PESTICIDE RESIDUES IN FOOD - 1982 Sponsored jointly by FAO and WHO EVALUATIONS 1982 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, 23 November - 2 December 1982 Food and Agriculture Organization of the United Nations Rome 1983 FENSULFOTHIONExplanation Fensulfothion was evaluated for ADI by the Joint FAO/WHO Meeting in 1972 (FAO/WHO 1973) 1. The ADI was allocated on the basis of the no-effect level observed in a 2-year study in dogs. Teratogenicity studies at higher levels and studies on human exposure were considered desirable. Mutagenicity and teratogenicity studies were from Industrial Bio-Test Laboratories. Since the previous evaluation, a new embryotoxicity/ teratogenicity study, mutagenicity studies and other studies have been presented and are summarized in this monograph addendum. EVALUATION FOR ACCEPTABLE DAILY INTAKE BIOCHEMICAL ASPECTS Effects on Enzymes A study was undertaken to evaluate the interaction potential of the widely used organophosphorous insecticide Dasanit (fensulfothion) with the local anaesthetic ester, procaine, and the analgesic and antipyretic amide, acetanilide, in the mouse and rat. Groups of 5 or 6 male mice were treated with 1-10 mg Dasanit/kg and sacrificed without challenge 1 h later. A dose of 5 mg/kg did not inhibit brain cholinesterase activity, yet caused greater than 50% inhibition of liver hydrolsysis of diethylsuccinate, triacetin and procaine. A time-course study indicated that liver hydrolysis of these substrates was maximally inhibited at 0.5-1 h after a dose of 7.5 mg/kg. Several 1 See Annex 2 for WHO and FAO documentation. additional substrates were used to study the interaction of Dasanit with procaine and acetanilide in the rat. It is suggested that commonly used insecticidal organophosphates, at apparently non-toxic doses, may alter the metabolism and toxicity of ester- and amide- containing drugs, which are dependent upon carboxylesterases for their biotransformation (Ouellette 1979). TOXICOLOGICAL STUDIES Special Studies on Embryotoxicity and Teratogenicity Groups of rabbits (12 pregnant Himalayan rabbits/group) were administered fensulfothion by gavage at dosages of 0, 0.1, 0.3 and 1.0 mg/kg bw from day 6 to 18 of gestation. The administered dosages were set on the basis of results of a tolerance test performed on non- pregnant rabbits, in which 3 mg/kg/day had a lethal effect. Himalayan rabbits are indicated to react sensitively to the embryotoxic effect of thalidomide. On day 29 of gestation, all pregnant animals were sacrificed and foetuses were delivered by caesarean section. At a dosage up to and including 1 mg/kg bw/day, administration of fensulfothion did not have any adverse effect on the physical appearance and behaviour patterns of the does or on their weight gain. Only one rabbit of the 1 mg/kg group died after 11 applications; the cause of its death could not be established. All other treated rabbits survived. There was no significant differences between the control and treated groups with respect to pregnancy quota, number of implantations, foetuses delivered, resorptions plus abortions, sex ratio of foetuses, average foetal weight and average placenta weight. The average number of stunted foetuses (i.e. weighing less than 25 grams) showed a slight increase in the 1 mg/kg group as compared with the controls. This result was brought about by one single mother delivering foetuses all with a reduced weight. Hence, this was an isolated case that was not characteristic of the group and, therefore, was not treatment-related. No foetuses with retardations of the skeletal system were seen in any of the groups. The only malformation observed in this study was indicated to be arthrogryposis of the left fore extremity. This finding was considered a typical spontaneous malformation of the rabbit breed. The no-effect dosage of fensulfothion on embryonic development was 1 mg/kg/day in this study on rabbits. There were no indications of any teratogenic effect (Machemer 1978). Special Study on a Mixture of Fensulfothion and its Metabolites Chicken Groups of laying hens (4 Breed Babcock 300, 32-week old hens/group), were fed fensulfothion and its major metabolites in the diet at a dosage level of 0, 0.25, 0.75 2.5 and 10.0 ppm (calculated in fensulfothion equivalents) for 28 days. In the diet, fensulfothion and its major metabolites (i.e. fensulfothion sulphone, fensulfothion oxygen analogue, fensulfothion oxygen analogue sulphone) were in the amount and ratio (1:1:2:2), representative of that found in field- weathered crops. A decrease (15-25%) in feed consumption was observed in birds of the 10.0 ppm group after the first seven days to the end of the study. Two of the four birds in the 10.0ppm group showed a decrease in egg production of 20%. Significant blood cholinesterase depression began with the 2.5 ppm group and was at 79% of normal in the 0.75 ppm group. No significant residues were found in any of the tissues or eggs from birds fed 2.5 and 10.0 ppm. The group fed 2.5 and 10.0 ppm showed average weight gains of only 50-60% of those of the control birds. Owing to the large variability of weight gains by individual chickens, this fact was not considered relevant. It was considered significant that none of the individual birds showed any weight loss over the observation period. No significant residues (less than 0.01 ppm) of fensulfothion and metabolites were found in tissues analysed at the end of the study. The no-effect level may be assumed to be 0.75 ppm, equal to 0.03 mg/kg/day of fensulfothion equivalent (Thornton 1975a). Dairy cattle Groups of cows (3 Holstein dairy cows/treated group; 1 in the control) were fed fensulfothion and its major metabolites in the diet at dosage levels of 0, 1.8, 3.6 and 7.2 ppm (calculated as fensulfothion equivalents) for 28 days. In the diet, fensulfothion and its major metabolites (i.e. fensulfothion sulphon, fensulfothion oxygen analogue, fensulfothion oxygen analogue sulphone) were in the amount and ratio (1:1:2:2), representative of that found in field- weathered crops. At the end of test period, the animals were sacrificed and analysed for residues of fensulfothion and metabolites in tissues and milk. A decrease of blood cholinesterase activity, feed consumption, milk production and body weight were noted in the animals fed the highest (10.8 ppm) dosage level. Blood cholinesterase was depressed 30% at the end of the test for cows fed 3.6 ppm. Animals fed the lowest (1.8 ppm) dosage level were not significantly affected. No significant residues (less than 0.01 ppm) of fensulfothion and metabolites were found in tissues analyses at the end of test period. The no-effect level is 1.8 ppm, equal to 0.07 mg/kg/day of fensulfothion equivalents (Thornton 1975b). Special Studies on Fensulfothion and its Major Metabolites Maize was sprayed in the field with Dasanit (fensulfothion) at 0, 0.56, 1.12 and 2.24 kg/ha and ensiled one day later. After 76 days of ensiling, maize treated as above contained residues of 16.5, 27.8 and 50.6 mg/kg. Resulting silages were fed to 4 cows/treatment. Silage intakes, milk production, body weight gains and blood cholinesterase activities of cows were severely and rapidly depressed by ingestion of Dasanit residues. These measures of performance were inversely related to the amount of treatment and recovery was slow. One cow fed silage from 2.24 kg/ha treatment (i.e. containing 50.6 ppm) died after ingesting Dasanit residues amounting to a total of 2.75 mg/kg bw during the first seven days of experimental feeding. Dasanit and/or its metabolites were in milk, urine and faeces from cows fed silage from 0.56, 1.12 and 2.24 kg/ha treatments. Total residues in milk, urine and faeces were free of residues within one week after the cows were withdrawn from treated silage (Johnson et al 1973), Special Studies on Potentiation Phenamiphos was administered orally to male Wistar II albino rats in combination with either fensulfothion or isofenphos or phoxim. Mixtures of phenamiphos with each of the other compounds were prepared with percentage ratios proportional to the LD50 of each (equitoxic amounts of the two compounds in the mixture). Increasing doses were administered to determine the LD50 of each combination, which was then compared to the expected LD50 of the respective combination. There was no evidence of greater than additive acute effects (Thyssen 1976). Special Studies on Mutagenicity Dominant lethal test In a dominant lethal test, groups of 50 NMRI/W77 male mice (8-12 weeks old) were given a single oral dose of 0 or 2 mg/kg bw of fensulfothion (95.1% purity) in 0.5% Cremophor emulsion. The dose was chosen after a range finding test in which five animals were given orally 1, 2 or 4 mg/kg bw, the intermediate dose being without symptoms. The mice strain was known to be sensitive to known mutagens, such as cyclophosphamide, MMS and Trenimon. Beginning on the day of treatment, each male of each group was mated with one un-treated virgin female for a period of 4 days, after which the female was removed and replaced by another female. This procedure continued for 12 consecutive mating periods. The females were sacrificed around the 14th day from each midperiod and uteri were removed for examination. Data were collected on the number of corpora lutea, total implantations, live implants and dead implants. Salmonella/microsome test An evaluation of the mutagenic potential of fensulfothion (95.1% purity) was carried out using the standard Ames assay. Four strains of Salmonella typhimurium (TA 1535, TA 100, TA 1537 and TA 98), with and without a metabolic activation system (S-9 mix) derived from liver of male Sprague-Dawley rats treated intraperitoneally with Arochlor 1254, were treated at concentrations up to and including 12 500 µg/plate. Positive controls were 2-amino anthracene (2-AA) for the four strains, cyclophosphamide only for TA 1535 and TA 100 and Tryplafavin only for TA 1537 and TA 98. Four plates for each strain, and for each compound and dose were used as were also for the negative controls. Two plates/group were used to determine the total number of bacteria. Negative controls were the respective solution media. Doses up to and including 500 µg/plate were not toxic to the bacteria. A dose of 2 500 µg had slight toxic effect to the bacteria and was useful for the test. The highest dose resulted in precipitation of the compound and could not be used. Neither dose-related nor significant (more than double of negative controls) increments of the number of mutants were observed with any of the strains at the concentrations tested. Positive controls displayed a clear mutagenic effect. Thus, at concentrations up to 2500 µg/plate, fensulfothion failed to show mutagenic potential in the Salmonella/microsome test (Herbold 1980). Short-Term Studies Rat - Inhalation Groups of rats (10 male and 10 female SPF albino rats/group, Wistar II strain) were exposed to fensulfothion in a dynamic flow inhalation apparatus for 6 hours daily over a 12-week period (total of 60 6-hour exposures). Average concentrations of fensulfothion in the aerosol (determined by gas chromatographic analysis) were 0, 0.097, 0.818 and 7.21 mg/m3 air. Intake of the aerosol by the rats was possible only together with inhaled air and not by another other route; 95% of the aerosol droplets had a diameter of 1.0 ± 0.5 µm, with the rest being less than 5.0 µm. Poisoning symptoms, mortalities, poor health conditions and lower body weight gains occurred in the rats exposed to 7.21 mg/m3 air. Lower body weight gains in male rats and significant differences in absolute and relative organ weights in male and female rats (heart, spleen, lung) were noted only for male rats exposed to a concentration of 7.21 mg/m3 air. Significant depression of plasma -, erythrocyte-, and brain-cholinesterase activity was noted in rats exposed to a concentration of 7,21 mg/m3 air. The threshold value (80%) of cholinesterase activity occurred at 0.818 mg/m3 air. Haematological, clinical-chemical and urinalysis values were all within the normal range for exposed rats and controls. Macroscopic and histopathological examinations of tissues showed no noteworthy alterations. The no- effect concentration with respect to cholinesterase activity was 0.097 mg/m3 air (Kimmerle 1976). The treated males exhibited no signs of toxicity. There were no compound-related mortalities in the treated group, one female in mating period 7 (due to bladder tumour) and one female in the mating period 9 (.due to autolysis) were not considered for the test. There were no statistically significant differences between the control and treated groups with respect to fertility rate and pre- implantations loss (estimated both directly as difference between corpora lutea and implantations, and indirectly through the comparison of the average number of implants per fertilized female in the control and treated group). The post-implantation loss was estimated on the basis of live and dead implants. More than the average of one dead implant per animal in the treated group was observed in mating periods 5 and 10, but a similar finding was also observed in mating periods 10 and 12 for the control group. These values for dead implants were considered within the normal fluctuation of the strain. Statistical analysis (comparison of the distribution of frequency) showed that there were no significant differences between the control and treated groups with respect to the ratio of dead implants to total implants or the number of dead implants to living implants, both within the single mating periods and in the whole test. In the dominant-lethal test on male mice, fensulfothion failed to show mutagenic potential at the acute oral dose of 2 mg/kg bw (Herbold 1981). COMMENTS Following the proposals of the 1972 JMPR, a new embryotoxicity/ teratogenicity study at increased dose levels has been submitted and evaluated. The new teratogenicity study confirmed that fensulfothion is not teratogenic to rabbit at dosages of up to 1.0 mg/kg bw. The new mutagenicity studies ( Salmonella/microsome test; dominant lethal test on male mice) failed to show a mutagenic potential of fensulfothion. The Meeting considered that a no-effect level in long-term studies had not been established. However, according to the 1972 Evaluations, a theoretical no-effect level in rats was estimated by plotting effect (serum, RBC, brain cholinesterase depression) against dose. A no-effect level has been demonstrated in the dog. The Meeting agreed to retain the present ADI. TOXICOLOGICAL EVALUATION Level Causing no Toxicological Effect Dog : 1 ppm in the diet, equivalent to 0.025 mg/kg bw. Estimate of Acceptable Daily Intake for Man 0 - 0.0003 mg/kg bw. FURTHER WORK OR INFORMATION Desirable Observations in humans. REFERENCES Herbold, B. Fensulfothion. Salmonella/Microsomen. Test zur 1980 Untersuchung auf Punkmutagene Wirkung. Report (No. 9481) from Institut Für Toxicologie, Bayer, F.R.G. submitted to the World Health Organization by Bayer, F.R.G. (Unpublished) 1981 Fensulfothion. Dominant-lethal Test an der mänlichen Maus zur Prufüng auf mutagene Wirkung. Report (No. 10263) from Institut für Toxicologie, Bayer, F.R.G., submitted to the World Health Organization by Bayer, F.R.G. (Unpublished) Johnson, J.C. Jr., Bowman, M.C., Lenk, D.B. and Knox, F.E. Persistence 1973 of Dasanit in corn silage and effects of feeding dairy cows the treated silage. J. Dairy Sci. 56 (6): 775-782. Kimmerle, G. Subchronic inhalation toxicity study on rats. Report (No. 1976 6101) from Institut für Toxicologie, Bayer, F.R.G. submitted to the World Health Organization by Bayer, F.R.G. (Unpublished) Machemer, L. Evaluation for embryotoxic and teratogenic effects on 1978 orally dosed rabbits. Report (No. 7745) from Institut für Toxicologie, Bayer, F.R.G., submitted to the World Health Organization by Bayer, F.R.G. (Unpublished) Oullette, R.E. Dasanit inhibition of tissue esterases and amidases and 1979 interaction with ester and amide drugs. Diss. Abstract. Int.B. 40:(2):698. Thornton, J.S. Effect of feeding Dasanit (R) and metabolites to 1975a chickens, Report (No. 45868, ref. 74-2, 75-69) from Chemagro Agricultural Division of Mobay Chemical Corp., submitted to the World Health Organization by Bayer, F.R.G. (Unpublished) 1975b The effect of feeding Dasanit (R) and metabolites to dairy cattle. Report (No. 46415, ref. 72-2, 75-137, 75-10) from Chemagro Agricultural Division of Mobay Chemical Corp., submitted to the World Health Organization by Bayer, F.R.G. (Unpublished) Thyssen, J. Toxicological studies to evaluate phenamiphos for acute 1976 oral toxicity when administered simultaneously with fensulfothion, isophenphos or phoxim. Report (No. 3958) from Institut für Toxicologie, Bayer, submitted to the World Health Organization by Bayer, F.R.G. (Unpublished)
See Also: Toxicological Abbreviations Fensulfothion (ICSC) Fensulfothion (WHO Pesticide Residues Series 2) Fensulfothion (Pesticide residues in food: 1983 evaluations)