Proposed rule · 2026-13263

Revisions To Establish the Sixth Unregulated Contaminant Monitoring Rule (UCMR 6) for Public Water Systems

The U.S. Environmental Protection Agency (EPA or agency) is proposing the sixth Unregulated Contaminant Monitoring Rule (UCMR 6). Under the Safe Drinking Water Act (SDWA), the UCMR program gathers data about unregulated contaminant occurrence in drinking water. The proposed UCMR 6 would require public water systems (PWSs) to collect national occurrence data for seven ultrashort organofluorine compounds (including certain PFAS), three pesticide metabolites, 13 semivolatile organic compounds, and seven purgeable organic compounds. Subject to the availability of appropriations, the EPA will require all community and non-transient non-community water systems (CWSs and NTNCWSs) serving 3,300 or more people, and a representative sample of PWSs serving fewer than 3,300 people, to conduct monitoring. These contaminants are not currently subject to national primary drinking water regulations (NPDWRs), and the EPA is proposing to require the collection of drinking water occurrence data to inform agency decisions. The data collected will be publicly available. The EPA is also announcing two public meetings (via webinar) to discuss this proposal of the sixth Unregulated Contaminant Monitoring Rule (UCMR 6).