1970 EVALUATIONS OF SOME PESTICIDE RESIDUES IN FOOD
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.
FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS
WORLD HEALTH ORGANIZATION
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.
RESIDUES IN FOOD AND THEIR EVALUATION
FATE OF RESIDUES
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.
RECOMMENDATIONS 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.
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