Chemical disinfection has provided protection against microbiological pathogens and greatly suppressed outbreaks of waterborne diseases. However, with their high oxidizing ability disinfectants also react with natural organic matter and chemical contaminants to form disinfection byproducts (DBPs), some of which are environmentally hazardous. This research quantitatively compared the toxicity of haloacetic acids (HAAs) and haloacetonitriles (HANs) as representative carbonaceous and nitrogenous DBPs using Chinese hamster ovary (CHO) cells as a model mammalian cell system. MonoHAAs and monoHANs have a similar chemical structure with a single halogen substituent at their a-carbon. Both DBP groups induced genomic DNA damage in the order of iodinated > brominated > chlorinated analogues but the repair efficiency of the induced lesions did not follow this same order. HAA-induced lesions required longer processing time compared to HAN-induced lesions. DNA damage induction, DNA repair, and cell cycle regulation are strongly associated in eukaryotic cells. Also recent HAA human cell toxicogenomic analysis focusing on DNA damage signaling pathway demonstrated that gene expression involving cell cycle regulation was highly affected. MonoHANs were shown to induce abnormally high DNA content in treated CHO cells in mitosis- and proliferation-dependent manner. MonoHAAs were expected to induce cell cycle delay as well. CHO cells were treated with chloroacetic acid, bromoacetic acid or iodoacetic acid using a wide range of concentrations and subsequently incubated in fresh cell culture medium. DNA content distribution of HAA-treated cells was not different from negative controls. Accumulation of abnormally high DNA content was not observed in the HAA-treated cells. Differences between monoHAAs and monoHANs in both DNA repair kinetics and cell cycle alteration suggested a fundamental difference in the mechanism of toxic action of these two classes of DBPs.

DNA damage induction, DNA repair, and cell cycle alterations by monohalogenated disinfection byproducts: Haloacetic acids and haloacetonitriles

248th National Meeting (2014)

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