Toxic and DNA-damaging activities of the fungicides mancozeb and thiram (TMTD) on human lymphocytes in vitro

The cytotoxic and mutagenic effects of the fungicides mancozeb and thiram were studied using human peripheral blood lymphocytes cultured in vitro with or without an S-9 mix microsomal metabolizing system. The results obtained suggested that the chemicals caused dose-dependent inhibition of thymidine uptake and unscheduled DNA synthesis on both resting and proliferating lymphocytes in the absence of the S-9 mix. In the presence of the S-9 mix, only thiram showed mutagenic activity by eliciting unscheduled DNA synthesis and a significantly higher frequency of sister chromatid exchanges than did controls.

Examination of the interaction of decis and dithane in rats

Acute (LD50) and short-term (14 days) toxicological examinations were performed in animal experiments on the interaction of a synthetic pyrethroid Decis 2,5 EC (25 g deltamethrin/l) and of ethylene-bisdithiocarbamate/Dithane M-45 (80% mancozeb), using a 1:5 deltamethrin/mancozeb mixture. LD50 value of the mixture was similar to that of the more toxic Decis. In the short-term examination, some pathologically high AST and ALT values were observed in the treated groups and the deltamethrin content of fatty tissue samples increased parallel with the increase of Decis consumption. The chymotrypsin and lipase activities in the small intestinal mucosa and gamma-GT and LAP activities in the content of the bowels were reduced in several treated groups. The administration of Dithane in a dose in accordance with 20% of the LD50 value (3125 mg/kg b.m.) proved to be more toxic than expected and caused the death of the animals.

Genotoxicity of zineb detected through the somatic and germ-line mosaic assays and the sex-linked recessive-lethal test in Drosophila melanogaster

The genotoxicity of zineb, a carbamate fungicide, has been tested through eye, wing and female germ line mosaic assays and the sex-linked recessive-lethal test in Drosophila melanogaster. Larvae of different instars, heterozygous for appropriate recessive genetic markers, were exposed to the fungicide in food for different durations of time. The adult eyes and wings were screened for induction of mosaic spots and the eggs laid by the females were checked for induction of female germ-line mosaicism. It is concluded that zineb is genotoxic to both somatic and germ-line cells of Drosophila.

Tumour-promoting ability of mancozeb, a carbamate fungicide, on mouse skin

In this study the tumour-promoting activity of a carbamate fungicide, mancozeb, has been observed following topical application on mouse skin in a two-stage initiation--promotion protocol for carcinogenesis. Female Swiss albino mice were initiated with a single subcarcinogenic dose (52 micrograms) of 7,12-dimethylbenz[a]anthracene painted on the interscapular region. Seven days after initiation the mice underwent topical application of mancozeb (100 mg/kg body wt) three times per week as promoter. Development of tumours was observed after 12 weeks of mancozeb application in 1/14 animals and 100% tumorigenesis was recorded after 17 weeks of mancozeb application. On histological examination, these tumours were found mostly to be benign in nature, e.g. squamous cell papillomas and keratocanthomas.

Failure of phenobarbitone to potentiate the adverse effects of two ethylene-bis-dithiocarbamate (EBDC) fungicides

The effects of Mancozeb and Zineb, two dithiocarbamate fungicides used to protect vegetables, on rat thyroid and liver function were studied in an acute and a chronic trial. These compounds may be spontaneously or metabolically transformed to ethylene thiourea, a goitrogenic, mutagenic and teratogenic molecule. Sex linked differences in sensitivity and the possibility that toxicity might be potentiated through induction of the microsomal drug metabolising system by phenobarbitone were investigated. When compared with the findings of Ugazio et al. (1985) on the toxicity of ethylene thiourea, the results obtained in this study, bearing in mind the doses employed and the fact that no potentiation by phenobarbitone was observed, suggest that the risks associated with exposure to these two fungicides are less severe than had been supposed.

Tumour initiating activity of mancozeb--a carbamate fungicide in mouse skin

Mancozeb is a protectant fungicide and is a polymeric complex of ethylene bis(dithiocarbamate)manganese (i.e. Maneb) with zinc salt. In this study, the tumour initiating ability of mancozeb has been observed by a 2-stage initiation-promotion protocol in mouse skin.

The measurement of ethylenethiourea and ethyleneurea in the rat and common marmoset Callithrix jacchus after zineb (zinc ethylenebisdithiocarbamate) dosing

The metabolism of the fungicide zineb, (zinc ethylenebisdithiocarbamate), has been studied in the rat and the marmoset. 2. It was found in both species that a relatively large proportion (21-22%) of the original zineb administered was detectable in the excreta as ethylenethiourea (ETU) a known mutagen, teratogen and carcinogen. 3. A further proportion (2-5%) was determined to be ethyleneurea which is a metabolite of ETU. 4. Results of comparative experiments in marmosets revealed that ETU was photolabile in the presence of excreta, thus showing the importance of conducting the studies in the dark.

[Teratogenic and goitrogenic activity of propineb and propylenethiourea in the rat]

The teratogenic and goitrogenic effects of Propineb, dithiocarbamate pesticide and Propylenthiourea (PLTU), its metabolite and degradation product have been studied. The aim of this study was to show the possible correlation between the two activities. Female Sprague-Dawley rats were treated with Propineb and PLTU starting from 6th to 16th day of pregnancy. The functional state of maternal and foetal thyroid, the toxicity of products versus dams and embryotoxic and teratogenic effects were examined. The observed goitrogenic effect may be compared to that reported in the previous studies of the authors, if considering time of sacrifice. In fact, the lesion quickly rises and as rapidly regresses when treatment is stopped. The foetal thyroid has not been affected by the product administered to the dams. PLTU showed a clear teratogenic activity at doses that did not show any maternal toxicity (45 and 90 mg/k).

Dithiocarbamate pesticides: activity of Propineb in the micronucleus test in mice

The possible clastogenic activity of Propineb, Propineb technical grade and of its main metabolite, propylene-thiourea (PLTU), was investigated by the micronucleus test in mice according to Schmid. No statistically significant increase in the percentage of micronuclei was observed at any of the tested doses of the above compounds. As positive controls, dose-effect curves were constructed for methyl methanesulfonate (MMS) and mitomycin C (MMC).

Evaluation of Propineb, a dithiocarbamate pesticide, in the mouse-sperm morphology assay

Propineb, a dithiocarbamate fungicide, was studied by using the sperm morphology assay in (C57BL6 male X C3H female) F1 mice. At all dose levels, no statistically significant increase in the percentage of sperm abnormalities was observed. Methyl methanesulfonate (MMS) and 2-acetylaminofluorene (2-AAF), which were tested as positive controls, induced a dose-effect-related increase in teratospermia.

Mutagenicity and DNA-damaging activity for several pesticides tested with Bacillus subtilis mutants

The active pure compounds of 4 pesticides were tested for DNA-damaging and mutagenic activity in Bacillus subtilis and Salmonella typhimurium tester strains. Included were zinc ethylenebisdithiocarbamate (dithane), 1,2-dihydropyridazine-3,6-dione (maleic hydrazide), O,O-dimethylphosphorodithioate (malathion), and 1,2-dibromoethane (fumazone). These agents gave either weak or negative mutagenic responses with the Salmonella/microsome tests for mutagenicity, but were all positive when the tester was B. subtilis strain TKJ6321. Of the 4 chemicals, only fumazone required metabolic activation with rat-liver S9 mix. Upon activation, it produced a volatile mutagenic product. Dithane, maleic hydrazide, and malathion were all mutagenic and did not require metabolic activation. Among these agents, dithane was strongly mutagenic while fumazone, maleic hydrazide and malathion were moderately mutagenic. Only dithane gave significant DNA-damaging activity when applied to a battery of repair-deficient B. subtilis mutants. For the chemicals reported, it is concluded that B. subtilis is superior to S. typhimurium in the detection of mutagenic activity. We strongly recommend its use for prescreening procedures in combination with the S. typhimurium testers.

Study on the long-term effects of some pesticides

The hygienic significance of the studies on pesticides from the aspect of their "long-term" effects upon the individual and the generations are emphasized. The basic methods and approaches used in the Laboratory of long-term effects with chemical etiology at the IHOH, Sofia, are discussed, namely for detecting the changes in gonads, reproduction and generation, embryotoxic and teratogenic effects, and changes in cardiovascular system. The results are discussed, namely: fundasol--the effect on gonads, generations, embryotoxic and teratogenic effects, changes in the cardiovascular system; endodan--changes in gonads, reproduction, embryotoxicity; basfungin--embryotoxic and teratogenic effects. All of these studies were performed for the purpose of threshold levels, establishment hygienic standardisation and prognosis of the potential risk for human.

Differences in carcinogenicity after transplacental and postnatal administration of drugs and pesticides

Comparative studies of the carcinogenic activity of procarbazine, methylphenylnitrosourea and ethylenethiourea after transplacental and postnatal administration showed that there were marked differences in frequency and spectrum of tumors induced. Possible causes of these differences are briefly discussed. It is suggested that transplacental experiments can provide special advantages in testing drugs and environmental chemicals for potential carcinogenicity and should be included in test programs.

Oral toxicity of ferric dimethyl-dithiocarbamate (ferbam) and tetramethylthiuram disulfide (thiram) in rodents

Single oral doses of ferbam, thiram, zineb, or maneb produced central nervous system stimulation followed by depression and alopecia. Ferbam and thiram were more toxic on the basis of weight than zineb; maneb was relatively nontoxic. There was no species difference in acute toxicity between rats and mice. In 13- and 80-wk feeding studies, the toxic effects of ferbam and thiram in rats were similar; however, thiram was more toxic on the basis of weight than ferbam. During the 80-wk feeding study, weight gain was reduced in ferbam-treated rats starting at daily doses of 8 mg/kg in males and 37 mg/kg in females and in thiram-treated rats staring at daily doses of 5 mg/kg in males and 26 mg/kg in females. Food consumption was reduced in proportion to the reduced weight gain. Death occurred in males fed 109 or 331 mg/kg.d ferbam and in males fed 58 or 132 mg/kg.d thiram. Female rats fed 96 mg/kg.d ferbam or 67 mg/kg.d thiram developed alopecia and ataxia, which led to paralysis of the hind limbs. Male rats fed ferbam or thiram had a more severe incidence of squamous metaplasia in the thyroid and fatty infiltration in the pancreas than control males. Ferbam or thiram reduced the incidence of spontaneous nephritis in both males and females. The male rats that were fed 109 or 331 mg/kg.d ferbam and died betweeen 1 and 5 wk had golden pigment in the reticuloendothelial cells of the spleen and in the enlarged mesenteric lymph nodes, associated with hemosiderosis. Moderate tubular degeneration of the testes with atypical spermatids in the epididymis occured in some rats fed 132 mg/kg.d thiram for 13 wk but not in rats fed up to 52 mg/kg.d for 80 wk. Periodic hematologic examination and terminal clinical blood tests did not reveal any severe changes. Ferbam and thiram did not alter the occurrence or latent period of the spontaneous tumors seen in control rats.