PESTICIDE RESIDUES IN FOOD - 1984 Sponsored jointly by FAO and WHO EVALUATIONS 1984 The monographs 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 Rome, 24 September - 3 October 1984 Food and Agriculture Organization of the United Nations Rome 1985 FENITROTHION EXPLANATION Fenitrothion was evaluated by the Joint Meeting in 1969, 1974, 1976, 1979, 1982 and 1983.1/ Information was required by the 1983 meeting on current good agricultural practices and on the results of supervised trials carried out on varieties of citrus fruit according to use recommendations. RESIDUES IN FOOD AND THEIR EVALUATION USE PATTERN The meeting received only minor information on recommended uses, national maximum residue limits, monitoring data and on the fate of residues in stored wheat and in chicken tissue. Information on registered uses has been received from Canada, the Netherlands and New Zealand. Codex maximum residue limits exist for all uses. RESIDUES RESULTING FROM SUPERVISED TRIALS In addition to trials made in Spain on fenitrothion on mandarins, which were reported in 1983, trials have been made on fenitrothion on oranges. Sumithion 50 percent EC and Folithion 50 percent EC were applied in Valencia on oranges at a rate of 4.5 kg a.i./ha in a concentration of 0.15 percent. The average residue in whole fruit was 1.18 mg/kg and 0.93 mg/kg 14 days and 28 days after treatment. Residue levels in pulp 14 days and 28 days after both treatments were 0.03 mg/kg or lower. FATE OF RESIDUES In Plants Although the fate of residues of fenitrothion in stored cereals has been reviewed previously (1974, 1976, 1977 and 1979), additional information was provided to this meeting. Earlier investigations were mainly on the degradation rate of the parent compound and to some minor extent on metabolism of fenitrothion to the oxygen analogue and 3-methyl-4-nitrophenol. An investigation has now been made on the degradation to other metabolites of fenitrothion in stored wheat. Hard red spring wheat with a moisture content of 12.5 percent was treated with fenitrothion to provide a deposit of 12 mg/kg. After mixing, the wheat was transferred to screw-capped jars and stored in the dark at 1/ See Annex 2 for FAO and WHO documentation. 20°C for 12 months. Samples were taken after 0, 1, 3, 6 and 12 months for quantitative determination of fenitrothion and the following metabolites: fenitro-oxon, O-dimethyl-fenitrothion, S-methyl-fenitrothion, 3-methyl-4-nitrophenol, dimethyl-phosphorothioate and O-dimethyl-S-methyl-fenitrothion. The samples were extracted with acidified acetone or methanol and, after concentration, separations were made by partitioning to organic solvents from acidified or basic aqueous solutions. The metabolites present were ethylated by diazoethane and clean-up was made by column chromatography. Determinations were made by GLC using a flamephotometric detector (phosphorus mode) and an EC-detector. The presence of the metabolites was confirmed by TLC and for dimethyl-fenitrothion also by chemical derivatization. After 12 months' storage, fenitrothion residue was decreased to 2 mg/kg. O-dimethyl-fenitrothion, 3-methyl-4-nitrophenol and dimethyl phosphorothioate were the major metabolites. The highest levels of O-dimethyl-fenitrothion and dimethyl-phosphorothioate were found after six months of storage; the residues, 2.01 mg/kg and 0.55 mg/kg, respectively, decreased after 12 months to 0.98 mg/kg and 0.21 mg/kg. Residues of 3-methyl-4-nitrophenol increased during the storage period from 0.38 mg/kg after one month to 0.96 mg/kg after 12 months. No fenitrothion or S-methyl-fenitrothion was detected throughout the study period. Detection limits were 0.001 mg/kg and 0.05 mg/kg, respectively (Abdel-Kader & Webster, 1982). In Animals The fate of residues of fenitrothion in mammals was reviewed in 1969 and 1974. A study has been made on residues of fenitrothion and its metabolites in chicken tissue after long-term exposure to small doses. The results from this study show that chicken tissues retain insignificant amounts of fenitrothion or its metabolites even after a long exposure to small doses of this insecticide. This is consistent with earlier observations made on tissues for mammals (Trottier & Jankowska, 1980). RESIDUES IN FOOD IN COMMERCE OR AT CONSUMPTION Monitoring data from 1981-83 have been received from Sweden (1984a) on fenitrothion in domestic and imported crops of carrot, dill, lettuce, lemon, mandarin and orange. A total of 483 samples of domestically grown crops and 1 720 samples of imported crops were analysed. In 98.5 percent of the samples residues were <0.11 mg/kg. One sample of dill had a residue higher than 0.5 mg/kg and 14 samples from 1 032 samples of mandarins and oranges contained residues between 0.29 and 0.8 mg/kg. NATIONAL MAXIMUM RESIDUE LEVELS REPORTED TO THE MEETING Updated lists of MRLs were provided to the meeting by the Netherlands (1984) and Sweden (1984b) Country Commodity MRL (mg/kg) The Netherlands Fruit 0.5 Vegetables 0.5 Cereals 0.5 Tea 0.5 Cocoa bean 0.1 Milk 0.002 (limit of determination) Meat 0.05 (limit of determin.) Other food 0 (0.02) (limit of determin.) Sweden Fruits and Vegetables 0.5 Potato 0.2 Cereals and bran 0.5 Flour from cereals 0.2 APPRAISAL Limited information was received on recommended uses, results of supervised trials, monitoring data, national maximum residue limits and the fate of fenitrothion in chickens and in stored wheat. The meeting received data from a supervised trial with oranges, which supplemented information received by the 1983 JMPR on trials with mandarins. Residues in the whole fruit were 1.2 mg/kg after 14 days and 0.93 mg/kg after 28 days. This supports the TMRL for oranges of 2 mg/kg proposed as an amendment to the Codex MRL. Residues in the pulp were 0.03 mg/kg or lower. Studies of the metabolism of fenitrothion in wheat stored at 20° in the dark showed that levels of O-dimethyl-fenitrothion and dimethyl-phosphorothioate increased for six months after treatment and then decreased, but with a considerable residue remaining even after 12 months. Levels of 3-methyl-4-nitrophenol increased during the whole 12-month period after treatment. No fenitro-oxon or S-methyl-fenitrothion was observed. The metabolism of fenitrothion has been investigated in the chicken after long-term exposure to small doses. No significant amounts of fenitrothion or metabolites were retained in the tissue. This is consistent with earlier observations made on mammalian tissues. REFERENCES Abdel-Kader, M.H.K. & Webster, G.R.B. Analysis of fenitrothion and 1982 metabolites in stored wheat. Intern. J. Environ. Anal. Chem., 11: 153-165. Netherlands. National maximum residue levels of fenitrothion. 1984 Sweden. Monitoring data from the National Food Administration, 1984a Uppsala. Sweden. National maximum residue levels of fenitrothion. 1984b Trottier, B.L. & Jankowska, I. In vivo study on the storage of 1980 fenitrothion in chicken tissues after long-term exposure to small doses. Bull. Environment. Contam. Toxicol., 24: 606-610.
See Also: Toxicological Abbreviations Fenitrothion (EHC 133, 1992) Fenitrothion (HSG 65, 1991) Fenitrothion (ICSC) Fenitrothion (FAO/PL:1969/M/17/1) Fenitrothion (WHO Pesticide Residues Series 4) Fenitrothion (Pesticide residues in food: 1976 evaluations) Fenitrothion (Pesticide residues in food: 1977 evaluations) Fenitrothion (Pesticide residues in food: 1979 evaluations) Fenitrothion (Pesticide residues in food: 1982 evaluations) Fenitrothion (Pesticide residues in food: 1983 evaluations) Fenitrothion (Pesticide residues in food: 1986 evaluations Part II Toxicology) Fenitrothion (Pesticide residues in food: 1988 evaluations Part II Toxicology) Fenitrothion (JMPR Evaluations 2000 Part II Toxicological)