PESTICIDE RESIDUES IN FOOD - 1983 Sponsored jointly by FAO and WHO EVALUATIONS 1983 Data and recommendations of the joint meeting of the FAO Panel of Experts on Pesticide Residues in Food and the Environment and the WHO Expert Group on Pesticide Residues Geneva, 5 - 14 December 1983 Food and Agriculture Organization of the United Nations Rome 1985 CYHEXATIN RESIDUES Explanation The 1978 Meeting proposed a maximum residue limit (MRL) of 2 mg/kg for cyhexatin on peaches.1 At the 15th Session of the Codex Committee on Pesticide Residues (CCPR) in 1983 the United States referred to agricultural practices in that country that could result in residues exceeding 2 mg/kg. New information was reviewed by the present Meeting, which indicated a need to increase the MRL. RESIDUES IN FOOD AND THEIR EVALUATION RESIDUES RESULTING FROM SUPERVISED TRIALS Peaches Residue studies were conducted at several locations in the United States and in Ontario, Canada on seven varieties of peaches. Treatments were up to three times with dilute sprays of 20 g a.i./100 1 applied to 3 400 to 9 000 l/ha or concentrated sprays of 0.84 kg or 1.68 kg a.i./ha applied at 450 l/ha. Sample peaches were harvested at intervals after the last application and analysed for total organotin residue, including cyhexatin, dicyclohexyltin oxide and cyclohexylstannoic acid. The method involved treating macerated fruit with hydrochloric acid, extraction with warm chloroform to separate organotin compounds from inorganic tin, evaporation of the chloroform, oxidation with nitric and sulphuric acids, conversion of the resultant Sn+4 to its iodide, formation of pyrocatechol violet complex and spectrophotometric measurement of the colour (M&T Chemicals 1972). The residues found are summarized in Table 1 (Getzendaner & Carbin 1973, 1975). All are expressed as cyhexatin, which predominates at any given time. Kiwi Fruit Cyhexatin is the preferred miticide for the control of phytophagus mites on kiwi fruit and has been used at between 12.5 g and 20 g a.i./100 l, with one or two applications per season. The volume varied from 1 200 l/ha to 3 400 l/ha, depending on application equipment, equivalent to 150 g to 700 g a.i./ha. Residue trials carried out in New Zealand in 1978, 1979 and 1981 are reported in Table 2. Table 1 Residues of Cyhexatin in Peaches Application AHI1 Total organotin found Year Country Variety Rate No. (days) (as mg/kg cyhexatin) Dilute sprays (20 a.i./100 l, 3 400-9 000 1/ha) 1969 United States Halford 1.7 3 0 2.0, 2.5, 2.8, 3.8 7 3.2, 3.2, 3.2, 3.6 14 2.4, 2.4, 3.2, 3.6 28 1.9, 2.0, 2.2, 2.7 2 53 0.6, 1.2, 1.4, 1.5 1 53 0.6, 0.9, 1.0, 1.1 1970 Halford 1.7 3 0 0.9, 1.5, 1.7, 2.3 7 1.1, 1.3, 2.1, 2.2 14 2.0, 2.1, 2.4, 2.6 28 1.2, 1.4, 1.5, 1.5 1970 Halford 3 0 1.5, 1.7, 1.7, 2.0 7 1.2, 1.4, 1.4, 1.5 14 0.9, 1.0, 1.1, 1.2 28 0.4, 0.5, 0.5, 0.6 1 See Annex 2 for FAO and WHO documentation. Table 1 (con't) Application AHI1 Total organotin found Year Country Variety Rate No. (days) (as mg/kg cyhexatin) 1970 United States Red Haven 1.8-2.2 3 0 1.6, 1.9, 2.3 (early) 7 1.7, 2.0, 2.0 14 0.5, 0.6, 0.8 28 0.9, 0.9, 1.0 1970 Richaven 1.1-1.8 3 0 1.8, 2.0, 2.2, 2.2 7 1.8, 2.1, 2.4, 2.5 8 0.9, 0.9, 1.3, 1.4 20 0.4, 0.6, 0.6, 0.7 1972 Canada Goldray 1.1 1 7 0.6, 0.6, 0.8, 1.6 17 0.2, 0.4, 0.5, 0.6 25 0.2, 0.3, 0.3, 0.5 30 0.1, 0.1, 0.1, 0.2 60 0.0, 0.0, 0.0, 0.0 Concentrated sprays (0.84 kg or 1.68 kg a.i./ha in 450 l/ha) 1971 United States Elberta 0.84 3 0 0.3, 0.4, 0.5, 0.5 1974 United States Elberta 1.68 3 1 3.0, 4.1, 4.3 14 1.2, 1.9, 2.6 1 AHI = Interval from last application to harvest. Table 2 Residues of Cyhexatin on Kiwi Fruit Rate Formulation Residues (mg/kg) No. (g a.i./ha) after last trial (days) 1 2 4 7 14 1979 1 680 1.9 - - 2.4 1.6 1978 1 700 1.0 - - 1.4 1.3 1981 2 (14-day interval) 600 (total) W.P. 1.7 - - 1.4 0.8 2 (14-day interval) 500 (total) aqueous susp. 2.1 1.9 1.4 1.6 2 (14-day interval) 300 (total) W.P. - 1.0 0.8 0.5 0.6 2 (14-day interval) 600 (total) W.P. - 1.6 2.4 0.5 0.5 In five trials the edible part was also analysed separately and was found to contain less than 10 percent of the level in whole fruit, except in the trial using an aqueous suspension when the proportion was about 15 percent. In general, the new data for peaches support those evaluated in 1978. However, it is clear that at shorter intervals between last application and harvest, and particularly if the chemical is applied in lower volumes than previously considered, then the earlier estimate of 2 mg/kg as MRL will be exceeded. Thus, the Meeting estimated a new MRL of 5 mg/kg, to take into account the new data and those in the 1978 evaluation, noting again that most of the residue was present in the peel and that lower residues are found in smooth-skinned varieties. The Meeting recommended that this estimate was suitable for establishing an MRL. APPRAISAL Residue data on kiwi fruit from five trials over three seasons have provided a basis for estimating an MRL. Levels in the edible part of the fruit were up to about 15 percent of the whole-fruit residue. Since MRLs are recommended for kiwi fruit on a whole-commodity basis, 5 mg/kg was proposed on the basis of a 3 to 4 day preharvest interval. The Meeting reviewed the limited data on residues of cyhexatin on beans in the 1978 evaluations and concluded that an estimated MRL of 0.2 mg/kg was more appropriate than the figure of 0.5 mg/kg previously estimated. REFERENCES - RESIDUES Getzendaner, M.E. & Carbin, H.B. Residues of organotin on peaches and 1973 nectarines, fresh and dried plums from applications of PLICTRAN 50W miticide. Dow Chemical Company report GH-C 643. (Unpublished) Getzendaner, M.E. & Carbin, H.B. A study of residues on stone fruit 1975 from concentrate spray applications of PLICTRAN 50W miticide. Dow Chemical Company report GH-C 800. (Unpublished) M&T Chemicals. Determination of small amounts of organotin in 1972 macerated fruit. Analytical method TA-27. (Unpublished)
See Also: Toxicological Abbreviations Cyhexatin (WHO Pesticide Residues Series 4) Cyhexatin (WHO Pesticide Residues Series 5) Cyhexatin (Pesticide residues in food: 1978 evaluations) Cyhexatin (Pesticide residues in food: 1980 evaluations) Cyhexatin (Pesticide residues in food: 1981 evaluations) Cyhexatin (Pesticide residues in food: 1989 evaluations Part II Toxicology) Cyhexatin (Pesticide residues in food: 1991 evaluations Part II Toxicology) Cyhexatin (JMPR Evaluations 2005 Part II Toxicological)