National Primary Drinking Water Regulation for Six PFAS
In April 2024, the U.S. Environmental Protection Agency (EPA) announced National Primary Drinking Water Regulations (NPDWR) for six per-and polyfluoroalkyl substances (PFAS). The regulations established Maximum Contaminant Levels (MCLs) for PFOA, PFOS, PFNA, PFHxS, and HFPO-DA (also known as GenX chemicals) as individual contaminants, and will regulate PFNA, PFHxS, HFPO-DA, and PFBS as a mixture through a Hazard Index. MCLs are enforceable maximum regulatory levels of a compound allowed in drinking water. The rule is expected to reduce PFAS exposure in drinking water for millions of people, preventing thousands of deaths and significantly lowering the incidence of PFAS-related illnesses.
The rule requires:
- Public water systems (PWSs) to monitor for these six PFAS. Systems have three years to complete initial monitoring (by 2027), followed by ongoing compliance monitoring (PDF). Water systems must also provide the public with information on the levels of these PFAS in their drinking water beginning in 2027. Monitoring Fact Sheet (PDF)
- Public water systems have five years (by 2029) to implement solutions that reduce these PFAS if monitoring shows that drinking water levels exceed these MCLs.
- Beginning in five years (2029), public water systems that have PFAS in drinking water that violate one or more of these MCLs must take action to reduce levels of these PFAS in their drinking water and must provide notification to the public of the violation.
U.S. EPA Unregulated Contaminant Monitoring Rule
EPA uses the Unregulated Contaminant Monitoring Rule (UCMR) to collect data for contaminants that are suspected to be present in drinking water and do not yet have health-based standards set under the Safe Drinking Water Act (SDWA). A select number of public water systems (PWS) are sampled under the UCMR.
Testing for the Third Unregulated Contaminant Monitoring Rule (UCMR3) occurred from 2013-2015. The EPA included six PFAS in this round of testing. Among 35 water systems tested in New Mexico, UCMR3 sampling returned only a single PFAS detection for PFHpA.
- U.S. EPA Third Unregulated Contaminant Monitoring Rule (UCMR3) (PDF) (posted 1/8/20, data collected 2013-2015)
- U.S. EPA Fifth Unregulated Contaminant Monitoring Rule (UCMR5) (posted 3/11/26, data collected through 12/3/25)
*Note: UCMR results are provided in units of micrograms per liter (µg/L, equivalent to parts per billion). To convert results in µg/L to ng/L, multiply the value by 1,000. Click here for an EPA summary of UCMR5 data.
