EPA is proposing nationally uniform and federally enforceable limits on six per- and polyfluoroalkyl substances (PFAS) in drinking water for the first time. This marks a key milestone in EPA's PFAS roadmap and establishes an important structural support in the developing body of PFAS regulation.

On March 14, 2023, EPA announced that it will propose drinking water limits for perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) that will be set at the lowest level at which those substances can currently be accurately detected in water by recognized laboratory test methods. The proposed Maximum Contaminant Level (MCL) is 4 parts per trillion (ppt) for PFOA and PFOS. If these limits are finalized, they will be lower than any binding limit that any states have set for either PFOA or PFOS to date.

For four other PFAS chemicals (perfluorohexane sulfonate (PFHxS), hexafluoropropylene oxide dimer acid and its ammonium salt (GenX chemicals), perfluorononanoic acid (PFNA), and perfluorobutanoic acid (PFBS), EPA proposes to use a novel Hazard Index calculation (an approach currently applied by some states) to determine whether the combined levels of those chemicals in drinking water poses a risk to human health. EPA plans to provide an online tool to allow utilities and interested members of the public to calculate the Hazard Index based on sampling results.

EPA has estimated the annual cost to industry for compliance at $772 million, mainly associated with improvements needed by drinking water utilities to come into compliance with the new standards. The EPA estimates the broader economic benefits of the rule, chiefly from human health benefits, to be $1.2 billion. However, industry has already criticized EPA's cost calculations, estimating that the cost to address just PFOA and PFOS in drinking water systems will exceed $3.8 billion annually. There are also concerns that EPA's cost estimates do not include costs of compliance with non-drinking water regulations that may be triggered by the new drinking water limits.

The proposed drinking water standards are not enforceable yet. EPA's proposed rule was published in the Federal Register on March 29, 2023 (88 Fed. Reg. 18,638), and the public comment period is now open until May 30, 2023. EPA also plans to hold a virtual public hearing on the rule, which is currently scheduled for May 4, 2023. EPA is required to finalize the standards within 18 months of issuance of the proposal, but has stated its intent to finalize the rule by late 2023.


In the near-term, these proposed standards will impose compliance obligations and significant costs on public drinking water utilities. Under the Safe Drinking Water Act, public drinking water systems will have three years after the standards are finalized to come into compliance. If capital improvements are required, utilities may request an additional two years to comply.

Costs associated with coming into compliance are likely to be passed through to water users in the form of higher rates for potable water. However, federal funding may be available for many communities to address PFAS in their drinking water; the Bipartisan Infrastructure Law makes up to $9 billion available for communities impacted by PFAS and other emerging contaminants.

In the longer term, the new standards may create a very conservative basis for states or EPA to attempt to establish maximum PFAS concentrations for discharges that have the potential to impact drinking water sources, including groundwater and surface water discharge standards.

For example, where rivers and lakes have been identified as a "public drinking water supply," direct discharges or stormwater discharges into those bodies may be subject to new discharge limitations, and dischargers may be required to initiate a sampling protocol for PFAS. Further, EPA's drinking water standards will trigger lower allowable limits for PFAS in groundwater and surface water where states have set groundwater cleanup standards based upon federal MCLs.

Where it goes from here

Given the significant costs involved, and the adoption of the novel "Hazard Index" approach to set limits for multiple constituents of concern, EPA's proposed rule is likely to face significant legal challenges by states, water utility industry groups, and other interested parties when adopted.

Industry is likely to revisit arguments it raised in challenges to the lifetime drinking water health advisory levels (HALs) (which are non-regulatory, non-enforceable values) that EPA issued for PFOA, PFOS and GenX in June 2022. In particular, industry is expected to challenge what it has characterized as "deeply flawed science" behind the HALs and now the MCLs. Further, industry has signaled that it expects to challenge EPA's use of the Hazard Index to regulate two chemicals for which it has not completed risk evaluations.

In the meantime, businesses and utilities may want to consider whether there are benefits to commenting on the proposed regulation to address topics like cost of compliance. Businesses may also want to evaluate potential exposure to increasing PFAS regulation, enforcement, and litigation more generally.

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