Assessment of the cytotoxicity and genotoxicity of haloacetic acids using microplate-based cytotoxicity test and CHO/HGPRT gene mutation assay

Haloacetic acids (HAAs) are the second most prevalent class of disinfection byproducts found in drinking water. The implications of HAAs presence in drinking water are a public health concern due to their potential mutagenic and carcinogenic effects. In the present study, we examined the cytotoxic and genotoxic effects of six common HAAs using a microplate-based cytotoxicity test and a hypoxanthine–guanine phosphoribosyltransferase (HGPRT) gene mutation assay in Chinese hamster ovary K1 (CHO-K1) cells. We found that their chronic cytotoxicities (72 h exposure) to CHO-K1 cells varied, and we ranked their levels of toxicity in the following descending order: iodoacetic acid (IA) > bromoacetic acid (BA) > dibromoacetic acid (DBA) > chloroacetic acid (CA) > dichloroacetic acid (DCA) > trichloroacetic acid (TCA). The toxicity of IA is 1040-fold of that of TCA. All HAAs except TCA were shown to be mutagenic to CHO-K1 cells in the HGPRT gene mutation assay. The mutagenic potency was compared and ranked as follows: IA > DBA > BA > CA > DCA > TCA. There was a statistically significant correlation between cytotoxicity and mutagenicity of the HAAs in CHO-K1 cells. The microplate-based cytotoxicity assay and HGPRT gene mutation assay were suitable methods to monitor the cytotoxicity and genotoxicity of HAAs, particularly for comparing the toxic intensities quantitatively.