Characterization and drivers of haloacetic acids in New York State

The formation of disinfection byproducts (DBPs) in finished drinking water is an ongoing challenge for public health agencies and water utilities. The Fourth Unregulated Contaminant Monitoring Rule data were used to assess the prevalence and drivers of haloacetic acids (HAAs)—a class of DBPs—in New York State's (NYS) public water systems, with a focus on total measured (HAA9), regulated (HAA5), brominated (HAA6Br), and unregulated (HAA4) HAAs. The concentrations of all HAA groups in NYS are found to be similar to those nationally, with HAA4 composing approximately 20% of HAA9. Concentrations of all HAA groups are lowest in groundwater and highest in surface waters across NYS systems. Higher total organic carbon (TOC) concentrations lead to elevated HAA9 and HAA5, while higher bromide concentrations favor more HAA4 and HAA6Br. HAA4 concentrations are well predicted with pre-oxidation/disinfection types, HAA5, TOC, and bromide concentrations, with an adjusted R² of 70%.