Per- and polyfluoroalkyl substances (PFAS or PFASs) are a group of synthetic organofluorine chemical compounds that have multiple fluorine atoms attached to an alkyl chain. Because of their high chemical and thermal stability, these compounds have long environmental lifetimes, and thus are commonly called "forever chemicals".
The first PFAS, polychlorotrifluoroethylene, was synthesized in 1934. Their widespread use began in 1938 with the invention of Teflon (polytetrafluoroethylene), a fluoropolymer coating that resists heat, oil, stains, grease, and water. Since their inception, thousands of PFAS compounds have been created. They are used in a wide variety of products including waterproof fabric, yoga pants, carpets, shampoo, mobile phone screens, wall paint, furniture, adhesives, food packaging, firefighting foam, electrical insulation, and cosmetics.
PFAS are often found in groundwater, wastewater and soil; wastewater treatment facilities and landfills have the highest levels of pollution. Furthermore, crop uptake of PFAS and bioaccumulation of PFAS into fish, livestock, and wildlife can act as potential routes of human exposure. In addition, areas near airports and air force bases are contaminated from the use of PFAS-containing firefighting foam.
Exposure to PFAS, some of which are carcinogens or endocrine disruptors, has been linked to diseases and health conditions including cancers, ulcerative colitis, thyroid disease, suboptimal antibody response or decreased immunity, decreased fertility, hypertensive disorders in pregnancy, fetal and child developmental issues, obesity, and high cholesterol. Due to the health and environmental concerns associated with many PFAS, PFOS and PFOA were listed in the Stockholm Convention on Persistent Organic Pollutants in 2009 and 2019, respectively. However, it is challenging to assess the potential risks of all PFAS due to the large data-gaps in toxicity and physicochemical properties. With thousands of compounds used in various application, only a few have undergone comprehensive biological testing.
In some jurisdictions, such as the European Union, further reductions and phase-outs of PFAS are planned. Several companies are voluntarily ending or planning to end the sale of PFAS and PFAS-containing products due to health and litigation concerns. However, major producers and users such as the United States, Israel, and Malaysia have not ratified the agreement and the chemical industry has lobbied governments to reduce regulations.
Definition
Per- and polyfluoroalkyl substances are a group of synthetic organofluorine chemical compounds that have multiple fluorine atoms attached to an alkyl chain. Different organizations use different definitions for PFAS, leading to estimates of between 8,000 and 7 million chemicals within the group. The EPA toxicity database, DSSTox, lists 14,735 unique PFAS chemical compounds. "List consists of all DTXSID records with a structure assigned, and using a set of substructural filters based on community input." 7 million are listed in PubChem.
An early definition stated that PFAS were "aliphatic substances that contain 1 or more C atoms on which all the H substituents (present in the nonfluorinated analogues from which they are notionally derived) have been replaced by F atoms, in such a manner that they contain the perfluoroalkyl moiety, ". Beginning in 2021, the OECD expanded its terminology, stating that "PFAS are defined as fluorinated substances that contain at least one fully fluorinated methyl or methylene carbon atom (without any H/Cl/Br/I atom attached to it), i.e., with a few noted exceptions, any chemical with at least a perfluorinated methyl group () or a perfluorinated methylene group () is a PFAS."
The United States Environmental Protection Agency (EPA) defines PFAS more narrowly in the Drinking Water Contaminant Candidate List 5 as substances that contain "at least one of the following three structures: , where both the and moieties are saturated carbons, and none of the R groups can be hydrogen; , where both the moieties are saturated carbons, and none of the R groups can be hydrogen; or , where all the carbons are saturated, and none of the R groups can be hydrogen.EPA. (2022-11-14). "Drinking Water Contaminant Candidate List 5–Final." Federal Register, A summary table of some PFAS definitions is provided in Hammel et al (2022).
Sample chemicals
Common PFAS include:
Perfluoroalkyl carboxylic acids (PFCAs), such as trifluoroacetic acid (TFA) Perfluorosulfonic acids (PFSAs), such as perfluorooctanesulfonic acid (PFOS) Precursors to PFCAs, such as fluorotelomers, including as fluorotelomer alcohols (FTOHs) Precursors to PFSAs, such as perfluorobutane sulfonamide (H-FBSA), perfluorooctanesulfonamide (PFOSA), perfluorobutanesulfonyl fluoride (PFOSB) or perfluorooctanesulfonyl fluoride (PFOSF) Fluoropolymers such as polytetrafluoroethylene (PTFE, aka Teflon)
Uses Products PFAS are used to produce fluoropolymers by emulsion polymerization. Because they resist heat, oil, stains, grease, and water, they are ingredients in stain repellents, polishes, paints, and coatings. They came into use with the invention of Teflon in 1938. They have been used in products including waterproof fabric such as nylon, yoga pants, carpets, shampoo, feminine hygiene products, mobile phone screens, wall paint, furniture, adhesives, food packaging, firefighting foam, the insulation of electrical wires, dental floss and sunscreen. PFAS have been used by the cosmetic industry in cosmetics and personal care products, including lipstick, eye liner, mascara, foundation, concealer, lip balm, blush, and nail polish. Pesticides including fluazinam and flufenacet break down to produce trifluoroacetic acid. In 2025, a report by the US FDA stated that in 2021, up to 1.4% of cosmetics sold in Europe contained PFAS and as of 2025, less than 1% of cosmetics sold in the US contained PFAS.
Fluorosurfactants
Fluorinated surfactants or fluorosurfactants are a subgroup of PFAS characterized by a hydrophobic fluorinated "tail" and a hydrophilic "head" that behave as surfactants. These are more effective at reducing the surface tension of water than comparable hydrocarbon surfactants.
Fluorosurfactants tend to concentrate at the phase interfaces. Fluorocarbons are both lipophobic and hydrophobic, repelling both oil and water. Their lipophobicity results from the relative lack of London dispersion forces compared to hydrocarbons, a consequence of fluorine's large electronegativity and small bond length, which reduce the polarizability of the surfactants' fluorinated molecular surface. Fluorosurfactants are more stable than hydrocarbon surfactants due to the stability of the carbon–fluorine bond. Perfluorinated surfactants persist in the environment for the same reason.
Fluorosurfactants such as PFOS, PFOA, and perfluorononanoic acid (PFNA) have caught the attention of regulatory agencies because of their persistence, toxicity, and widespread occurrence in the blood of general populations.
Market The market for PFAS was estimated to be US$28 billion in 2023. The majority are produced by 12 companies: 3M, AGC Inc., Archroma, Arkema, BASF, Bayer, Chemours, Daikin, Honeywell, Merck Group, Shandong Dongyue Chemical, and Solvay. Sales of PFAS, which cost approximately $20 per kilogram, generated a total industry profit of $4 billion per year on 16% profit margins in 2023.
Environmental effects
Prevalence in rain, soil, water bodies, and air In 2022, levels of at least four perfluoroalkyl acids (PFAAs) in rain water worldwide greatly exceeded the EPA's lifetime drinking water health advisories as well as comparable Danish, Dutch, and European Union safety standards, leading to the conclusion that "the global spread of these four PFAAs in the atmosphere has led to the planetary boundary for chemical pollution being exceeded". The most common PFAS found in the environment is Trifluoroacetic acid (TFA). Its presence is ubiquitous in the environment, especially in aquatic ecosystems, where it persists with increasing concentrations globally.
It had been thought that PFAAs would eventually end up in the oceans, where they would be diluted over decades, but a field study published in 2021 by researchers at Stockholm University found that they are often transferred from water to air when waves reach land, are a significant source of air pollution, and eventually get into rain. The researchers concluded that pollution may impact large areas. Soil is also contaminated and the chemicals have been found in remote areas such as Antarctica. Soil contamination can result in higher levels of PFAS found in foods such as white rice, coffee, and animals reared on contaminated ground. In 2024, a worldwide study of 45,000 groundwater samples found that 31% of samples contained levels of PFAS that were harmful to human health; these samples were taken from areas not near any obvious source of contamination.
Contamination has also been seen in water wells and other sources of drinking water. This contamination is seen in US, United Kingdom, Germany, Japan, and Canada, but information from most developing countries is nearly nonexistent. The lack of information on PFAS contamination in developing countries, especially those in Africa, are due to structural socioeconomic inequality and lack of access to the expensive laboratory capabilities required for PFAS quantification.
Bioaccumulation and biomagnification In marine species of the food web Bioaccumulation controls internal concentrations of pollutants, including PFAS, in individual organisms. When bioaccumulation is looked at in the perspective of the entire food web, it is called biomagnification, which is important to track because lower concentrations of pollutants in environmental matrices such as seawater or sediments, can very quickly grow to harmful concentrations in organisms at higher trophic levels, including humans. Notably, concentrations in biota can even be greater than 5000 times those present in water for PFOS and C10–C14 PFCAs. PFAS can enter an organism by ingestion of sediment, through the water, or directly via their diet. It accumulates mainly in areas with high protein content, in the blood and liver, but it is also found to a lesser extent in tissues.
In a study undertaken on a macrotidal estuary in Gironde, in south-west France, PFOA and PFNA were found to be highly bioaccumulative. PFOS, a long-chain sulfonic acid, was found at the highest concentrations relative to other PFAS measured in fish and birds in northern seas such as the Barents Sea and the Canadian Arctic. A global meta-analysis found that PFAS concentrations increase, on average, twofold with each trophic level, with substantial variation among compounds. Notably, the industrial replacement compound F-53B exhibited the highest trophic magnification, exceeding that of several legacy PFAS it was intended to replace.
A study published in 2023 analyzing 500 composite samples of fish fillets collected across the United States from 2013 to 2015 under the EPA's monitoring programs showed freshwater fish ubiquitously contain high levels of harmful PFAS, with a single serving typically significantly increasing the blood PFOS level.