TECNAZENE JMPR 1978 Explanation Limited available information was reviewed in 1974 (FAO/WHO, 1975) but the meeting reported that before an ADI or residue limits could be recommended the following data were required. 1. Adequate toxicological data. 2. Full information on specifications for the chemical and the formulated products (including impurities, e.g., HCB), present use patterns, residue data from supervised trials, fate of residues in crops other than potatoes and in soils, etc. The data received in response to these published requirements are evaluated in this monograph. IDENTITY Chemical name 1,2,4,5-Tetrachloro-3-nitrobenzene Synonyms 2,3,5,6-Tetrachloronitrobenzene, TCNB, FusarexR, FumiteR, Folosan DB 905. Structural formulaOther information on identity and properties Molecular weight: 261 Physical state: Colourless, odourless, crystalline solid Melting point: 99°C Volatility: Appreciably volatile at room temperature Solubility: Practically insoluble in water; soluble in ethanol; readily soluble in acetone, benzene, carbon disulphide, chloroform, etc. Stability: Generally very stable; can be dispersed by pyrotechnic mixtures. Decomposes slowly in solution when irradiated with ultra-violet light. Purity of technical material: The test material was more then 99% pure and contained less than 0-1% of hexachlorobenzene. Full information was available to the Meetings. EVALUATION FOR ACCEPTABLE DAILY INTAKE BIOCHEMICAL ASPECTS Biotransformation One of the major metabolites identified in the urine following oral administration of 1-3 g of 2,3,5,6-tetra-chloronitrobenzene to rabbits was mercapturic acid, being excreted at a rate of 11% within 48 hours after application. Further metabolites excreted were an ether glucuronide (12%), 2,3,5,6-tetrachloroaniline (10%), unconjugated 4-amino-2,3,5,6-tetrachlorophenol (2%) and an etheral sulphate (1%) (Bray et al., 1953; Betts et al., 1955). Similar amounts of mercapturic acid were excreted in the urine of rats (Barnes et al., 1959). Rat liver contains an enzyme catalysing the formation of glutathione S-conjugates with replacement of the active halogen of aromatic compounds, known to be excreted as mercapturic acid. Evidence was presented by Al-Kassab et al., 1963, that the enzyme, that catalyses the displacement of halogen will also replace the labile nitro group of polychloronitrobenzenes with glutathione and of the carcinogen 4-nitroquinoline-N-oxide. Studies in pigeons showed that orally administered 2,3,5,6-tetrachloronitrobenzene is also converted to mercapturic acid (Wit et al., 1969). TOXICOLOGICAL STUDIES Special studies on carcinogenicity Tests were performed to study the carcinogenic action of polychloronitrobenzenes, its tumour initiating activity and its action on carcinogenesis induced by benz(a) pyrene: one of the reasons for performing these tests was the similarity in biotransformation of TCNB and the carcinogenesis 4-nitroquinoline-N-oxide. Skin application of 0.2 ml of 0.3% acetone solutions to 10 males and 10 females twice weekly for 12 weeks was followed by croton oil treatment for 20 weeks. Controls (10 of each sex) were treated according the same schedule, instead of tecnazene only acetone was given in the first phase. By the end of the croton oil treatment, 41 papillomas had been observed in treated males and 13 in treated females versus 7 and 5 in controls. Tecnazene (> 99% pure) was administered continuously in the diet to 65 male and 65 female CD-1 animals in each dose group at dietary levels of 09 750 and 1500 ppm for a period of 80 weeks. The treatment did not adversely affect the general condition, behavioural patterns, body weight gain and food intake. Survival in males was poorer in the controls than in treated groups; mice alive at 80 weeks were 16, 17 and 31 males and 27, 37 and 25 females at 0, 750 and 1500 ppm respectively. Several macroscopic pathological alterations with increased incidences in the dose-groups were observed, but because no distinct dose-relationship is found, no biological significance could be attached to these changes. No dose-related group distribution of neoplasms was observed, with the only exception of a higher frequency of pulmonary adenoma in the male animals of the 1500 ppm group; 8 animals showing this lesion compared to 4 animals in the control and low dose group (Ben-Dyke et al., 1978b). Skin carcinogenesis by benzo(a)pyrene was not affect by TCNB (Searle, 1966). Groups of 65 male and 65 female rats were fed with a diet containing tecnazene (purity > 99%) at concentrations of 0, 750 and 1500 ppm for a period of 104 weeks. The feeding did not affect general appearance, behaviour, mortality and food consumption. In all groups survival at 78 weeks was 50% or more. In the first half of the treatment period body-weights were unaffected, whereas in the second half a slight reduction of body weights was observed in treated males at 1500 ppm. The macropathological findings and non-neoplastic histologic changes were those commonly found in the rat strain used; they were not considered to be treatment-related and did not show clear dose-relationships. Liver hyperplastic nodules were seen in one female at 750 ppm and in 3 males and 2 females at 1500 ppm. Benign or malignant tumours of the mammary glands were seen in 39 females of the control group versus 48 females given 750 ppm and 50 animals given 1500 ppm. Adenocarcinomas were found in 4 females of the control group compared to 5 and 8 females at the 750 and 1500 ppm level respectively. These differences are of borderline statistical significance (p approx. 0.05). Only one liver-cell tumour was seen and this was in a control rat (Ben-Dyke et al., 1978a). Special studies on teratogenicity 2,3,5,6-tetrachloronitrobenzene did not show embryotoxic or teratogenic properties when orally administered at doses of up to 200 mg/kg b.w. to CD rats and C 57 B 1/6 mice on gestation day 7-18 or to CD-1 mice on day 7-16 (Courtney et al., 1976). Acute toxicity The acute intraperitoneal LD50 of 2,3,5,6-tetrachloronitrobenzene in the rat is approximately 3500 mg/kg (Wit et al., 1960) Short Term Studies Pig Groups of two pigs were maintained an a diet containing potatoes that have been treated with a dust-mixture of tecnazene at levels of 0, 60, 400 and 600 mg/lb potatoes for 26 weeks. The highest dose level of 600 mg/lb potatoes being ten times as high as that which will be used for the routine dressing of potatoes, corresponds to 7.1 g tecnazene per pig per day or approximately to 50 mg/kg b.w. and caused reduction in body weight gains in the first half of the study. No other abnormal findings with respect to general health condition, haematological parameters or gross and microscopic examination of liver and kidney were detected. No methaemoglobinanaemia was produced by the treatment (Abrams et al., 1950). Rat In a 10 week-feeding study rats were maintained on a diet with 2000 ppm tecnazene. No abnormalities in general health, blood picture, autopsy findings and histological picture of liver and kidney were detected. In the male animals increased liver- and testis-weights were observed (no other details described) (Wit et al., 1960). COMMENTS Following oral administration of tecnazene to rabbits the material absorbed is excreted mainly as an ether glucuronide, 2,3,5,6-tetrachloraniline and mercapturic acid. The study of the biotransformation of some polychloronitrobenzenes in rats and rabbits showed that these compounds were converted to mercapturic acids; the formation of S-substituted glutathione by replacing the labile nitro groups with glutathione seems to be the first stage in mercapturic acid formation. An experiment on mice on skin carcinogenesis is suggestive of a tumour-initiating effect of tecnazene, but, a full evaluation is impaired by the small number of animals used. The results of the carcinogenicity tests with feeding of the test compound over 104 weeks to rats and 80 weeks to mice gave no clear indication of a carcinogenic activity in tecnazene. The increased number of mammary tumours in female rats was of borderline statistical significance. In the study on mice the tumour incidence was not increased. In the 80 week study in mice with 750 and 1500 ppm tecnazene in the diet no treatment revealed effects were noted. In the two year study on rats with dose levels of 750 and 1500 ppm a slight reduction of weight gain occurred in the males of the high dose group. Tecnazene showed no teratogenic activity in mice. No studies relating to mutagenicity, effects an reproduction or metabolism in different mammalian species were made available since the last evaluation by the 1974 Meeting. In view of come uncertainties in regard to the carcinogenic potential of tecnazene and the lack of adequate reproduction data only a temporary ADI was allocated. TOXICOLOGICAL EVALUATION Level causing no toxicological effect Rat: 750 ppm in the diet equivalent to 38 mg/kg bw Mouse: 1500 ppm in the diet equivalent to 200 mg/kg bw Dog: 15 mg/kg bw Estimate of temporary acceptable daily intake for man 0 - 0.01 mg/kg bw RESIDUES IN FOOD AND THEIR EVALUATION USE PATTERN Tecnazene is used on potatoes after harvest, as a 3% dust formulation at the rate of 10 1b product per ton,(4.5g product/kg), to reduce sprouting during storage. This recommendation produces a theoretical initial loading on the potatoes of 134 mg/kg. Tecnazene displays the additional merits of not inhibiting would healing in freshly-clamped potatoes and of controlling dry rot, Fusarium caeruleum (Brown, 1947; Reavill, 1954). Tecnazene is also used as a smoke generator formulation at 15 mg/m3 to control Botrytis spp. on tomatoes, lettuce, chrysanthemums and other ornamental plants, and as a dust in chicory (witloff) culture. RESIDUES RESULTING FROM SUPERVISED TRIALS When potatoes were treated at 4.5g kg with 3% tecnazene dust, stored for 4-5 months, commercially graded and transported, mean residues on the tubers were of the order of 2 mg/kg. Increasing the storage period to six months caused a farther reduction to approximately 1 mg/kg. The original concentration applied (134 mg/kg) is reduced mainly by handling, both before and after storage, but losses by evaporation were shown to occur during storage. Washing reduced residues still further and no tecnazene was detected in the flesh of peeled potatoes (limit of determination approximately 0.1 mg/kg) (Wilson and Dawson, 1953). In a similar study (Bullock, 1973), when potatoes treated as above were stored commercially for 4-5 months, tecnazene residues on tubers with adhering soil were normally less than 10 mg/kg; the mean residue was approximately 3 mg/kg. Washing the potatoes reduced residues to below 1 mg/kg (mean approximately 0.4 mg/kg). Residue levels in stored potatoes treated with a 30% liquid tecnazene formulation by means of a fogging machine have been reported (Wheatley Chemical Co., 1978). Three application rates were chosen, giving the recommended rate of 15 mg a.i./kg and one half and twice this rate (i.e. 25, 50 and 100 ml/ton); results are shown in Table 1. TABLE 1. Residues of tecnazene in treated potatoes Tecnazene residue (mg/kg) Day 1 Day 60 Day 100 Application Whole Whole Whole rate (mg ai/kg) tuber skin tuber tuber skin 7.5 6.4 76.8 4.05 1.0 7.6 15 13.2 151.8 6.8 2.6 24.2 30 23.3 276.0 17.3 3.1 41.0 Data from trials usage of tecnazene on 7 samples of glasshouse grown lettuce in 1972 showed residues ranging from 1.3 to 2.2 mg/kg (mean 1.7 mg/kg) at 11-19 days after treatment (Race, 1978). Fodderbeets treated at 90 mg/kg with tecnazene and stored for five months contained residues of 0.1-13 mg/kg, with most samples containing less than 5 mg/kg tecnazene (Wit et al., 1960). In the culture of chicory (witloff) tecnazene can be used as a fungicidal powder on the roots when they are forced. Residues were determined in the sprouts, and in the remaining roots which are used as fodder, six weeks after treatment at 150 g product per m2 (4.5 g a.i. per m2). Residues in the sprouts did not exceed 0.05 mg/kg and in the roots were less than 3 mg/kg (Wit et al., 1960). Confirmatory studies at a 3 g m2 treatment rate showed residues not exceeding 0.11 mg/kg in the sprouts and less than 0.3 mg/kg in the roots approximately seven weeks after treatment (Bullock, 1973). FATE OF RESIDUES In plants As reviewed above, tecnazene residues on potatoes are readily lost by evaporation. Under commercial conditions the major losses occur by handling, both before and after storage, although some losses also occur during storage, Washing treated potatoes reduces residues significantly (Wilson and Dawson, 1953; Bullock, 1973). Limited evidence indicated that washing chicory (witloff) roots was much less effective in reducing the residue content (Netherlands, 1978), In soil Tecnazene was rapidly lost from a sandy soil; over 50% in two months and all but 2% in ten months. Volatility of tecnazene is likely to have been a major contributory factor. The rate of loss was similar from both sterile and non-sterile sandy soil and at 100 mg/kg in this soil tecnazene had no effect on respiration or nitrification (Caseley, 1968: Caseley and Broadbent, 1968). EVIDENCE OF RESIDUES IN FOOD IN COMMERCE OR AT CONSUMPTION Washing, peeling and cooking potatoes all cause considerable reductions in tecnazene residue levels. As stated above, when potatoes treated at 4.5 g kg with 3% tecnazene dust were stored commercially for 4-5 months, mean tecnazene residues on tubers with adhering soil were approximately 3 mg/kg. Washing the potatoes reduced residues to below 1 mg/kg (mean approximately 0.4 mg/kg). After peeling, residues in uncooked edible flesh were normally below 0.1 mg/kg (mean approximately 0.04 mg/kg) (Bullock, 1973), Boiling reduces the level of tecnazene in peeled edible flesh by 50% or more (Bullock, 1973; Dalzeil and Duncan, 1974). Although baking unpeeled potatoes caused a slight increase in residues in edible flesh (up to two-fold), it caused a major reduction of tecnazene levels in peel and an overall reduction in the residue level in the potato (Bullock, 1973). Potatoes grown in the U.K. in 1976 and 1977 were purchased on the market and examined for residues of tecnazene. In addition to the whole tubers analysed from both crops, some samples from the 1977 crop were washed and peeled before analysis. Results obtained are shown in Table 2. Although most results on whole tubers were below 10 mg/kg, an appreciable number were greater than 5 mg/kg in both years (Anon, 1978). TABLE 2. Residues of tecnazene in marketed potatoes Year Commodity No. of Tecnazene residue (mg/kg) samples Range Mean 1976 Whole tubers 3 10.5 - 19.3 15.3 Whole tubers 13 3.0 - 9.0 5.7 Whole tubers 7 0.6 - 1.5 1.1 1977 Whole tubers 17 2.2 - 7.6 4.6 Whole tubers 26 <0.1 - 1.7 0.3 Washed and peeled tubers 19 <0.1 - 0.25 <0.1 Over a 10 year period (June 1964 - August 1974), about 300 samples of potatoes were collected during a series of market basket surveys in the USA. Of these 14 were found to contain detectable residues of tecnazene, ie 0.001 mg/kg or above; the highest level found was 0.37 mg/kg, Over 3500 samples of other foodstuffs were also analysed in which trace residues (0.01 mg/kg or less) were reported in 15 samples representing a wide range of foodstuffs (Corneliussen, 1969, 1970, 1972; Duggan et al., 1966, 1967; Johnson and Manske 1975; Manske and Corneliussen, 1974; Manske and Johnson, 1975, 1977; Martin and Duggan, 1968). Of 60 samples of lettuce examined in Belgium in 1972, 52 contained less than 0.01 mg/kg and only one contained more than 2 mg/kg of tecnazene. Similarly, of 54 samples of chicory examined, only two contained more than 0.01 mg/kg but none more than 2 mg/kg (Valange, 1974). No tecnazene was detected in 17 samples of maize, and only one of 23 samples of dried sugar beet pulp contained a detectable residue of 0.03 mg/kg (Valange and Henriet, 1974). A survey of canned peas, haricot beans, carrots, celery, salsify, asparagus and cherries in Belgium showed no residues of tecnazene above 0.001 mg/kg (Biston et al., 1975). Westöö and Noren (1973) examined about 2500 samples of fresh and canned, home grown and imported foods in Sweden during the period 1968 to June 1972. Of the foods analysed, detectable residues of tecnazene appeared most commonly in lettuces; of 230 samples tested 15 contained 0.02 to 0.1 mg/kg, 14 contained 0.11 to 0.5 mg/kg and 9 contained 0.51 to 1.4 mg/kg of tecnazene. A few samples of carrots (6 of 140), tomatoes (3/240), paprika (1/65) and parsley (4/13) had residues of tecnazene in the range 0.02 to 0.1 mg/kg. Similar studies in Sweden in 1976-77 showed no residues of tecnazene above 0.1 mg/kg in mushrooms (9 samples), carrots (187), sweet peppers (166), parsley (16), beetroots (4) tomatoes (467) or apples (931). Of 253 samples of potatoes, 2 were in the range 0.11 to 0.5 mg/kg, 2 from 0.51 to 1.0 mg/kg and 4 between 1.1 and 5.0 mg/kg (Sweden, 1973). METHODS OF RESIDUE ANALYSIS Gas chromatography with an electron-capture detector is the preferred method of residue analysis. Crop samples are macerated with light petroleum, dried and filtered, and an aliquot is injected into the gas chromatograph. The limit of determination is 0.01 mg/kg or better. Recoveries in excess of 90% are normally obtained from potatoes and chicory, for which the method is suitable for use as a regulatory method. Confirmation of the residue can be obtained by clean-up of the extract by thin-layer chromatography and further gas chromatographic determination (Bullock, 1973). The use of gas chromatography with a flame ionisation detector has also been reported. Tecnazene residues could be determined in hexane extracts applied directly to the gas chromatograph; however, the accumulation of charred plant residues on the column and overlap with natural components using this detector limited the value of this approach. Solvent partition and an alumina column were used successfully to clean-up the extracts and a method of avoiding the formation or troublesome emulsions has been described (Dalziel and Duncan, 1974). Polarographic and colorimetric methods have also been described (Webster and Dawson, 1952; Auerbach, 1950; Canbäck and Zajaczkowska 1950; Higgons and Toms, 1957). NATIONAL MRLs REPORTED TO THE MEETING National MRLs reported to the meeting are shown in Table 3. TABLE 3. National MRLs for tecnazene reported to the meeting Country Commodity MRL (mg/kg) Belgium Vegetables and strawberries 2 Federal Republic Strawberries, chicory, lettuce, of Germany tomatoes 0.03 Other vegetables 0.05 Netherlands Vegetables and strawberries 2 United States Potatoes of America 25 Zambia Potatoes 25 APPRAISAL Tecnazene is used on potatoes as a post-harvest sprout suppressant and as a fungicide on chicory (witloof) and glasshouse grown tomatoes and lettuce. Residue data were available from supervised trials on potatoes, lettuce and chicory (witloof). Some data from marketed samples, and market basket surveys showed detectable residues in potatoes and, occasionally, in other crops such as lettuce, tomatoes, carrots, etc. No information was forthcoming on the fate of residues in crops other than potatoes. Information concerning the purity specification for the technical material was available and acceptable to the Meeting; the content of hexachlorobenzene in this material was below 0.1%. Sufficient data were available to allow the following recommendations to be made for temporary maximum residue limits in certain crops. Gas chromatographic methods of analysis are available and suitable for regulatory purposes. RECOMMENDATIONS The following temporary maximum residue limits apply to tecnazene. Commodity Temporary MRL, mg/kg Lettuce 2 Potatoes (washed before analysis) 1 Chicory (witloof) 0.2 Other vegetables 0.1 Tomatoes 0.1 FURTHER WORK OR INFORMATION Required (by 1981) 1. Clarification of the tumour initiating activity observed in a skin painting experiment on mice. 2. Adequate study on reproduction. Desirable 1. Short-term tests on mutagenicity. 2. Metabolism in different mammalian species. 3. Information regarding levels of residues occurring in meat and milk resulting from consumption of treated chicory roots or potatoes by cattle. REFERENCES Abrams J.T., Scorgie, N.J. and Willis, G.A. Pig feeding trials (1950) with 2,3,5,6-tetrachloronitrobenzene. British Veterinary Journal 106, 413-420. Al-Kasseb, S., Boyland, E. and Williams, K. An enzyme from rat (1963) liver catalysing conjugations with glutathione. 2. Replacement of nitro groups. Biochem. Journal 87, 4-9. Anon. Residues of tecnazene on market samples of potatoes. Data (1978) from the Food Research Institute. Norwich, UK (unpublished). Auerbach, M.E. Colorimetric estimation of tetrachloronitrobenzene. (1950) Analyt. Chem., 22: 1287-1288. Barnes, M.M., James S.P. and Wood, P.B. The formation of mercapturic (1959) acids. 1. Formation of mercapturic acid and the levels of glutathione in tissues. Biochem. Journal 71, 680-690. Ben-Dyke, R., McSheehy. T.W., Cummins, H.A., Finn, J.P. and Newman, (1978a) A.J. 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Biol., 34: 422-429. Bullock, D.J.W. and Burgess, J.G. Tecnazene: Residues in potatoes (1973) following application of `Fusarex' dust. ICI Plant Protection Ltd., Report No. AR 2404A (unpublished). Canbäck, T. and Zajaczkowska, H. The photometric determination of (1950) 2:3:5:6-tetrachloronitrobenzene. J. Pharm. Pharmacol. 2: 545-548. Caseley, J. C. The loss of three chloronitrobenzene fungicides (1968) from the soil. Bull. Environ. Contarm. Tox., 3: 180-193. Caseley, J.C. and Broadbent, F.E. The effect of five fungicides (1968) on soil respiration and some nitrogen transformations in Yolo fine sandy loam. Bull. Environ. Contam. Tox., 3: 58-64. Corneliussen, P.E. Pesticide residues in total diet samples (IV). (1969) Pestic. Monit. J., 2: 140-152. Corneliussen, P.E. Pesticide residues in total diet samples (V). (1970) Pestic. Monit. J., 4: 89-105. Corneliuseen, P.E. Pesticide residues in total diet samples (VI). (1972) Pestic, Monit. J., 5: 313-330. 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See Also: Toxicological Abbreviations Tecnazene (EHC 42, 1984) Tecnazene (HSG 12, 1988) Tecnazene (WHO Pesticide Residues Series 4) Tecnazene (Pesticide residues in food: 1981 evaluations) Tecnazene (Pesticide residues in food: 1994 evaluations Part II Toxicology)