LEGAL UPDATE: EPA Announces Proposed National Primary Drinking Water Regulation (NPDWR)

English Lucas Priest and Owsley, LLP

On March 14, 2023, EPA announced the proposed National Primary Drinking Water Regulation (NPDWR) to establish legally enforceable levels, called Maximum Contaminant Levels (MCLs), for six PFAS in drinking water – PFOA and PFOS as individual contaminants, PFHxS, HFPO-DA (commonly referred to as GenX Chemicals), PFNA, and PFBS as a PFAS mixture. EPA is also proposing health-based, non-enforceable Maximum Contaminant Level Goals (MCLGs) for these six PFAS. A pre-publication version of the proposed rule can be found here.

The proposed MCLs for these six PFAS are as follows:

  • PFOS – 4 parts per trillion
  • PFOA – 4 parts per trillion
  • PFHxS, GenX Chemicals, PFNA, and PFBS Mixture – Hazard Index = 1.0
    • The Hazard Index is a tool used to evaluate health risks from simultaneous exposure to mixtures of certain chemicals. To determine the Hazard Index for these four PFAS, water systems would monitor and compare the amount of each PFAS in drinking water to its associated Health Based Water Concentration (HBWC), which is the level below which no health effects are expected for that PFAS. Water systems would add the comparison values for each PFAS contained within the mixture. If the value is greater than 1.0, it would be an exceedance of the proposed Hazard Index MCL. EPA intends to provide water systems with a web-based form that will automatically calculate the Hazard Index.

The proposed rule would also require public water systems to:

  • Monitor. EPA proposes monitoring requirements for the six PFAS that build upon EPA’s existing monitoring frameworks under which monitoring frequency depends on previous results.
  • Notify consumers. Public water systems would be required to notify the public if monitoring detects these PFAS at levels that exceed the proposed regulatory standards.
  • Treat to achieve the MCLs. Public water systems would be required to take actions to reduce the levels of these PFAS in drinking water if they exceed the proposed regulatory standards. This could include removing the chemicals through various types of treatment or switching to an alternative water supply that meets the standard.

The proposed PFAS NPDWR does not require any actions until it is finalized. EPA anticipates finalizing the regulation by the end of 2023. The public comment period for the NPDWR will be open for 60 days from the date that the proposed rule is published in the Federal Register.

EPA is hosting an informational webinar for Drinking Water Professionals on March 29, 2023 from 2-3 PM (ET). Registration is required.

EPA also plans to hold a virtual public hearing on May 4, 2023. Registration is required to attend the public hearing. The last day to register as a speaker is April 28, 2023.


Sarah P. Jarboe

Sarah P. Jarboe is a partner in the law firm of English, Lucas, Priest & Owsley, LLP and one of Kentucky's leading attorneys in the practice of Environmental Law. As part of her practice, Sarah has represented clients in permitting and policy issues and enforcement actions. She has advised clients on various environmental matters, including the Clean Air Act, the Clean Water Act, the Underground Injection Control Program under the Safe Drinking Water Act, the Comprehensive Environmental Response, Compensation, and Liability Act (Superfund), Oil Pollution Act, and the Resource Conservation and Recovery Act, and the Nonindigenous Aquatic Nuisance Prevention and Control Act.