Ecological screening assessment report on perfluorooctane sulfonate, salts and precursors: introduction


An ecological screening assessment was undertaken on perfluorooctane sulfonate (PFOS), its salts and its precursors containing the perfluorooctylsulfonyl (C8F17SO2, C8F17SO3 or C8F17SO2N) moiety. The assessment was undertaken on the basis that some of these compounds were identified as part of a Domestic Substances List (DSL) pilot for screening as they met the criteria for persistence, bioaccumulation and/or inherent toxicity, pursuant to Paragraph 73(1)(b) of the Canadian Environmental Protection Act,1999 (CEPA 1999) and in response to a request to the Minister of the Environment to add these compounds to the Priority Substance List (PSL) for assessment of ecological and human health.

PFOS, its salts and its precursors form part of a larger chemical class of fluorochemicals referred to as perfluorinated alkyl (PFA) compounds. The term PFOS may refer to any of its anionic, acid or salt forms. The perfluorooctylsulfonyl (C8F17SO2, C8F17SO3 or C8F17SO2N) moiety is incorporated in a variety of compounds which have the potential to transform or degrade back to PFOS in the environment. For the purpose of this assessment, the term “precursor” refers to compounds that contain the C8F17SO2 or C8F17SO3, or C8F17SO2N moiety and, therefore, have the potential to transform or degrade to PFOS. The term “precursor” applies to, but is not limited to, some 50 substances identified in the ecological assessment. This assessment addresses PFOS and also considers its precursors given their similar use applications and given that PFOS is the final degradation product of PFOS precursors. While the assessment did not consider the additive effects of PFOS and its precursors, it is recognized that the precursors to PFOS contribute to the ultimate environmental loading of PFOS. Precursors may also play a key role in the long-range transport and subsequent degradation to PFOS in remote areas.

The approach taken in this ecological screening assessment was to examine the available information and develop conclusions based on a weight of evidence approach as required under Section 76.1 of CEPA 1999. Particular consideration was given to risk quotient analyses, persistence, bioaccumulation and presence in the Canadian Arctic environment and wildlife. Other concerns that affect current or potential risk, such as chemical transformation and precursors, were also examined. This ecological screening assessment report does not present an exhaustive review of all available data. Rather, this report presents the most critical information in a weight of evidence approach to support the conclusions.

Data relevant to the ecological screening assessment of PFOS and its precursors was identified in original literature, review documents, international assessments (e.g., European Commission 2005, OECD 2002a, and Swedish Chemicals Inspectorate et al. 2004) and industry research reports. A supporting document was prepared using degradation modeling (CATABOLFootnote 1 software) to predict PFOS precursors. On-line literature database searches were conducted for select perfluoroalkyl compounds. Direct contacts were made with researchers, academics, industry and other government agencies to obtain relevant information on PFOS, its salts and its precursors. Ongoing scans were conducted of the open literature, conference proceedings and the Internet. Data up to November 2005 were considered. In addition, a survey on certain perfluoroalkyl and fluoroalkyl substances, their derivatives and polymers was conducted through a Canada Gazette Notice under the authority of Section 71 of CEPA 1999 (Environment Canada, 2001). This survey required industry to provide data on the Canadian manufacture, import and export of certain perfluorinated alkyl compounds from 1997-2000. Existing toxicological studies submitted by industry under Section 70 of CEPA 1999 were also examined.

Following internal and external science reviews, a draft ecological screening assessment of PFOS, its salts, and its precursors was made available for a 60-day public comment period (October 2 to December 2, 2004). Following consideration of comments received, the ecological screening assessment and its associated, unpublished Supporting Working Document were subsequently revised, as appropriate, by Environment Canada. A summary of the comments and responses is available on the Evaluating Existing Substances website. The external science peer review was conducted by Canadian and international experts from government, industry and academia. These peer reviewers included S. Beach (3M), W. De Coen (University of Antwerp, Belgium), P. de Voogt (University of Amsterdam), W. de Wolf (DuPont, Germany), S. Dimitrov (Prof. As Zlatarov University, Bourgas, Bulgaria), J. Giesy (Michigan State University), O. Hernandez (US Environmental Protection Agency), S. Mabury (University of Toronto), R. Medsker (private consultant), O. Mekenyan (Prof. As Zlatarov University, Bourgas, Bulgaria), D. Muir (Environment Canada, National Water Research Institute), R. Purdy (private consultant), E. Reiner (3M), M. Santoro (3M) and B. Scott (Environment Canada, National Water Research Institute). The conclusion of this screening assessment report does not necessarily reflect the opinion of the peer reviewers. All peer reviewer comments were considered carefully and, where appropriate, used by Environment Canada.

The associated, unpublished Supporting Working document is available upon request by e-mail from Information on ecological screening assessments under CEPA 1999 is available at the Evaluating Existing Substances section within Environment Canada website. Information on the human health screening assessment is available at Health Canada.

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