Addressing contaminants of emerging concern in the United States public water systems.

Contaminants of emerging concern (CECs) represent a growing yet inadequately governed threat to drinking water safety in the USA. Advances in analytical technologies have detected widespread, low-level contamination from substances like per- and polyfluoroalkyl substances (PFAS), pharmaceuticals, agrochemicals, and personal care products. This raises concerns about the long-term health of humans and ecosystems. Despite growing scientific knowledge, regulatory and policy frameworks have lagged, leading to uneven protections across public water systems. Here, we assess the policy and regulatory infrastructure related to CECs nationwide across all 50 states. Only four states (8%), California, Maine, Wisconsin, and Vermont, had strong, multi-CEC policy infrastructure with enforceable standards, systematic monitoring, and investments in advanced treatment. Many states (36; 72%), distributed across regions, exhibited moderate capacity, typically focusing on PFAS rather than on comprehensive CEC management. In contrast, ten states (20%), mainly in the South and rural West, exhibited poor policy infrastructure with limited regulation, technology, and weak enforcement. These disparities reveal substantial geographic and institutional gaps in drinking water governance. By comparing US and international policies, we propose phased, practical recommendations that combine precautionary regulation, polluter accountability, innovation incentives, and transparency. These steps aim to update drinking water governance to match current chemical challenges, safeguard vulnerable communities, and prepare US water systems for an expanding list of emerging contaminants.