Effect of herbicide 2,4,5-trichlorophenoxyethanol (TCPE) containing dioxin on mutation and induction of sister chromatid exchanges.

Previous studies have indicated that both herbicide 2,4,5-trichlorophenoxyethanol (TCPE) and its contaminant 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) enhance liver tumor incidence in male Swiss mice in a dose-dependent manner. In this report the mutagenicity of TCPE (containing 0.1 p.p.m. TCDD) in the Salmonella/microsome assay was studied, and the effect of this herbicide on the colony-forming ability and on the frequency of sister chromatid exchange (SCE) in Chinese hamster cells were determined. TCPE (1-500 micrograms/plate) appeared non-mutagenic in strains TA 1535, TA 1537, TA 1538, TA 98 and TA 100 either in the absence or presence of S-9 mix from male Wistar rat, male Swiss mouse and male hamster liver pre-treated by Aroclor 1254, using the standard plate incorporation and the pre-incubation assay. Male mouse urine, after a single administration of TCPE to the animal, also proved to be non-mutagenic in strains TA 98 and TA 100. In mammalian cell systems, however, TCPE directly induced a dose related increase in SCE frequency. The dose required to double the control SCE frequency was in the slightly toxic range of the survival curve for TCPE. The cytotoxicity was diminished both in bacterial and mammalian systems in the presence of S-9 mix from male Swiss mouse liver. This S-9 mix strongly reduced SCE frequency induced by TCPE. The induction of SCE observed cannot be attributed to the contaminant TCDD alone, because the SCE production was not influenced by the appropriate low concentration of pure TCDD.