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Per- and polyfluoroalkyl substances (PFAS[1] or PFASs[2]) are a group of synthetic organofluorine chemical compounds that have multiple fluorine atoms attached to an alkyl chain; there are 7 million such chemicals according to PubChem.[3] They were branded as "Forever Chemicals" in an article in the Washington Post in 2018.[4] PFAS came into use after the invention of Teflon in 1938 to make fluoropolymer coatings and products that resist heat, oil, stains, grease, and water. They are now 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, heat-resistant non-stick cooking surfaces such as Teflon,[5] firefighting foam, and the insulation of electrical wire.[6][7][8] PFAS are also used by the cosmetic industry in most cosmetics and personal care products, including lipstick, eye liner, mascara, foundation, concealer, lip balm, blush, and nail polish.[9][10]
Many PFAS such as PFOS and PFOA pose health and environmental concerns because they are persistent organic pollutants or "forever chemicals"; they have half-lives of up to over eight years due to a carbon-fluorine bond, one of the strongest in organic chemistry.[11][12][13][14][15][16] They move through soils and bioaccumulate in fish and wildlife, which are then eaten by humans. Residues are now commonly found in rain and drinking water.[11][17][18][7] Since PFAS compounds are highly mobile, they are readily absorbed through human skin and through tear ducts, and such products on lips are often unwittingly ingested.[19] Due to the large number of PFAS, it is challenging to study and assess the potential human health and environmental risks; more research is necessary and is ongoing.[20][11][21][6]
Exposure to PFAS, some of which have been classified as carcinogenic, has been linked to cancers such as kidney, prostate and testicular cancer, ulcerative colitis, thyroid disease, suboptimal antibody response / decreased immunity, decreased fertility, reduced infant and fetal growth and developmental issues in children, obesity, dyslipidemia (abnormally high cholesterol), and higher rates of hormone interference.[6][22][23]
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[24] or has moved production to countries such as Thailand, where there is less regulation.[25][26] In the United States, the Republican Party has filibustered bills regulating the chemicals.[24] Cover-ups and the suppression of studies in 2018 by the Trump administration led to bipartisan outrage.[27][28]
The market for PFAS was estimated to be $28 billion in 2023 and the majority are produced by 12 companies: 3M, AGC Inc., Archroma, Arkema, BASF, Bayer, Chemours, Daikin, Honeywell, Merck Group, Shandong Dongyue Chemical, and Solvay.[29] Sales of PFAS, which cost approximately $20 per kilogram, generate a total industry profit of $4 billion per year on 16% profit margins.[30] Due to health concerns, several companies have ended or plan to end the sale of PFAS or products that contain them; these include W. L. Gore & Associates (the maker of Gore-Tex), H&M, Patagonia, REI, and 3M.[31][32][33][34][35][36] 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.[37] 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".[38] External costs, including those associated with remediation of PFAS from soil and water contamination, treatment of related diseases, and monitoring of PFAS pollution, may be as high as US$17.5 trillion annually, according to ChemSec.[30] The Nordic Council of Ministers estimated health costs to be at least €52–84 billion in the European Economic Area.[39] In the United States, PFAS-attributable disease costs are estimated to be US$6–62 billion.[40][41]
Definition
Per- and polyfluoroalkyl substances are defined as a group of synthetic organofluorine chemical compounds that have multiple fluorine atoms attached to an alkyl chain.
An early definition, from 2011, required that they contain at least one perfluoroalkyl moiety, −CnF2n+1.[12] A 2018 report by the Global PFC Group, a collaboration between the Organisation for Economic Co-operation and Development (OECD) and the United Nations Environment Programme (UNEP), instead focused on substances "that contain a perfluoroalkyl moiety with three or more carbons (i.e. −CnF2n−, n ≥ 3) or a perfluoroalkylether moiety with two or more carbons (i.e. −CnF2nOCmF2m−, n,m ≥ 1)."[42][43] Beginning in 2021, the OECD expanded its terminology, stating that "PFASs 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 (−CF3) or a perfluorinated methylene group (−CF2−) is a PFAS."[2][44] At least 4,730 distinct PFASs that meet the 2018 OECD/UNEP definition are known,[45] while PubChem lists more than 7 million under the 2021 OECD definition.[3]
In 2023, for rulemaking under the Toxic Substances Control Act of 1976, the United States Environmental Protection Agency defined PFASs as substances that contain "at least one of the following three structures: R−CF2−CF(R′)R″, where both the CF2 and CF moieties are saturated carbons; R−CF2OCF2−R′, where R and R′ can either be F, O, or saturated carbons; or CF3C(CF3)R′R″, where R′ and R″ can either be F or saturated carbons."[46][47] The EPA toxicity database, DSSTox, lists 14,735 unique PFAS chemical compounds.[48][49]
PFAS chemicals are characterized by a carbon-fluorine bond, one of the strongest bonds in organic chemistry, which gives these chemicals environmental half-lives of up to over eight years.[11]
Fluorosurfactants
The fluorinated surfactants or fluorosurfactants subgroup has a fluorinated "tail" and a hydrophilic "head" and are thus considered surfactants. These are more effective at reducing the surface tension of water than comparable hydrocarbon surfactants. They include the perfluorosulfonic acids, such as perfluorooctanesulfonic acid (PFOS), and the perfluorocarboxylic acids like perfluorooctanoic acid (PFOA).
Fluorosurfactants are surfactants containing fluorocarbon chains such as those in PFASs. Their hydrophobic nature can reduce the surface tension of water below what is attainable by using hydrocarbon surfactants,[50] so fluorosurfactants tend to concentrate at the liquid-air interface.[51] Fluorocarbons are both lipophobic and hydrophobic, which allows them to repel both oil and water. Their lipophobicity results from the relative lack of London dispersion forces when 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 and fit for harsher conditions than hydrocarbon surfactants because of the stability of the carbon–fluorine bond. Perfluorinated surfactants persist in the environment for the same reason.[17]
Fluorosurfactants such as PFOS, PFOA, and PFNA have caught the attention of regulatory agencies because of their persistence, toxicity, and widespread occurrence in the blood of general populations.[52][53]
PFASs are used in emulsion polymerization to produce fluoropolymers, used in stain repellents, polishes, paints, and coatings.[54]
