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Alerts and Updates

Proposed EPA Rule Sets PFAS Limits for Public Drinking Water

March 15, 2023

Proposed EPA Rule Sets PFAS Limits for Public Drinking Water

March 15, 2023

Read below

The proposed rule would also require compliance within three years of promulgation. 

On March 14, 2023, the Environmental Protection Agency (EPA) announced a proposed new National Primary Drinking Water Regulation (NPDWR), which standardizes and sets the legally enforceable maximum contaminant levels (MCLs) of six per- and polyfluoralkyl substances (PFAS) in drinking water. The proposed regulation also sets nonenforceable maximum contaminant level goals (MCLGs).

The Safe Drinking Water Act vests the EPA with authority to set a national standard for maximum allowable drinking water contaminants. The proposed NPDWR comes in the wake of the EPA’s March 2021 final determination to regulate PFOA and PFOS—which also included an initial determination to regulate PFNA, HFPO-DA, PFHxS and PFBS (defined below).

The proposed rule sets MCLs and MCLGs for the following PFAS:

  • Perfluorooctanoic acid (PFOA)
  • Perfluorooctane sulfonic acid (PFOS)
  • Perfluorononanoic acid (PFNA)
  • Hexafluoropropylene oxide dimer acid (HFPO-DA)[1]
  • Perfluorohexane sulfonic acid (PFHxS)
  • Perfluorobutane sulfonic acid (PFBS). 

The below table depicts the MCLs and MCLGs set forth in the proposed NPDWR:



Proposed MCLG

Proposed MCL


0.0 ppt

4.0 ppt


0.0 ppt

4.0 ppt


1.0 (unitless)[2]

1.0 (unitless)


The NPDWR—in addition to setting MCLs and MCLGs—would require public water system operators to monitor for these PFAS, inform the public of the PFAS levels and take remedial action if any PFAS level exceeds the MCLs.

The proposed rule would also require compliance within three years of promulgation. Water system operators serving more than 10,000 people may comply by demonstrating baseline PFAS concentration using quarterly sampling data over a year. Water system operators serving fewer than 10,000 people may comply by showing baseline PFAS from two samples collected at least 90 days apart. System operators currently using an FDA-approved method for testing and sampling will not be required to conduct separate initial PFAS monitoring, testing or sampling.

In addition to sampling and testing requirements, the proposed rule would require water system operators to report the test results to the operative state. These reports must include the location, number of samples, date and results from previous sampling. Additionally, such reports must detail whether the water system has levels above the MCLs provided. Violations will be determined by an annual average of the test results of each sampling location.

The proposed rule identifies certain technology—granular activated carbon, anion exchange and high pressure membranes—as the preferred technology to remediate contamination. According to the EPA, such technologies are capable of high removal efficiency, have a proven history of removal on a large scale, are generally available, have a reasonable cost, have a reasonable service life, are compatible with other water treatment processes, and have the ability to bring all water into compliance.


The proposed rule’s MCLs are lower than the MCLs prescribed by states that are already regulating PFAS in drinking water, and the rule also includes additional PFAS that are not regulated by many states. For example, Pennsylvania’s MCL for PFOA is 14 ppt and 18 ppt for PFOS, and the state does not set the drinking water MCL for PFNA, PFBS, PFHxS or HFPO-DA. Neighboring New Jersey’s MCL for PFOA is 14 ppt and 13 ppt for PFOS and for PFNA, but the state has no drinking water MCL for PFBS, PFHxS or HFPO-DA.

If promulgated, the NPDWR would unify an otherwise disjointed set of state-specific PFAS regulations and require public water suppliers in states that currently have no MCLs for PFAS in drinking water to adopt policies and procedures for compliance.

While the proposed rule would affect only public water suppliers, it may serve as a preview for additional EPA regulations concerning PFAS. The proposed rule recognizes that statutory authority—other than the Safe Water Drinking Act—exists that may have direct implications for drinking water. The rule highlights that the EPA is currently addressing PFAS in the context of the Toxic Control Substances Act, the Clean Water Act and the Clean Air Act. Additionally, the EPA is committed to additional research on PFAS, as well as moving forward with enacting new ways to treat, remediate, destroy and dispose of these chemicals. With this in mind, manufacturers that currently use PFAS in their products need to pay close attention to the EPA’s publications and potential forthcoming regulations that may limit or otherwise detail actions manufacturers must take with respect to PFAS.

Upon publication, the EPA will accept comments on the proposed NPDWR and, on May 4, 2023, will hold a public hearing where members of the public can register to attend and provide verbal comments on the proposed rule.

About Duane Morris

Duane Morris has an active PFAS team to help organizations and individuals plan, respond to and execute on PFAS issues and initiatives in order to manage risk, ensure compliance and minimize litigation risk. We are available to discuss your concerns and objectives and how new rules, regulations and rulings might apply to you.

For More Information

If you have any questions about this Alert, please contact Lindsay Ann Brown, Brad A. Molotsky, Sharon L. Caffrey, Alyson Walker Lotman, Ethan R. Feldman, any of the attorneys in our Products Liability and Toxic Torts Group, any of the attorneys in our Environmental Group or the attorney in the firm with whom you are regularly in contact.


[1] HFPA-DA is commonly known as the GenX chemical.

[2] The proposed rule uses a hazard index approach to quantify the MCL for PFNA, PFHxS, PFBS, and HFPO-DA. According to the proposed rule, the EPA suggests this approach because such compounds are known to co-occur, and the presence of one of these chemicals on its own likely does not rise to health risk, but, taken together, the aggregate is likely to result in a health risk. The proposed rule sets forth the way to calculate the hazard index for these chemicals.

Disclaimer: This Alert has been prepared and published for informational purposes only and is not offered, nor should be construed, as legal advice. For more information, please see the firm's full disclaimer.