CHINOMETHIONAT EXPLANATION Chinomethionat was evaluated by the JMPR in 1968 (as oxythioquinox), 1974, 1977, and 1981 (Annex 1, FAO/WHO 1969a, 1975a, 1978a, and 1982a). At the 1974 and 1977 JMPR the following investigations were requested: 1. Studies on the identity and relative toxicity of metabolites. 2. An additional carcinogenicity study in another species, in view of hepatic toxicity observed in rodents. In 1981 new studies regarding mutagenicity, teratogenicity and eye and dermal irritation were received. The mutagenicity and teratogenicity studies are included and evaluated in the present monograph addendum. The 1984 JMPR decided to withdraw the temporary ADI (established at the meeting of 1977) of 0.003 mg/kg bw because requested studies had not been submitted. The outstanding study requirements and some additional studies have become available now and are summarized and discusses in this monograph addendum. EVALUATION FOR ACCEPTABLE DAILY INTAKE BIOLOGICAL DATA Toxicological Studies Special studies on carcinogenicity See under long-term studies. Special studies on teratogenicity Rats Groups of 25 female Wistar rats received 0, 10, 25, or 62.5 mg chinomethionat (purity, 95.1%)/kg bw by gavage from days 6-15 of gestation. The fetuses where delivered by caesarian section on day 20 of pregnancy. The dams were observed daily ofr mortality and body weight. The number of implantations, live and dead fetuses, early and late resorptions and placenta weight were recorded. The fetuses were counted, sexed and weighed and studied for visceral and skeletal malformations. There were no effects observed on the dams and offspring except for a significantly decreased body weight gain in high dosed dams and a decrease in fetal and placental weight at all dose levels (not clearly and not significant at the highest dose (Renhof, 1986). Rabbits Groups of 15 rabbits (Himalayan strain) received 13 daily oral doses of either 0, 10, 30 and 100 mg chinomethionat (Purity, 91.5%)/kg bw from day 6-18 of gestation. The fetuses were delivered by caesarian section on day 29 of pregnancy. Maternal toxicity was observed in high dosed dams (e.g. diarrhoea, reduced feed intake, loss of weight) and in the same dose group a significant decrease in both the number and size of fetuses was found. Examination of the offspring by standard methods and the evaluation of the results gave no indication of teratogenicity (Schlülter, 1981). Special studies on mutagenicity Chinomethionat gave no mutagenic response in test with Bacillus subtilis, Escherichia coli and Salmonella typhimurium and the CHO/HGPRT cell mutation assay as well as in the micronucleus test with mice (see table 1.). Table 1. Special studies on the mutagenicity of chinomethionat Type of test Test object Concentration of Purity Results References chinomethionat In vitro Ames test (with Salmonella 1 µg up to 91% negative Shirasu et al., 1979 and without typhimurium 5000 µg/plate metabolic TA98, TA100 activation) TA1535, TA 1537 & 1538 Reverse mutation Escherichia 1 µg up to 91% negative Shirasu et al., 1979 assay (with and coli 5000 g/plate without metabolic WP2 hcr activation) Recombination Bacillus 20 µg up to 91% negative Shirasu et al., 1979 assay subtilis 2000 µg/plate M45 & H17 CHO/HGPRT Chinese Non activated: 94.4% negative Yang, 1986 mutation assay hamster ovary 0.1, 0.5, 1.0, (1) (with and without cells 1.5 and 2.0/µg/ml metabolic (CHO-K1-BH4) Activated: 0.1, negative activation) 0.5, 1.0, 3.0 (1) and 5.0 µg/ml dissolved in acetone Table 1. (cont'd). Type of test Test object Concentration of Purity Results References chinomethionat In vivo Micronucleus NMRI mice 500 and 1000 mg/kg 95.2% negative Herbold, 1982 test (administered (1) orally twice, 24 hr apart) (1) Positive control yielded positive results. Special studies on reproduction Rats Groups of 10 male and 20 female SPF/Cpb rats were fed diets containing 0, 15, 60 and 240 ppm chinomethionat (purity 94.6%) in a two generation (two litters/generation) study. Diets were maintained during mating, gestation and lactation. Observations were made on general condition and behaviour, food consumption and body weight. Indices for fertility, gestation, viability, lactation and insemination as well as litter-and pupweight and abnormalities were recorded. Organ weights (liver, kidneys and gonads) were measured for the F1b parents only. All parental rats and pups of the highest dose group had yellow coats. Maternal toxicity was observed at 240 ppm and sometimes at 60 ppm as indicated by a lower body weight gain. F0 females, F1b parents and F1b, F2a and F2b pups had decreased body weight gain at 240 ppm and F0 females and F2b pups also at 60 ppm. F2a mean littersize was significantly reduced in the highest dose group. Viability was significantly reduced in F1a, F2a and F2b pups at 240 ppm. Fib females had increased relative liver and kidney weights at 240 ppm. No effects were observed at 15 ppm (Eiben, 1984). Dogs The effect of chinomethionat on semen quality was evaluated in groups of beagle dogs (6/group) fed diets containing 0, 25, 75 and 225 ppm chinomethionat (purity 91.5%). The study was part of the one year feeding study in dogs (see under short-term studies). Semen samples were obtained at 4 month intervals throughout the one-year study. Clinical abnormalities were not observed in the dogs before each semen collection. Semen samples were observed for volume, motility, status, sperm count, total viable sperm, color, viscosity, morphology and cellular debris. Evaluations of the three collections gives no evidence of reduced semen quality and quantity (Dahlgren, 1981; Hayes, 1983). Special studies on thyroid function Groups of 100 male SPF/Cpb rats were fed diets containing 0, 10, 25, 60, 150, and 500 ppm chinomethionat (purity 95.2%) for 8 weeks, surviving animals were observed for another 4 weeks. Besides growth and food intake, clinical chemical examinations, including T3 and T4, were measured on day 7, 21, 63, 70 and 84. At the same times radioiodine uptake by the thyroid was measured in 10 animals which were killed 24 hours after 131I administration. The fur of the animals of the 500 ppm group was yellow colored. In the highest dose group decreased body weight gain (also at 150 ppm) and increased relative liver weight were observed to occur in a dose-related manner. Thyroid function tests (T3 and T4, and iodine uptake) did not provide any indications of a dose- or time-related effect on functioning. No consistent differences were observed in these parameters nor in other clinical chemical parameters. No effects on weight or histopathology of the thyroid were found (Krötlinger et al., 1984). Short-term studies Rats Groups of SPF/Cpb rats (20/sex/group) were orally administered 0, 10, 25, 60, 150, and 500 ppm chinomethionat (purity 95.2%) in the diet for three months. All animals were observed daily for mortality and clinical signs while body weight and food consumption were observed weekly. Hematology, blood chemistry and urinalysis examinations were recorded on 10 rats/group after one month and at termination of the study. After three months all animals were killed, selected organs weighed and complete gross and histopathological examinations were performed. There were no effects on appearance, behaviour and mortality except for high dosed rats which showed a yellow fur. Reduced body weight gain and food intake was observed in rats receiving 150 and 500 ppm. At the highest dose level Hb, Ht, RBC and MCH were significantly decreased in both sexes. At the same dose level, females had a lower WBC count and males a higher thrombocyte count. In females Hb, Ht, RBC and MCH were also significantly decreased at 150 ppm. At 60 ppm MCH values were still decreased in females after 3 months. Decreased protein levels in the urine were found in males and females (only after 3 months) at 500 ppm. Relative brain weight was significantly increased at 60 (males only), 150 and 500 ppm in both sexes. Relative liver and kidney weight were significantly increased in females at 150 and 500 ppm and relative lung and relative testes weight in males at the same dose levels. At 60 ppm, equal to 4 (males) - 4.6 (females) mg/kg bw, only marginal effects were observed (Krötlinger & Kaliner, 1983). Dogs Beagle dogs (6/sex/group) were orally administered 0, 25, 75, or 225 ppm chinomethionat (purity 95.8%) in the diet for 52 weeks. No compound related effects were observed on clinical signs, mortality, urinalysis or ophthalmoscopy. Body weight was decreased in males and females at 225 ppm (sometimes significantly). Food consumption was significantly reduced in males at 225 ppm from week 36 onwards. Hb, Ht, and RBC were reduced sometimes significantly in males and females at 225 ppm and sometimes also at 75 ppm. Alkaline phosphatase and alanine amino transferase values were increased in males and females receiving 225 ppm. In males absolute heart weight was significantly decreased at all dose levels and absolute liver and absolute adrenal weight decreased and relative spleen weight increased at 225 ppm. In females relative liver and kidney weight were increased at 225 ppm At histopathology, marked hepatopathy with early cirrhosis at 225 ppm and an increased severity of centrilobular hepatocellular pigmentation at 75 and 225 ppm were observed in both male and female dogs. Increased splenic hemosiderosis was noted in dogs fed 225 ppm. The NOAEL in this study is 25 ppm in the diet, equivalent to 0.6 mg/kg bw (Hayes, 1983). Long-term studies Groups of 70 male and 70 female mice (NMRI) were fed diets containing 0, 90, 270 and 800 ppm chinomethionat (purity 95.2%) for 21 months. Twenty male and 20 female mice per group were used for interim kill after 12 months. Observations included clinical signs, mortality, body weight, food consumption, hematology and clinical chemistry. Surviving mice were sacrificed after 21 months. Organs were weighed and comprehensive histopathological examinations were made. The mortality of males was significantly lower at 800 and 270 ppm, whereas females showed a higher mortality at 800 ppm throughout the study and, at some examination times, also at 270 ppm. At 800 ppm growth rate was significantly reduced throughout the study in male mice and from week 75 onwards in female mice. At 800 ppm significantly decreased values for Hb, Ht and RBC and number of leucocytes (a nonsignificant decrease in Hb and Ht was also observed at 270 and 90 ppm) were observed in males after 52 weeks. At the end of the study males and females showed a nonsignificant decrease in Hb, Ht and RBC and a significant increase in MCH and MCV (males). Reticulocyte count was increased in females at both times. No consistent effects were found on clinical chemistry parameters with the possible exception of significantly increased urea values in females at 270 and 800 ppm after 21 months. Relative adrenal weight was not increased in a dose-related manner in males after 52 weeks. Relative testes and brain weight were significantly increased in males at 800 ppm. Relative spleen weight was significantly increased in females at all dose levels and in males at 270 and 800 ppm (only after 52 weeks). Relative kidney weight was significantly increased in males and females (only after 52 weeks) at 800 ppm. Relative liver weight was increased in females at 270 and 800 ppm after 52 weeks. Relative heart weight was significantly increased in females at 800 ppm. At macroscopy an increased incidence of pale kidneys and a rough kidney surface was observed in females at 270 and 800 ppm. The incidence of progressive nephropathy was increased at 800 ppm. No enhanced tumor incidence was observed. At 90 ppm, equal to 16 (males) - 21 (females) mg/kg bw, only marginal effects on the red blood cells were observed (Krötlinger, 1986). COMMENTS The 1984 JMPR withdrew the temporary ADI of chinomethionat because the required data, sufficient to carry out a new toxicological evaluation, had not been supplied. The data supplied to this meeting included studies on reproduction, teratogenicity, mutagenicity, carcinogenicity, a short-term study in rats and a 1-year study in dogs. In reproduction studies, chinomethionat caused decreased litter-size, pup weight and viability at maternally toxic dose levels. No adverse effects were found at 15 ppm. In teratogenicity studies with rats and rabbits, fetotoxicity and maternal toxicity were observed but no teratogenic effects were seen. The semen of dogs was not affected by chinomethionat administration. Chinomethionat was not mutagenic in a battery of tests. In a short-term study in the rat, the main effects were reduced body weight gain, reduced food intake, and anaemia. Marginal effects on red cells were observed at 60 ppm. In a special study with rats, changes in thyroid function were not observed. In a one-year study with dogs, growth inhibition, anaemia, an increase in serum alkaline phosphatase and in alanine amino transferase, as well as histopathological changes in the liver and spleen were found. In this study the NOAEL was 25 ppm. In a long-term toxicity/carcinogenicity study in mice, the same effects were found on body weight and hematological parameters. Relative organ weights were increased, especially those of the spleen. The kidneys showed histopathological changes (progressive nephropathy). With the lowest dose level tested (90 ppm) only marginal hematological changes were observed. The tumor incidence was not enhanced. The meeting considered these data together with the data previously evaluated in 1974 (acute toxicity and chronic toxicity in rats) and 1977 (biotransformation and acute toxicity of chinomethionat and its main metabolite) sufficient to allocate an ADI. The NOAEL for the rat was based on the long-term study evaluated at the 1974 Meeting, showing no adverse effects at 12 ppm, the highest dose level tested. TOXICOLOGICAL EVALUATION LEVEL CAUSING NO TOXICOLOGICAL EFFECT Rat: 12 ppm in the diet, equivalent to 0.6 mg/kg bw/day Dog: 25 ppm in the diet, equivalent to 0.6 mg/kg bw/day ESTIMATE OF ACCEPTABLE DAILY INTAKE FOR MAN 0-0.006 mg/kg bw. STUDIES WHICH WILL PROVIDE INFORMATION VALUABLE IN THE CONTINUED EVALUATION OF THE COMPOUND 1. Observations in man. 2. Ongoing studies to identify metabolites in rats and plants. REFERENCES Dahlgren, R.R., 1981. Evaluation of the effects of oxythioquinox on the semen quality in Canines. Unpublished report no. 222 d.d. 11-11-1981 from Raltech Scientific Services. Submitted to WHO by Bayer AG, Bayerwerk, 5090 Leverkusen, FRG. Eiben, R., 1984. SS 2074 (new designation SAS 2074) (c.n. chinomethionat). Two generation study with rats. Unpublished report no. 12794 d.d July, 6 1984 from Institute of Toxicology, Bayer AG. Submitted to WHO by Bayer AG, Bayerwerk, 5090 Leverkusen, FRG. Hayes, R.H., 1983. Chronic dietary toxicity of oxythioquinox (Morestan) to dogs. Unpublished toxicology report no. 363 d.d. March 7, 1983 from Mobay Chemical Corporation, Stilwell, Kansas 66085 USA. Submitted to WHO by Bayer AG, Bayerwerk, 5090 Leverkusen, FRG. Herbold, B., 1982. SS 2074/Chinomethionat (ISO), Oxythioquinox (BSI), Morestan active ingredient/Micronucleus test on the mouse to evaluate for mutagenic effect. Unpublished report no. 10616 d.d 5-12-1982 from Institute of Toxicology, Bayer AG. Submitted to WHO by Bayer AG, Bayerwerk, 5090 Leverkusen, FRG. Krötlinger, F., 1986. SAS 2074 (Chinomethionat, Morestan active ingredient). Chronic toxicology investigation with mice (Feeding study over 21 months). Unpublished report no. 14973 d.d August 8, 1986 from Institute of Toxicology, Bayer AG. Submitted to WHO by Bayer AG, Bayerwerk, 5090 Leverkusen, FRG. Krötlinger, F. & Kaliner, G., 1983. SS 2074 (Chinomethionat, Morestan active ingredient). Subchronic study of toxicity to rats (feeding study over three months). Unpublished report no. 12313 d.d December 19, 1983 from Institute of Toxicology, Bayer AG. Submitted to WHO by Bayer AG, Bayerwerk, 5090 Leverkusen, FRG. Krötlinger, F. Weber, H. & Kaliner, G., 1984. SS 2074 (Chinomethionat, Morestan active ingredient). Subchronic toxicological study with rats to establish the dose-time-effect relationship for the thyroid. Unpublished report no. 12485 d.d February 23, 1984 from Institute of Toxicology, Bayer AG. Submitted to WHO by Bayer AG, Bayerwerk, 5090 Leverkusen, FRG. Renhof, M., 1986. SS 2074, common name chinomethionat. Study for embryotoxic effects on rats after oral administration. Unpublished report no. 14278 d.d 27.1/86 and 14278 d.d. 11.8.86 from Institute of Toxicology, Bayer AG. Submitted to WHO by Bayer AG, Bayerwerk, 5090 Leverkusen, FRG. Schluter, G., 1981. SS 2074 (Morestan Active Ingredient) evaluation for embryotoxic and teratogenic effects in orally dosed rabbits. Unpublished report no. 9784 d.d. February 5, 1981 from Institute of Toxicology, Bayer AG. Submitted to WHO by Bayer AG, Bayerwerk, 5090 Leverkusen, FRG. Shirasu, Y., 1979. Chinomethionat (Morestan) mutagenicity test on bacterial systems. Institute of Environmental Toxicology, Japan, November 16, 1979. Unpublished report, submitted to WHO by Bayer AG, Bayerwerk, 5090 Leverkusen, FRG. Yang, Li.L., 1986. CHO/HGPRT mutation assay in the presence and absence of exogenous metabolic activation microbiological associates. Unpublished report no. 772 d.d. 15-7-1986 from Mobay Corporation. Submitted to WHO by Bayer AG, Bayerwerk, 5090 Leverkusen, FRG.
See Also: Toxicological Abbreviations Chinomethionat (WHO Pesticide Residues Series 4) Chinomethionat (Pesticide residues in food: 1977 evaluations) Chinomethionat (Pesticide residues in food: 1981 evaluations) Chinomethionat (Pesticide residues in food: 1983 evaluations) Chinomethionat (Pesticide residues in food: 1984 evaluations)