Occurrence, cytotoxicity contribution, and formation characteristics of iodinated phenolic disinfection byproducts in drinking water.

Recently iodinated disinfection byproducts (DBPs) have received increasing attention due to their high toxicity. Iodinated phenolic DBPs have been identified in drinking water, but their occurrence, toxicity contribution and formation characteristics have not been clarified. In this study, four categories of iodinated phenolic DBPs were investigated, including iodinated phenols (IPs), iodinated nitrophenols (INPs), iodinated hydroxybenzaldehydes (IHBALs), and iodinated hydroxybenzoic acids (IHBAs). Their occurrence and cytotoxicity contribution in drinking water were examined and their formation characteristics were explored. The results reveal that 17 iodinated phenolic DBPs were present in tap water with concentrations of 0.13-2.54 ng/L. The IPs in tap water exhibited relatively high concentrations and cytotoxicity contribution among the four categories of iodinated phenolic DBPs. The total concentrations and DBP-associated cytotoxicity of iodinated phenolic DBPs in chloramination were significantly higher than that in chlorination, while trihalo-phenols, dihalo-nitrophenols/hydroxybenzaldehydes/hydroxybenzoic acids were the dominant species in the chloraminated drinking water samples. The formation of iodinated phenolic DBPs in chloramination followed pseudo-first-order kinetics and the formation rate constants of IPs were higher than INPs, IHBALs, and IHBAs. Additionally, the total concentrations and DBP-associated cytotoxicity of iodinated phenolic DBPs in chloramination were affected by the monochloramine dose, bromide/iodide concentration, pH and temperature.