Critical Review Sources, Fate and Transport of Perfluorocarboxylates KONSTANTINOS PREVEDOUROS, † IAN T. COUSINS,* ,† ROBERT C. BUCK, ‡ AND STEPHEN H. KORZENIOWSKI ‡ Department of Applied Environmental Science (ITM), Stockholm University, SE-10691 Stockholm, Sweden, and E. I. duPont de Nemours & Co., Inc., P.O. Box 80023, Wilmington, Delaware 19880-0023 This review describes the sources, fate, and transport of perfluorocarboxylates (PFCAs) in the environment, with a specific focus on perfluorooctanoate (PFO). The global historical industry-wide emissions of total PFCAs from direct (manufacture, use, consumer products) and indirect (PFCA impurities and/or precursors) sources were estimated to be 3200-7300 tonnes. It was estimated that the majority (∼80%) of PFCAs have been released to the environment from fluoropolymer manufacture and use. Although indirect sources were estimated to be much less important than direct sources, there were larger uncertainties associated with the calculations for indirect sources. The physical-chemical properties of PFO (negligible vapor pressure, high solubility in water, and moderate sorption to solids) suggested that PFO would accumulate in surface waters. Estimated mass inventories of PFO in various environmental compartments confirmed that surface waters, especially oceans, contain the majority of PFO. The only environmental sinks for PFO were identified to be sediment burial and transport to the deep oceans, implying a long environmental residence time. Transport pathways for PFCAs in the environment were reviewed, and it was concluded that, in addition to atmospheric transport/degradation of precursors, atmospheric and ocean water transport of the PFCAs themselves could significantly contribute to their long-range transport. It was estimated that 2-12 tonnes/ year of PFO are transported to the Artic by oceanic transport, which is greater than the amount estimated to result from atmospheric transport/degradation of precursors. Introduction Production of perfluoroalkyl carboxylates [F(CF2)nCO2, n g 7; PFCAs] began in 1947 using an electrochemical fluorination process (1). Early uses documented in 1966 for this “new class of compounds” were based upon their chemical stability, surface tension lowering properties, and ability to create stable foams, and included metal plating and cleaning, coating formulations, fire-fighting foams, polyurethane production, inks, varnishes, vinyl polymerization, lubricants, gasoline, and oil, and water repellents for leather, paper, and textiles (2). Many of these uses were still in practice in the 1990s (3). PFCAs and their potential precursors are of increasing scientific and regulatory (4) interest because they have been found globally in wildlife and in humans (5-15). However, the sources of PFCAs in the environment, their physical- chemical properties, and fate and transport are not well understood or described. This paper provides the first detailed accounting of the direct and indirect sources of PFCAs released into the environment. Typical PFCA compositions are described and historical global emissions from production and use as well as PFCA emissions from potential degradation of poly- and perfluorinated precursors are estimated for the period 1951- 2004. Recent industry actions to reduce PFCA global emis- sions are described. The paper additionally reviews the physical-chemical properties, fate, and transport of PFO for which there is the most available information as representa- tive of PFCAs in general. PFO mass inventories in different environmental compartments are estimated to provide an indication of environmental distribution. Finally, key PFO environmental sinks and transport pathways are scrutinized. Sources of PFCAs There are both direct and indirect sources of PFCA emissions to the environment (Figure 1). Direct sources result from the manufacture and use of PFCAs, while indirect sources in the environment are those where PFCAs are present as chemical reaction impurities or where substances may degrade to form PFCAs. The historical period of use or production and an estimation of the global industry-wide emissions for each PFCA “source” are shown in Table 1. The historical emission estimations are provided as ranges based on available data to account for the uncertainty in production, use, and emissions values over time. Computational details for the ranges reported and a summary of chemical substances, their acronyms, and chemical structures are provided in the Supporting Information. Direct Sources of PFCAs. PFCA Manufacture. PFCAs have been manufactured as salts by four distinct synthesis routes, namely: electrochemical fluorination (ECF), fluorotelomer iodide oxidation, fluorotelomer olefin oxidation, and fluo- rotelomer iodide carboxylation. Historically, commercial PFCA products were mixtures containing linear eight- or nine- carbon PFCAs as their major component. Depending upon the synthesis route and raw material, the PFCA products also contained homologues ranging from four to thirteen carbons with as much as 30 wt % branched PFCAs present (16, 17). An overview of the chain length composition, predominance of even (E) or odd (O) and straight (S) or branched (B) character from PFCA manufacture is shown in Figure 2. Direct PFCA sources are highlighted in the upper part of Figure 2. The chemical synthesis routes and com- position of some representative commercial PFCA products are provided in the Supporting Information. From 1947 through 2002, the ECF process (16) was used worldwide to manufacture the majority (80-90% in 2000) of * Corresponding author phone: (+46)(0) 8 16 4012; fax: (+46)(0) 8 674 7638; e-mail: ian.cousins@itm.su.se. † Stockholm University. ‡ E. I. duPont de Nemours & Co., Inc. 32 9 ENVIRONMENTAL SCIENCE & TECHNOLOGY / VOL. 40, NO. 1, 2006 10.1021/es0512475 CCC: $33.50  2006 American Chemical Society Published on Web 12/01/2005