EPA Releases Long-Awaited Proposed Regulation for PFAS Drinking Water Standards

Today (March 14), EPA announced and released the proposed National Primary Drinking Water Regulation (NPDWR) for PFOA and PFOS, along with four additional PFAS. EPA is proposing to set a Maximum Contaminant Level (MCL) of 4 parts per trillion (ppt) for PFOA and 4 ppt for PFOS, levels at which they can be reliably measured. In addition to these two MCLs, EPA is proposing to address four additional PFAS (GenX, PFBS, PFNA, and PFHxS) as a mixture using a Hazard Index. The Hazard Index is a tool used to evaluate potential health risks from exposure to chemical mixtures. This approach has been used in other EPA programs, such as the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), but this is the first time it has been used for a drinking water standard. Additionally, EPA is proposing Maximum Contaminant Level Goals (MCLGs) for each of the six PFAS. The MCLs and MCLGs are as follows.

PFAS Compound Proposed MCLG Proposed MCL
PFOA 0 ppt 4.0 ppt
PFOS 0 ppt 4.0 ppt

1.0 (unitless Hazard Index)


1.0 (unitless Hazard Index)


For the Hazard Index, the rule proposes a ratio for each of the four PFAS to be used to calculate a compliance value based on detected levels of the four PFAS. If the combination of those four ratios is at or above 1.0, then water systems will be expected to reduce the levels of these PFAS. Depending on the level of contamination found, water systems may need to take action even if only one of the four PFAS is present. EPA will be creating a webpage with a calculator tool for water systems to determine their Hazard Index.

Once the proposal is published in the Federal Register, the public will be given 60 days to provide comments. EPA will be holding two informational webinars about the proposed PFAS NDPWR on March 16, 2023, and March 29, 2023. The webinars will be similar, with each intended for specific audiences. Registration is required to attend. The webinar recordings and presentation materials will be made available following the webinars.

EPA will also be holding a public hearing on May 4, 2023, where members of the public can provide verbal comments to EPA on the rule proposal. Registration is required to attend and the last day to register to speak at the hearing is April 28, 2023.

Additionally, EPA has provided facts sheets for the public to help with the rollout of this proposal.