16 March 20238 minute read

EPA proposes first-ever PFAS drinking water maximum contaminant limits

On March 14, 2023, in the latest step in its PFAS Strategic Roadmap, the US Environmental Protection Agency (EPA) released its highly anticipated proposed rule which would establish the first-ever enforceable limits for PFAS in drinking water under the Safe Drinking Water Act (SDWA).

The rule would establish limits for six PFAS compounds – setting Maximum Contaminant Levels (MCLs) for PFOA and PFOS, individually, and for a mixture of one or more of PFNA, PFHxS, PFBS, and HFPO-DA and its ammonium salt (GenX chemicals), as follows:

  • For PFOA and PFOS: an MCL of 4 parts per trillion (ppt) and
  • For each, or any mixture containing one or more of PFNA, PFHxS, PFBS, and GenX: based on a combined Hazard Index (HI) formula that cannot exceed 1 (described below).

Given the significant debate over whether a technologically and economically feasible method actually exists to measure PFOA and PFOS at the low concentrations necessary to signal a potential public health risk, many had argued EPA would instead prescribe a “treatment technique” rather than an MCL. But EPA’s proposed rule concludes it believes such technology is available – a conclusion that is unsettled in the science community and is certain to receive pushback from, in particular, public water systems that will soon be required to use such technology to detect and treat the compounds.

Further, given that EPA set the non-enforceable PFOA and PFOS advisory levels for drinking water at “near zero” under the June 2022 Interim Updated Health Advisory Levels, which had been reduced from the combined 70 ppt Health Advisory Levels that reigned for the prior six years, it was hotly debated what limit EPA would find appropriate now. In the end, EPA proposes MCLs for PFOA and PFOS lower than any state-promulgated MCL to date and – as foreshadowed – proposes MCLs as a “mixture” for four additional PFAS, two of which EPA has not yet formally evaluated.

EPA’s approach is sure to garner extensive comments and, in many instances, opposition, from the science community, municipalities, water districts, non-government organizations, and industry stakeholders alike. EPA’s assertions surrounding an association between long-term exposure to certain PFAS compounds in drinking water and cancer, as well as a decrease in certain vaccine antibodies, in particular, will spur significant debate within the regulated and scientific communities.

A 60-day comment period for the proposed rule will go into effect as soon as it is published in the Federal Register.

How MCLs are created

Under the SDWA, EPA issues National Primary Drinking Water Regulations (NPDWRs), which include health goals, legally enforceable limits, and treatment techniques for drinking water contaminants. Through its NPDWRs, EPA first sets MCL goals (MCLGs), which are conservative risk-based health goals intended to represent the maximum level of a contaminant in drinking water at which no known or anticipated adverse effect on health would occur within an adequate margin of safety. MCLGs are non-enforceable levels that exclusively consider public health impacts and do not take technical detection limits or treatment technology effectiveness into account.

Once MCLGs are determined, EPA sets MCLs, which represent the enforceable maximum levels allowed of a contaminant in drinking water delivered to any public water system user. In addition to public health considerations, EPA must take both cost and technological feasibility into account when setting MCLs to ensure that the benefits of any new MCL justify the costs.

MCLs are risk-based limits grounded in a precautionary approach in which EPA incorporates considerable safety margins. EPA and other agencies are tasked with protecting all consumers, including those considered to be in sensitive populations, regardless of age, lifestyle, preexisting medical conditions, genetic profile, living conditions, working conditions, and other factors that may impact the interplay between an individual’s exposure to a contaminant and the manifestation of an injury. Hence, the existence of an MCL does not establish that a causal relationship exists between any single individual consumer’s injury and exposure to a contaminant in drinking water – many other factors are highly relevant when evaluating causation.

The proposed rule - EPA’s MCLGs and MCLs for six PFAS

The proposed rule applies to public water systems, which are systems that provide water for human consumption to at least 15 service connections or regularly serve at least 25 individuals.

EPA’s proposed MCLGs for PFOA and PFOS are both zero because EPA has concluded that both chemicals are likely carcinogens. Whether and to what extent this is reasonably supported by the published science is an ongoing debate that is certain to be a focal point of the comment period – including how EPA has relied on animal versus human studies and what, if any, conclusions may be extrapolated from such studies.

Based on EPA’s feasibility analysis, including what it describes as currently available analytical methods to measure and treat these chemicals in drinking water, the proposed rule would establish enforceable MCLs for PFOA and PFOS at 4 ppt each, respectively.

EPA also proposes a combined unitless 1.0 MCL for PFAS mixtures composed of one or more of PFNA, PFHxS, PFBS, and GenX. This MCL is based on an HI formula, through which public water systems would monitor and compare the amount of each of these four PFAS analytes in a mixture to their Health-Based Water Concentrations (the non-enforceable advisory levels set by EPA which represent the levels at which no health effects are expected), add the comparison values together, and determine whether the average HI value for samples taken in the past year exceeds the MCL’s 1.0 limit for PFAS mixtures. EPA purports to have selected the HI approach based on its review of recent science, which, according to EPA, suggests that low levels of multiple PFAS combined in a mixture act in a dose-additive manner which is allegedly expected to result in adverse health effects. The credence given to this “mixture” approach, and how it will be implemented and enforced, will also garner many questions from the regulated community. How EPA responds to comments, if at all, will elucidate the feasibility of implementing and enforcing this unique approach. 

The formula for calculating the HI for each collected sample may be found on EPA’s Fact Sheet.

The proposed rule will require public water systems to monitor drinking water for the six regulated PFAS. Where monitoring efforts determine that PFAS levels exceed the MCLs, public water systems must notify the public and take action to reduce PFAS levels through various treatment techniques or by switching to an alternative water supply that complies with the MCLs. EPA has identified activated carbon, anion exchange, and high-pressure membranes as proven technologies which can remove PFAS in drinking water and bring public water systems into compliance with the MCLs – messaging to water districts around the country that EPA believes PFAS can be feasibly, and cost-effectively, treated.  If history repeats, the public water systems will question this notion during the comment period.

EPA’s determination that technology exists to reliably test for the six PFAS compounds down to the prescribed MCLs and treat – on a large scale – drinking water sources down to the MCLs is expected to be a focus of debate in the coming months as to whether such technologies have been proven at the scale EPA would impose.

When will the MCLs go live?

EPA currently anticipates finalizing this regulation by the end of 2023 and will host two informational webinars about the proposed rule on March 16, 2023, and March 29, 2023. The formal public hearing will be held on May 4, 2023, where the Agency will accept verbal comments on the proposal.

If enacted, the PFAS SDWA limits will go into effect three years post-promulgation – or somewhere around 2026.

Looking ahead

The proposed PFAS SDWA MCLs indicate that EPA is, and will continue, to press ahead in implementing its multi-faceted Strategic Roadmap. The PFAS regulatory landscape will only continue to grow, as will the legal implications for entities throughout the US. It is crucial that stakeholders take direct, preemptive action to prepare.

DLA Piper’s PFAS Task Force coordinates lawyers across many practice areas, seamlessly integrating resources so that our breadth of knowledge and experience is deployed efficiently and effectively to counsel clients on matters across the US and internationally. Stay tuned for Part Two of this series on the PFAS SDWA rule and the legal implications companies may face as the regulatory and litigation landscape evolves.

For more information, please contact the authors.