EPA proposes to regulate PFAS in drinking water



On March 14, 2023, the United States Environmental Protection Agency (EPA) revealed its long-awaited proposal to regulate per- and polyfluoroalkyl substances (PFAS) under the Safe Drinking Water Act through issuance of a proposed National Primary Drinking Water Regulation (the Regulation) for six PFAS compounds. If finalized, the Regulation will establish the first Maximum Contaminant Level (MCL) to be promulgated under the Safe Drinking Water Act in decades. EPA has emphasized that establishing a national drinking water standard for PFAS is a top priority since releasing its PFAS Strategic Roadmap back in October 2021.

The Regulation proposes to establish nationwide, legally enforceable drinking water MCLs for six PFAS compounds. The proposed Regulation also sets non-enforceable, health-based Maximum Contaminant Level Goals (MCLGs) for the same six PFAS compounds. In support of its Regulation, EPA detailed numerous harmful health effects associated with consuming drinking water containing PFAS above certain levels.

Upon finalization, the proposed Regulation would require public water systems to monitor drinking water for these six PFAS, to reduce the levels of PFAS in drinking water if monitoring shows exceedances of the proposed standards, and to notify the public of the monitoring results.

The proposed Regulation does not require any specific action unless and until it is finalized, which EPA forecasts to occur by the end of 2023. Given the anticipated significant impact of the Regulation on public water systems, the Regulation proposes a compliance deadline of three years from finalization. 

EPA will accept public comments on the proposed Regulation for 60 days following publication in the Federal Register (on or before May 30, 2023). Comments can be provided at www.regulations.gov under Docket ID: EPA-HQ-OW-2022-0114.  EPA will also hold a public hearing on May 4, 2023, for the public to provide verbal comments. 

PFAS compounds

The six specific PFAS compounds that the Regulation covers include:

  • PFOA: perfluorooctanoic acid
  • PFOS: perfluorooctane sulfonic acid
  • PFNA: perfluorononanoic acid
  • GenX Chemicals: hexafluoropropylene oxide dimer acid (HFPO-DA)
  • PFHxS: perfluorohexane sulfonic acid
  • PFBS: perfluorobutane sulfonic acid

Maximum Contaminant Levels (MCLs)

An MCL is the maximum level of a contaminant or mixture of contaminants allowed to be present in drinking water delivered to any user of a public water system. To develop an MCL, EPA must consider the feasibility of and currently available analytical methods to measure and treat the chemical in drinking water. The Safe Drinking Water Act generally requires EPA to set MCLs as close to the MCLG (discussed below) as feasible.

For PFOA and PFOS, EPA has proposed an MCL of 4 parts per trillion (ppt) (4.0 nanograms/Liter). Significantly, EPA determined that this is the lowest feasible level possible, based on the ability to reliably measure and remove these contaminants from drinking water.

EPA has also proposed an MCL for the remaining four PFAS (PFNA, PFHX, PFBS, and GenX Chemicals) using a more complicated method that considers the additive effects of multiple PFAS when occurring together. Water systems would be required to use a hazard index approach to determine if the combined levels of any of these four PFAS pose a potential risk. The hazard index requires the use of an EPA calculator tool, using site-specific sampling results. A calculation resulting in a value greater than 1.0 would be considered an exceedance of the proposed MCL.

Maximum Contaminant Level Goals (MCLGs)

An MCLG is the maximum level of a contaminant in drinking water at which no known or anticipated adverse effect on the health of persons would occur, allowing for an adequate margin of safety. MCLGs are not enforceable, as they consider only public health and not the limits of detection or treatment technology effectiveness. 

With its Regulation, EPA has proposed setting an MCLG for PFOA and PFOS at zero – in effect determining that there is no safe level of PFOA and PFOS in drinking water. EPA stated that “[f]ollowing a systematic review of available human epidemiological and animal toxicity studies, EPA has determined that PFOA and PFOS are likely to cause cancer (e.g., kidney and liver cancer) and that there is no dose below which either chemical is considered safe.”

In summary, the MCLs and MCLGs proposed by the Regulation are:

PFAS Compound

Proposed MCL (enforceable)

Proposed MCLG


4.0 parts per trillion (ppt)



4.0 parts per trillion (ppt)


PFNA, PFHxS, PFBS, GenX Chemicals

1.0 Hazard Index (unitless)

1.0 Hazard Index (unitless)


Monitoring, public notice and follow-up actions

Similar to other contaminants regulated under the Safe Drinking Water Act, the Regulation also proposes monitoring, reporting, and remedial measures to ensure public water systems will meet the PFAS limits in the Regulation. Public water systems would be required to conduct initial monitoring for PFAS within three years of final promulgation of the Regulation. If monitoring reveals PFAS levels that exceed the proposed MCLs, a public water system would need to take action, such as installing additional water treatment, switching to a new uncontaminated source water or connecting to an uncontaminated water system. Public water systems would also be required to notify the public of any exceedances of the regulatory standards.


In discussing its health risk cost benefit analysis and associated determination that the benefits of the proposed rule justify the costs, EPA cites to the funds authorized by the Bipartisan  Infrastructure Law for assistance to disadvantaged communities or small systems where the costs of installation of treatment present challenges. Specifically, $9 billion was designated to invest in drinking water systems impacted by PFAS and other emerging contaminants. These funds are available primarily through the Drinking Water State Revolving Funds and through EPA’s new Emerging Contaminants in Small or Disadvantaged Communities Grant Program.

What’s next?

If the Regulation goes into effect, states delegated primacy to regulate their own programs under the Safe Drinking Water Act would be required to establish standards that are as strict as the federal rule. A number of states have already adopted their own state-based MCLs, which must be reconsidered if they are less stringent than EPA’s proposed levels. 

Some level of debate regarding EPA’s scientific basis for its proposed MCLs and MCLGs can be anticipated, as the Safe Drinking Water Act obligates EPA to use best available science when setting standards. Challenges to the proposed Regulation, and the costs of implementing it, are likely to follow.

While the brunt of the Regulation will fall on public water systems to implement, the impacts of the rule will surely be apparent across industries. 

How will this impact Ohio?

Ohio has not yet adopted its own state-based MCLs for any PFAS compounds. However, pursuant to Governor DeWine’s December 2019 Statewide PFAS Action Plan, Ohio EPA tested 1,500 public water systems across the state for PFAS in 2019 and 2020, the results of which Ohio announced in 2021. Ohio EPA tested for the same PFAS contaminants covered by the Regulation.  Ohio EPA set state action levels at 70 ppt for PFOA and PFOS (and other action levels set for the other four PFAS compounds, which ranged between 21 ppt for PFNA to 140,000 ppt for PFBS), and found two detections of PFAS above the state’s action levels; six percent of drinking water systems had detections of PFAS well below the action levels; and 94 percent had no detections. 

While the state’s action levels were consistent with EPA Health Advisory Levels at the time, they are now higher than EPA’s proposed Regulation (though the action levels for PFNA, PFBS, PFHxS, and GenX Chemicals do not directly translate to the Regulation’s Hazard Index method). Additionally, the state’s method reporting limits were at 5 ppt (except for GenX, which had a method reporting limit of 25 parts per trillion) – 1 ppt higher than the 4 ppt MCL proposed for PFAS and PFOS in the Regulation. 

Ohio EPA has stated that it is reviewing and evaluating EPA’s proposed PFAS Regulation documents.

Sources of information and additional resources:

Pre-Publication Federal Register Notice: PFAS National Primary Drinking Water Regulation
Fact Sheet: EPA’s Proposal to Limit PFAS in Drinking Water
Frequently Asked Questions and Answers: Proposed PFAS National Primary Drinking Water Regulation
Frequently Asked Questions and Answers: Proposed PFAS National Primary Drinking Water Regulation FAQ for Drinking Water Primary Agencies
Fact Sheet: Understanding the PFAS National Primary Drinking Water Proposal Hazard Index
Ohio EPA: PFAS in Drinking Water


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