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.