Substance Identity

Information on the identity of perfluorooctanoic acid (PFOA) is presented in Table 1. PFOA is an anthropogenic compound with a chain length of eight carbons, seven of which are perfluorinated. It belongs to the broad class of chemicals known as perfluorocarboxylic acids (PFCAs), which, in turn, belong to the broader class of chemicals known as perfluoroalkyls (PFAs). The term “PFOA” may refer to the acid, its conjugate base or its principal salt forms (Table 2). The term PFOA is not interchangeable with commercial mixtures containing PFOA, as these mixtures are often not well characterized and could include any product that contains even a small amount of PFOA. PFOA may also be referred to as C8, as well as by other synonyms or trade names. A more detailed discussion of the identity, nomenclature and trade names of PFOA is provided in Ellis et al. (2004b). The most common commercially used salt form of PFOA is the ammonium salt, referred to as APFO (see chemical structure in Table 1).

Table 1. Substance Identity

Environment Canada considered perfluoroalkyl compounds on the basis of expert judgement, chemical structures and biodegradation estimation modelling using CATABOL (c2004–2008) (Mekenyan et al. 2002). Using these approaches, the structures were analyzed for their potential to degrade to PFOA. CATABOL (c2004–2008) was trained on the basis of the Japanese Ministry of International Trade and Industry (MITI) biodegradation test results and predicts biodegradation over a period of 28 days. It is acknowledged that due to the limited perfluorinated degradation data in the training set, some degradation products generated by CATABOL (c2004–2008) may be of limited reliability. It should be noted that the degradation process will be longer for perfluorinated chemicals, but it is difficult to estimate how much longer, especially for high-molecular-weight substances such as oligomers and polymers.

Precursors to PFOA (Table 2) have been considered in this assessment; however, this list should not be considered exhaustive. A more complete list can be found under the Notice with respect to certain perfluoroalkyl and fluoroalkyl substances at: https://www.canadagazette.gc.ca/rp-pr/p1/2005/2005-01-15/pdf/g1-13903.pdf (PDF 2.2 MB). It should also be noted that some precursors to PFOA may also be considered as precursors to long-chain (C9-C20) perfluorocarboxylic acids. This assessment defines precursors as substances where the perfluorinated alkyl moiety has the formula C_nF_2n+1 (where n= 7 or 8) and is directly bonded to any chemical moiety other than a fluorine, chlorine or bromine atom.

Table 2. List of PFOA and its Principal Salts and Precursors¹