Disinfection Byproducts: Health Risks, Occurrence, Control, and Implications for Regulatory Revision

ABSTRACT Research on drinking water disinfection continues to find both supporting and non‐supporting evidence that trihalomethanes (THMs) and haloacetic acids (HAAs) are causative agents for adverse human health effects such as bladder cancer and that they are appropriate surrogates for reducing adverse health effects through further regulation. The EPA is revising the microbial/disinfection byproduct (M/DBP) rules to further protect public health; however, the decision to change or add regulations is hindered by uncertainty about the causative agents of DBP‐associated risk and the role of compliance strategies to protect public health. Research conducted since the Stage 2 DBP rule was established helps fill some gaps and outlines lingering uncertainties that should be acknowledged as part of revised rulemaking. This thematic review summarizes regulatory implications of the state of the science in epidemiology, toxicology, occurrence/monitoring, and treatment/compliance, and identifies actions toward meaningful regulatory revisions despite ongoing uncertainty of DBP‐associated human health risk drivers.