CHLORPYRIPHOS
Explanation
This non-systemic organophosphorus insecticide was evaluated by
the Joint Meeting in 1972 and an ADI of 0.0015 mg/kg/day was
recommended (FAO/WHO, 1973). Tolerances were proposed for a number of
foods of animal origin, fruits and vegetables for which residue data
at that time were available. For commodities other than those listed,
additional residue data from supervised trials were required before
tolerances could be recommended. Since then, additional data on citrus
fruits have become available.
RESIDUES IN FOOD AND THEIR EVALUATION
USE PATTERN
Chlorpyriphos has been found active against the major citrus
pest, Red Scale (Aonidiella aurantii), in some citrus growing areas,
such as Australia, Mediterranean countries and South Africa. The
citrus is often sprayed at in early stage of fruit development,
although a practice of spraying until 1-2 months before harvest has
developed in some countries, e.g. Israel and South Africa. No
official, national registrations of such uses were known to the
meeting.
Pre-harvest treatments
For general use, application rates of 25-100 g a.i./100 litre
(using about 100 hl per ha) are recommended.
RESIDUES RESULTING FROM SUPERVISED TRIALS
Residues in Citrus
Table 1 summarizes the levels of chlorpyriphos residues found in
and on citrus fruits in a series of supervised trials (Webb, 1974).
Initial deposits ranging from about 0.2 - 1.3 mg/kg decrease gradually
during the first months and then tend to level off. Within the
recommended pre-harvest interval, residues do not exceed 0.25 mg/kg on
a whole fruit basis.
It is evident from the data in Table 2 that chlorpyriphos
residues are largely concentrated in peel, and only a small proportion
will penetrate into the inner, edible parts of fruits. Other data show
that, with an occasional value as high as 0.1 mg/kg, most recorded
residues in fruit flesh are below 0.05 mg/kg.
TABLE 1.
Residues of chlorpyriphos in citrus
Application
Country a.i. Interval after Residues,
Fruit concentration rate treatment, mg/kg,
% kg a.i./ha months in whole fruit
AUSTRALIA
Oranges 0.025 1.7 0 0.37-0.47
1 0.048-0.077
3 0.051-0.091
8 0.003-0.016
0.05 3.4 8 0.018
ITALY
Oranges 0.06 0-1 0.14-0.17
1-2 0.10-0.15
ISRAEL
Oranges 0.048 4.8-5.8 6´ 0.07
0.072 7-2-8.6 6´ 0.11-0.16
0.096 9.6-11.5 6´ 0.11-0.19
0.048 8.6 0 0.56
1 0.21
2 0.09
0.096 17.2 0 1.34
1 0.25
2 0.15
Grapefruit 0.048 8.6 0 0.37
1 0.18
2´ 0.18
0.096 17.2 0 0.57
1 0.24
2´ 0.22
MOROCCO
Clementines 0.048 1.9 3 0.22
0.060 2.4 5-6 0.03-0.04
TABLE 2.
Chlorpyriphos distribution in citrus
Interval after Chlorpyriphos residue, mg/kg
Application treatment, Whole
Fruit % a.i. days Flesh Peel fruit
Oranges 0.06 15 <0.01 0.55 0.17
30 <0.01 0.45 0.14
45 <0.01 0.49 0.15
60 <0.01 0.33 0.10
APPRAISAL
New data on chlorpyriphos residues in and on citrus fruits have
been made available, meeting the requirement for supervised trials of
an earlier Joint Meeting (FAO/WHO, 1973).
RECOMMENDATIONS
The following tolerance, additional to those of 1972, is
recommended.
TOLERANCE
mg/kg Pre-harvest interval
on which recommendation
is based
Citrus fruit (whole) 0.3 1 month
REFERENCES
FAO/WHO (1973). 1972 Evaluations on some pesticide residues in food.
Report of the 1972 Joint Meeting of the FAO Working Party on Pesticide
Residues and the WHO Expert Committee on Pesticide Residues, WHO
techn. Rep. Ser., No. 525; FAO Agricultural Studies, No. 90.
Webb, C. (1974). Request for a tolerance for chlorpyriphos in citrus
fruit. Toxicology & Registration Section, Dow Chemical Company Ltd.,
King's Lynn, Norfolk, U.K. (Unpublished)