FENCHLORPHOS JMPR 1972 Explanation This insecticide was previously evaluated in 1968 (FAO/WHO, 1969) at which time an acceptable daily intake and temporary tolerances were recommended. Five requirements for further work or information were set forth. Since the previous evaluation, additional data and information have become available. At the Sixth Session of the Codex Committee on Pesticide Residues it was requested that further consideration be given to this compound by the FAO/WHO Joint Meeting on Pesticide Residues in the light of new use patterns and new residue data. RESIDUES IN FOOD AND THEIR EVALUATION FULFILLMENT OF REQUIREMENTS In the following paragraphs, the numbers refer to the corresponding requirement laid down by the 1968 Joint Meeting. 1. Extension of use on fruit and vegetables There is no anticipated extension of use on fruits or vegetables beyond those few commodities currently registered (such as bananas for importation into the United States of America and Canada), and there would be no need for international tolerances for this type of application. 2. Animal use pattern and resultant residues from countries other than the United States of America and the United Kingdom Data in the form of registered labels and tables of registered uses did not indicate a use pattern in Canada or residues in animals significantly different from that in the United States. Supervised trials in Lebanon (Kowar, 1968) in which dairy cattle were treated with one application each at levels of 0.38 and 0.75% fenchlorphos had initial milk residues of about 1.8 ppm one day after treatment (high rate). By four days after application, no residues were detectable in milk. 3. Residue levels in raw agricultural products moving in commerce No Information was available. 4. Residue levels found in total diet studies in countries other than the United States Out of 462 subsamples analysed in the total diet survey in England and Wales (Abbott, 1970) only one had positive residues of fenchlorphos (at 0.09 ppm). 5. Evaluation of methods of analysis for regulatory purposes Since the 1968 Joint Meeting, several new methods of analysis have been developed. One in support of the registration of fenchlorphos is based on an adaptation of the procedure of Claborn (1965) and utilizes electron capture gas chromatography (Dow, 1967). The method has been validated down to 0.01 ppm for fenchlorphos and to 0.1 ppm for the total metabolites in animal tissues. A method for determining fenchlorphos and its oxygen analogue in tissues of cattle has recently been published (Ivey, 1971), which utilizes flame photometric gas chromatography and can detect 0.002 ppm fenchlorphos and 0.005 ppm of the oxygen analogue. Recoveries were 75-95% for fenchlorphos and 80-100% for the oxygen analogue. Since fenchlorphos is listed as one of the compounds detectable by the multi-residue gas chromatographic method of analysis of Abbott et al. (1970), that method is recommended for regulatory use. For confirmation, a gas chromatographic method with thermionic detection appears suitable (Watts, 1969). The paper describes retention times and response data on three different GLC columns. EVALUATION OF NEW RESIDUE DATA A large amount of data was available on residues in fat of cattle, sheep, and pigs, in poultry, and eggs, and in milk from a wide variety of applications. Table 1 summarizes those data and reflects the maximum residues found among all of the applications tested. The data in Table 1 indicate that for cattle and sheep (and by extrapolation, goats) the possibility exists for residues in fat to exceed 7 ppm, but it would never exceed 10 ppm at the recommended withdrawal interval. The previously recommended tolerances for meat (fat basis) of 7.5 ppm should therefore be increased to 10 ppm for cattle, sheep and goats. However, the data further indicate that residues in fat of pigs would rarely exceed 2 ppm and residues in poultry would not exceed 0.01 ppm; therefore, the tolerances should be lowered accordingly. TABLE 1 Residues of fenchlorphos in fat of cattle, sheep and pigs Animal Ronnel Days Maximum Recommended (route of (mg/kg/day withdrawal residue in withdrawal application) × days) before fat or milk prior to slaughter (ppm) slaughter (days) Cattle (oral, 18 × 7 1 43 10 in capsule) 8 6.7 15 0.51 Cattle (oral 15 × 22 1 31 10 mineral feed) 7 8.5 27 <0.05 Cattle (oral 8.76 × 14 0 9.5 10 mineral feed) 10 0.40 21 0.026 28 0.001 35 <0.001 Cattle (spray, 1.0% 7 7.5 14 aqueous) 14 1.6 21 0.7 35 <0.05 Sheep (dip, 0.5% 7 51 28 1 time, aqueous) 14 30 21 14 28 9 Pigs (sprays 0.5% 8 0.66 0 aqueous) (100 mg/kg) 14 0.21 21 0.20 28 0.13 Poultry (litter, 0.5% 42 <0.005 (in mixed muscle) water spray) 60 <0.005 (in mixed muscle) Dairy cattle 17.6 × 7 1 0.029 in milk 10 (oral, 32P 2 0.041 " labelled feed 3 0.064 " additive) 7 0.092 " 8 0.072 " 9 0.064 " 10 0.043 " TABLE 1 (Cont'd.) Animal Ronnel Days Maximum Recommended (route of (mg/kg/day withdrawal residue in withdrawal application) × days) before fat or milk prior to slaughter (ppm) slaughter (days) Dairy cattle 0.5% 0.3 0.120 in milk 7 (spray, aqueous) 1 application 1 0.210 " 3 0.144 " 5 0.052 " 10 0.006 " 17 0.001 " 21 <0.001 " The data for milk residues indicate that a low probability exists for values in excess of 0.04 ppm. However, it was considered desirable to change the previous recommendation for the commodity whole milk to milk and milk products (fat basis), in order to indicate where the residue would be found (fat) and to accommodate milk products. Using the accepted factor of 25 (representing 4% butterfat) the calculated residue in milk (fat basis) would be 1.25 ppm. This figure should be rounded off to 2 ppm to reflect the degree of sampling error expected at such low levels and to conform to the current practice of recommending values to only one significant figure in these monographs. APPRAISAL The five items of further work or information required by the 1968 Joint Meeting are considered to have been met. There was no indication of a need to include recommendations for tolerances on fruit and vegetables. The use pattern appears to be about the same throughout the world. Total diet studies in England and Wales have not shown a significant incidence of residues of fenchlorphos in food. Existing multi-residue methods of analysis are suitable for regulatory purposes and are recommended. Consideration of new data on residues likely to occur in meat, milk and eggs from a wide variety of new application procedures on livestock and poultry has shown that a higher tolerance is required for fat of meat of cattle, goats and sheep, but that lower tolerances would suffice for poultry and fat of meat of pigs. The previously recommended tolerance on whole milk of 0.04 ppm was changed to 2 ppm in milk and milk products (fat basis), which is equivalent to 0.08 ppm in whole milk, on the basis of the new data examined. RECOMMENDATIONS TOLERANCES The temporary tolerances in effect until 1972 are replaced by the following tolerances, which include the oxygen analogue. ppm Fat of meat of cattle, goats and sheep 10 Fat of meat of pigs, milk and milk products (fat basis) 2 Eggs (shell free) 0.05 Poultry 0.01* * at or about the limit of determination FURTHER WORK OR INFORMATION None REFERENCES 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. Organophosphorous pesticides residues in the total diet. Pestic. Sci., 1: 10-13. Claborn, H.V. and Ivey, M.C. (1965) Determination of O,O-dimethyl O-2,4,5-trichlorophenyl phosphorothioate in animal tissues and milk. J. Agr. Food Chem., 13: 353-354. Dow Chemical U.S.A. (1968) Gas chromatographic determination of Ronnel, O,O-dimethyl-O-(2,4,5-trichlorophenyl) phosphorothioate, and Ronnel phenolic metabolites in animal tissues. AGR. 68.15, 1968. (unpublished) FAO/WHO. (1969) 1968 evaluations of some pesticide residues in food. FAO/PL:1968/M/9/1; WHO/Food Add./69.35. Ivey, C. and Claborn, H.V. (1971) Gas-liquid chromatographic determination of ronnel (O,O-dimethyl-O-2,4,5-trichlorophenyl phosphorothioate) and the oxygen analogue of Ronnel (dimethyl 2,4,5-trichlorophenyl phosphate) in tissues of cattle. J. Agr. Food Chem., 19(6): 1256-1258. Kowar, S., Bostonian, J. and Badawi, S. (1968) Insecticidal residues in the milk of dairy cows treated for control of ectoparasites. J. Dairy Sci., 51(7): 1023-1025. Watts, R. and Storherr, R.W. (1969) Gas chromatography of organophosphorus pesticides: Retention times and response data on three columns. J. Ass. off. analyt. Chem., 52(3): 513-521.
See Also: Toxicological Abbreviations