March 14, 2023 / Comments (0)


Good morning State Administrators,

This morning at 10 AM ET, EPA 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. 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 typically 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. A breakdown of the MCLs and MCLGs is shown on the table below.

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.

The proposal has not yet been published in the Federal Register. The public will be given 60 days to provide comments after final publication, expected in the coming weeks. ASDWA will submit a 30-day extension request asking for a total of 90 days to provide comment. ASDWA expects that the extension will not be granted due to EPA’s desire to finalize the rule quickly. 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.

EPA has provided facts sheets for the public and FAQs specifically for primacy agencies to help with the rollout of this proposal. See the links below:

Additionally, ASDWA has contracted with WaterPIO to create our own communication materials to help states communicate with the public regarding these proposed regulations. We will be sending out the initial drafts of these materials later today. Due to the size of the documents, you will be receiving two separate emails. If you do not receive these emails by the end of the day, please let me know. We also intend to post them on the states-only section of our website. A link to that page will be sent out once it is ready. We anticipate making changes to these documents now that the rule has been proposed. In particular, the additional four PFAS were not included in these materials. If there is specific information you would like to see in later drafts of these materials, please let me know.

ASDWA staff will be reviewing the proposal closely over the coming days and will be working with our PFAS workgroup and the seven topical subgroups to draft ASDWA’s comments over the next two months. Please let me know if you have any questions. We’re in for a long sixty days!



Stephanie Schlea, Senior Water Policy Advisor | Association of State Drinking Water Administrators

1300 Wilson Blvd. Suite 875 | Arlington, VA | 703-812-4772 | [email protected] Twitter: @StephanieSchlea

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