PFAS GLOSSARY

Aqueous Film-Forming Foam (AFFF) is a firefighting foam formulated with fluorosurfactants, typically PFOS-based or fluorotelomer-based PFAS, to suppress flammable liquid fires (Class B fires). AFFF creates a thin aqueous film that spreads over the fuel surface, cutting off oxygen and preventing reignition. Due to the persistence and toxicity of the PFAS it contains, AFFF has become one of the most significant point sources of PFAS contamination in soil and groundwater globally.

Under the TSCA Section 8(a)(7) PFAS Reporting Rule (40 CFR Part 705), an “article” is a manufactured item that is formed to a specific shape or design during manufacture, where its end-use function is dependent in whole or in part upon its shape or design during end use. This includes finished goods, components, and subassemblies that contain or were manufactured using PFAS. Importers of articles containing PFAS are subject to reporting obligations under TSCA 8(a)(7), though the November 2025 proposed revisions would exempt imported articles from reporting.

Bioaccumulation refers to the progressive build-up of PFAS in living organisms over time, where the rate of intake exceeds the rate of elimination. PFAS bioaccumulate due to their extreme chemical stability—the carbon-fluorine bond resists metabolic breakdown. Certain PFAS, particularly long-chain perfluoroalkyl acids like PFOA and PFOS, bind to proteins in blood serum and liver tissue and can have half-lives of several years in the human body. Bioaccumulation is a key criterion in hazard classification under REACH, the Stockholm Convention, and EPA risk assessments.

In the context of TSCA Section 8(a)(7), a byproduct is a chemical substance produced without a separate commercial intent during the manufacture, processing, use, or disposal of another chemical substance or mixture. PFAS byproducts can form during manufacturing processes (e.g., fluoropolymer production) or during thermal decomposition of PFAS-containing materials. Under the original October 2023 rule, byproducts were reportable; the November 2025 proposed revision would exempt PFAS manufactured as byproducts from reporting.

The carbon-fluorine (C–F) bond is the defining chemical feature of all PFAS. With a bond dissociation energy of approximately 485 kJ/mol, it is one of the strongest single bonds in organic chemistry. This exceptional strength is what makes PFAS resistant to heat, water, oil, chemical solvents, and biological degradation—properties that are commercially valuable but environmentally persistent. The C–F bond is the structural reason PFAS are called “forever chemicals.”

Under the Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA, also known as “Superfund”), the EPA has designated PFOA and PFOS as hazardous substances. This designation means that releases of these PFAS above reportable quantities must be reported to the National Response Center, and responsible parties may be held liable for cleanup costs at contaminated sites. The Trump Administration (2025–) has retained these designations and is developing a framework for future PFAS hazardous substance designations that incorporates economic impact considerations.

PFAS are classified by the length of their perfluorinated carbon chain. Long-chain PFAS include perfluoroalkyl carboxylic acids with 8 or more carbons (C8+, e.g., PFOA) and perfluoroalkyl sulfonic acids with 6 or more carbons (C6+, e.g., PFOS/PFHxS). Short-chain PFAS have fewer perfluorinated carbons (e.g., PFBS at C4, PFHxA at C6 carboxylic). This classification matters because long-chain PFAS tend to be more bioaccumulative, while short-chain PFAS are more mobile in water and harder to remove in treatment.

Under TSCA Section 8(a)(7), manufacturers may claim certain reported PFAS data as Confidential Business Information (CBI). CBI claims protect proprietary information such as specific chemical identities, manufacturing volumes, and processing details from public disclosure. However, EPA applies substantiation requirements—companies must justify why the data qualifies for confidential treatment. EPA retains the data for regulatory use but withholds it from public access if the CBI claim is upheld.

A de minimis exemption establishes a minimum concentration threshold below which PFAS in a product, mixture, or article is not subject to reporting or restriction requirements. In the EPA’s November 2025 proposed revision to the TSCA 8(a)(7) PFAS Reporting Rule, a 0.1% (1,000 ppm) by weight de minimis threshold was proposed for PFAS in mixtures and articles. The original October 2023 final rule contained no de minimis threshold, requiring reporting of any known PFAS presence regardless of concentration.

A derogation is a time-limited exemption that permits the continued manufacture, placing on the market, or use of a restricted substance for specific applications where technically feasible alternatives are not yet available. In the EU’s universal PFAS restriction proposal under REACH Annex XVII, the dossier submitters have proposed multiple derogations for sectors including medical devices, semiconductors, defense, aerospace, and certain industrial applications. Derogation periods typically range from 5 to 13.5 years after the restriction enters into force.

Drinking water standards for PFAS set maximum contaminant levels (MCLs) or quality thresholds for PFAS compounds in public water supplies. In the U.S., EPA finalized the National Primary Drinking Water Regulation (NPDWR) in April 2024, setting individual MCLs of 4 parts per trillion (ppt) for PFOA and PFOS, and a hazard index-based limit for mixtures of PFHxS, PFNA, HFPO-DA (GenX), and PFBS. The EU Drinking Water Directive (EU) 2020/2184 sets a limit of 0.1 µg/L for 20 specified PFAS and 0.5 µg/L for total PFAS, applicable from January 2026.

Under the TSCA Section 8(a)(7) Reporting Rule (40 CFR Part 705), EPA defines PFAS as any chemical substance or mixture containing a chemical substance that structurally contains at least one of three sub-structures: (1) R–(CF2)–CF(R’)R”, where both CF2 and CF moieties are saturated carbons; (2) R–CF2OCF2–R’, where R and R’ can be F, O, or saturated carbons; and (3) CF3C(CF3)R’R”, where R’ and R” can be F or saturated carbons. This definition requires at least two fluorinated carbons, making it narrower than the OECD definition.

Essential use is a policy framework concept used to evaluate whether the continued use of a hazardous substance (such as PFAS) is justified because no technically and economically feasible alternatives exist and the use is necessary for health, safety, or critical societal functions. While not yet a formal legal criterion in all jurisdictions, essential use has been referenced in the EU’s Chemicals Strategy for Sustainability, in the universal PFAS restriction proposal’s derogation framework, and in several U.S. state PFAS laws as a basis for granting or denying exemptions.

Fluoropolymers are a subclass of PFAS consisting of high-molecular-weight polymers with a carbon-only backbone in which some or all hydrogen atoms are replaced by fluorine. Common fluoropolymers include polytetrafluoroethylene (PTFE, brand name Teflon), polyvinylidene fluoride (PVDF), fluorinated ethylene propylene (FEP), and perfluoroalkoxy alkane (PFA). Fluoropolymers are widely used in industry due to their exceptional chemical resistance, thermal stability, low friction, and electrical insulation properties.

A fluorosurfactant is a surface-active agent (surfactant) in which at least one of the hydrocarbon tails has been partially or fully fluorinated. Fluorosurfactants lower the surface tension of water far more effectively than hydrocarbon surfactants, making them essential in applications requiring wetting, leveling, or film formation on low-energy surfaces. Common PFAS-based fluorosurfactants include PFOS, PFOA salts, and fluorotelomer-based products. They are used in firefighting foams, metal plating, semiconductor manufacturing, and textile treatments.

A fluorotelomer is a type of polyfluoroalkyl substance produced via the telomerization process, in which tetrafluoroethylene (TFE) is reacted with a telogen to create fluorinated carbon chains of varying lengths. Fluorotelomer-based products include fluorotelomer alcohols (FTOHs, e.g., 6:2 FTOH, 8:2 FTOH), fluorotelomer acrylates, and fluorotelomer sulfonates. The nomenclature ‘X:Y’ indicates X perfluorinated carbons followed by Y non-fluorinated carbons. Fluorotelomers are widely used in textile treatments, paper coatings, and food packaging.

“Forever chemicals” is a widely used informal term for per- and polyfluoroalkyl substances (PFAS). The term reflects the defining characteristic of these substances: their extreme environmental persistence. The carbon-fluorine bonds in PFAS resist thermal, chemical, photolytic, and biological degradation under normal environmental conditions. As a result, PFAS accumulate in soil, water, air, and living organisms indefinitely. While not a regulatory or scientific term, “forever chemicals” has become the dominant public and media framing for PFAS and drives public pressure for regulatory action.

GenX is the trade name for a processing technology using hexafluoropropylene oxide dimer acid (HFPO-DA, CAS No. 13252-13-6) and its ammonium salt as replacements for PFOA in fluoropolymer manufacturing. GenX chemicals were introduced by Chemours as a shorter-chain alternative to PFOA but have since been identified as persistent and toxic. HFPO-DA has been added to the REACH Candidate List as an SVHC and is subject to EPA drinking water standards (Hazard Index approach).

In the context of TSCA Section 8(a)(7), an impurity is a PFAS substance that is unintentionally present in a chemical substance, mixture, or article as a result of manufacturing processes, raw material contamination, or environmental exposure. The November 2025 proposed revision to the PFAS Reporting Rule would exempt PFAS present as unintentional impurities from reporting requirements. This recognizes that many manufacturers have no knowledge of or control over trace PFAS contamination in incoming materials.

“Intentionally added PFAS” refers to PFAS that are deliberately included in a product, mixture, or manufacturing process for a functional purpose (e.g., water resistance, oil repellency, chemical resistance, non-stick properties). This is distinct from PFAS present as unintentional impurities or contaminants. Several U.S. state laws (e.g., Maine, Minnesota, Washington, Colorado, New York) use “intentionally added” as the threshold for product bans and disclosure requirements, rather than a numeric concentration limit.

The lookback period under TSCA Section 8(a)(7) is the historical timeframe for which manufacturers (including importers) must report PFAS-related data. The rule requires reporting for each year between January 1, 2011, and December 31, 2022, in which a company manufactured or imported PFAS or PFAS-containing products. This 12-year retrospective window was mandated by the National Defense Authorization Act (NDAA) for Fiscal Year 2020.

Under TSCA, the term “manufacturer” includes any person who manufactures or imports a chemical substance. For TSCA Section 8(a)(7) PFAS reporting, this means that any company that manufactured PFAS domestically or imported PFAS—in any form including as a component of a mixture or article—at any time between 2011 and 2022 is subject to reporting obligations. The TSCA definition of “manufacture” is broad: it covers production, preparation, compounding, and processing of a chemical substance.

A Maximum Contaminant Level (MCL) is the highest concentration of a contaminant allowed in public drinking water under the U.S. Safe Drinking Water Act (SDWA). In April 2024, EPA finalized MCLs for six PFAS: 4 ppt for PFOA, 4 ppt for PFOS, 10 ppt for PFHxS, 10 ppt for PFNA, 10 ppt for HFPO-DA (GenX), and a Hazard Index of 1 for mixtures of PFHxS, PFNA, HFPO-DA, and PFBS. Public water systems must comply with these standards by 2029.

Minnesota’s PFAS reporting law (SF 2744, enacted 2024) is one of the most comprehensive state-level PFAS regulations in the United States. It requires manufacturers selling products containing intentionally added PFAS in Minnesota to report PFAS usage data to the Minnesota Pollution Control Agency (MPCA) through the PRISM reporting platform. The first major reporting deadline is July 1, 2026. The law covers all product categories and requires disclosure of PFAS identity, function, and concentration.

The National Defense Authorization Act (NDAA) for Fiscal Year 2020 (§7351) provided a statutory definition of PFAS for the purposes of TSCA Section 8(a)(7) reporting. The NDAA defines a perfluoroalkyl substance as “a man-made chemical of which all of the carbon atoms are fully fluorinated carbon atoms” and a polyfluoroalkyl substance as “a man-made chemical containing a mix of fully fluorinated carbon atoms, partially fluorinated carbon atoms, and nonfluorinated carbon atoms.” This congressional definition framed EPA’s subsequent rulemaking.

A non-isolated intermediate is a PFAS substance that is produced and consumed within a continuous chemical manufacturing process without being deliberately removed from the reaction vessel, accumulating in storage, or being transferred between facilities. The November 2025 proposed revision to TSCA 8(a)(7) would exempt non-isolated intermediates from reporting, recognizing that these transient substances may never exist outside the reactor and are often uncharacterizable.

The Organisation for Economic Co-operation and Development (OECD) defines PFAS as “fluorinated substances that contain at least one fully fluorinated methyl (–CF3) or methylene (–CF2–) carbon atom (without any H/Cl/Br/I atom attached to it).” This 2021 definition is the broadest widely-adopted PFAS definition, covering an estimated 10,000+ substances. It serves as the basis for the EU’s universal PFAS restriction proposal under REACH and is the most commonly referenced definition in international regulatory and scientific contexts.

PBT stands for Persistent, Bioaccumulative, and Toxic—three hazard properties that, when a substance meets all three criteria, trigger the highest level of regulatory concern. Under REACH Annex XIII, PBT criteria include specific half-life thresholds for persistence, bioconcentration factors, and toxicity endpoints. Many PFAS meet PBT or the related vPvB (very Persistent, very Bioaccumulative) criteria, which is the primary basis for their SVHC identification under REACH.

Perfluorooctane sulfonic acid (PFOS, CAS No. 1763-23-1) is a fully fluorinated eight-carbon sulfonic acid and one of the earliest PFAS to face global regulatory action. PFOS was widely used in firefighting foams (AFFF), metal plating, and stain-resistant treatments. It was listed under the Stockholm Convention in 2009 (initially with acceptable purposes, further restricted in 2019), restricted under the EU POPs Regulation, and designated as a hazardous substance under U.S. CERCLA.

Perfluorooctanoic acid (PFOA, CAS No. 335-67-1) is a fully fluorinated eight-carbon carboxylic acid and one of the most widely studied and regulated PFAS. PFOA was historically used as a processing aid in fluoropolymer manufacturing (e.g., PTFE production) and as a component of surface treatment formulations. It is classified as a Group 1 carcinogen by IARC (2023), is listed as a Persistent Organic Pollutant under the Stockholm Convention (2019), is restricted under REACH, and is designated as a hazardous substance under CERCLA.

Undecafluorohexanoic acid (PFHxA, CAS No. 307-24-4) is a short-chain (C6) perfluorocarboxylic acid. PFHxA and its salts and related substances face restriction under EU REACH Annex XVII, with the restriction entering into force in April 2026. This restriction was proposed by German authorities in 2019 and adopted by the European Commission. It covers PFHxA, its salts, and precursors that can degrade to PFHxA in the environment.

Perfluorohexane sulfonic acid (PFHxS, CAS No. 355-46-4) is a six-carbon perfluoroalkyl sulfonic acid that was widely used as a shorter-chain alternative to PFOS. PFHxS was listed under the Stockholm Convention (Annex A, elimination) in 2022 with no acceptable purposes or specific exemptions—making it the most strictly controlled PFAS under the treaty. PFHxS is also on the REACH Candidate List as an SVHC.

The EU Persistent Organic Pollutants Regulation ((EU) 2019/1021, recast) implements the Stockholm Convention on POPs within EU law, banning or severely restricting the production, placing on the market, and use of listed persistent organic pollutants. Several PFAS are listed as POPs: PFOS (2009), PFOA and its salts and related compounds (2019), PFHxS (2022), and long-chain PFCAs (C9–21, listed in 2025 with a global ban from December 2026). The POPs Regulation takes precedence over REACH for listed substances.

A PFAS precursor is a substance that can be transformed—through environmental degradation, biological metabolism, or industrial processing—into a terminal perfluoroalkyl acid (PFAA) such as PFOA, PFOS, or other persistent PFAS. Common precursor classes include fluorotelomer alcohols (FTOHs), perfluoroalkyl sulfonamides, and side-chain fluorinated polymers. Approximately 90% of the 4,700+ PFAS identified in the OECD’s 2018 database are potential precursors to PFAAs.

RAC (Committee for Risk Assessment) and SEAC (Committee for Socio-Economic Analysis) are the two independent scientific committees within ECHA that evaluate restriction proposals under REACH. RAC assesses whether a proposed restriction appropriately addresses risks to human health and the environment. SEAC evaluates socio-economic impacts, alternatives availability, and proportionality. Both must issue opinions before the European Commission can adopt a restriction.

The universal PFAS restriction is a proposed amendment to REACH Annex XVII that would restrict the manufacture, placing on the market, and use of all per- and polyfluoroalkyl substances in the EU/EEA. Submitted in January 2023 by five national authorities (Denmark, Germany, Netherlands, Norway, Sweden), it is the broadest chemical restriction ever proposed under REACH. ECHA’s RAC adopted its final opinion in March 2026 confirming PFAS warrant a group-wide restriction. SEAC agreed its draft opinion in March 2026, with a 60-day public consultation closing May 2026. SEAC’s final opinion is expected by end of 2026, after which the European Commission will draft the restriction regulation.

The REACH Candidate List is a published list of Substances of Very High Concern (SVHCs) identified under REACH Article 59. Several PFAS have been added to the Candidate List, including PFOA, PFHxS, HFPO-DA (GenX), C9–14 PFCAs, and additional PFAS groups identified in 2019, 2020, and 2023. SVHC identification triggers communication and notification obligations for companies placing articles containing SVHCs above 0.1% w/w on the EU market.

Under the TSCA Section 8(a)(7) PFAS Reporting Rule, manufacturers (including importers) must retain records supporting their PFAS data submissions. Records include raw data, calculations, estimates, supplier communications, analytical test results, and any documentation used to prepare reports. Records must be retained for at least five years from the date of submission and be made available to EPA upon request.

PFAS remediation refers to the treatment and cleanup of PFAS-contaminated soil, groundwater, surface water, and other environmental media. Unlike conventional contaminants, PFAS are extremely difficult and expensive to remediate due to their chemical stability. Common remediation technologies include granular activated carbon (GAC) adsorption, ion exchange, high-pressure membranes (reverse osmosis/nanofiltration), and emerging destruction technologies such as supercritical water oxidation and electrochemical treatment. Remediation can also involve soil excavation and containment or in-situ stabilization.

The R&D exemption, proposed in EPA’s November 2025 revision to TSCA 8(a)(7), would exempt PFAS manufactured in small quantities solely for research and development purposes from reporting obligations. This recognizes that R&D-scale PFAS production is typically exploratory and involves minimal quantities.

Under TSCA, a small manufacturer is a company that meets the small business size standards defined by the Small Business Administration (SBA) for its NAICS code, typically based on employee count or annual revenue thresholds. Under TSCA 8(a)(7), small manufacturers reporting solely as PFAS article importers receive an extended reporting window: 12 months from the start of the submission period, versus 6 months for other manufacturers. The proposed revisions would potentially remove approximately 127,469 small businesses from reporting requirements through the imported article, byproduct, and de minimis exemptions.

U.S. state-level PFAS laws are an increasingly complex patchwork of regulations that restrict, ban, or require disclosure of PFAS in various product categories. As of early 2026, over 15 states have enacted PFAS-specific legislation, with approaches ranging from product-specific bans to comprehensive all-product bans (Maine by 2030), reporting requirements (Minnesota by July 2026), labeling mandates (New Jersey from January 2028), and drinking water standards. Each state defines PFAS differently and uses different thresholds.

The Stockholm Convention on Persistent Organic Pollutants (POPs) is an international treaty that restricts or eliminates the production, use, import, and export of the world’s most dangerous chemicals. Several PFAS are listed: PFOS and its salts (Annex B, 2009), PFOA, its salts and PFOA-related compounds (Annex A, 2019), PFHxS, its salts and PFHxS-related compounds (Annex A, 2022), and long-chain perfluorocarboxylic acids C9–21 PFCAs, their salts and related compounds (Annex A, 2025, with a global ban from December 2026).

Under REACH, a Substance of Very High Concern (SVHC) is a chemical meeting one or more criteria defined in Article 57: carcinogenic, mutagenic, or toxic to reproduction (CMR); persistent, bioaccumulative, and toxic (PBT); very persistent and very bioaccumulative (vPvB); or of equivalent concern. Several PFAS have been identified as SVHCs and added to the REACH Candidate List based on PBT/vPvB properties or equivalent concern. SVHC identification triggers supply chain communication, SCIP notification, and potential authorization requirements.

Supply chain data collection for PFAS refers to the systematic process of gathering PFAS presence, identity, concentration, and function data from upstream suppliers to satisfy regulatory reporting, restriction compliance, and product transparency requirements. This includes issuing PFAS-specific questionnaires, collecting material declarations, validating supplier responses against regulatory thresholds, and maintaining auditable records. Effective PFAS data collection covers all tiers of the supply chain, from raw material suppliers through contract manufacturers to finished product assemblers.

The Toxics Release Inventory (TRI) is a U.S. EPA program under the Emergency Planning and Community Right-to-Know Act (EPCRA) that requires certain facilities to report annual releases and transfers of toxic chemicals. PFAS were first added to the TRI in stages: the NDAA FY2020 added PFOA and PFOS; subsequent NDAA authorizations expanded the list. As of 2025, EPA tracks 205 PFAS under TRI. EPA is finalizing a rule (expected February 2026) to add additional individual PFAS and PFAS categories to TRI, along with criteria for automatic future additions.

TSCA Section 8(a)(7) is a one-time, retrospective reporting requirement mandated by the NDAA FY2020 that requires any person who manufactured (including imported) PFAS or PFAS-containing articles in any year between 2011 and 2022 to report data to EPA. Reportable data includes PFAS identity, categories of use, volumes manufactured or imported, byproducts, environmental and health effects, worker exposure, and disposal methods. The final rule was published October 11, 2023. The submission period has been delayed multiple times; as of April 2026, EPA has moved the start date to January 31, 2027, or 60 days after the effective date of a forthcoming final revision rule, whichever is earlier.

The universal PFAS restriction refers to the proposed EU-wide restriction under REACH Annex XVII that would ban or restrict the manufacture, placing on the market, and use of all per- and polyfluoroalkyl substances across all applications. Submitted by five national authorities (Denmark, Germany, Netherlands, Norway, Sweden) in January 2023, it is the broadest chemical restriction ever proposed under any regulatory framework globally. The proposal covers an estimated 10,000+ substances under the OECD definition and has identified 231 sectors where PFAS are used. ECHA’s RAC adopted its final opinion on March 2, 2026, confirming PFAS warrant group-wide restriction. SEAC agreed its draft opinion on March 11, 2026, with a 60-day public consultation closing May 25, 2026.

Wastewater and biosolids are critical pathways for PFAS entering the environment. Conventional wastewater treatment plants (WWTPs) do not remove or destroy PFAS—they pass through treatment processes and are discharged in effluent or concentrated in biosolids (sewage sludge). When biosolids are applied to agricultural land as fertilizer, PFAS can contaminate soil and groundwater. EPA is developing regulatory approaches for PFAS in biosolids under the Clean Water Act and has completed draft risk assessments for PFOA and PFOS in biosolids.