material picked on the day of spraying contained 1.5 ppm parathion and
    0.05 ppm paraoxon.

    However, if the material was sterilized by heating to 115°C during the
    storage period, paraoxon was degraded to undetectable levels. Spinach
    gathered 29 days after spraying had no detectable residue of either
    parathion or paraoxon. Abbott et al. (1970) did not detect paraoxon in
    any sample in their whole-diet studies.

    Evidence of residues in food in commerce

    Analyses of fruit and vegetables entering commerce in the German
    Federal Republic (Krause and Kirchhoff, 1969) showed that only 14 out
    of 228 samples contained measurable amounts of parathion (>0.01 ppm).
    In most of these cases, the residue was less than 0.1 ppm, but two

    samples of lettuce bore 0.15 and 1.5 ppm, respectively, and one of
    parsley bore 0.4 ppm.


    Total diet studies over a year in England and Wales have shown that
    parathion was absent from all classes of food except fats, in which it
    was present to the extent of 0.01 ppm on one occasion.

    The oxygen analogue, paraoxon, has a much shorter persistence on or in
    plant material than parathion. It was detected on lettuce on the day
    that parathion was applied but not thereafter. It was also detected in
    spinach on the day that parathion was applied, but was not detectable
    when the crop was harvested a month later. It was not detected in the
    whole-diet studies conducted over a year in England and Wales.

    Parathion was present in measurable amounts in only 14 out of 228
    samples of vegetable and fruits in West Germany; in most of these
    cases, the level was less than 0.1 ppm, but this level was exceeded in
    two samples of lettuce and one of parsley.

    It was agreed that no justification exists for the grouping together
    of parathion and parathion-methyl for tolerances.


    There are no grounds for changing the figures recommended by the 1969
    Joint Meeting, but the 'temporary' qualification can now be withdrawn.
    The recommendations therefore are for tolerances, which are as

    Vegetables (except carrots)                  0.7 ppm

    Peaches, apricots, citrus fruits             1.0 ppm

    Other fresh fruits                           0.5 ppm


    REQUIRED (before tolerances can be recommended for these

    1. Data on residues resulting from pre-harvest treatment of cereals.

    2. Data on residues in cotton seed, seed oil and seed cake.

    3. Data on the fate of parathion in storage and processing in the
       above mentioned products.


    Abbott, D.C. Crisp, S., Tarrant, K.R. and Tatton, J.O'G. (1970)
    Pesticide residues in the total diet in England and Wales, 1966-1967.
    III. Organophorphorous pesticides residues in the total diet. Pestic.
    Sci.,1: 10-13

    Krause, C. and Kirchhoff, J. (1969) Organophosphat -  Rückstände auf
    Marktproben von Obst und Gerüse sowie auf Getreideerzeugnisson.
    Nachrichtenblatt d. Deutschen Pflanzenschmtz - dienst., 21: 81-84

    Müllhoff, E. (1968a) Contribution to the question of residues and
    their determination in plants treated with (R) E605 and (R) Agnitox.
    Pflanzenschmtz - nachrichten Bayer, 21: 327-354 (English Edition)

    Möllhoff, E. (1968b) Pflanzenschmtzmittel-Rückstände. Internal
    reports, Biologisches Institut der Farbenfabriken Bayer AG,
    Leverkusen, 55/132, no. 27 a-d/68

    See Also:
       Toxicological Abbreviations
       Parathion (HSG 74, 1992)
       Parathion (ICSC)
       Parathion (FAO Meeting Report PL/1965/10/1)
       Parathion (FAO/PL:1967/M/11/1)
       Parathion (FAO/PL:1969/M/17/1)
       Parathion (Pesticide residues in food: 1984 evaluations)
       Parathion (Pesticide residues in food: 1995 evaluations Part II Toxicological & Environmental)
       Parathion (IARC Summary & Evaluation, Volume 30, 1983)