Safe Drinking Water Act (SDWA) specifies that every five years EPA is required to monitor for priority contaminants that may be present in drinking water but are not yet subject to EPA drinking water regulations. EPA uses the Unregulated Contaminant Monitoring Rule (UCMR) to provide the agency and other interested parties with nationally representative data on the occurrence of contaminants in drinking water, the number of people potentially being exposed, and an estimate of the levels of that exposure. These data can support future regulatory determinations, the development of national primary drinking water regulations (NPDWRs), and other actions to protect public health. EPA’s Fifth Unregulated Contaminant Monitoring Rule (UCMR 5) requires sample collection for 30 chemical contaminants (29 PFAS and lithium) between 2023 and 2025 using analytical methods developed by EPA and consensus organizations.

Today, the U.S. Environmental Protection Agency released the first set of data collected under the fifth Unregulated Contaminant Monitoring Rule (UCMR 5) one of the actions in EPA’s PFAS Strategic Roadmap.  This data is designed to the understanding of the frequency that 29 PFAS and lithium are found in the nation’s drinking water systems, and at what levels. The monitoring data on PFAS and lithium will help EPA make determinations about future actions under the Safe Drinking Water Act.

This initial data release represents approximately 7% of the total results that EPA expects to receive over the next three years. EPA intends to update the results quarterly and share them with the public in EPA’s National Contaminant Occurrence Database (NCOD) until completion of data reporting in 2026.

In March 2023, EPA proposed standards to limit certain PFAS in drinking water. The proposal, if finalized, would allow public water systems to use results from UCMR 5 to meet the rule’s initial monitoring requirements and to inform communities of actions that may need to be taken. In the interim period before the PFAS drinking water standard is final, EPA has established Health Advisories for four PFAS included in the UCMR 5.

For more information visit EPA’s Ground Water and Drinking Water webpage.