Comparative Nontargeted Analysis and Toxicity of Brominated Disinfection Byproducts from Chlorination and Chloramination of Natural Organic Matter

Brominated disinfection byproducts (Br-DBPs) generated during water treatment pose significant health risks due to their high toxicity. This study conducted a comparative nontargeted analysis of Br-DBPs generated during chlorination and chloramination using ultra-performance liquid chromatography (UPLC) coupled with high-resolution (HR) mass spectrometry (MS), including MS and tandem MS experiments. An advanced halogen extraction code identified halogenated compounds via isotopic patterns of chlorine (Cl) and bromine (Br), with MFAssignR assigning molecular formulas. Chlorination resulted in a total of 154 Br-DBPs, most containing carbon, hydrogen, oxygen, and bromine (CHOBr), whereas chloramination generated 79 Br-DBPs, predominantly nitrogenous Br-DBPs (CHONBr), including 57 CHOBr and 22 CHONBr, effectively preserving aromatic structures within natural organic matter (NOM). Several Br-DBPs with strong instrument responses, including brominated aliphatic carboxylic acids and aromatic phenolic acids formed primarily during chlorination, were identified, whereas nitrogenous Br-DBPs were exclusive to chloramination. In silico toxicity assessments indicate that many Br-DBPs identified in this study, particularly those with multiple bromine substitutions and functional groups such as nitro and carboxylic acids in aromatic structures, exhibit substantially higher acute toxicity and mutagenic potential compared to regulated DBPs like bromoform and dibromacetic acid. These findings highlight the need to prioritize polybrominated, aromatic, and nitrogenous Br-DBPs in water treatment research and regulation.