Over 700 DBPs are known; U.S. EPA regulates 11. Of these regulated DBPs, the trihalomethanes (THMs) are employed as indicators of exposure in epidemiological studies for adverse human health effects. Over the past 15 years analytical chemical and analytical biological analyses of over 130 DBPs revealed that many unregulated DBPs were more toxic than those regulated by the EPA. In general, DBPs express additivity of their toxicity based on their concentration; this allowed for the development of predictive quantitative structure activity relationship models. Using these analytical approaches, the regulated THMs and haloacetic acids were not the drivers of toxicity in disinfected water. Iodinated DBPs and nitrogenous DBPs (N-DBPs) were the major drivers of cytotoxicity, genotoxicity and altered adverse gene expression pathways in biological systems. These data question if we are regulating the correct DBPs to protect human health. Employing new cytotoxicity and genotoxicity information integrated with TIC-Tox additivity models the haloacetonitriles emerged as a major class of forcing agents of toxicity. Using a Precautionary Principle approach the regulation of this class of N-DBPs should be considered. In addition to THMs, the use of N-DBPs as exposure markers in epidemiological studies may provide higher levels of resolution in defining human health risks.

Regulated DBPs are not the forcing agents of toxicity in disinfected water

ACS Fall 2021

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