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Draft Screening Assessment Perfluorooctanoic Acid, its Salts, and its Precursors

Sources

PFOA and its salts are of anthropogenic origin with no known natural sources (Kissa 1994). Surveys of industry conducted in 2000 and 2004 under the authority of section 71 of CEPA 1999, were used to collect data on the Canadian manufacture, import and export of certain perfluoroalkyl and fluoroalkyl substances, their derivatives and polymers, including PFOA (Canada 2000b, Canada 2004).

Results from the 2000 survey indicated that PFOA and its salts were not manufactured in Canada. Approximately 600 000 kg of PFAs were imported into Canada between 1997 and 2000. Imports of PFOA and its salts were reported by one company. The import of PFOA and its salts (< 1000 kg) represented a very small proportion of the PFAs imported and consisted almost exclusively of the ammonium salt used in industrial applications. The volumes reported do not include quantities possibly imported in manufactured items (Environment Canada 2001). The reported uses for PFOA and its salts included use as a polymer, component of a formulation and other uses (i.e., batteries, coatings, lubricants) (Environment Canada 2001). Owing to its physicochemical properties, PFOA may be used as a replacement for perfluorooctane sulfonate (PFOS) in applications that had not previously used PFOA (US EPA 2002).

Industrial information was also obtained for the 2004 calendar year on the Canadian manufacture, import and export of perfluoroalkyl and fluoroalkyl (PFA/FA) substances, including PFCAs (Canada 2004). Information from this survey indicated no known manufacture of PFA/FA substances in Canada. The survey also indicated that the PFOA ammonium salt was imported into Canada in quantities ranging between 100 – 100 000 kg (Environment Canada 2005) under the North American Industry Classification System (NAICS) code “Chemical and Allied Product Wholesaler”.

PFOA has been synthesized by two main industrial processes: Simons electrochemical fluorination and telomerization (US EPA 2002). The first method relies on an electric current that is passed through a solution of anhydrous hydrogen fluoride containing, typically, an octanoic acid derivative. In this manner, all hydrogen atoms are replaced by fluorine, yielding 30–45% linear perfluorooctanoyl fluoride, along with a variable mixture of other isomers, homologues and by-products (US EPA 2002). The perfluorooctanoyl fluoride is then separated and hydrolyzed to yield PFOA. The salts of PFOA are prepared by the base neutralization of the parent acid using the appropriate metal-containing base. The second method, telomerization, involves the reaction of a molecule known as a telogen (e.g., pentafluoroethyl iodide) with two or more molecules called taxogens (e.g., tetrafluoroethylene). This process yields telomer iodides, which can be oxidized to produce a carboxylic acid--for instance, >99% pure PFOA (Prevedouros et al. 2006)--and reacted with ethylene to produce a further iodide. These iodides can then be reacted to form a multitude of functional materials. The telomerization process generally results in mixtures of compounds with even ranges of carbon numbers.

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