Perfluorooctanoic acid

Perfluorooctanoic acid (PFOA) (conjugate base perfluorooctanoate) is a perfluorinated carboxylic acid produced and used worldwide as an industrial surfactant in chemical processes and as a material feedstock, and is known as an emerging health concern and subject of regulatory action and voluntary industrial phase-outs. PFOA is considered a surfactant, or fluorosurfactant, due to its chemical structure consisting 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; The tail group is inert and does not interact strongly with polar or non-polar chemical moieties; the head group is reactive and interacts strongly with polar groups, specifically water. The 'tail' is hydrophobic due to being non-polar and lipophobic because fluorocarbons are less susceptible to the London dispersion force than hydrocarbons.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 Perfluorooctanoic acid (PFOA) (conjugate base perfluorooctanoate) is a perfluorinated carboxylic acid produced and used worldwide as an industrial surfactant in chemical processes and as a material feedstock, and is known as an emerging health concern and subject of regulatory action and voluntary industrial phase-outs. PFOA is considered a surfactant, or fluorosurfactant, due to its chemical structure consisting 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; The tail group is inert and does not interact strongly with polar or non-polar chemical moieties; the head group is reactive and interacts strongly with polar groups, specifically water. The 'tail' is hydrophobic due to being non-polar and lipophobic because fluorocarbons are less susceptible to the London dispersion force than hydrocarbons. PFOA is used for several industrial applications, including carpeting, upholstery, apparel, floor wax, textiles, sealants, and cookware. 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, some cookware 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. Other studies have not found a conclusive link between the chemical and human health. 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: 3M (then 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 the fall of 2000, lawyer Rob 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, products manufactured with PFOA were such an integral part of DuPont's earnings, $1 billion in annual profit, they chose to continue using PFOA. Billott 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 toxin. 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. 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. 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.