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As for related perfluorinated hydrocarbons, the properties of PFOA arise from the nature of the carbon-] (C-F) bond in tandem with its polar head group. The C-F bond is one of the strongest in organic chemistry, and ] they result in molecules with high chemical and thermal stability, see ]. (While throwing ] on a fire will only fuel it, ] are used in fire-fighting foams). C-F bonds also strengthen the underlying backbone carbon-carbon bonds. The C-F bond is rarely found in nature. As for related perfluorinated hydrocarbons, the properties of PFOA arise from the nature of the carbon-] (C-F) bond in tandem with its polar head group. The C-F bond is one of the strongest in organic chemistry, and ] they result in molecules with high chemical and thermal stability, see ]. (While throwing ] on a fire will only fuel it, ] are used in fire-fighting foams). C-F bonds also strengthen the underlying backbone carbon-carbon bonds. The C-F bond is rarely found in nature.


The perfluorinated chain of PFOA has a minimized potential for the formation of the fleeting dipoles that form the basis for ] because the highest ] of ] reduces the ] of the constituent elements. The fluorinated portion of PFOA is thus ], like other ]. The carboxylic acid group is hydrophilic as indicated by the modest water solubility of PFOA. The carboxlic acid group is the means by which PFOA binds proteins that bind ] or ] ] such as ]<ref>Han X, Snow TA, Kemper RA, Jepson GW.: , Chem Res Toxicol. 2003 Jun;16(6):775-81.</ref>, liver fatty acid-binding protein<ref>Luebker DJ, Hansen KJ, Bass NM, Butenhoff JL, Seacat AM. , Toxicology. 2002 Jul 15;176(3):175-85.</ref>, and the ] ]<ref>Maloney EK, Waxman DJ.: Toxicol Appl Pharmacol. 1999 Dec 1;161(2):209-18.</ref>. The perfluorinated chain of PFOA has a minimized potential for the formation of the fleeting dipoles that form the basis for ] because the highest ] of ] reduces the ] of the constituent elements. As a result, fluorinated surfactants like PFOA are ]<ref>Park KH, Berrier C, Lebaupain F, Pucci B, Popot JL, Ghazi A, Zito F.: , Biochem J. 2007 Apr 1;403(1):183-7.</ref>, despite the perfluorinated chain being non-polar, unlike other ]. The carboxylic acid group is hydrophilic as indicated by the modest water solubility of PFOA. The carboxlic acid group is the means by which PFOA binds proteins that bind ] or ] ] such as ]<ref>Han X, Snow TA, Kemper RA, Jepson GW.: , Chem Res Toxicol. 2003 Jun;16(6):775-81.</ref>, liver fatty acid-binding protein<ref>Luebker DJ, Hansen KJ, Bass NM, Butenhoff JL, Seacat AM. , Toxicology. 2002 Jul 15;176(3):175-85.</ref>, and the ] ]<ref>Maloney EK, Waxman DJ.: Toxicol Appl Pharmacol. 1999 Dec 1;161(2):209-18.</ref>.


The eight-carbon fluorosurfactants such as PFOA and ] are the most effective for the manufacture of Teflon. Being the most effective, the two have found wide production and are thus typically found in the highest concentrations in the environment. Thus, they are the most studied and most subject to health, environmental, and regulatory concerns. Ironically, the very properties that make PFOA useful - its stability and bipolar character - also contribute to its toxicological and environmental impacts. The eight-carbon fluorosurfactants such as PFOA and ] are the most effective for the manufacture of Teflon. Being the most effective, the two have found wide production and are thus typically found in the highest concentrations in the environment. Thus, they are the most studied and most subject to health, environmental, and regulatory concerns. Ironically, the very properties that make PFOA useful - its stability and bipolar character - also contribute to its toxicological and environmental impacts.

Revision as of 00:22, 26 August 2008

Template:Chembox new Perfluorooctanoic acid (PFOA), also known as C8, is a man-made surfactant. PFOA can designate the acid itself or its principal salts (like ammonium perfluorooctanoate, also known as APFO).

Perfluorooctane sulfonate (PFOS) is a related compound.

Uses

PFOA is used as an industrial surfactant. It is an emulsifier for the processing of fluoropolymers such as polytetrafluoroethylene (PTFE), most widely recognized under the brand name Teflon by DuPont.

Properties

As for related perfluorinated hydrocarbons, the properties of PFOA arise from the nature of the carbon-fluorine (C-F) bond in tandem with its polar head group. The C-F bond is one of the strongest in organic chemistry, and en masse they result in molecules with high chemical and thermal stability, see perfluorocarbons. (While throwing hydrocarbons on a fire will only fuel it, fluorocarbons are used in fire-fighting foams). C-F bonds also strengthen the underlying backbone carbon-carbon bonds. The C-F bond is rarely found in nature.

The perfluorinated chain of PFOA has a minimized potential for the formation of the fleeting dipoles that form the basis for van der Waals/London dispersion forces because the highest electronegativity of fluorine reduces the polarizability of the constituent elements. As a result, fluorinated surfactants like PFOA are lipophobic, despite the perfluorinated chain being non-polar, unlike other organohalogens. The carboxylic acid group is hydrophilic as indicated by the modest water solubility of PFOA. The carboxlic acid group is the means by which PFOA binds proteins that bind fatty acid or hormone substrates such as serum albumin, liver fatty acid-binding protein, and the nuclear receptor PPARα.

The eight-carbon fluorosurfactants such as PFOA and PFOS are the most effective for the manufacture of Teflon. Being the most effective, the two have found wide production and are thus typically found in the highest concentrations in the environment. Thus, they are the most studied and most subject to health, environmental, and regulatory concerns. Ironically, the very properties that make PFOA useful - its stability and bipolar character - also contribute to its toxicological and environmental impacts.

Indirect sources of PFOA

PFOA, usually pronounced "P - F - O - A", is also a by-product of the telomerization process taking place on industrial scale in Asia, North America, and Europe by several international chemical companies. The telomerization process produces perfluorinated alcohol, which is commonly used in many household surface finishes and indirect contact applications in flexible food packaging. PFOA by-product is also in the fabrication of water- and stain-resistant clothes and other materials, including the products StainMaster, and Gore-Tex. (3M Scotchgard complied with a voluntary phase out of PFOS, a competing technology to the Zonyl trade name). PFOA by-product is also found in aqueous film forming foam (AFFF), a component of fire-fighting foams.

Fluorotelomer compounds (produced by several international companies) are used in food packaging to make them resistant to grease; however, these compounds may form PFOA when ingested. According to a USA Today article, these compounds have been used in "microwave popcorn bags, fast food and candy wrappers, and pizza box liners" . In particular, microwave popcorn bags have the most fluorotelomers of any food wrapper, and the high cooking temperatures increase the migration of these chemicals into the popcorn oil. It is estimated that microwave popcorn may account for more than 20% of the average PFOA levels measured in American residents. Its elimination half-life is reported as being 4 years .


Health concerns

The durability of PFOA leads to bioaccumulation in food chains and elsewhere. For example, traces of PFOA and related compounds (PFOS, PFNA, and PFHxS) have been detected in the blood of nearly all Americans. and in the environment worldwide including oceans, rivers, arctic snow, and surface and drinking waters. In light of concerns about these risks, its major manufacturer, 3M, to announce in May 2000 that it would cease producing the PFOA. DuPont, one of the largest users of PFOA, then built its own plant in Fayetteville, North Carolina to manufacture PFOA.

Actions in the US

DuPont has used PFOA for over 50 years at its Washington Works plant near Parkersburg, WV. Area residents sued DuPont in 2001, claiming that the chemical contaminated area drinking water. As part of the settlement, DuPont is paying for blood tests and health surveys of residents believed to be affected. Up to 60,000 people are expected to participate in the study, which will be reviewed by epidemiologists to determine any long-term health effects.

In 2004, DuPont was investigated by the Environmental Protection Agency (EPA) for allegedly covering up knowledge of possible health effects of PFOA exposure in a study of pregnant employees, including evidence of PFOA in umbilical cord blood.

The EPA pursued charges against DuPont for failure to report violations filed under the Toxic Substances Control Act and the Resource Conservation and Recovery Act. On December 13, 2005 DuPont announced a settlement with the EPA in which DuPont will pay US$10.25 million in fines and an additional US$6.25 million for two supplemental environmental projects without any admission of liability.

On January 25, 2006, the EPA announced a long-term, voluntary program to reduce PFOA emissions and to eliminate PFOA use in products by the year 2015. While a New York Times article the next day claimed that companies would "stop using" PFOA, the EPA described its objective as "elimination of PFOA...from emissions and products" but not as a chemical intermediate to produce other substances.

On February 15, 2006, the EPA's Science Advisory Board recommended that PFOA should be considered a likely carcinogen.

On May 26, 2006, an EPA Science Advisory Board letter was addressed to EPA Administrator Stephen L. Johnson, which included an Executive Summary of EPA Science Advisory Board positions regarding the carcinogenic potential of PFOA to humans from PPARα agonism. Only about 1/4 of the advisers agreed with the EPA's own PFOA hazard descriptor of “suggestive evidence of carcinogenicity, but not sufficient to assess human carcinogenic potential" while about 3/4 of the advisers thought the stronger designation of PFOA as "likely to be carcinogenic" was warranted.

On November 21, 2006, EPA ordered DuPont company to offer alternative drinking water or treatment for public or private water users living near DuPont's Washington Works plant in West Virginia (and in Ohio), if the level of PFOA detected in drinking water is equal to or greater than 0.50 parts per billion (ppb). This measure lowered action level and replaced the previous 150 ppb threshold that had been established in March 2002.

European action

Recently, PFOA was found in German drinking water samples in concentrations of up to 0.60 ppb

See also

External links

  • United States Environmental Protection Agency - PFOAs
  • The Environmental Working Group, PFC page
  • Chemical in Teflon, other goods is turning up in disturbing places, Seattle Times Oct 1, 2004
  • DuPont, Now in the Frying Pan, NY Times Aug 8, 2004
  • US Environmental Protection Agency, PFOA Stewardship Program, Jan 25, 2006
  • Perfluorooctanoic Acid (PFOA) by Richard Clapp, a case study at DefendingScience.org

References

  1. Park KH, Berrier C, Lebaupain F, Pucci B, Popot JL, Ghazi A, Zito F.: "Fluorinated and Hemifluorinated Surfactants as Alternatives to Detergents for Membrane Protein Cell-Free Synthesis", Biochem J. 2007 Apr 1;403(1):183-7.
  2. Han X, Snow TA, Kemper RA, Jepson GW.: "Binding of Perfluorooctanoic Acid to Rat and Human Plasma Proteins", Chem Res Toxicol. 2003 Jun;16(6):775-81.
  3. Luebker DJ, Hansen KJ, Bass NM, Butenhoff JL, Seacat AM. "Interactions of Fluorochemicals with Rat Liver Fatty Acid-Binding Protein", Toxicology. 2002 Jul 15;176(3):175-85.
  4. Maloney EK, Waxman DJ.: "trans-Activation of PPARalpha and PPARgamma by Structurally Diverse Environmental Chemicals" Toxicol Appl Pharmacol. 1999 Dec 1;161(2):209-18.
  5. Calafat AM, Wong LY, Kuklenyik Z, Reidy JA, Needham LL.: "Polyfluoroalkyl Chemicals in the U.S. Population: Data from the National Health and Nutrition Examination Survey (NHANES) 2003-2004 and Comparisons to NHANES 1999-2000", Environ Health Perspect 2007 Nov;115(11):1578-83.
  6. Yamashita N, Kannan K, Taniyasu S, Horii Y, Petrick G, Gamo T.: "A Global Survey of Perfluorinated Acids in Oceans", Mar Poll Bull. 2005;51(8-12):658-68.
  7. McLachlan MS, Holmstrom KE, Reth M, Berger U.: "Riverine Discharge of Perfluorinated Carboxylates from the European Continent", Environ Sci Technol. 2007 Nov 1;41(21):7260-5.
  8. Young CJ, Furdui VI, Franklin J, Koerner RM, Muir DC, Mabury SA.: "Perfluorinated Acids in Arctic Snow: New Evidence for Atmospheric Formation"., Environ Sci Technol. 2007 May 15;41(10):3455-61.
  9. Skutlarek D, Exner M, Färber H.: "Perfluorinated Surfactants in Surface and Drinking Waters.", Environ Sci Pollut Res Int. 2006 Sep;13(5):299-307.
  10. USEPA: "SAB Review of EPA’s Draft Risk Assessment of Potential Human Health Effects Associated with PFOA and Its Salts", p.2 (May 30, 2006).
  11. Mid-Atlantic Enforcement (2007-05-10). "Fact Sheet: EPA, DuPont Agree on Measures to Protect Drinking Water Near the DuPont Washington Works". Environmental Protection Agency. Retrieved 2008-05-11.
  12. "Perfluorinated surfactants contaminate German waters – Mislabeled waste in fertilizer leads to a water scandal". Environmental Science & Technology Online. 2006-11-01. Retrieved 2008-05-11.
  • Farkas, Brian (Associated Press). "Plant tests thousands for exposure to Teflon chemical". Austin American-Statesman (November 18, 2005), p A27.
  • Hekster, FM, de Voogt, P, Laane, RWPM, Peijnenburg, J, 2002, Perfluoroalkylated substances: an aquatic environmental assessment,
  • "DuPont reaches $16.5M deal with EPA". CNNMoney. Retrieved Dec. 15, 2005.
  • Michael Janofsky, "E.P.A. seeks to phase out a toxic chemical," New York Times, Jan 26, 2006
  • Martin, J.W.; Smithwick, M.M.; Braune, B.M.; Hoekstra, P.F.; Muir, D.C.G.; Mabury, S.A. "Identification of Long-Chain Perfluorinated Acids in Biota from the Canadian Arctic." Environmental Science and Technology 2004, 38 (2), pp. 373-380.
  • Ellis, D.A.; Mabury, S.A.; Martin, J.W.; Muir, D.C.G. "Thermolysis of fluoropolymers as a potential source of halogenated organic acids in the environment." Nature 2001, 412 (6844), pp. 321-324.
  • Lau C, Thibodeaux JR, Hanson RG; et al. (2006). "Effects of perfluorooctanoic acid exposure during pregnancy in the mouse". Toxicology Science. 90: 510–518. doi:10.1093/toxsci/kfj105. PMID 16415327. {{cite journal}}: Explicit use of et al. in: |author= (help)CS1 maint: multiple names: authors list (link)
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