The EPA has a new, enforceable definition for PFAS. What does it actually cover?


Oct. 04, 2023

As part of its new PFAS reporting rule, the Environmental Protection Agency has published a newly enforceable definition of PFAS that significantly increases the number of chemicals covered by the definition, and therefore, the rule. This AgencyIQ analysis will review the new definition compared to previous agency definitions, and what it may mean for future agency policy.

PFAS and the EPA

  • Per- and polyfluoroalkyl substances (PFAS) are a wide group of synthetic chemicals that do not occur naturally in the environment and have been produced since the 1940s. PFAS contain at least one alkyl carbon with its hydrogen atoms replaced by fluorine atoms. Carbon-fluorine bonds are some of the strongest in nature, leading to wide adoption of PFAS for a diverse array of industrial and commercial uses since the chemicals began to be produced. However, this has also led to those PFAS not readily breaking down under traditional environmental stressors and persisting in the environment. Certain PFAS may also bioaccumulate in humans and remain in the body for long periods of time.
  • Under the Toxic Substances Control Act (TSCA) section 8(a)(1), the Environmental Protection Agency (EPA) may require entities who manufacture or process certain substances to submit reports of those substances to the EPA. This can include a suite of information, such as the chemical identity and molecular structure of the chemical, categories of use, total amount of the substance manufactured or processed, and more.
  • In the National Defense Authorization Act (NDAA) for fiscal year 2020, Congress required the EPA to issue a rule under TSCA section 8(a)(7) that would require any person who has manufactured or imported PFAS since 2011 to report a wide range of information to the agency. The EPA published a proposed rule for the reporting structure on June 28, 2021, which provided a basic overview of what the rule could look like.
  • The EPA issued a prepublication version of the final rule on September 28, 2023. The finalized rule will be published in the Federal Register, which will begin the information collection period 30 days after the rule is published in the Federal Register. AgencyIQ put together a detailed review of the major sections of the rule, available for subscribers here.

Older definitions

  • In the proposed rule, the EPA used a structural definition to define PFAS. The action defines the scope of reportable chemicals as per- and polyfluorinated substances that structurally contain the unit R-(CF2)-C(F)(R′)R″. Both the CF2 and the CF moieties (distinct parts of the molecule) must be fully saturated carbons, and none of the R groups listed can contain hydrogens. This definition was based off the same definition that the EPA’s Office of Pollution Prevention and Toxics (OPPT) had used when identifying PFAS to place on the TSCA Inventory.
  • On June 28, 2023, the EPA published a framework for how it planned to address new PFAS and new uses of PFAS. Under the framework, the EPA will expect that new PFAS and new uses of PFAS will be considered persistent in the environment based on carbon-fluorine bonds, but additionally notes that many PFAS may also be considered bioaccumulative and toxic, making them PBT chemicals which will receive additional regulation from the EPA. In addition, the agency provided yet another structural definition. In this definition, the EPA determined a “PFAS” was a chemical that included any of the following three structures: (1) R–(CF2)–CF(R′)R″, where both the CF2 and CF moieties are saturated carbons; (2) R–CF2OCF2–R′, where R and R′ can either be F, O, or saturated carbons; or (3) CF3C(CF3)R′R″, where R′ and R″ can either be F or saturated carbons. However, this was not an “enforceable” definition in the traditional sense as it was released as a non-binding guidance, rather than a rule itself.

New definitions

  • In the new rule, the EPA utilizes the same definition from the framework as the new, enforceable definition for PFAS. Under the finalized rule, “PFAS” were defined as any chemical that includes at least one of the following three structures: (1) R-(CF2)-CF(R’)R’’, where both the CF2 and CF moieties are saturated carbons; (2) R-CF2OCF2-R’, where R and R’ can either be F, O, or saturated carbons; and (3) CF3C(CF3)R’R’’, where R’ and R’’ can either be F or saturated carbons.
  • The new definition removed R group requirements from the proposed rule’s definition to include additional substances that may be persistent. The EPA explained that the proposed rule’s definition was developed to focus on substances that are most likely persistent in the environment, it did not cover substances that are “lightly fluorinated.” A “lightly fluorinated” substance contains only unconnected CF2 or CF3 moieties but may similarly be persistent in the environment despite not be a fully fluorinated substance. The agency stated that the persistence of these substances is more related to the density and number of carbon-fluorine bonds within a target molecule, rather than the existence of fully fluorinated carbon rings. The definition notably does not include substances that only have a single fluorinated carbon, such as fluorinated aromatic rings or olefins, which are more susceptible to chemical transformation and less likely to persist in the environment than fully saturated carbons.
  • The two other substructures also provide a wealth of new chemicals that will be considered PFAS under the new definition. The second substructure, R-CF2OCF2-R’, where R and R’ can either be F, O, or saturated carbons, was included to cover certain fluorinated ethers that the EPA believes that are likely to find in water. The agency explained that these chemicals may not have been reported to the TSCA Inventory or as a low volume exception (LVE), and would not have been included in prior definitions, which were focused on the chemicals known in the TSCA universe. These chemicals may exhibit properties similar to hexafluoropropylene dimer acid (HFPO-DA, commonly known as GenX), such as PFMOAA (CAS RN 674-13-5), which has been detected in the Cape Fear River.
  • The third substructure is focused on different types of branching for highly fluorinated substances that would not meet the previous definition of a PFAS due to non-adjacent fully fluorinated carbon atoms. The EPA explained that it believes that these substances are likely to be persistent and may have similar properties to well-studied PFAS like perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS). The agency explained that a substance like 4,4,4-Trifluoro-2,2,3,3-tetra)kis(trifluoromethyl)butanoic acid (CAS RN 1882109-62-7) has the same number of carbon, fluorine, and oxygen atoms as PFOS, but its structure contains non-adjacent fluorinated carbons. The agency explained that these substances which have highly fluorinated carbon moieties that are non-adjacent may still be persistent and therefore were covered under the definition.

Other definitions and the future of the EPA definition

  • Commenters on the proposed rule have suggested that the EPA use the Organisation for Economic Co-operation and Development (OECD) definition for PFAS. Commenters supportive of the rule recommended that the OECD definition “incorporates sound science based on input” from leading research countries around the world and may make reporting complicated for PFAS manufacturers around the world.
  • In its response, the EPA explained that while it appreciated the differences in definitions for PFAS between organizations, it chose its own definition. The agency explained that it did not believe that those definitions would not suit the EPA’s obligations under TSCA section 8(a)(7) and instead decided to focus on substances with a minimum of two fluorine atoms on at least one carbon (e.g., -CF2-). The agency stated that it considered using the OECD definition for the purpose, but eventually decided not to do so. The OECD definition covers any chemical with one or more fluorinated alkyl groups, which covers chemicals with structures that are not similar to the structures of PFAS of concern, which have more fluorinated carbons and may persist more easily. The agency stated that it believes that substances with only a single fluorinated alkyl group and no additional fluorinated moieties do not share the same level of environmental or human health impacts as other targeted PFAS. The OECD definition would cover about 23,000 chemicals based on the EPA’s CompTox review, but about 17,000 of those chemicals would be covered due to having a single terminal -CF3 but no additional fluorine, which would not be covered by the EPA’s definition.
  • The EPA has previously not stayed with a singular definition for PFAS across its various programs, however this new definition could prove to be the “durable” definition the agency and Congress have been looking for. The Senate Environment and Public Works Committee (EPW) previously released draft legislation that would require the EPA to create a definition for PFAS that could be used by federal agencies across the government. However, as Congress stays deadlocked over long-term funding bills, it is unlikely that the bill will continue to advance in the short term, even if it has significant bipartisan support.
  • The new definition may be challenged in court by organizations that wish to avoid a “PFAS” designation for any of their products or chemicals. Although in the past, the EPA would receive significant deference in scrutiny towards how it phrases its regulations, the current thrust of judicial interpretation of agency regulations and enabling statutes has significantly carved back this deference. This may mean that if plaintiffs can find a preferred venue with judges that are traditionally more regulation-adverse, they may be able to pare back or render unenforceable the EPA’s new PFAS definition.

To contact the author of this analysis, please email Walker Livingston.
To contact the editor of this analysis, please email Patricia Iscaro.

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