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 PHENTHOATE EXPLANATION Phenthoate was evaluated by the Joint Meeting on Pesticide Residues in 1980 (FAO/WHO 1981) at which time only a temporary ADI was allocated on the basis that a chronic toxicity in a rodent was needed. The required chronic toxicity/carcinogenicity study has been submitted and is summarized in this monograph addendum. EVALUATION FOR ACCEPTABLE DAILY INTAKE TOXICOLOGICAL STUDIES Special Studies on Carcinogenicity (see under long-term studies) Long-Term Studies Rat Groups of Sprague-Dawley rats (60 males and 60 females per group) were fed diets containing Phenthoate (technical grade, 93.9 percent purity at levels of 0, 20, 100 or 500 ppm for 116 weeks. Animals were observed three times a day for morbidity and mortality. Food and water consumption, body weights and adverse clinical (including neurological, ocular and behavioural) signs were recorded weekly for the first 13 weeks and bi-weekly thereafter. At periodical intervals haematology, clinical chemistry (including cholinesterase activity) and urine analyses were performed on ten animals/group/sex. Gross pathology and histopathology examinations were performed on all animals. No clinically detectable pathological signs were observed. There were no significant differences between control and treated groups with respect to mortality, growth, food and water consumption, haematology, clinical chemistry (except cholinesterase activity) and urine analyses. Plasma cholinesterase activity was significantly depressed in males and females of the 500 ppm group from week 26 to termination and in females at 100 ppm from week 78. Erythrocyte cholinesterase depression from 22-25 percent for females and 12-19 percent for males, in the 20 ppm group as compared to the control and is considered the marginal effect level. Brain cholinesterase activity was depressed about 20 percent in the high-dose group only. Absolute and relative organ weights were not significantly different between control and treated groups. No specific gross pathological changes attributable to the treatment were noted. Histopathologically, nodular hyperplasia of hepatic cells was significantly increased, although not dose-related, in treated groups when compared to the controls. There were no statistically significant differences between control and treated groups with respect to type, incidence, distribution or latency time of observed tumours. Under the conditions of the test, phenthoate did not display any carcinogenic potential. Detailed histopathological examinations performed to assess the potential neurotoxic effects of phenthoate did not reveal any lesions. (Maltoni, 1984). COMMENTS Phenthoate was evaluated in 1980 when a temporary ADI was allocated. In the rat long-term toxicity/carcinogenicity study submitted, phenthoate did not show oncogenic potential. No changes in haematology, clinical chemistry or urine analyses, nor any lesions in nervous tissues examined, were observed. The 20 ppm dose level was identified as producing a marginal effect on erythrocyte cholinestase in this study. The meeting allocated a full ADI. Level causing no toxicological effect Dog: 10 ppm in the diet, equal to 0.29 mg/kg b.w. Rat: 10 ppm in the diet, equal to 1.0 mg/kg b.w. Mouse: 30 ppm in the diet, equivalent to 4.5 mg/kg b.w. Estimate of acceptable daily intake for humans 0 - 0.003 mg/kg b.w. Further work or information Desirable: Observation in humans. Further information on impurities in the technical products in order to evaluate the degree to which these impurities affect the acute toxicity of phenthoate. REFERENCES Maltoni, C. Long-term carcinogenicity and chronic toxicity of 1984 phenthoate (CAS No.2597-03-7) on Sprague-Dawley rats (oral dosing study) Bologna, Italy. Inst. Oncology. Report No. BT 5005. Submitted by Farmoplant, Italy, to WHO.
See Also: Toxicological Abbreviations Phenthoate (Pesticide residues in food: 1980 evaluations) Phenthoate (Pesticide residues in food: 1981 evaluations)