PFAS


Per- and polyfluoroalkyl substances are a group of synthetic organofluorine chemical compounds that have multiple fluorine atoms attached to an alkyl chain; 7 million such chemicals are listed in PubChem.
Widespread use of PFAS began in 1938 with the invention of Teflon, a fluoropolymer coating that resists heat, oil, stains, grease, and water. 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.
Many PFAS such as PFOS and PFOA pose health and environmental concerns because they are persistent organic pollutants; they were branded as "forever chemicals" in an article in The Washington Post in 2018. They move through soils and bioaccumulate in fish and wildlife, which are then eaten by humans. Residues are now commonly found in rain, drinking water, and wastewater. Due to the large number of PFAS, it is challenging to assess the potential human health and environmental risks.
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.
The use of PFAS has been regulated internationally by the Stockholm Convention on Persistent Organic Pollutants since 2009, with some jurisdictions, such as China and the European Union, planning further reductions and phase-outs. 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.
Due to health concerns, several companies have ended or plan to end the sale of PFAS or products that contain them. PFAS producers have paid billions of dollars to settle litigation claims, the largest being a $10.3 billion settlement paid by 3M for water contamination in 2023. Studies have shown that companies have known of the health dangers since the 1970s – DuPont and 3M were aware that PFAS was "highly toxic when inhaled and moderately toxic when ingested". External costs, including those associated with remediation of soil and water contamination, treatment of related diseases, and monitoring of pollution, may be as high as US$17.5 trillion annually, according to ChemSec. The Nordic Council of Ministers estimated health costs to be at least €52–84 billion in the European Economic Area. In the United States, PFAS-attributable disease costs are estimated to be $6–62 billion. In January 2025, the cost of cleaning up toxic PFAS pollution in the UK and Europe was stated to exceed £1.6 trillion over the next 20 years, averaging £84 billion annually.
The market for PFAS was estimated to be US$28 billion in 2023 and the majority are produced by a small number of multinational companies. 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.

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. 7 million are listed in PubChem.
An early definition required that PFAS contain at least one 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, 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 defines PFAS 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. A summary table of some PFAS definitions is provided in Hammel et al.

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 have caught the attention of regulatory agencies because of their persistence, toxicity, and widespread occurrence in the blood of general populations.

Sample chemicals

Common PFAS include:

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 are 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, and the insulation of electrical wires. PFAS are used by the cosmetic industry in the majority of 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.

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 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. 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.

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 namely 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 done on a macrotidal estuary in Gironde, SW 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.
Bioaccumulation and biomagnification of PFAS in marine species such as fish and shellfish can have important impacts on human populations. PFAS have been frequently documented in both fish and shellfish that are commonly consumed by human populations, which poses health risks to humans and studies on the bioaccumulation in certain species are important to determine daily tolerable limits for human consumption, and where those limits may be exceeded causing potential health risks. This has particular implications for populations that consume larger numbers of wild fish and shellfish species. PFAS contamination has also resulted in disruptions to the food supply, such as closures and limits on fishing.
PFAS are brought to the Arctic from polluted southern waters by migrating birds. Although it is much less than compared to the introduction by wind and the oceans, the birds become vectors, transmitting the toxic chemicals. Rainer Lohmann, an oceanographer at the University of Rhode Island, noted that this has a significant localized affect that is devastating for Arctic predators who accumulate toxins in their bodies because the contaminants from the birds often enter the food chain directly since the birds are the prey of many species.
Fluorosurfactants with shorter carbon chains may be less prone to accumulating in mammals; there is still some concern that they may be harmful to both humans and the environment.