perfluorooctanoic acid perfluorooctanoic acid perfluorooctanoic acid (pfoa; conjugate base perfluorooctanoate; also known colloquially as c8, for its 8 carbon chain structure) is a perfluorinated carboxylic acid produced and used worldwide as an industrial surfactant in chemical processes and as a material feedstock. pfoa is considered a surfactant, or fluorosurfactant, due to its chemical structure, which consists of a perfluorinated, n-octyl "tail group" and a carboxylate "head group". the head group can be described as hydrophilic while the fluorocarbon tail is both hydrophobic and lipophobic. perfluorooctanoic acid names preferred iupac name pentadecafluorooctanoic acid other names perfluorooctanoic acid, pfoa, c8, perfluorooctanoate, pfo, perfluorocaprylic acid, c8-pfca, fc-143, f-n-octanoic acid identifiers cas number 335-67-1 y 3d model (jsmol) interactive image chebi chebi:35549 y chembl chembl172988 y chemspider 9180 y echa infocard 100.005.817 ec number 206-397-9 pubchem cid 9554 rtecs number rh0781000 unii 947vd76d3l y comptox dashboard (epa) dtxsid8031865 inchi inchi=1s/c8hf15o2/c9-2(10,1(24)25)3(11,12)4(13,14)5(15,16)6(17,18)7(19,20)8(21,22)23/h(h,24,25) ykey: sngrezuhaywors-uhfffaoysa-n yinchi=1/c8hf15o2/c9-2(10,1(24)25)3(11,12)4(13,14)5(15,16)6(17,18)7(19,20)8(21,22)23/h(h,24,25)key: sngrezuhaywors-uhfffaoyaq smiles fc(f)(c(f)(f)c(=o)o)c(f)(f)c(f)(f)c(f)(f)c(f)(f)c(f)(f)f properties chemical formula c8hf15o2 molar mass 414.07 g/mol appearance white solid density 1.8 g/cm3 melting point 40 to 50 °c (104 to 122 °f; 313 to 323 k) boiling point 189 to 192 °c (372 to 378 °f; 462 to 465 k) solubility in water soluble, 9.5 g/l (pfo) solubility in other solvents polar organic solvents acidity (pka) ~0 hazards occupational safety and health (ohs/osh): main hazards strong acid, known carcinogen, persistent organic pollutant ghs labelling: pictograms signal word danger hazard statements h302, h318, h332, h351, h360, h362, h372 precautionary statements p201, p202, p260, p261, p263, p264, p270, p271, p280, p281, p301+p312, p304+p312, p304+p340, p305+p351+p338, p308+p313, p310, p312, p314, p330, p405, p501 nfpa 704 (fire diamond) 3 0 0 safety data sheet (sds) related compounds related compounds perfluorooctanesulfonic acid (pfos), perfluorononanoic acid (pfna),perfluorooctanesulfonamide (pfosa), trifluoroacetic acid (tfa) except where otherwise noted, data are given for materials in their standard state (at 25 °c , 100 kpa). y verify (what is yn ?) infobox references pfoa is one of many synthetic organofluorine compounds collectively known as per- and polyfluoroalkyl substances (pfass). pfoa is used in several industrial applications, including carpeting, upholstery, apparel, floor wax, textiles, fire fighting foam and sealants. pfoa serves as a surfactant in the emulsion polymerization of fluoropolymers and as a building block for the synthesis of perfluoroalkyl-substituted compounds, polymers, and polymeric materials. pfoa has been manufactured since the 1940s in industrial quantities. it is also formed by the degradation of precursors such as some fluorotelomers. pfoa is used as a surfactant because it can lower the surface tension of water more than hydrocarbon surfactants while having exceptional stability due to having perfluoroalkyl tail group. the stability of pfoa is desired industrially but is a cause of concern environmentally. a study of workers living near a dupont teflon plant found an association between pfoa exposure and two kinds of cancer as well as four other diseases. a positive exposure-response trend for kidney cancer is supported by many studies. pfoa has been detected in the blood of more than 98% of the general us population in the low and sub-parts per billion (ppb) range, and levels are higher in chemical plant employees and surrounding subpopulations. how general populations are exposed to pfoa is not completely understood. pfoa has been detected in industrial waste, stain-resistant carpets, carpet-cleaning liquids, house dust, microwave popcorn bags, water, food, and teflon (ptfe) products. as a result of a class-action lawsuit and community settlement with dupont, three epidemiologists conducted studies on the population surrounding a chemical plant that was exposed to pfoa at levels greater than in the general population. studies have found correlation between high pfoa exposure and six health outcomes: kidney cancer, testicular cancer, ulcerative colitis, thyroid disease, hypercholesterolemia (high cholesterol), and pregnancy-induced hypertension. the primary manufacturer of pfos, the 3m company (known as minnesota mining and manufacturing company from 1902 to 2002), began a production phase-out in 2002 in response to concerns expressed by the united states environmental protection agency (epa).: 2 eight other companies agreed to gradually phase out the manufacturing of the chemical by 2015.: 3 by 2014, epa had listed pfoa and perfluorooctanesulfonates (salts of perfluorooctanesulfonic acid, pfos) as emergent contaminants: pfoa and pfos are extremely persistent in the environment and resistant to typical environmental degradation processes. are widely distributed across the higher trophic levels and are found in soil, air and groundwater at sites across the united states. the toxicity, mobility and bioaccumulation potential of pfos and pfoa pose potential adverse effects for the environment and human health.: 1 history 3m (then the minnesota mining and manufacturing company) began producing pfoa by electrochemical fluorination in 1947. starting in 1951, dupont purchased pfoa from 3m for use in the manufacturing of specific fluoropolymers—commercially branded as teflon, but dupont internally referred to the material as c8. in 1968, organofluorine content was detected in the blood serum of consumers, and in 1976 it was suggested to be pfoa or a related compound such as pfos. in 1999, epa ordered companies to examine the effects of perfluorinated chemicals after receiving data on the global distribution and toxicity of pfos. for these reasons, and epa pressure, in may 2000, 3m announced the phaseout of the production of pfoa, pfos, and pfos-related products—the company's best-selling repellent. 3m stated that they would have made the same decision regardless of epa pressure. because of the 3m phaseout, in 2002, dupont built its own plant in fayetteville, north carolina, to manufacture the chemical. the chemical has received attention due to litigation from the pfoa-contaminated community around dupont's washington works facility in washington, west virginia, along with epa focus. in 2004, chemrisk—an "industry risk assessor" that had been contracted by dupont, reported that over 1.7 million pounds of c8 had been "dumped, poured and released" into the environment from dupont's parkersburg, west virginia-based washington works plant between 1951 and 2003. research on pfoa has demonstrated ubiquity, animal-based toxicity, and some associations with human health parameters and potential health effects. additionally, advances in analytical chemistry in recent years have allowed the routine detection of low- and sub-parts per billion levels of pfoa in a variety of substances. in 2013, gore-tex eliminated the use of pfoas in the manufacture of its weatherproof functional fabrics. major companies producing pfoa signed with the global pfoa stewardship program with the goal of elimination of pfoa by 2015. since then it has been eliminated from the production of non-stick materials used in cookware. genx has been introduced as a replacement for pfoa, but in a 2015 study which tested the effects on rats, genx caused many of the same health problems as pfoa, but required much higher concentrations. this is because genx (c3) is a short chain alternative to pfoa. genx also has a significantly shorter half-life than pfoa so it is not as bio-persistent as pfoa or other long chain perfluorinated chemicals. robert bilott investigation in the fall of 2000, lawyer robert bilott, a partner at taft stettinius & hollister, won a court order forcing dupont to share all documentation related to pfoa. this included 110,000 files, consisting of confidential studies and reports conducted by dupont scientists over decades. by 1993, dupont understood that "pfoa caused cancerous testicular, pancreatic and liver tumors in lab animals" and the company began to investigate alternatives. however, because products manufactured with pfoa were such an integral part of dupont's earnings, $1 billion in annual profit, they chose to continue using pfoa. bilott learned that both "3m and dupont had been conducting secret medical studies on pfoa for more than four decades", and by 1961 dupont was aware of hepatomegaly in mice fed with pfoa. later research eventually found that pfoa had an outsized effect based on gender on several negative health outcomes in mice that had been exposed to the chemical. the pfoa exposure in these mice led to a modification of genetic expression. this led to the development of fatty tissue which caused the exposed mice to develop varying rates of hypercholesterolemia (high cholesterol). the impact of pfoa on this health outcome varied greatly between mice of different genotypes across relevant parts of the genome. also, notably, female mice across all genotypes saw significantly higher rates and more severe cases of hypercholesterolemia. bilott exposed how dupont had been knowingly polluting water with pfoas in parkersburg, west virginia, since the 1980s. in the 1980s and 1990s, researchers investigated the toxicity of pfoa. for his work in the exposure of the contamination, lawyer robert bilott has received several awards including the right livelihood award in 2017. this battle with dupont is featured in the documentary the devil we know, which premiered at the sundance film festival in 2018, and dark waters, directed by todd haynes. synthesis pfoa has two main synthesis routes, electrochemical fluorination (ecf) and telomerization. the ecf route sees octanoyl chloride (the acid chloride of octanoic acid) reacted with hydrofluoric acid. multiple products are formed by ecf with the target acid fluoride f(cf2)7cof being produced as only 10–15% of the yield, while the main products are perfluorinated cyclic ether isomers, including fc-75. this acid fluoride is hydrolyzed to yield pfoa as a mixture of straight-chain (78%), terminally branched (13%), and internally branched (9%) molecules, because ecf induces rearrangements the carbon tail of the acid chloride. ecf also results in production wastes. 3m synthesized ecf pfoa at their cottage grove, minnesota facility from 1947 to 2002 and was the world's largest producer. ecf production continues on a smaller scale in europe and asia. pfoa is also synthesized by the telomerization represented below, where the telogen is the organoiodine compound and the taxogen is the tetrafluoroethylene. each step is an addition reaction where the carbon-iodine bond of the telogen is added across the carbon-carbon double bond of the unsaturated taxogen, resulting in the formation of a new telogen. cf3cf2i + f2c=cf2 → cf3cf2cf2cf2i cf3(cf2)3i + f2c=cf2 → cf3(cf2)5i cf3(cf2)5i + f2c=cf2 → cf3(cf2)7i the product is oxidized by so3 to form pfoa. since each addition produces a new teleomer, fluorotelomers like these form with varying length chains containing an even number of carbon atoms, depending on reaction conditions. typically, most products within will contain between two and six taxogens (that is, from cf3(cf2)5i to cf3(cf2)13i). after oxidation, distillation is used to separate pfoa from the other perfluorinated carboxylic acids. the telomerization synthesis of pfoa was pioneered by dupont, and is not well suited to the laboratory. pfoa formed by telomerization is completely linear, in contrast to the mixture of structures formed by ecf. applications pfoa has widespread applications. in 1976, pfoa was reported as a water and oil repellent "in fabrics and leather and in the production of floor waxes and waxed papers"; however, it is believed that paper is no longer treated with perfluorinated compounds, but with fluorotelomers with less than 0.1% pfoa. the compound is also used in "insulators for electric wires, planar etching of fused silica", fire fighting foam, and outdoor clothing. as a protonated species, the acid form of pfoa was the most widely used perfluorocarboxylic acid used as a reactive intermediate in the production of fluoroacrylic esters. adona, ammonium 4,8-dioxa-3h-perfluorononanoate, is 3m's pfoa replacement in the emulsion polymerization of fluoropolymers. as a salt, its dominant use is as an emulsifier for the emulsion polymerization of fluoropolymers such as ptfe, polyvinylidene fluoride, and fluoroelastomers. for this use, 3m subsidiary dyneon has a replacement emulsifer despite dupont stating pfoa is an "essential processing aid". in the past pfoa was used in the production of gore-tex as it is ptfe-based. in ptfe processing, pfoa is in aqueous solution and forms micelles that contain tetrafluoroethylene and the growing polymer. pfoa can be used to stabilize fluoropolymer and fluoroelastomer suspensions before further industrial processing and in ion-pair reversed-phase liquid chromatography it can act as an extraction agent. pfoa also finds uses in electronic products and as an industrial fluorosurfactant. in a 2009 epa study of 116 products, purchased between march 2007 and may 2008 and found to contain at least 0.01% fluorine by weight, the concentrations of pfoa were determined. concentrations shown below range from not detected, or nd, (with the detection limit in parenthesis) to 6750 with concentrations in nanograms of pfoa per gram of sample (parts per billion) unless stated otherwise. product range, ng/g pre-treated carpetingnd (<1.5) to 462 carpet-care liquids19 to 6750 treated apparel5.4 to 161 treated upholstery0.6 to 293 treated