It is universally acknowledged that drinking water disinfection byproducts (DBPs) can pose adverse health risks over long-term exposure, since epidemiological issues such as the induction of cancer and birth defects in human populations have been proved to be associated with the consumption of disinfected water. Regulation of DBPs from drinking water disinfection has focused upon trihalomethanes (THMs) and haloacetic acids (HAAs). Despite their ubiquitous occurrence, the members of these classes have been identified as unlikely to cause health risks of the magnitude that have been suggested by epidemiological data. On the other hand, some other emerging disinfection byproducts, such as the nitrogenous haloacetonitriles (HANs) and haloacetamides (HAMs) are identified as more genotoxic than the regulated compounds. Due to the unstable nature of these nitrogenous DBPs, there exists a distribution transition among DBPs classes over time from HANs to the corresponding HAMs and ultimately to HAAs, while the extent of this shift is governed by the choice of disinfectants, treatment conditions and residence time. The changing concentration of these DBPs will consequently lead to the changes in aggregate DBPs toxicity, which is of primary concern to drinking water management and regulation. Although comprehensive databases have been developed on the mammalian cell chronic cytotoxicity and acute genotoxicity of DBPs, this information has not generally been combined with data on temporal changes in the concentrations of HANs, HAMs and HAAs for the purposes of predicting time-based toxicity profiles of disinfected drinking waters. The purpose of this research was to establish mathematical predictive models of HAN, HAM and HAA formation and degradation kinetics based on circumstances of treatment and to develop toxicity profiles by combining specific toxicity of each DBPs class and the predicted concentrations from the established the kinetics model. The resulting toxicity profiles are of exceeding significance to drinking water managers to either help predict health risks posed by the amount and distribution of DBPs given the circumstances of treatment and disinfection, or to help optimize disinfection processes in terms of minimizing environmental and biological risks.

Kinetic toxicity profile of haloacetonitriles, haloacetamides, and haloacetic acids

249th National Meeting (2015)

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