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)
See Also: Toxicological Abbreviations