Join our mailing list to receive the latest updates and alerts Flag Subscribe

The U.S. Environmental Protection Agency (EPA), on April 10, 2024, issued a final rule establishing National Primary Drinking Water Regulations (NPDWR) for per- and polyfluoroalkyl (PFAS) chemicals. See Pre-Publication Version, 40 C.F.R. pts. 141 & 142. The new regulations establish the agency’s first drinking water standards addressing PFAS chemicals, a group of several thousand synthetic chemicals that persist in the environment and have adverse impacts upon human health and the environment. The new standards—which become effective 60 days after publication in the Federal Register—will have significant ramifications for drinking-water providers and other regulated parties.

EPA’s PFAS Drinking Water Standards

The final rule establishes legally enforceable levels, called Maximum Contaminant Levels or MCLs, for the maximum amount of five individual PFAS in drinking water. The rule also sets a Hazard Index MCL for a mixture of two or more of four PFAS chemicals. A “Hazard Index” is a sum of fractions that compares the level of each PFAS to the highest level below which there is no health effect; it is designed to account for the additive health impacts of exposure to mixtures of chemicals. The rule also sets an unenforceable Maximum Contaminant Level Goal (MCLG) for the same six categories.

The EPA enacted this rule under the Safe Drinking Water Act (SDWA), 42 U.S.C. § 300f et seq., which authorizes the agency to set drinking water standards that must be met by any “public water system,” i.e., “a system for the provision to the public of water for human consumption through pipes or other constructed conveyances, if such system has at least fifteen service connections or regularly serves an average of at least twenty-five individuals.” 42 U.S.C. § 300f(4). “Public water systems” include not only municipal drinking water plants that supply tap water, but also more localized facilities which may have their own drinking water systems, such as some schools, factories, office buildings, campgrounds or hospitals. In Minnesota, the SDWA is implemented by the Department of Health.

MCLGs represent the maximum level of a contaminant in drinking water at which no known or anticipated adverse effect on human health would occur, factoring in an adequate margin of safety. MCLGs are established based solely on public health, and do not consider the limits of detection or treatment technologies. By contrast, the enforceable MCLs represents the “maximum permissible level of a contaminant in water which is delivered to any user of a public water system.” 42 U.S.C. § 300f(3). Under the SDWA, the MCL must be set at the level that is as close as possible to the MCLG, while factoring in the types of treatment technology that may be available as well evaluating the costs and benefits. See 42 U.S.C. § 300g-1. EPA’s MCLs and MCLGs in the new regulations are as follows:

PFAS Chemical

Enforceable Maximum Contaminant Level (MCL)

Maximum Contaminant Level Goal (MCLG)


4.0 ppt



4.0 ppt



10 ppt

10 ppt


10 ppt

10 ppt

HFPO-DA (or GenX chemicals)

10 ppt

10 ppt

A mixture of two or more of the following: PFNA, PFHxS, HFPO-DA, and PFBS

Hazard Index of 1

Hazard Index of 1

Public Water Systems have five years to comply with the MCLs. In addition to establishing these standards, EPA’s final rule imposes other requirements on public water system operators, including (a) PFAS monitoring requirements, (b) a requirement to notify the public if monitoring detects PFAS levels that exceed the MCLs after 2029, and (c) a requirement for public water systems to install PFAS treatment systems or take other actions to reduce the levels of these PFAS if they exceed the MCLs.

Notably, the standards set by the EPA in the final rule go beyond the proposed rule by establishing individual MCLs for PFNA, PFHxS and HFPO-DA; the proposed rule only included them in the Hazard Index standard for a mixture of these PFAS. To support implementation of the new rule, the EPA also announced $1 billion in new funding for implementing PFAS testing and treatment at public water systems, and to help owners of private wells in addressing PFAS contamination.

Ramifications of the New PFAS MCLs

The ramifications of the new PFAS MCLs will be felt most keenly by municipal and other operators of public water systems. Municipalities have long argued that existing and proposed funding for infrastructure improvements will not be sufficient to cover the extreme costs of PFAS-removal treatment to meet the proposed PFAS standards. A March 4, 2024, editorial by four U.S. mayors gives a sense of the potential costs for one operator of a public water system, the city of Columbia SC, to meet the proposed standards:

For the City of Columbia, South Carolina, implementing this new MCL limit would require adding new treatment capabilities estimated to cost the municipality $150 million. On top of that, the additional operation and maintenance costs would be $20 million annually, increasing annual treatment costs from $17 million to $37 million. Columbia’s water system is expansive, but the system’s revenue will not be able to cover these extreme upgrades to be in compliance. Therefore, ratepayers—the citizens of Columbia—will have to help foot this hefty bill.

—Daniel Rickenmann, et al, “EPA Has Miscalculated a Major Water Pollution Problem” (Real Clear Policy, 3-4-2024).

In addition, the new MCLs are likely to have ramifications beyond public water systems. For example, in Minnesota, the state’s Class 1 water quality standards in Minn. R. 7050.0221 incorporate the federal MCLs by reference; that is, the federal MCLs, with minor exceptions, are Minnesota’s Class 1 water quality standards. The language of part 7050.0221 suggests that the new PFAS MCLs, once they become effective, will constitute Class 1 water quality standards in Minnesota, meaning they could be enforced in waters that have the Class 1 designation (including groundwater) and potentially translated into water discharge permit limits.

A second example is that the remediation goals set in CERCLA remedial action plans are often based on “Applicable or Relevant and Appropriate Requirements.” MCLs are often used as ARARs for impacted groundwater or surface waters, meaning that at least some CERCLA cleanups could be required to attain the PFAS MCLs. Additionally, many states, including Minnesota, consider MCLs when determining groundwater cleanup levels at contaminated sites.

Jump to Page

Necessary Cookies

Necessary cookies enable core functionality such as security, network management, and accessibility. You may disable these by changing your browser settings, but this may affect how the website functions.

Analytical Cookies

Analytical cookies help us improve our website by collecting and reporting information on its usage. We access and process information from these cookies at an aggregate level.