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.