Mutagenicity study of butachlor and its metabolites using Salmonella typhimurium.

Butachlor is the most commonly used herbicide in Taiwan and many other countries. It has been reported to be an indirect mutagen and carcinogen in various in vitro assay systems. Previous investigation has also demonstrated that butachlor stimulates cell proliferation, transforms normal embryonic cells, and induces stomach tumors in Spraque-Dawley rats. However, the mechanism of butachlor carcinogenicity is still not clear. In order to clarify the toxicologic and carcinogenic properties of butachlor, we proposed a metabolic pathway, and synthesized the authentic metabolites by chemical methods. In addition, we tested the mutagenicity of butachlor and these metabolites on Salmonella typhimurium. The results indicate that butachlor might manifest its carcinogenicity via the mutagenicity of its metabolic products. Although the molecular mechanism of butachlor-induced cellular toxicity is still not clear, it is likely that the cellular transformation ability of butachlor is partly associated with its mutagenicity.