Mammalian cell DNA damage and repair kinetics of monohaloacetic acid drinking water disinfection by-products.

Haloacetic acids (HAAs) are the second most common class of chlorinated water disinfection by-products (DBPs). The single cell gel electrophoresis genotoxicity assay using Chinese hamster ovary (CHO) cells was modified to include liquid holding recovery time to measure genomic DNA damage and repair kinetics of three monoHAAs: chloroacetic acid (CAA), bromoacetic acid (BAA), and iodoacetic acid (IAA). The rank order of genotoxic potency was IAA > BAA >> CAA from previous research. The concentration of each HAA was chosen to generate approximately the same level of genotoxic damage. No cytotoxicity was expressed during the 24 h liquid holding period. Nuclei from CHO cells treated with BAA showed the lowest rate of DNA repair (t(50) = 296 min) compared to that of CAA or IAA (t(50) = 134 and 84 min, respectively). The different rates of genomic repair expressed by IAA or CAA versus BAA suggest that different distributions of DNA lesions are induced. The use of DNA repair coupled with genomic technologies may lead to the understanding of the biological and genetic mechanisms involved in toxic responses induced by DBPs.