Per- and Polyfluoroalkyl Substances (PFAS)

Final PFAS National Primary Drinking Water Regulation

Summary

On April 10, 2024, EPA announced the final National Primary Drinking Water Regulation (NPDWR) for six PFAS.  To inform the final rule, EPA evaluated over 120,000 comments submitted by the public on the rule proposal, as well as considered input received during multiple consultations and stakeholder engagement activities held both prior to and following the proposed rule. EPA expects that over many years the final rule will prevent PFAS exposure in drinking water for approximately 100 million people, prevent thousands of deaths, and reduce tens of thousands of serious PFAS-attributable illnesses.

EPA is also making unprecedented funding available to help ensure that all people have clean and safe water. In addition to the final rule, EPA announced $1 billion in available funding through the Infrastructure Investment and Jobs Act to help states and territories implement PFAS testing and treatment at public water systems and to help owners of private wells address PFAS contamination.

EPA established legally enforceable levels, called Maximum Contaminant Levels (MCLs), for six PFAS in drinking water: PFOA, PFOS, PFHxS, PFNA, and HFPO-DA as contaminants with individual MCLs, and PFAS mixtures containing at least two or more of PFHxS, PFNA, HFPO-DA, and PFBS using a Hazard Index MCL to account for the combined and co-occurring levels of these PFAS in drinking water. EPA also finalized health-based, non-enforceable Maximum Contaminant Level Goals (MCLGs) for these PFAS. 

Compound Final MCLG Final MCL (enforceable levels)1
PFOA Zero 4.0 parts per trillion (ppt) (also expressed as ng/L)
PFOS Zero 4.0 ppt
PFHxS 10 ppt 10 ppt
PFNA 10 ppt 10 ppt
HFPO-DA (commonly known as GenX Chemicals) 10 ppt 10 ppt
Mixtures containing two or more of PFHxS, PFNA, HFPO-DA, and PFBS

1 (unitless)

Hazard Index

1 (unitless)

Hazard Index

1 Compliance with MCLs is determined by running annual averages at the sampling point.

The final rule requires:

  • Public water systems must monitor for these PFAS and have three years to complete initial monitoring (by 2027), followed by ongoing compliance monitoring. Water systems must also provide the public with information on the levels of these PFAS in their drinking water beginning in 2027.
  • 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 which violates 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. 

Supporting Materials

General Information

Communications Toolkit

EPA has developed this toolkit of materials for  entities that need to communicate about PFAS.

Information for States, Tribes, and Water Systems

Regulatory Information

Webinars

EPA held three informational webinars for communities, water systems, and other drinking water professionals about the final PFAS NPDWR. The three webinar webinars were similar, with each intended for specific audiences. 

Background

Under the Safe Drinking Water Act, EPA has the authority to set enforceable National Primary Drinking Water Regulations (NPDWRs) for drinking water contaminants and require monitoring of public water systems. In March 2021, EPA published Regulatory Determinations for Contaminants on the Fourth Contaminant Candidate List which included a final determination to regulate PFOA and PFOS in drinking water. As a part of that final determination, EPA indicated it would also evaluate additional PFAS and consider regulatory actions to address groups of PFAS.

On March 24, 2023, EPA proposed the PFAS NDPWR. Concurrent with the proposed rule, EPA also announced preliminary regulatory determinations for PFHxS, PFNA, HFPO-DA, and PFBS in accordance with the Safe Drinking Water Act regulatory development process. EPA proposed to regulate PFOA and PFOS with individual MCLs and PFHxS, PFNA, HFPO-DA, and PFBS using a Hazard Index which accounts for co-occurring mixtures of these four PFAS. Concurrent with the final PFAS NPDWR announced on April 10, 2024, EPA also announced final individual regulatory determinations for PFHxS, PFNA, and HFPO-DA, and final regulatory determination for mixtures containing two or more of these three PFAS and PFBS. This regulation will also remove many other PFAS when they co-occur with these regulated PFAS. 

Further Information

To learn more about PFAS and to find important background information to support understanding the details of specific actions EPA takes to address PFAS and other emerging events related to PFAS.

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Last updated on February 19, 2025