Releases to the Environment

Releases to the environment may occur during manufacturing and processing operations and throughout the service life and subsequent disposal of articles containing PFOA. Potential point sources thus include direct releases from manufacturing or processing facilities. Indirect releases may result from the degradation or transformation of precursors in wastewater treatment plants (WWTPs) and landfills. Such precursors may include parent compounds or chemical products containing PFOA. Potential precursors include related fluorochemicals that are detectable in the atmosphere (e.g., 8:2 fluorotelomer alcohols [FTOH], which have eight fluorinated carbons and a two-carbon ethyl alcohol group) and can degrade or transform to PFOA through biotic or abiotic pathways.

PFOA and its salts are not manufactured in Canada (Environment Canada 2001). There are no published data on direct releases to air, water or land from Canadian industrial facilities (Ellis et al. 2004b).

Muir and Scott (2003), Scott et al. (2003) and Boulanger et al. (2005) reported the presence of PFOA in sewage treatment plant (STP) effluents entering the Great Lakes. Measured PFOA concentrations in treated effluents from STPs in Thunder Bay and Sault Ste. Marie, Ontario, ranged from 7.9 to 24 ng/L (Scott et al. 2003). PFOA was also measured in a North Toronto STP effluent at 38 ng/L (Muir and Scott 2003). Crozier et al. (2005) measured PFOA in effluent waters (concentrations ranging from 7 – 55 ng/L) and biosolids (concentrations ranging from 0.7 – 0.9 ng/g) from Ontario sewage treatment plants. Crozier et al. (2005) also noted that PFOA was detected at 7 ng/L in one STP influent and then measured at 7 ng/L in the same STP’s effluent suggesting that PFOA may have formed during the sewage treatment plant processes.

Boulanger et al. (2005) conducted a lakewide mass budget analysis of eight perfluorooctane surfactants, includingPFOA, for Lake Ontario. Boulanger et al. (2005) cited and used a 3M Company 1999 study which analyzed the finished effluents from six wastewater treatment plants (WWTP) for three perfluorinated compounds, including PFOA. Four WWTPs were located in US cities with known sources of manufacture or industrial use of perfluorinated compounds, and two WWTPs were located in US cities with no known sources. All WWTPs had detectable concentrations of PFOA, ranging from 41.2 to 2420 ng/L. Boulanger et al. (2005) used a PFOA concentration in WWTP effluent of 549 ± 840 ng/L from this 3M Company 1999 study for the mass budget analysis. Boulanger et al. (2005) noted that there was a high degree of uncertainty associated with this concentration owing to the limited number of samples studied, and the study did not include actual WWTP effluent discharge to the Great Lakes system. The Boulanger et al. (2005) mass budget calculations showed the inflow from Lake Erie and wastewater discharges to be the major sources, whereas outflow through the St. Lawrence River was the dominant loss mechanism, indicating that there are unaccounted sources to Lake Ontario. Boulanger et al. (2005) suggested that the cleaning and care of surface-treated products by consumers and uses of perfluorooctane surfactants in industrial processes may lead to the presence of these substances in WWTP discharges. It was also suggested that discarded treated articles in landfills and the subsequent treatment of landfill leachates by municipal water treatment works may introduce significant amounts of perfluorooctane surfactants into the environment. Dinglasan-Panlilio and Mabury (2006) found that different fluorinated materials and/or products all contained free or unbound fluorinated alcohols. The authors suggested that the residual fluorinated alcohol contribution to the atmospheric load of telomer alcohols is significant and may be the dominant source, given that the release of these residual fluorinated alcohols may occur all along the supply chain from production through application to actual consumer use.

There are some Canadian data on releases of PFOA from landfills (Ikonomou 2006). PFOA was detected in the Arctic landfill sediment at 22–1083 ng/g and in Kamloops, British Columbia landfill sediments up to 186 ng/g. Landfill leachates from across Canada were also analyzed forPFOA.PFOA was detected in landfill leachates in Waterloo, Ontario (458 ng/L), Cambridge, Ontario (1144 ng/L), Moncton, New Brunswick (88 ng/L), Halifax, Nova Scotia (2040 ng/L), Charlottetown, Prince Edward Island (642 ng/L), Toronto, Ontario (880 ng/L), Kelowna, British Columbia (146 ng/L), and Calgary, Alberta (238 ng/L). PFOA has been detected in landfill leachates (91.3–516 ng/L) (Kallenborn et al. 2004) in other countries that, like Canada, do not manufacture perfluorochemicals.

Potential sources for the formation of PFOA, such as the degradation or transformation of precursors, could lead to indirect environmental releases and contribute to the total amount of PFOA found in the environment.

D’Eon et al. (2007) determined that PFOA can be formed from polyfluoroalkyl phosphate surfactants (PAPS) such as 8:2PAPS via cleavage of the phosphate ester linkage, releasing free 8:2 FTOH, with subsequent biotransformation to PFOA.

PAPS are approved by the U.S. EPA as an inert defoaming additive to pesticide formulations and as nonpolymeric fluorinated surfactants approved for application to food contact paper products (D’Eon et al. 2007).

Wallington et al. (2006) used a three-dimensional global atmospheric chemistry model (IMPACT) to indicate thatn-C₈F₁₇CH₂CH₂OH (i.e., 8:2 FTOH) degrades in the atmosphere to give PFOA and other PFCAs. Schenker et al. (2008) used a global-scale multispecies model (CliMoChem) to indicate that, until the year 2000, the contribution of atmospheric fluxes from perfluorooctanesulfonyl fluoride–based substances to the atmospheric deposition of PFOA in the Arctic was similar to the contribution from fluxes from FTOHs. Depending on the location and season, molar PFOA concentrations in the atmosphere are considered to be the correct order of magnitude to explain observed levels in Arctic biota (Wallington et al. 2006). The seasonal behaviour of PFOA is such that relatively high PFOA concentrations (>1.5 × 10³ molecules/cm³) extend throughout the Arctic during the Arctic summer, whereas winter PFOA concentrations are lower by an order of magnitude (Wallington et al. 2006).

The formation of PFOA through the thermolysis of fluoropolymers has been reported by Ellis et al. (2001, 2003). The results from these studies indicate the potential for this process to produce PFOA. However, Ellis et al. (2001, 2003) stated that this process is unlikely to release significant quantities of PFOA to the environment and would not contribute to its long-range transport. The onset of thermolysis of fluoropolymers occurs at 365°C (not an environmentally relevant temperature). These temperatures could be reached in industry and in household applications and, as such, the thermolysis of fluoropolymers could be considered a source of PFOA.

FTOHs have been shown to metabolize to PFOA in rats (Hagen et al. 1981). A ß-oxidation mechanism was proposed by Hagen et al. (1981) to account for the formation of PFOA. Dinglasan et al. (2004) showed aerobic degradation of 8:2 FTOH with an initial half-life of ~0.2 day per milligram of initial biomass protein followed by a second half-life of 0.8 day per milligram in a mixed microbial culture obtained from sediment and groundwater taken from a contaminated site, enriched on 1,2-dichloroethane and subsequently maintained using ethanol as the sole carbon source. This mixed culture was chosen because it was acclimated to degradation of chlorinated alkanes and alcohols and, therefore, considered to be active on fluorinated alcohols. The degradation of the alcohol occurred primarily through a mechanism leading to a telomer acid, which then underwent ß-oxidation to yield PFOA, accounting for 3% of the total mass of FTOH initially at day 81. However, because this study was limited to identification and quantification of known or predicted transformation products, potential unknown transformation products were not identified. FTOHs were capable of metabolizing to PFOA in municipal wastewater treatment sludge (Pace Analytical 2001). Liu et al. (2007b) showed the microbial transformation of 8:2 FTOH to PFOA in clay soil and two pure soil bacterial cultures (Pseudomonas species).

Wang et al. (2005) conducted aerobic biodegradation studies of¹⁴C-labelled 8:2 FTOH in diluted activated sludge from a WWTP. Three transformation products were identified: 8:2 saturated acids, 8:2 unsaturated acids and PFOA, representing 27%, 6.0% and 2.1%, respectively, of the initial ¹⁴C mass after 28 days. Results suggested that perfluorinated acid metabolites such as PFOA account for only a very small portion of the transformation products observed over the time frame considered (Wang et al. 2005). Wang et al. (2005) also suggested that the biological fate of 8:2 FTOH is determined by multiple degradation pathways, with neither ß-oxidation nor any other enzyme-catalyzed reaction as a single dominant mechanism. A study by Dinglasan et al. (2005) showed that the oxidation of the 8:2 FTOH to the telomer acid occurred via the transient telomer aldehyde. The telomer acid was then further transformed via a ß-oxidation mechanism, leading to the unsaturated acid and PFOA. However, a complete mass balance was not achieved, and the authors attributed this to binding of metabolites to biomass and other biological macromolecules, unaccounted metabolites, uptake of intermediates (formation of covalent linkages) or alternative degradation pathways (Dinglasan et al. 2005).

FTOHs may be released from polymeric materials or chemicals that incorporate FTOHs, or residual amounts of FTOHs that failed to be covalently linked to polymers or chemicals during production may be released. FTOHs are used in fire-fighting foams, personal care and cleaning products, and oil, stain, grease and water repellent coatings on carpet, textiles, leather and paper (US EPA 2006a). FTOHs are also used in the manufacture of a wide range of products, such as paints, adhesives, waxes, polishes, metals, electronics and caulks. During the years 2000–2002, an estimated 5 × 10⁶ kg of these compounds per year were produced worldwide, 40% of which was in North America (Dinglasan et al. 2004). Fluorotelomer-based raw materials and products are manufactured by a series of steps, beginning with Telomer A. Global Telomer A production between 2000 and 2002 was between 5000 and 6000 tonnes per year (Prevedouros et al. 2006).

Measured vapour pressures of FTOHs range from 140 to 990 Pa. The calculated dimensionless Henry’s Law constants for this class of compounds (e.g., 270 at 25°C for 8:2 FTOH) using the limited data available for water solubility and vapour pressure reveal the propensity of these compounds to partition to air (Dinglasan et al. 2004). Ellis et al. (2004a) showed the potential for FTOHs to react in the atmosphere with hydroxyl radicals to yield PFOA. Smog chamber studies indicate that FTOHs can degrade in the atmosphere to yield a homologous series of PFCAs (Ellis et al. 2004a). It is believed that oxidation of FTOHs in the atmosphere is initiated by reaction with hydroxyl radicals (Dinglasan et al. 2004; Ellis et al. 2004a). It was shown that perfluorooctyl sulphonamides react with hydroxyl radicals to yield PFOA (Hatfield et al. 2002). Although these experiments were conducted at environmentally unrealistically high concentrations of hydroxyl radicals and the results were qualitative rather than quantitative, they do show the potential for related products to react atmospherically to producePFOA.

Stock et al. (2004, 2007) showed that there is a significant concentration of FTOHs present and widely disseminated in the North American atmosphere. A recent air sampling campaign detected FTOHs at tropospheric concentrations typically ranging from 17 to 135 pg/m³, with urban locations having higher concentrations than rural areas (Martin et al. 2002; Stock et al. 2004). Loewen et al. (2008) studied atmospheric concentrations of FTOHs and lake water concentrations over an altitudinal transect in western Canada. Lake water samples were collected at Cedar Lake (a small lake near Golden, British Columbia), at Bow Lake in Banff National Park (Banff, Alberta) and at another unnamed small lake in Banff National Park (Banff, Alberta). Passive air samplers were deployed on altitudinal transects (800–2740 above sea level) from Golden, British Columbia, to Banff National Park. Loewen et al. (2008) noted that the amount of 8:2 and 10:2 FTOHs (< 2.0 ng/sampler) increased with increasing altitude. Lake water concentrations of PFOA along the elevation transect were below 1 ng/L. No clear trend was evident between altitude and PFOA concentrations. Ellis et al. (2004a) and Wallington et al. (2006) indicated that telomer alcohols may be responsible in part for the presence of PFCAs in the Arctic and other non-urban areas where concentrations of peroxy radicals far exceed those of nitrogen oxides. It was noted that since the reaction of 8:2 FTOH with nitric oxide competes with the reaction that forms PFOA, the formation of PFOA should decrease with increasing nitrogen oxide concentrations. The production of PFOA is therefore suppressed in source regions that typically have nitrogen oxide concentrations of 100 parts per trillion (ppt) or greater.

In conjunction with the atmospheric measurements of the alcohols made by Martin et al. (2002) and Stock et al. (2004) and with the profile of the linear to branched isomers observed in Canadian Arctic samples (De Silva and Mabury 2004), Ellis et al. (2004a) concluded that telomer alcohols were a plausible source for some PFOA in remote regions. This conclusion is supported by Stock et al. (2007), who measured FTOHs in air at Cornwallis Island, Nunavut, in 2004. Mean concentrations of FTOHs ranged from 2.8 to 14 pg/m³. This conclusion is also supported by observations of PFOA in US rainwater (Scott et al. 2003, 2006b). These results indicate that FTOHs are widely disseminated in the troposphere and are capable of long-range atmospheric transport. In addition, De Silva et al. (2009) detected branchedPFOA isomers in Arctic and Lake Ontario sediment and surface water, Lake Ontario biota and humans; however, branched PFOA isomers were not detected in ringed seals and polar bears above the detection limits (3.6 ng/g).