DICHLOFLUANID JMPR 1974 Explanation In 1969 the Joint Meeting evaluated dichlofluanid in the light of the information then available. No ADI could be established and no tolerances were recommended. The Meeting listed 10 items on which further work or information was required before tolerances could be recommended (FAO/WHO, 1970). New information has been received on toxicology, composition of the technical product, rates and frequencies of application, pre-harvest intervals, residues and the influence of residues on the fermentation of must. This information is summarized in the following monograph addendum. IDENTITY Synonyms Elvaron(R) Other relevant chemical and physical properties The purity of the technical material is at least 96%, and the maximum levels of the impurities are as shown in Table 1. In practice, the average content of dichlofluanid in the technical product is approximately 98%, so that the by-products normally amount to only about half of the amounts given in Table 1. TABLE 1. Maximum levels of impurities in dichlofluanid Maximum Impurity content, % N,N-dimethyl-N-phenylsulphamide (DMSA) 1.5 N,N-dimethylbenzylamine (C6H5-CH2-N(CH3)2) 1.0 "difluoro-dichlofluanid" (R-CF2Cl) 0.3 chlorides (expressed as HCl) 0.3 up to 6 unidentified trace impurities, total 1.0 EVALUATION FOR ACCEPTABLE DAILY INTAKE BIOCHEMICAL ASPECTS Absorption, distribution, biotransformation and excretion No information is available on the rate of absorption or on the distribution of dichlofluanid in the animal body. Studies in rats indicate that the absorption is small. Within 72 hours, 45-92 percent of the administered dose could be isolated from the faeces. Most of the dichlofluanid found was in an unchanged form; approximately 12 percent was isolated as N,N-dimethyl-N'-phenylsulphamide. After oral administration of dichlofluanid the unchanged form of the compound was not detectable in the serum or urine; however when either dichlofluanid or its metabolite dimethylphenylsulphamide was administered orally, four metabolites could be isolated from the urine. The structures of these compounds have now been determined and are given below:N,N-dimethyl-N'-phenylsulphamide (I)
N-methyl-N'-phenylsulphamide (II)
N,N-dimethyl-N'-(4-hydroxyphenyl) sulphamide (III)
N-methyl-N'-(4-hydroxyphenyl)-sulphamide (IV) All the metabolites are excreted in the free form and the metabolites III and IV are also excreted as glucuronides. Metabolites I and II can also be found in serum. The metabolites found in urine and serum after oral administration of dichlofluanid are the same as those found after oral administration of dimethylphenylsulphamide. From these studies it is evident that dichlofluanid is absorbed only very slightly from the G.I. tract (Eben and Kimmerle, 1968; Anon., 1969). In the studies on the metabolism of dichlofluanid there is no information on the fate of the dichlorofluoromethylthio portion of the molecule, and it is not known if the fluorine atom appears ultimately as fluoride ion. However, alkaline hydrolysis of dichlofluanid in methanol solution is reported to yield N,N-dimethyl-N'-phenylsulphamide and fluorodichloromethanethiol (Cl2FCSH) which is susceptible to oxidation. No information is given on the nature of the oxidation products (Nangniot et al., 1967). TOXICOLOGICAL STUDIES Special studies on the metabolite, N,N-dimethyl-N'-phenylsulphamide Rat Groups of 30 rats (15 of each sex) were fed 0, 1000, 3000, and 10 000 ppm of dimethylphenylsulphamide in their diets for four months. Mortality, food consumption, growth, haematology, urinalysis gross and microscopic pathology (10 animals from each group) were closely comparable in the experimental and the control groups. Also the final average body and organ weights were comparable in the different groups, except in the 10 000 ppm group where the female rats displayed a decrease in the adrenal weight, and in both sexes an increase in the liver weight was found. Although no histopathological changes in the liver and the kidney of these rats were reported, such changes might be camouflaged by the histological changes due to infections (Lorke, 1965). Special studies on mutagenicity Mouse A dominant-lethal-test was carried out by administering 500 mg dichlofluanid/kg bodyweight to twenty male mice. Untreated female mice mated with three males did not show any difference in the early and late resorptions, the number of corpora lutea or living and dead foetuses when compared to those mated with control males. This study at one relatively high dose level, did not reveal any dominant lethal mutagenic effect of dichlofluanid (Machemer, 1974b). Special studies on reproduction Rat Groups of rats, each comprising 10 males and 20 females received dietary levels of 0, 150, 500, 1500 and 4500 ppm of dichlofluanid (90.2% pure; 8% inert material; 0.3% DMSA) for a period extending over three generations. Two litters per generation were studied. No information is available on the selection of animals from one generation to the next. None of the dosed groups indicated any abnormal effects on fertility throughout all three generations. The groups fed 150, 500 and 1500 ppm displayed no abnormal effects compared to controls with respect to group averages of birth weight, litter-size and percentage of survival to weaning. Data for still births and resorptions are not given in the report of this study. Only in the group given 4500 ppm, the body weights of the young animals were lower both at birth and at weaning in all generations except the F1a at birth. The lactation index was also slightly reduced in one of the six matings at this level. Although the experiment was not designed to study teratological effects it may be noted that no malformations were seen at any dose level (Löser, 1969a). An additional study of the histology of organs of some animals of the F3b generation showed no dose related effects of dichlofluanid (Vince and Spicer, 1971). Groups of 20-23 pregnant female rats were administered dichlofluanid by stomach tube, on days 6 to 15 of gestation, at doses of 30, 100, and 300 mg/kg/day. Symptoms of toxicity were observed in all test groups and body-weight gains were decreased compared to the controls both during the ten days treatment and during the total gestation period. The effect was similar in all test groups and not dose-dependent. The number of implantations, resorptions and foetuses were within normal limits in all groups, whereas the average weight of the placenta and the foetuses were slightly decreased in the groups administered 300 mg/kg, possibly owing to the general toxic effect on the maternal animals. In this study comprising only doses with maternal toxicity no indication of teratogenic potential of dichlofluanid was found (Machemer, 1974a). Acute toxicity TABLE 2. Acute toxicity of dichlofluanid LD50mg/kg Animal Route body-weight References Mouse (F) i.p. 7.8 DuBois and Raymund, 1963 Mouse (M) i.p. 6.0 Dubois and Raymund, 1963 Chicken oral >1000 Dubois, 1963 Rat (M) i.p. 15 Dubois and Raymund, 1963 Rat (F) i.p. 15 Anon., 1962 DuBois and Raymund, 1963 Rat (M) oral 500-1000 DuBois and Raymund, 1963 Rat (F) oral 525 Anon., 1962 DuBois and Raymund, 1963 Guinea-pig (M) i.p. 35 DuBois and Raymund, 1963 Guinea-pig (M) oral 250 DuBois and Raymund, 1963 The symptoms of poisoning were non-typical and consisted mainly in a decrease in activity which began several hours after administration of the compound. With doses around the LD50, death occurred in one to four days (DuBois and Raymund, 1963). Short-term studies Rat Groups of 30 rats (15 of each sex) were fed 0, 30, 100, 300, 1000, 3000, and 10 000 ppm of dichlofluanid in their diets for four months. Food consumption, growth, haematology, urinalysis, mortality, and gross and microscopic pathology were closely comparable in the 30 to 3000 ppm experimental groups and the control groups. The same was the case with final average body and organ weights except in the 3000 ppm group where the male rats displayed reduction of heart weights and the female rats an increase in liver weights. In the rats fed 20 000 ppm there was a deterioration of general condition, decreased food intake, smaller weight gains and higher mortality than the control group. The male rats showed a decrease in heart weights, while in both sexes there was a decrease in the weight of adrenal glands and an increase in liver weights. Histopathological changes were found in the liver (vacuolization, inflation in size and shrunken nuclei of some cells), kidneys (increased protein precipitation in the proximal tubuli) and the spleen (reduction of the lymphatic tissue) (Anon., 1964). Dog Groups of four dogs (two of each sex) were fed 0, 500, 1500, and 4500 ppm of dichlofluanid in their diets for four months. Behaviour, food consumption, body-weight changes, mortality, function tests of the liver and kidney, urinalysis, gross pathology and final average body weights and average organ weights were closely comparable in the 500 ppm and the control group. The same was the case with the male dogs of the 1500 ppm group while in the females changes in liver-function tests and decrease in body weight pointed at an impaired liver-function. Three of the four dogs fed 4500 ppm of dichlofluanid died. Before death these dogs and also the surviving animal displayed signs of impaired liver and kidney function (Lorke and Löser, 1966). Groups of 4 male and 4 female dogs were fed 0, 100, 300, 1000 and 3000 ppm dichlofluanid (97.7% pure) in their diet for 2 years. Behaviour, body weights, food consumption, mortality, blood and urine analyses, liver and kidney function tests and absolute and relative organ weights for the groups fed 100, 300 and 1000 ppm did not differ from the values of these parameters in the controls. In the groups fed 3000 ppm increased mortality, reduced body weight and food consumption and decreased absolute and relative testis weight were found. Microscopic examination of the organs revealed an increase in interstitial tissue of the testis and vacuolation and degeneration of the adrenal cortex of the 3000 ppm group as the only dose-dependent pathological changes (Löser, 1969b; Mawdesley-Thomas et al., 1971). Long-term studies Rat Groups of 80 rats (40 of each sex) were fed 0 (two groups), 150, 500, 1500 and 4500 ppm of dichlofluanid in their diets for two years. Behaviour, food consumption and mortality of the test groups did not differ from the parameters of the control groups. The same was the case with haematology (at 4 and 24 months) and liver function and urine examination (at 24 months). Gross pathology of animals which died during the experiment, and of sacrificed test rats at the end of the study, did not reveal any changes that might be caused by dichlofluanid, but no histological examination of the organs is recorded. Female rats in the 4500 ppm group showed decreased weight gain and relative kidney weights, while both sexes showed elevated relative liver weights, but normal enzyme function tests (Löser, 1968). Histological examinations were made on tissues of five male and five female rats at the end of the study and on animals that died during the experiment. No significant pathological changes were found at dietary levels including the 4 500 ppm level. A separate study of all tumours found at autopsy was performed, and there was no indication that dichlofluanid produced an increased tumour incidence (Mawdesley-Thomas, 1969). Comments In a 2-year study in dogs a 1 000 ppm level of dichlofluanid in the diet appears to have no untoward effect, although no data are given on the individual animals. A long term study in rats indicated 1 500 ppm in the feed as the level without apparent toxic effect. There was no indication of teratogenic effect when female rats were administered a dose as high as 300 mg/kg bw. Reproduction parameters were not affected in a 3-generation feeding test with levels up to 1500 ppm dichlofluanid. However, there is a lack of information on absorption, distribution, excretion and pharmacokinetics on the dichloro-fluoromethylthio moiety which may produce some carbon-fluoride compounds resistant to cleavage. The Meeting allocated a temporary acceptable daily intake for man based on the no-effect level in the dog, the more sensitive species. TOXICOLOGICAL EVALUATION Level causing no toxicological effect Rat: 1 500 ppm in diet equivalent to 75 mg/kg bw. Dog: 1 000 ppm, in diet equivalent to 25 mg/kg bw. ESTIMATE OF TEMPORARY ACCEPTABLE DAILY INTAKE FOR MAN 0 - 0.3 mg/kg bw RESIDUES IN FOOD AND THEIR EVALUATION USE PATTERN Pre-harvest treatments Uses (Table 3) are additional to those listed in FAO/WHO, 1970. They are all recommendations of the Federal Republic of Germany (FRG). TABLE 3. Pre-harvest treatments with dichlofluanid recommended in the Federal Republic of Germany Number of Rate of application Crop applications (kg a.i./ha) Pome fruits 4 - 11 1.5 Stone fruits plums 4 1.5 - 2.0 cherries 3 - 8 2.0 peaches 3 1.5 Soft fruits strawberries 1 - 6 2.5 - 3.0 red and black currants 4 - 7 2.0 - 2.4 raspberries 1 -4 2.0 - 2.4 Grapes 2 - 10 1.9 - 2.5 Vegetables cucumbers 1 - 4 1.5 - 2.0 tomatoes 1 - 3 1.5 - 2.0 lettuce (field grown and under glass) 2 - 4 0.6 - 1.0 Beans 1 - 3 1.0 Hops 4 - 17 2.0 TABLE 4. Residues of dichlofluanid (I) and DSMA (II) resulting from supervised trials. Crop Application Residue, mg/kg, after interval (days) (Country) Rate Reference1 kg/ha No. Compound 0-3 4-7 8-14 15-21 22-28 29-35 36-42 Apples (FRG) 1.1- 4- I 0.7-3.4 0.2-2.8 <0.1-2.2 <0.1 <0.1-0.4 <0.1 1.25 11 II 0.3-1.1 <0.1-1.1 <0.1-1.1 <0.1-0.4 <0.1 <0.1 Beans green incl. 1.0- 1- I 0-1-0.3 0.1-0.2 <0.1-0.2 0.1 pods (FRG; UK) 3.4 3 II 0.1-0.2 0.1-0.2 <0.1 0.1 Cherries (morello) 1.1 6-8 I 0.6-2.5 <0.1-0.4 <0.1 <0.1 (FRG) II 0.2-1.2 <0.1-0.2 <0.1 <0.1 Cucumbers (outdoor); 1.5 3 I <0.1-0.2 <0.1-0.2 <0.1 (FRG) II 0.2-0.5 <0.1-0.3 <0.1 Cucumbers (under 1.5- 1- I 0.3-3.6 0.2-0.3 <0.1 <0.1 glass); (FRG; 6.3 3 II 0.1-0.5 <0.1 <0.1 <0.1 Netherland Currants, black 2.5/? 2-7 I 2.4-48 2.0-16 2.0-6.3 0.9-5.1 0.5-1.4 0.2 (Denmark2/UK) II 0.5-3.2 1.1-1.5 0.5-1.0 0.4-0.7 0.2-0.3 0.3 Currants, red (FRG; 0.2- 3-5 I 5-39 3-23 2-46 1-40 0.3-3.2 Netherland3) 2.5 II 1.9-6.9 1.1-3.0 0.4-16 0.5-3.0 0.2-0.4 Gooseberries (UK) 5 I 0.3 II 0.2 Wheat, barley (France) 1.3 1-2 I <0.1 Grapes (FRG4) 0.6- 2- I 0.2-48 0.2-33 0.7-10.6 <0.1-21 <0.1-16 1.3-11 <0.1-12 3.6 10 II <0.1-0.8 <0.1-3.8 <0.1-3.6 <0.1-2.7 <0.1-2.6 0.3-3.4 <0.1-3.8 TABLE 4. (Cont'd.) Crop Application Residue, mg/kg, after interval (days) (Country) Rate Reference1 kg/ha No. Compound 0-3 4-7 8-14 15-21 22-28 29-35 36-42 Hops (FRG) 2.0 9- I 69 6-140 5 0.3-0.7 17 II 14 3-11 Lettuce (outdoor) 0.6 1-4 I 7.8-30 0.2-2.7 0.1-0.2 <0.1-0.3 <0.1 <0.1 II 2.1-5.8 0.2-2.3 <0.1 <0.1-0.3 0.1-0.2 <0.1 Lettuce (under glass) 0.6- 1-6 I 4.7-55 0.3-8.3 <0.1-1.9 <0.1-0.3 <0.1-5.6 0.6-2.2 (FRG; UK) 3.4 II 3.0-13 0.2-2.8 <0.1-2.5 <0.1 <0.1-1.6 Onions (UK) 1.1 5 I (100 days) <0.1 Peaches (FRG) 1.1 3 I 2.2-2.9 0-7-1.2 0.3-1.6 II 0.5-0.8 0.2-1.4 0.5-0.9 Raspberries (FRG; 2.0- 1-4 I 21-32 6-14 <0.1-10.5 <0.1-4.7 1.7 Netherland 2.3 II 1.0-6.2 0.7-6.4 0.6-4.0 0.8-1.0 0.9 Strawberries (outdoor) 0.8- 1-4 I 0.3-27 0.1-5.0 <0.1-6.3 <0.1-2.4 <0.1-1.6 <0.1-1.7 0.7-1.7 (FRG: Netherland 3.8 II 0.3-8.8 0.5-1.8 <0.1-3.7 0.2-2.4 0.3-1.9 <0.1-0.3 0.1 N.Z.6; Switzerland; UK) (Australia7) 1.4- 3 I + II 1.2-15.5 0.4-8.4 <0.1-3.2 <0.1-0.6 0.6 <0.1 2.1 expr. as I Strawberries (under glass) 1.2- 3-6 I 4-9 0.5-3.5 0.4-7.1 2.2-4.1 1.7-3.5 1.5-4.7 <0.1-3.6 (Netherland 9.5 (total) TABLE 4. (Cont'd.) Crop Application Residue, mg/kg, after interval (days) (Country) Rate Reference1 kg/ha No. Compound 0-3 4-7 8-14 15-21 22-28 29-35 36-42 Tomatoes (FRG) 1-3 I <0.1 <0.1-0.2 II <0.1-0.2 <0.1-0.9 1 Bayer AG (1964-1973) unless otherwise stated 2 Government Plant Pathology Institute, Lyngby; National Pood Institute, Gladsaxe, April 20, 1970 3 Keuringsdienst van Waren Amsterdam (1967a, 1969a) 4 Lemperle et al. (1969, 1970); Bayer (1964-1973) 5 Keuringsdienst van Waren Amsterdam (1965) 6 Brewerton and Gibbs (1968) 7 Tate at al. (1973) 8 Keuringsdienst van Waren Amsterdam (1969b) RESIDUES RESULTING FROM SUPERVISED TRIALS Table 4 shows the residues of dichlofluanid and its metabolite dimethylphenylsulphamide (DMSA) found in crops after recommended applications in supervised trials. The analyses were carried out by Farbenfabriken Bayer AG and various institutes. FATE OF RESIDUES In storage and processing Additional information on the fate of residues during processing, including wine making, and on the effect of residues on fermentation, has been received since the previous evaluation. Analyses of commercial deep-frozen strawberries from two factories (3 samples from each) showed residues of 0.26 - 0.36 and 0.06 - 0.12 mg/kg dichlofluanid. In canned strawberries residues were <0.02 mg/kg dichlofluanid and DMSA could not be found (Grevenstuk, 1971). Strawberries were treated with dichlofluanid at flowering and analysed with and without caps (Government Plant Pathology Institute, Lyngby, Denmark, 1969). Most of the dichlofluanid residue was in the caps (Table 5). TABLE 5. Residues of dichlofluanid and DMSA in strawberries with and without caps (Denmark) Rate of Waiting Residues (mg/kg) application No. of Period With cap Without cap (kg.a.i./ha) applications (days) Dichlofluanid DMSA Dichlofluanid DMSA 1.9 3 24 1.6 0.4 0.2 - (treated 28 1.3 0.3 - - at flowering) 35 1.7 - 0.1 0.1 42 0.7 - 0.1 0.1 Apples containing residues of about 0.8 mg/kg dichlofluanid plus 0.2 mg/kg DMSA were cold pressed. The juice contained approx. 0.2 mg/kg dichlofluanid and approx. 0.7 mg/kg DMSA. After heating the juice for 30 min. at 90°C the residues were 0.1 and 0.7 mg/kg respectively. Processing the apples to stewed fruit, baby food or jelly resulted in residues of approx. 0.05 mg/kg dichlofluanid and 0.3 - 0.7 mg/kg DMSA (Maier-Bode, 1972). Residues of 2 mg/kg dichlofluanid plus 0.7 mg/kg DMSA on apples when stored at -18°C were stable for at least 6 months (Bayer, 1973). Several series of experiments were carried out to determine the effect of wine-making processes on residues in grapes, and the effect of dichlofluanid residues on fermentation. At residues of 1.5 - 10.8 mg/kg dichlofluanid and 0.02 - 0.1 mg/kg DMSA on grapes the corresponding residues (mg/kg) in the marc were <0.05 - 8.0 and 0.1 - 1.4; in must (not clarified) <0.1 - 6.9 and 0.1 - 1.3; in clarified must <0.05 - 0.2 and 0.3 - 0.8 and in wine <0.05 and 0.1 - 4.0 (Lemperle et al., 1970). There is no direct correlation between the residues on grapes and those in the processed products. In a further study residues up to 48 mg/kg dichlofluanid and 1.6 mg/kg DMSA on grapes resulted in corresponding residues (mg/kg) up to 6.9 and 4.5 mg/kg in must (not clarified), 0.4 and 2.3 mg/kg in clarified must and <0.05 and 4.0 mg/kg in wine (Lemperle et al., 1973). In other experiments (Lemperle and Kerner, 1969; Lemperle et al., 1970), grapes were treated two or three times at recommended concentrations. Residues of dichlofluanid and DMSA were determined in grapes harvested at intervals from 32 to 63 days after the last application, and in the wine made from them. Residues in the grapes (19 samples) ranged from 1.5 to 12 mg/kg dichlofluanid and 0.02 to 0.8 mg/kg DMSA. In the wine, dichlofluanid could not be detected in any of the samples (limit of detection 0.02 - 0.05 mg/kg) and DMSA residues ranged from 0.1 to 4.0 mg/kg. Bayer (1967-1973) report trials in FRG in which grapes were treated at various rates with dichlofluanid. The results (Table 6) show residues of dichlofluanid from 0.02 - 5.4 mg/kg on the grapes which have been eliminated during processing to wine. DMSA residues are again carried through into the wine. TABLE 6. Residues of dichlofluanid (I) and DMSA (II) on grapes and in wine produced therefrom Application Days after Residues, mg/kg* Rate last Grapes Grapes kg a.i./ha No. treatment I II I II - 7 28 - - n.d. - 0.6 4 56 5.4 1.35 n.d. - 1.5 - 2.0 2 57 0.9 0.15 n.d. - 2.0 - 2.5 4 47 0.7 0.25 n.d. 0.2 2.0 - 2.5 5 35 0.4 0.6 n.d. 0.25 2.0 - 2.5 6 22 1.6 0.95 n.d. 0.4 3.0 - 5.0 3 34 3.9 0.2 n.d. n.d. 2.0 - 4.0 4 59 - - n.d. 2.4 3.6 2 60 - - n.d. n.d. 1.8 5 71 1.0 - 0.03 - 0.8 8 54 0.02 - n.d. - * Limit of detection: dichlofluanid 0.02 mg/kg; DMSA 0.1 mg/kg. Fermentation experiments were conducted to determine the concentration of dichlofluanid required to inhibit yeast growth. At 1 mg/l in must the fermentation was retarded and at > 1.5 mg/l it was inhibited. The inhibitory effect of dichlofluanid on yeast was abolished by cysteine, beta-mercapto-ethylamine and other SH-compounds. Dichlofluanid can therefore be regarded as an "SH-blocker." The inhibitory effect decreases with increasing pH. The activity of most enzymes depends on free SH-groups which are part of cysteine. Therefore the enzymes alcohol-dehydrogenase and glycerinaldehyde-3-phosphate-dehydrogenase which contain essential SH-groups were strongly inhibited in vitro and in vivo while maleic dehydrogenase was not affected. The fluorodichloromethylthio (-S-CCl2F)-part of the dichlofluanid molecule was shown to be the inhibiting group (Dittrich and Issinger, 1969). Retardation of the fermentation process can be overcome by pre-clarification of the grape juice (must) and addition of about 1% of a fermenting pure yeast strain preparation, or in the case of red grape juice, by the addition of 2.5% pure yeast while still in contact with the skins. In general the fermentation process seems to be less influenced by dichlofluanid than by folpet. No differences between wines originating from dichlofluanid-treated and non-treated vines could be observed either analytically or by tasting (Lemperle et al., 1970, 1973). RESIDUES IN FOOD IN COMMERCE OR AT CONSUMPTION Residues in 52 samples of red currants examined in the Netherlands were <0.1 mg/kg (Keuringsdienst van Waren, 1966). Of 276 samples of strawberries, 256 contained <0.1 mg/kg dichlofluanid, 17 contained 0.1 - 1 mg/kg and 3 contained 1 mg/kg (Keuringsdienst van Waren, 1966). Results of food inspection reported in 1973 (Netherlands) are shown in Table 7. TABLE 7. Residues of dichlofluanid found during food inspection. Netherlands, 1973 Number of samples in range Range, red mg/kg blackberries raspberries currants strawberries 0 - 0.1 15 1 23 257 >0.1-0.2 2 7 111 >0.2-0.5 7 3 11 215 >0.5-1 5 3 8 168 >1 - 2 4 2 5 134 >2 - 5* 2 4 2 58 >5 - 10 3 3 >10 1 (10.3 mg/kg) Total 38 13 56 947 * The tolerance was 5 mg/kg in all cases. METHODS OF RESIDUE ANALYSIS A multiresidue GLC method, with electron-capture detection (Becker, 1972/74), has been adopted by Deutsche Forschungsgemeinschaft (DFG, 1974) for the determination of dichlofluanid. The method in principle is based on the GLC method of Vogeler and Niessen (1967) already mentioned in FAO/WHO, 1970. For stewed apples, pears, plums, cherries, peaches, grapes, cabbage, carrots, green beans and lettuce the recovery at the 0.1 mg/kg level is > 80%. For leeks, parsley and celery the recovery is below 70%. The method is suitable for regulatory purposes for dichlofluanid residues in a number of crops, but further evaluation is desirable before it can be recommended without reservation. It does not determine DMSA. A similar analytical method has been elaborated, in which isopropanol-benzene extracts of the crop are cleaned-up with Nuchar-Attaclay. The method has been checked for many green vegetables, tomatoes and fruit. Interferences have sometimes been found for leek, onion, cabbage and carrots (Rijks Instituut voor de Volksgesondheid, Bilthoven, 1972). NATIONAL TOLERANCES REPORTED TO THE MEETING National tolerances and safety intervals reported to the Meeting are given in Table 8. TABLE 8. National Tolerances for dichlofluanid reported to the Meeting Safety interval Tolerance, Count Crop (days) mg/kg Australia General 14 Austria General 14 Belgium Fruit, vegetables 5.0 (excl. potatoes) Strawberries (outdoor), raspberries, mulberries 7 Strawberries (under glass) 14 Currants 21 Bulgaria General 14 TABLE 8. (Cont'd.) Safety interval Tolerance, Count Crop (days) mg/kg Denmark Fruit, including strawberries 14 Finland General 14 Strawberries ( 4.0 Other fruit (proposed) ( 1.0 France General 7 Germany Small fruit (berry dichlofluanid ( 15.0 (FRG) fruit excluding + DMSA ( strawberries), calculated as ( grapes dichlofluanid ( ( Strawberries, ( lettuce, ( 10.0 ( all other fruit ( 5.0 ( Beans, cucumbers, ( tomatoes ( 3.0 ( Onions ( 1.0 Lettuce (field grown) 21 Lettuce (under glass) 28 Tomatoes (field grown and under glass) 3 Cucumbers (field grown and under glass) 3 Pome-fruit 7 Stone-and small fruit (excluding strawberries) 14 TABLE 8. (Cont'd.) Safety interval Tolerance, Count Crop (days) mg/kg (Germany) Strawberries 10 Grapes 35 Italy Grapes 40 All other crops 20 Japan Cucumbers, tomatoes, strawberries (under glass) 1 Netherlands General 5.0 Tomatoes, peppers, cucumbers, melons 3 Strawberries (outdoor), blackberries, raspberries 7 Strawberries 14 (underglass) Currants 21 Kohlrabi 14 New Zealand Fruit and vegetables 5.0 General 14 Norway General 7 Poland Vegetables, fruit 14 Field grown crops (excluding, potatoes, beets) 14 Grapes 42 Portugal Strawberries 14 TABLE 8. (Cont'd.) Safety interval Tolerance, Count Crop (days) mg/kg South Africa General 5.0 Table grapes 28 - 42 Wine grapes, peaches, apricots, plums and prunes 14 Spain Pome fruit, grapes strawberries, onions, vegetables 20 Sweden General 7 Switzerland Grapes 21 1.0 Apples, pears 21 0.5 Strawberries 21 7.0 United Apples, blackberries, Kingdom red and white currants, black currants, grapes grown outdoors, loganberries, autumn-sown salad onions, outdoor lettuce, leaf brassicas, seedlings under glass, lettuce under glass, treated with dust formulation 21 Strawberries, raspberries 14 Tomatoes under glass, direct spray on flowering trusses 3 Yugoslavia Strawberries 14 2.0 + 2.0 DMSA APPRAISAL The 1969 Joint Meeting, after reviewing the information on dichlofluanid, concluded that further work was necessary, before tolerances could be recommended. Some of the required information has been supplied. Data on the composition of technical dichlofluanid, including its impurities have been presented. Dimethyl-N-phenylsulphamide (DMSA) is known to be a metabolite, but detailed information on the pathway of dichlofluanid degradation, especially on the fate of the fluorine-containing moiety in plants, is not yet available. Studies are known to be in progress, and results will presumably be available to the 1976 Joint Meeting. The biological activity of dichlofluanid and similar fungicides (e.g. captan, folpet) is presumed to be localized in the trihalogeno-methylthio part of the molecule (Kühle et al., 1964). The inhibitory effect of dichlofluanid on yeast is antagonized by SH-compounds. The enzymes alcohol dehydrogenase and glycerinaldehyde-3-phosphate dehydrogenase and the co-factor co-enzyme A which contain essential SH-groups are strongly inhibited in vitro and/or in vivo (Lemperle et al., 1973). Dichlofluanid can therefore be regarded as an "SH-blocker." Processing of apples containing 0.8 mg/kg dichlofluanid plus 0.2 mg/kg DMSA to stewed fruit, baby food or jelly resulted in residues of 0.05 mg/kg dichlofluanid and 0.3 - 0.7 mg/kg DMSA. Cold pressed juice contained 0.2 mg/kg and heated juice 0.1 mg/kg dichlofluanid plus 0.7 mg/kg DMSA. Wine originating from grapes with residues up to 48 mg/kg dichlofluanid contained up to 4 mg/kg DMSA and always less than 0.05 mg/kg dichlofluanid. During crushing and fermentation much of the residue seems to be absorbed by the solid particles of the mash. In addition to the crops mentioned in FAO/WHO, 1970 the pre-harvest application of dichlofluanid has been extended to kohlrabi, leaf brassicas, melons, paprika, blackberries, loganberries, mulberries, raspberries, gooseberries, wheat and barley. In many cases dichlofluanid can be used as a substitute for other fungicides, e.g. dithiocarbamates and thiuram disulfides. Numerous data on rates and frequencies of application, pre-harvest intervals and the resulting residues of dichlofluanid and the degradation product DMSA have been supplied from Australia, Denmark, France, Germany, the Netherlands, Switzerland and the United Kingdom. The residue data, especially for currants, raspberries, strawberries and grapes, still show inconsistencies however. More data from supervised trials and on raw agricultural products moving in commerce are desirable for re-evaluating residue levels. Nevertheless the data on maximum residues so far obtained from supervised trials could be accommodated by the temporary tolerances recommended below, which seem to be in accordance with the toxicologically permissible level. The tolerances should refer only to the parent compound. This would substantially facilitate the determination of residues, because a gas-chromatographic multiresidue method could be used. This method is suitable for regulatory purposes in a range of crops, but further evaluation is desirable. DMSA can only be determined by a colorimetric method which is less suitable for regulatory purposes. The determination of DMSA is not considered necessary because available data indicate that excessive residues of this compound would be accompanied by excessive residues of dichlofluanid. RECOMMENDATIONS The following temporary tolerances are recommended. They refer to dichlofluanid only. TEMPORARY TOLERANCES dichlofluanid (mg/kg) Currants (red, black and white), grapes, raspberries 15 Lettuce, strawberries 10 Apples, pears, cucumbers, peaches 5 Beans (green, including pods), cherries, tomatoes 2 FURTHER WORK OR INFORMATION REQUIRED (by 1977) 1. Studies on absorption, distribution in various organs, and excretion of dichlofluanid in the rat. 2. Pharmacokinetics of the dichlorofluoromethylthio moiety. DESIRABLE 1. Metabolism studies on dichlofluanid. 2. Results from current studies on the pathway of degradation, especially the fate of the fluorine-containing moiety of the molecule, in and on plants. These data are expected to be available during 1975. 3. Further residue data from supervised trials, to resolve certain inconsistencies in the existing data or to provide new information, on blackberries, gooseberries, loganberries, mulberries, raspberries, currants, hops, kohlrabi, leaf brassicas, melons, onions, paprika and eventually wheat and barley. 4. Further residue data for raw agricultural products moving in commerce. 5. Further evaluation of the analytical method of Becker for regulatory purposes. REFERENCES Bayer AG (1962). Product KU 13-032-C. Report prepared and submitted by the Institute of Toxicology, Bayer AG. (Unpublished) Bayer AG (1964). Report of 4-months feeding study on rats with active ingredient 47531. Report prepared and submitted by the Institute of Toxicology. Bayer AG. (Unpublished) Bayer AG (1969). 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Rijks Instituut voor de Volksgezondheid, Bilthoven (1972). 109/72 Tox-Rob, Zuivering van plantenextracten met beheelp van actieve kool voorafgaande aan de gaschromatografische bepaling van een aantal bestrijdingsmiddelen. Tate, K.G., van der Mespel, G.J., Levin, P.B., Brewerton, H.V., Gibbs, M.M. and McGrath, H.J.W. (1973). Dichlofluanid ('Euparen') residues on strawberries. N.Z. J. Exp. Agric., 1(1):100-104. Vince, A.A. and Spicer, E.J.F. (1971). Pathology report of Bay 47531. Generation experiment in rats. Report from Huntingdon Research Centre, submitted by Bayer AG. (Unpublished) Vogeler, K. and Niessen, H. (1967). Kolorimetrische und gaschromatographische Bestimmungen von Rückständen in Pflanzen nach Anwendung von Euparen. Pflanzenschutz-Nach. Bayer, 20:534-549.
See Also: Toxicological Abbreviations Dichlofluanid (FAO/PL:1969/M/17/1) 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) Dichlofluanid (Pesticide residues in food: 1983 evaluations)