PESTICIDE RESIDUES IN FOOD - 1983 Sponsored jointly by FAO and WHO EVALUATIONS 1983 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 Geneva, 5 - 14 December 1983 Food and Agriculture Organization of the United Nations Rome 1985 DICHLOFLUANID TOXICOLOGY Explanation Dichlofluanid was evaluated by the Joint Meetings in 1969, 1974, 1977, 1979, 1981 and 1982 (see FAO/WHO 1970, 1975, 1978, 1980, 1982 and 1983).1 A temporary acceptable daily intake (ADI) of 0 - 0.3 mg/kg body weight was established at the 1974 JMPR and extended at the same level in 1977. The temporary ADI was based on the no-effect level observed in a 2-year study in dogs at 25 mg/kg body weight. Further work and information were required to elucidate the effects of the possible accumulation in the thyroid of this organic fluorine compound. The meetings in 1979 and 1982 did not consider dichlofluanid and the temporary ADI was extended for a further year, pending submission of the requested information. Some information was available from Belgium, Finland, Norway, and The Netherlands on use patterns, results of supervised trials, residues in commerce and national maximum residue levels. The additional data submitted to WHO and FAO have been reviewed and are summarized in the following monograph addendum. EVALUATION FOR ACCEPTABLE DAILY INTAKE TOXICOLOGICAL STUDIES Special Studies on Mutagenicity Dichlofluanid was tested for potential mutagenicity by the sister chromatid exchange method in the bone marrow of male and female Chinese hamsters. Cyclophosphamide was used as the positive control. Groups of five male and five female Chinese hamsters were administered doses of 1 000 and 2 000 mg/kg b.w. orally by intubation. The positive control group received 20 mg/kg/b.w. of cyclophosphamide and the negative control the suspension agent only (0.5 percent cremophor emulsion). Animals were killed after 24h. Two hours before the administration of the test substance, a tablet of 50 mg 5-bromo-deioxyuridine was implanted subcutaneously into each animal and 2 h before sacrifice they received 4 mg/kg b.w. colchicin by intra-peritoneal injection to arrest mitoses at the metaphase stage. For each animal, 50 metaphases were examined and the incidence of sister chromatid exchanges per metaphase was established. Wilcoxon's non-parametric rank sum test was used for the statistical evaluation of the results. 1 See Annex 2 for FAO and WHO documentation. There were no indications of a mutagenic effect for doses up to 2 000 mg/kg/b.w., no biologically relevant increase in the SCE rate was noted compared to the distinct mutagenic effects seen in the positive control group (Herbold 1980). Special Studies on Embryotoxicity Rabbit Groups of 15 inseminated Himalayan female rabbits were dosed orally by gavage with 0, 10, 30, 100 mg/kg b.w, dichlofluanid from day 6 through day 18 of gestation. All dams survived and generally no changes were observed. The results demonstrated that pregnant rabbits tolerated oral administration of 10 and 30 mg/kg dichlofluanid without evidence of maternal toxicity. Administration of 100 mg/kg induced moderate maternal toxicity as evidenced by weight loss, reduced food consumption and premature delivery of two litters. Administration of dichlofluanid at doses of 10 and 30 mg/kg did not alter significantly the incidence of resorbed implantations among the faetal population, indicating that the test compound was not embryo-lethal. Neither of these doses, when administered during the period of organogenesis, produced a faetotoxic response in rabbits; no deleterious effects on faetal body weight, placental weight or weight of gravid uteri were observed. In the 100 mg/kg dose group, the weights of the gravid uteri, the number of implantation sites and live foetuses were significantly lower in comparison with the control group. The higher incidence of the number of litters with anomalies in the 30 or 100 mg/kg group was of no biological significance and was not considered related to dichlofluanid, as these anomalies occasionally occur spontaneously in this strain of rabbits. In conclusion 30 mg/kg can be considered as the no-effect level (NOEL) for maternal, embryotoxic and/or faetotoxic effects. No teratogenic effects were noted (Parish 1982). Special Study on Skin and Eye Irritation Skin treatment in White New Zealand rabbits by dichlofluanid produced slight irritation, not completely reversible after 72 h. When placed in the conjunctival sac of the rabbit's eye, a moderate mucosal irritation was observed (Pauluhn 1982). Special Study on the Effect on the Thyroid Rat The dose-time effect relationship on the thyroid of dichlofluanid was evaluated in groups of 80 male rats fed for nine weeks at dietary concentrations of 0, 150, 500, 1 500 and 4 500 ppm. The animals showed no alterations in appearance, behaviour or mortality that could be related to the treatment during the entire period. Food consumption was about 5 percent lower than the controls at 4 500 ppm. Body weight did not differ significantly from the controls up to doses of 500 ppm. In the 1 500 ppm group, body weights were significantly lower compared to the control up to the third study week. Body weight gain was slightly retarded in the 4 500 ppm group over the entire period. Slight or significant differences from the controls were found in the serum levels of calcium and inorganic phosphate in all dose groups, but the values obtained were within the biological range for rats of this age, confirming the lack of any effect on the parathyroids by dichlofluanid. Iodine accumulation in the thyroid, both in respect of percentage and concentration, was not affected up to 1 500 ppm. In the 4 500 ppm dose group, a significantly increased value was noted in the first examination. At doses up to 1 500 ppm, the clinical-chemical (T4) and radioimmunological (T3, T4) determination of the thyroid hormone did not indicate any treatment-induced effects on the thyroid. The significantly lower concentrations of both hormones in the 4 500 ppm group at two successive points (7 and 21 days) might be considered a result of treatment and would point to a slight effect on the synthesis and/or secretion phase of the thyroid. A permanent decompensation of the thyroid control system was, however, not detected. Gross pathology and histopathology produced no evidence of treatment-induced damage of the thyroid in any of the dose groups. Organ weights and subsequent histopathological examination did not reveal any alterations in the adrenals during the treatment. The lower liver weight at 4 500 ppm for 21 study days is considered a consequence of the significantly lower animal weights. The higher liver weights noted at the end of the study might be interpreted as substance-induced. Histopathological examination did not reveal any treatment-related alterations in the organs and tissues examined (thyroid, liver, adrenal and skeletal musculature). The NOEL was considered to be 500 ppm in the diet, corresponding to 39.3 mg/kg b.w./day (Krötlinger & Luckhaus 1981). Acute Toxicity The symptoms and lethality of a 1:1 combination of the equitoxic compounds dichlofluanid and captan were determined in an acute oral toxicity test in rats. No significant additive effect was observed (Mihail 1980). No synergistic effects were found when a single combined dose of equitoxic doses of dichlofluanid and triadimefon was administered orally to male rats (Mihail 1982). Long-Term Toxicity Mouse Groups of 50 male and 50 female mice were fed dichlofluanid for 24 months in their diet at levels of 0, 200, 1 000 and 5 000 ppm. Ten additional animals/sex/dose were used for laboratory tests; of these animals, five/sex/dose were sacrificed and dissected after blood samples had been taken, after six and twelve study months. During the entire test period, no alterations in appearance, behaviour or the mortality rate were noted when compared to the control group. Growth was not affected in the groups up to 1 000 ppm but was significantly retarded for both sexes at 5 000 ppm over the entire period. Specific changes in haematological parameters were noted at the dosages administered but the deviations were considered to be without toxicological significance. Clinical chemistry, gross pathology and histopathology did not reveal any indication of liver damage in any of the dose groups. However, the raised alkaline phosphatase activity in the 5 000 ppm group after 24 h of the study might be considered treatment-related. This finding was an isolated one and not confirmed in later tests. It may have been related to the observed bone proliferation. Clinical chemistry provided no indications of a treatment-induced effect on the kidney. Higher values for blood sugar and cholesterol found at 5 000 ppm at the end of the study were, however, within the physiological range. An increased thymus weight was noted in males at the 5 000 and 1 000 ppm level. However, no pathological alteration was observed and these differences were therefore not treatment-related. The bone proliferation detected in the femurs and/or ribs by gross pathology and histopathology and the hardened crania on female animals of the 5 000 ppm group can be considered as skeletal alterations induced by the active ingredient. The findings of gross pathology and histopathology noted in other organs provided no indications of substance-induced organ damage. Doses up to 5 000 ppm gave no indication of any significant dose-related increase in location, types and total number of tumours. Therefore, in these conditions, dichlofluanid was non-carcinogenic in the experimental conditions employed. The NOEL of dichlofluanid was 1 000 ppm, corresponding to 252 mg/kg b.w./day for male mice, or 273 mg/kg b.w./day for female mice (Krötlinger and Löser 1982). COMMENTS The 1979 Meeting, which extended the temporary ADI for dichlofluanid, required studies to elucidate the accumulation seen in the thyroid. A study on rats, over a period of nine weeks, investigated the dose/time relationship of the thyroid effect at dose levels up to 4 500 ppm. Increased iodine uptake was observed early in the study at 4 500 ppm, while decreases in T3 and T4 levels were noted on days 7 and 21 of the study. The NOEL for the thyroid effects was greater than 1 500 ppm. However, decreased body weight gain indicates an overall NOEL of 500 ppm for the study. Additional data evaluated included a sister-chromatid exchange study which was negative at doses of 2 000 mg/kg, and a teratogenicity study in the rabbit, which demonstrated embryotoxicity, but not teratogenicity, at a dose level of 100 mg/kg b.w. A mouse long-term carcinogenicity study did not indicate any evidence of oncogenicity at dose levels up to 1 000 ppm in the diet. Since all the requirements of the 1979 Meeting have been satisfied the present Meeting was able to estimate an ADI. TOXICOLOGICAL EVALUATION Level Causing no Toxicological Effect Rat: 500 ppm in the diet, equivalent to 30 mg/kg/b.w. Dog: 1 000 ppm in the diet, equivalent to 25 mg/kg/b.w. Estimate of Acceptable Daily Intake for Man 0-0.3 mg/kg/b.w. FURTHER WORK OR INFORMATION Desirable Observations in humans. REFERENCES - TOXICOLOGY Herbold, B. Dichlofluanid - sister chromatid exchange on the Chinese 1980 hamster in vivo to evaluate for mutagenic effect. Report 9391 submitted to WHO by Bayer A.G., F.R.G (Unpublished) Krötlinger F. & Loser, E. Dichlofluanid - chronic toxicological study 1982 on mice (including pathologic report by Newman, A.J. and Wood, C.M.). Report No. 10810 submitted to WHO by Bayer A.G., F.R.G. (Unpublished) Krötlinger, F. & Luckhaus, G. Dichlofluanid - subchronic toxicological 1981 study to ascertain the dose time-effect relationship in the effect on the thyroid. Report No. 10312 submitted to WHO by Bayer A.G., F.R.G. (Unpublished) Mihail, F. Dichlofluanid and captan - study for acute combination 1980 toxicity. Report No. 9388 submitted to WHO by Bayer A.G., F.R.G. (Unpublished) Mihail, F. Dichlofluanid - study for acute combination toxicity. 1982 Report No. 11206 submitted to WHO by Bayer A.G., F.R.G. (Unpublished) Parish, H.M. Embryotoxicity study in rabbits with oral application of 1982 dichlofluanid. Report R2415 from the Institute of Toxicology, Regensburg, submitted to WHO by Bayer A.G., F.R.G. (Unpublished) Pauluhn, J. Dichlofluanid - study for primary skin and mucosa irritant 1982 effect. Report submitted to WHO by Bayer A.G., F.R.G. (Unpublished) RESIDUES RESIDUES IN FOOD AND THEIR EVALUATION USE PATTERN Dichlofluanid is registered for use in Finland (Finland 1983) on apples (0.15-0.2 percent solution) and strawberries and currants (both 0.25 percent solution) and ornamentals. The waiting period is 14 days. Dichlofluanid is approved in Norway (Norway 1983) for use on stone fruits, berries, lettuce, onions, tomatoes, cucumbers and ornamentals. Application rates are 50-125 g a.i./100 1 water. The preharvest intervals are seven days for stone fruits and berries (except strawberries), 14 days for onions and lettuce and four days for cucumbers and tomatoes. The Netherlands (1983) provided some new information on uses on grapes (125 g/100 1, 6 weeks preharvest interval, PHI), eggplant (125 g/100 1, 3 days PAI; 75 mg/m2 of 7.5 percent dust as preventive, 3 days PHI) and zucchini (75 mg/m2 of 7.5 percent dust as preventive). Information on a food survey taken in The Netherlands in 1981 and 1982 showed that most residues in 1981 were less than 2 mg/kg with only six samples (currants (2), raspberry (3) and strawberry (1) out of 200 having residues above the maximum residue limit (MRL) of 5 mg/kg, with a maximum of 6.7 mg/kg in currants). In 1982, five samples of currants (4) and raspberry (1) had residues above the MRL, with a maximum of 32.7 mg/kg in currants. The method of analysis used was not stated. RESIDUES RESULTING FROM SUPERVISED TRIALS Additional data was received from Norway on residues in greenhouse tomatoes from five treatments at 10 to 14 day intervals, using 0.75 g a.i./100 l. Residues determined at 2, 4, 6 and 8 days after spraying ranged from 0.1 to 0.2 mg/kg after the first, treatment, 0.4 to 0.5 mg/kg after the third treatment and 0.6 to 0.7 mg/kg after the fifth treatment. The method of analysis used was not stated. FATE OF RESIDUES The hydrolytic stability of dichlofluanid was determined at pHs 4, 7 and 9 and at temperatures of 20°, 30° and 40°C. Decomposition was rapid at pH 7, with only 25-30 percent remaining after 40 h. At pH 4, 47 percent remained after eight days at 30°, while 17 percent was left after seven days at 40°. The hydrolysis constant at 20° and pH 7 was 7.5 x 10-6/sec (Wilmes 1982a). About 1 mg of dichlofluanid was applied to a thin-layer plate and exposed to artificial light for four weeks, at which time 30-42 percent of the original concentration remained. In aqueous solution (2.6 mg/l) exposed to a mercury vapour lamp, dichlofluanid had a half- life of about 10 h. In addition to the hydrolysis product dimethylsulfanilid, an unidentified polar photoproduct was formed (Wilmes 1982b). RESIDUES IN FOOD IN COMMERCE OR AT CONSUMPTION Information was available from Belgium on the results of a survey conducted over the years 1979-1982 for residues occurring in food in commerce. Dichlofluanid never exceeded the Belgian tolerance of 5 mg/kg and was non-detectable in the range of 73-100 percent of the samples. When present, it was found in a maximum of 27 percent of samples at values not exceeding 0.8 mg/kg (Geloux 1983). Surveys of domestic and imported food in commerce in Finland were reported to the meeting (year unspecified). For domestic food, the distribution and frequency is shown in Table 1 while Table 2 gives the results for imported food. Again the analytical methodology employed was not stated. No residues were found in or on other fruits and vegetables. Only 15 samples of food (all strawberries) out of a total of 1 081 had residues exceeding 1 mg/kg. APPRAISAL New information was received from Finland on permitted uses (apples, strawberries, and currants, with a waiting period of 14 days). Surveys of domestic and imported food in commerce showed that residues of dichlofluanid were rarely found, usually at less than 0.1 mg/kg, and only exceeded 1 mg/kg in 15 samples out of 1 081. Information on the results of surveys of food in commerce in Belgium covering the years 1979-1982 showed that dichlofluanid never exceeded the local MRL of 5 mg/kg, with the maximum level found being 0.8 mg/kg. It was non-detectable in 73 to 100 percent of the samples. Table 1. Dichlofluanid Residues in Domestic Commodities, Finland Commodity No. Residue (mg/kg) <0.1 0.11-1.0 1.1-2.0 >2.1 Strawberries 486 221 164 6 8 Currants 114 1 1 Gooseberries 15 Apples 129 2 Table 2. Dichlofluanid Residues in Imported Commodities, Finland Commodity No. Residue (mg/kg) <0.05 0.05 0.51 1.1->2.0 Max. 0.20 1.0 2.0 Cabbage (chinese) 130 1 2 0.13 Plums 142 1 1 0.10 Strawberries 54 1 1 0.68 Brussels sprouts 11 1 0.17 Information on approved uses in Norway was available, where it is permitted on stone fruits, berries, lettuce, onions, tomatoes and cucumbers. The results of supervised trials on greenhouse tomatoes in Norway, treated at recommended rates, gave a maximum residue of 0.7 mg/kg two days after a fifth biweekly treatment. The Netherlands provided new information on uses on grapes, eggplant and zucchini, along with data from their 1981 and 1982 food surveys. Residues in excess of the MRL of 5 mg/kg occurred in about 3- 4 percent of the samples, mainly in currants and raspberries. In all of the preceding submissions, it was not clear whether the analytical method employed measured parent compound only or parent plus metabolites. Only the procedure measuring dichlofluanid alone can be properly used in evaluations. Data from Germany was available on the results of hydrolytic and photo stability tests. Decomposition in water at pH 7 and 20° was rapid, with only 25-30 percent remaining after 48 h. Photodegradation on a TLC plate resulted in 30-42 percent remaining after four weeks exposure to artificial light. In aqueous solution, it had a photolytic half-life of about 10 h. RECOMMENDATIONS All previous temporary MRLs are replaced by MRLs at the same levels. REFERENCES-RESIDUES Finland. Information on uses of dichlofluanid in Finland. 1983 Norway. Information on uses of dichlofluanid in Norway. Data on 1983 residues in greenhouse tomatoes from supervised trials. Netherlands. Information on uses and food surveys in The Netherlands. 1983 Wilmes, R., Behaviour of crop protection products in water. Bayer A.G. 1982a report PF-A/CE-PIQ-ENA. (Unpublished) Wilmes, R., Orientating studies on stability to light. Bayer A.G. 1982b report PF-A/CE-PIQ-ENA. (Unpublished) Geloux, M. Note technique du Central de Recherches Agronomiques de 1983 l'Etat, Gembloux, Belgique, No. 9/25, 9/26, 9/31 and 9/32, Sept. 1979 - June 1982.
See Also: Toxicological Abbreviations Dichlofluanid (FAO/PL:1969/M/17/1) Dichlofluanid (WHO Pesticide Residues Series 4) Dichlofluanid (Pesticide residues in food: 1977 evaluations) Dichlofluanid (Pesticide residues in food: 1979 evaluations) Dichlofluanid (Pesticide residues in food: 1981 evaluations) Dichlofluanid (Pesticide residues in food: 1982 evaluations)