On April 10, 2024, U.S. EPA announced a National Primary Drinking Water Regulation (NPDWR) establishing legally enforceable Maximum Contaminant Levels (MCLs) and non-enforceable Maximum Contaminant Level Goals (MCLGs) for six per- and polyfluoroalkyl substances (PFAS) in drinking water under the Safe Drinking Water Act (SDWA).

The final rule requires public water systems to: (1) complete initial monitoring for these PFAS by 2027 and provide public notice of initial monitoring results beginning in 2027; (2) implement solutions by 2029 to reduce these PFAS if drinking water levels exceed the MCLs; and (3) starting in 2029, take action to reduce PFAS in response to violations of the MCLs and to provide public notice of any such violations. EPA PFAS NPDWR Summary.

A pre-publication version of EPA’s final rule is available here.

Why is EPA Concerned About PFAS?

PFAS are a class of manmade chemicals that have been used in industry and consumer products since the 1940s because of their useful properties, including resistance to heat, fire, stains, and water. Despite their usefulness, PFAS have been linked to serious health concerns, such as cancer, and have been detected in water, soil, air, food, household, workplace materials, and blood across the world.

In light of the known harmful effects of PFAS exposure, EPA’s goal is to “provide health protection against these individual and co-occurring PFAS in public water systems”. Pre-Publication Final Rule, pg. 3. Despite recent efforts to limit and/or phase out PFAS use in the United States, the chemicals are still widely present in the environment and in humans. Id.

The EPA examined drinking water and determined that PFAS can be found in varying combinations: “The high likelihood for different PFAS to co-occur in drinking water; the additive health concerns when present in mixtures; the diversity and sheer number of PFAS; and their general presence and persistence in the environment and the human body are reflective of the environmental and public health challenges the American public faces with PFAS, which poses a particular threat for overburdened communities that experience disproportionate environmental impacts.” Id. at 4.

The following table contains the six PFAS subject to EPA’s final rule as well as the  MCLs and MCLGs for each PFAS:

As stated, only the MCLs are legally enforceable standards. The MCLGs are non-enforceable and merely reflect EPA’s desired goals for PFAS levels. EPA PFAS NPDWR Summary.

The Hazard Index MCLs account for mixtures of PFAS that include two or more of PFHxS, PFNA, HFPO-DA, and PFBS. Pre-Publication Final Rule, pg. 5. “The Hazard Index [(HI)] is a long-established approach that EPA regularly uses to understand health risk from chemical mixture. The HI is made up of a sum of fractions. Each fraction compares the level of each PFAS measured in the water to the highest level determined not to have risk of health effects.” EPA PFAS FAQs, pg. 2.


EPA’s final rule highlights the government’s focus on PFAS exposure and associated health risks. EPA expects this rule to reduce PFAS exposure for roughly 100 million Americans. PFAS Final Rule Fact Sheet, pg. 2.

Public drinking water systems are officially on the clock to start monitoring and addressing PFAS contamination in their drinking water, which will require substantial efforts and costs. EPA expects compliance with this rule to cost roughly $1.5 billion annually. Id. In light of such costs, the Biden-Harris Administration and EPA have announced billions of dollars in available funding to help states and their drinking water utilities comply with this final rule. Id. at 2-3. More information about this funding is available here.  Taft and its legal team is also assisting and representing water providers across the county in litigation to hold the proper parties responsible for theses costs.  To date, settlements valued at over $14 billion already have been reached through those litigation efforts. 

“EPA estimates that between about 6% to 10% of the 66,000 public drinking water systems subject to this rule may have to take action to reduce PFAS to meet these new standards.” EPA PFAS Press Release. States and their affected drinking water systems should closely review EPA’s final rule and begin taking steps to monitor and address PFAS contamination in compliance with this rule.

For further information on potential litigation options to recover costs associated with complying with these new rules, contact a member of Taft’s Environmental group.