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Exposure to disinfection byproducts (DBPs) in chlorinated drinking water has been positively associated with increased risk of colon, bladder, and rectum cancers. Iodinated DBPs (I-DBPs) are of concern as this class exhibits enhanced cytotoxicity and genotoxicity compared to those of chlorinated and brominated equivalents in Chinese hamster ovary (CHO) cells. We tested the impact of six I-DBPs on immortalized normal human colon epithelial cells (CCD 841 CoN). Our assay showed the following rank order of cytotoxicity of the I-DBPs: iodoacetic acid (IAA) > iodoacetamide (IAcAm) > bromoiodoacetamide (BIAcAm) > chloroiodoacetamide (CIAcAm) > bromoiodoacetic acid (BIAA) ≈ diiodoacetic acid (DIAA). The enhanced cytotoxicity of IAA compared with those of other haloacetic acids agrees with studies conducted on CHO cells. IAcAm was found to be 3.5 times more cytotoxic than BIAcAm and 9.4 times more cytotoxic than CIAcAm. The cytotoxicity of both dihaloacids (i.e., BIAA and DIAA) was <1% of that of the monohaloacid IAA. Apart from IAA, the nitrogenous I-DBPs demonstrated cytotoxicity greater than that of the carbonaceous I-DBPs. The results are consistent with previous CHO studies of dihalogenated I-DBPs but not monohalogenated ones. This study has implications for drinking water management strategies aimed at minimizing the formation of I-DBPs associated with enhanced cytotoxicity.

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The formation of disinfection byproducts (DBPs) in finished drinking water is an ongoing challenge for public health agencies and water utilities. The Fourth Unregulated Contaminant Monitoring Rule data were used to assess the prevalence and drivers of haloacetic acids (HAAs)—a class of DBPs—in New York State's (NYS) public water systems, with a focus on total measured (HAA9), regulated (HAA5), brominated (HAA6Br), and unregulated (HAA4) HAAs. The concentrations of all HAA groups in NYS are found to be similar to those nationally, with HAA4 composing approximately 20% of HAA9. Concentrations of all HAA groups are lowest in groundwater and highest in surface waters across NYS systems. Higher total organic carbon (TOC) concentrations lead to elevated HAA9 and HAA5, while higher bromide concentrations favor more HAA4 and HAA6Br. HAA4 concentrations are well predicted with pre‐oxidation/disinfection types, HAA5, TOC, and bromide concentrations, with an adjusted R2 of 70%.