Disinfection byproducts (DBPs) in chlorinated waters have been associated with adverse health outcomes such as bladder cancer. To quantify the toxic potency of various DBPs, cell-based in vitro assays using Chinese hamster ovary (CHO) cells have been conducted on &gt;100 individual DBPs to obtain LC50 values of these compounds. As the contribution of a DBP to the toxicity of disinfected waters depends on both the concentration and toxic potency of the compound, previous studies have weighted the measured concentrations of individual DBPs by the LC50 values of those DBPs. This approach has revealed that unregulated DBPs, such as haloacetonitriles (HANs) and haloacetamides (HAMs), may be more important toxicity drivers than are regulated DBPs. Furthermore, the sum of toxic potency-weighted DBP concentrations has been used as a metric to compare the quality of various conventional drinking and potable reuse waters. These calculations assume that DBP-associated toxicity is additive rather than synergistic or antagonistic, but little information is currently available regarding the interactions of unregulated DBPs in complex mixtures of DBPs. To assess whether the cytotoxicity of DBPs in mixtures is additive, we prepared 9 defined mixtures (each containing 11 to 29 DBPs) based on concentrations that were measured in different waters. We compared the observed cytotoxicity of defined DBP mixtures on CHO cells with the additive cytotoxity calculated using toxic potency-weighted DBP concentrations. This comparison shows that cytotoxicity is additive in most of the defined mixtures. Our results also confirm that unregulated DBPs contribute more significantly to the overall cytotoxicity of the mixtures than regulated DBPs. Overall, our findings support the validity of using the sum of toxic potency-weighted DBP concentrations as a metric to compare the DBP-associated toxicity of disinfected waters.

Disinfection byproducts (DBPs) in mixtures: Is cytotoxicity additive and what are the toxicity drivers?

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

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