FAO, PL:CP/15 WHO/Food Add./67.32 EVALUATION OF SOME PESTICIDE RESIDUES IN FOOD The content of this document is the result of the deliberations of the Joint Meeting of the FAO Working Party and the WHO Expert Committee on Pesticide Residues, which met in Geneva, 14-21 November 1966.1 1 Report of a Joint Meeting of the FAO Working Party and the WHO Expert Committee on Pesticide Residues, FAO Agricultural Studies, in press; Wld Hlth Org. techn. Rep. Ser., 1967, in press PHOSPHAMIDON (Addendum to 1965 Monograph) This pesticide was evaluated by the Joint Meeting of the FAO committee on Pesticides in Agriculture and the WHO Expert Committee on Pesticide Residues in its 1965 report (FAO Meeting Report No. PL/1965/10/1; WHO/Food Add./27.65). Since its publication some new experimental work has been reported on the compound. This new work in presented and discussed in the following monograph addendum. BIOLOGICAL DATA AND TOXICOLOGICAL EVALUATION Biochemical aspects The alpha- and beta-isomer of desethylphosphamidon was isolated from bean plants (Vicia faba) in the ratio 1:2 (CIBA, 1964a). Acute toxicity In acute oral toxicity studies in male albino rats, the toxicity of phosphamidon was not potentiated when administered in combination with azinphos-methyl, carbaryl, carbophenothion, demeton, diazinon, dioxathion, EPN, ethion, malathion, methyl parathion, parathion, mevinphos, naled and schradan (Kay & Calandra, 1961). The oral LD50 in rats of desethylphosphamidon is: for beta-isomer, 8.5 mg/kg; for alpha-isomer, 250 mg/kg body-weight (CIBA, 1964a). The oral LD50 of desmethylphosphamidon in male rats is 2500 + 420 mg/kg. The oral LD50 of gamma-chlorophosphamidon is 126 + 6.8 mg/kg in rats and 117 + 25 mg/kg in mice (CIBA, 1964b; Cervenka et al., 1964). In man a fatal case of oral poisoning and a probable case of mild poisoning is described. In the fatal case, post-mortem examination revealed a fatty liver, congestion of internal organs and brain damage of the type seen in anoxia. The clinical picture in both cases resembled that seen in poisoning with other organophosphates (Gitelson at al., 1965). Short-term studies Rat. Groups of 5 male and 5 female rats were exposed to inhalation of phosphamidon at concentrations of 0.05 and 0.5 mg/m3 or 4 hours a day for 6 weeks. A temporary decrease of cholinesterase activity in erythrocytes and in plasma was compensated after 2 weeks (CIBA, 1965). Groups of 50 male and 50 female rats were fed diets containing 0, 1, 2, 3, 5 and 7.5 ppm phosphamidon for 12 weeks. The cholinesterase activity was measured in plasma, erythrocytes and brain. No significant inhibition of cholinesterase was found at the 2.0 ppm dietary level. (Kay & Calandra, 1961). Groups of 15 male and 15 female rats were fed phosphamidon in the diet for 13 months. The doses were 0, 0.1, 0.5, 1.25 and 5.0 mg/kg body-weight/day and were periodically compensated for change in body-weight and food consumption. A significant decrease of growth and depressed food intake was recorded only in the males fed 1.25 and 5.0 mg/kg/day. The other 2 groups (0.1 and 0.5 mg/kg/day) were comparable with the control group. No difference in mortality, tumour incidence, peripheral blood picture, urine, and gross and microscopic appearance of tissues was seen between the groups. (Kohn et al., 1964). A 3-generation reproduction study was performed in rats. Three groups of 8 male and 16 female rats were fed 1.0, 7.5 and 15 ppm of a phosphamidon mixture (75 per cent phosphamidon, 22 per cent desethylphosphamidon, 3 per cent N,N-diethyl-a-chloroacetoacetamide) in the diet. Two other groups served as controls. The rats were mated at 74 and 105 days. The second litter served to produce 2 F2 generations. In all three generations, body weight and weight gain were similar to those of the controls. No abnormal reaction was noted, and none of the deaths in the course of the experiment was attributed to the substance tested. Mating indices, fertility indices, incidence of pregnancy, parturition and gestation times, body-weight and histology were essentially comparable with control animals. Lactation indices were slightly lower in the P and F2 groups fed the highest dose (15 ppm). Litter survival was reduced at 15 ppm (Kennedy et al., 1966). Dog. Groups of 3 male and 3 female beagles were given phosphamidon orally in capsules at dose levels of 0, 0.05, 0.1, 0.5, 1.0, 2.0, 3.0, 4.0 and 5.0 mg/kg body-weight/day. The doses of 0.05-1 mg/kg/day were administered for 90 days. Plasma and erythrocyte cholinesterase activity was determined by an electrometric method. At a dose of 1 mg/kg/day and higher significant inhibition of cholinesterase was caused in 9-16 days. No depression of cholinesterase was observed at dose levels of 0.5 mg/kg/day or lower within 90 days. (Kay & Calandra, 1961). Four groups of dogs (2 males and 2 females in each group) were given phosphamidon orally in gelatin capsules at dose levels of 0, 0.1, 2.5 and 5.0 mg/kg body-weight/day for 2 years. Body-weight and food consumption, behavioural reactions and mortality were followed up, and haematologic studies, blood urea nitrogen determination, urine analyses including examinations for albumin, glucose and microscopic elements and liver function tests were conducted. The test was concluded by the determination of organ-weights together with their histopathologic examination. The dogs in the highest dose group (5 mg/kg/day) perished in the course of the test, as a consequence of phosphamidon ingestion. In the group receiving a dose of 2.5 mg/kg/day, slight muscular tremors were observed in females in the first year of the test, and in the second year slight muscular tremors appeared also in males, together with a slight salivation. At the highest dose level, alterations in organ weights and ratios were found. However, histologic examination revealed no alterations which could have been caused by Phosphamidon. No degenerative changes were noted in the myelin sheath. There were no significant effects detected at a dose level of 0.1 mg/kg/day. (Cervenka et al., 1964). Comments In a 12-week experiment using rats, 2 ppm in the diet did not cause any significant decrease of cholinesterase in the plasma, erythrocytes and brain; in a 90-day test using dogs, 0.5 mg/kg/day did not result in any inhibition in plasma and erythrocytes. A mixture of phosphamidon and 2 of its metabolites had no effect on the reproductive capacity of rats at a dietary level of 7.5 ppm, equivalent to 0.37 mg/kg/day. Biochemical and metabolic fate studies in man exposed to this compound by different routes, reproduction studies in at least one more species other than the rat, and short-term toxicity studies of metabolites and break-down products of phosphamidon are desirable. TOXICOLOGICAL EVALUATION Level causing no toxicological effect Rat ppm, equ. 0.1 mg/kg/day Dog 0.5 mg/kg/day Estimate of acceptable daily intake for man 0-0.001 mg/kg body-weight REFERENCES Cervenka, H., Kay, J. H. & Calandra, J. C. (1964) Unpublished report submitted by CIBA. CIBA (1964a) Unpublished report by R. Anliker & E. Kühl. CIBA (1964b) Unpublished report by J. Tripod & R. Anliker CIBA (1965) Unpublished report by Bericht von A. Hoffman & K. H. Bergert (Batelle-Institut E.V.-Frankfurt am Main). Gitelson, S., Davidson, J. T. & Werczberger, A. (1965) Brit. J. industr. Med., 22, 236 Kay, J. H. & Calandra, J. C. (1964) Unpublished report submitted by CIBA. Kennedy, G., Fancher, O. E. & Calandra, J. C. (1966) Unpublished report submitted by CIBA Kohn, F. E., Kay, J. H. & Calandra, J. C. (1964) Unpublished report submitted by CIBA Palazzolo, R. J., Kay, J. H. & Calandra, J. C. (1964) Unpublished report submitted by CIBA
See Also: Toxicological Abbreviations Phosphamidon (ICSC) Phosphamidon (PIM 454) Phosphamidon (FAO Meeting Report PL/1965/10/1) Phosphamidon (FAO/PL:1968/M/9/1) Phosphamidon (FAO/PL:1969/M/17/1) Phosphamidon (WHO Pesticide Residues Series 2) Phosphamidon (WHO Pesticide Residues Series 4) Phosphamidon (Pesticide residues in food: 1982 evaluations) Phosphamidon (Pesticide residues in food: 1986 evaluations Part II Toxicology)