Proposed Conclusion for the Environment

The approach taken in this environmental screening assessment was to examine various supporting 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 and persistence, bioaccumulation and presence in the Canadian Arctic.

PFOS and its precursors are part of a larger chemical class of fluorochemicals typically referred to as perfluorinated alkyl compounds. This screening assessment of PFOS and its precursors defines PFOS precursors as substances containing the perfluorooctylsulfonyl (C₈F₁₇SO₂) or C₈F₁₇SO₃ moiety that have the potential to transform or degrade to PFOS. It includes, but is not limited to, PFOS and some 50 substances and precursors identified in Appendix 1. While the assessment did not consider additive effects of PFOS and all its precursors, it is recognized that precursors contribute to the ultimate loadings of PFOS. Precursors may also play a key role in the long-range transport of PFOS to remote areas.

Risk quotient analyses, integrating known or potential exposures with known or potential adverse environmental effects, were performed for PFOS (see Table 4). An analysis of exposure pathways and subsequent identification of sensitive receptors were used to select environmental assessment endpoints (e.g., adverse reproductive effects on sensitive fish species in a community). For each endpoint, a conservative Estimated Exposure Value (EEV) was selected based on empirical data from monitoring studies. Data from the Canadian and North American environment were used preferentially for EEVs. EEVs usually represented worst-case scenarios, as an indication of the potential for these substances to reach concentrations of concern and to identify areas where those concerns would be most likely.

PFOS has been detected throughout the world, including in areas distant from sources. While it is recognized that limited sampling of North American surface waters has indicated that concentrations of PFOS are low (ng/L to µg/L) and may not represent an immediate concern for acute toxicity, the use of non-Canadian quiet water data to calculate risk quotients was considered reasonable given the concern for the possible long-term impact of this substance. PFOS has been found at high levels in certain Canadian wildlife (e.g., polar bears) and globally (e.g., fish in Japan and the Netherlands). In the environment, higher concentrations of this persistent substance have been detected in sediments near industrial effluents.

The highest measured ambient or “background” PFOS concentration in water in the United States was used as a surrogate for Canadian data, after excluding potential outliers, as there were few data available for water in Canada. Although concentrations measured near manufacturing or processing plants are known to be higher, these concentrations were not considered to be reflective of the Canadian situation and were not used in calculating risk quotients. The highest measured ambient concentration exceeded the effects threshold, indicating a potential for effects on aquatic biota, birds and mammals.

Maximum concentrations in liver of wildlife in remote areas of the Canadian Arctic include the following: mink (20 µg/kg), common loon (26 µg/kg), ringed seal (37 µg/kg), brook trout (50 µg/kg), Arctic fox (1400 µg/kg) and polar bear (>4000 µg/kg) (Martin et al. 2003b). Concentrations in liver of higher trophic level biota appear to be higher than those found in lower trophic level biota.

An Estimated No-Effects Value (ENEV) was determined by dividing a CTV by an application factor. CTVs typically represented the lowest ecotoxicity value from an available and acceptable data set. Preference was generally given for chronic toxicity data, as long-term exposure was a concern. Where these data were not available, acute toxicity data were used.

The toxicity of PFOS has been studied in a variety of aquatic and terrestrial species, including aquatic plants, invertebrates and vertebrates and terrestrial invertebrates, birds and mammals. Adverse effects range from growth inhibition, histopathological effects, atrophied thymus, disruption of reproductive cycle, change in species diversity in a microcosm and mortality. The most sensitive endpoint for aquatic species was the mortality of bluegill (Lepomis macrochirus) after a 35-day exposure to PFOS potassium salt (LOEC 0.87 mg/L; NOEC 0.086 mg/L). Adverse histopathological effects were observed in rats exposed to PFOS in a 2-year laboratory study (LOELs were established at 40.8 µg/g in liver and 13.9 mg/L serum). Reduced body weight gain was observed in mallard (Anas platyrhynchos) exposed to PFOS in dietary studies, with the LOEC at 29.7 mg/kg liver. Given available information that PFOS appears to distribute preferentially in liver and blood (Taniyasu et al. 2002; Martin et al. 2003b), risk quotients in these tissues were developed for birds and terrestrial mammals.

Application factors were derived using a multiplicative approach, which uses 10-fold factors to account for various sources of uncertainty associated with making extrapolations and inferences related to the following: intra- and interspecies variations; differentially sensitive biological endpoints; laboratory to field impact extrapolation, required to extrapolate from single-species tests to ecosystems; and potential effects from concurrent presence of other substances. For substances that meet persistence and bioaccumulation criteria as outlined in the CEPA 1999 Persistence and Bioaccumulation Regulations (Government of Canada 2000), an additional application factor of 10 is applied to the CTV.

Risk quotients derived for PFOS and its precursors are summarized in Table 4. Exposure data used as EEVs are found in Table 4. Toxicity data used to determine CTVs are summarized in the section Fate, Exposure and Effects.

The risk quotient analysis indicates that the greatest potential risk from PFOS in the environment occurs in higher trophic level mammals (risk quotient >98) and fish-eating birds (risk quotient 21.9 in liver; 160 in serum); there is also some level of risk for fish (risk quotient 3.4).

While certain data gaps and uncertainties exist, there is nonetheless a substantial body of information on PFOS and its precursors. For example, while the mechanism of transport of PFOS and its precursors to the Arctic is not clear, they appear to be mobile in some form, as PFOS has been measured in biota in the Canadian Arctic far from known anthropogenic sources. Environmental pathways of PFOS to biota are not well understood because information on degradation is lacking, as are monitoring data on concentrations of various precursors in air, water, effluents and sediment in Canada. Concentrations of PFOS and its precursors in the surface water microlayer are unknown; however, given the physical properties of PFOS and its precursors, these may be considerably higher than concentrations in the water column as a whole. While mechanisms of toxic action of PFOS are not well understood, a range of toxicological effects have been reported in a variety of species. Finally, while toxicological studies have focused on the effect of PFOS itself, data on potential impacts of combined exposure to PFOS and its different precursors are limited or unknown.

PFOS is resistant to hydrolysis, photolysis, microbial degradation and metabolism by vertebrates and is persistent as defined in the Persistence and Bioaccumulation Regulations of CEPA 1999 (Government of Canada 2000).

The weight of evidence, given information on PFOS persistence, degradation of precursors to PFOS, volatilization and atmospheric transport, indicates that while PFOS has little potential to move in the environment, the precursors that will degrade to PFOS have the potential to do so, which may explain the high levels reported in the Arctic. Once the precursors degrade to PFOS, they are expected to persist indefinitely in the environment. The precursor POSF is persistent in air, with an atmospheric half-life of 3.7 years (US EPA OPPT AR226-1030a104). In water, PFOS persisted over 285 days in microcosms under natural conditions (Boudreau et al. 2003). While the vapour pressure of PFOS is similar to those of other globally distributed compounds (e.g., PCBs, DDT), its water solubility indicates that PFOS itself is less likely to partition to and be transported in air (Giesy and Kannan 2002). Although PFOS itself has low volatility, several PFOS precursors are considered volatile, including N-EtFOSE alcohol, N-MeFOSE alcohol, N-MeFOSA and N-EtFOSA (US EPA OPPT AR226-0620). When present in residuals in products, these PFOS precursors could evaporate into the atmosphere when the products containing them are sprayed and dried (US EPA OPPT AR226-0620). There is therefore potential for atmospheric transport of PFOS precursors. However, further data are required to accurately characterize this potential.

The available information suggests that the potential contribution of PFOS to stratospheric ozone depletion and to ground-level ozone formation is negligible, and its potential contribution to global warming is not known.

PFOS is present in biota, notably in vertebrates, throughout the world, including in a range of fish, birds and mammals in remote sites, including the Canadian Arctic, far from sources or manufacturing facilities of PFOS and its precursors. This indicates that PFOS is persistent in the environment and that its precursors may undergo long-range transport.

PFOS has high potential for bioaccumulation, and the weight of evidence for bioaccumulation includes estimates for BAFs and BCFs that exceed the bioaccumulation criteria in the Persistence and Bioaccumulation Regulations of CEPA 1999 (Government of Canada 2000). BAFs based on measured concentrations in biota in Canada, notably the Arctic, and in the United States and Japan range from 830 to 125 000. BCF values for fish range from 274 to 41 600. While fish may be able to eliminate PFOS via their gills, this mode of elimination is not available to higher trophic level predators (e.g., polar bear, mink and eagles) that consume fish. In addition to information on PFOS, estimated BCFs for N-EtFOSEA and N-MeFOSEA using structure–activity models were 5543 and 26 000, respectively.

CEPA 1999 recognizes the particular concerns associated with persistent and bioaccumulative substances. As indicated in the federal Toxic Substances Management Policy, “persistence and bioaccumulation can be used as qualitative surrogates for long-term exposure of environmental biota.”

Given the inherent properties of PFOS and its precursors, together with demonstrated or potential environmental concentrations that may exceed the effect levels for higher trophic level biota such as fish and fish-eating birds and mammals; given the widespread occurrence of PFOS in biota, including in remote areas; and given that PFOS precursors may contribute to the overall presence of PFOS in the environment, it is therefore concluded that PFOS, its salts and its precursors are entering the environment in a quantity or concentration or under conditions that have or may have an immediate or long-term harmful effect on the environment or its biological diversity and thus satisfy the definition of “toxic” under Paragraph 64(a) of CEPA 1999. PFOS and its salts meet the criteria for persistence and bioaccumulation as defined in the Persistence and Bioaccumulation Regulations of CEPA 1999 (Government of Canada 2000). Based on available data for PFOS, its salts and its precursors, their presence in the environment results primarily from human activity. PFOS, its salts and its precursors are not naturally occurring radionuclides or naturally occurring inorganic substances.

It is proposed that PFOS, its salts and its precursors be considered “toxic” as defined in Section 64 of CEPA 1999.

It is proposed that consideration be given to the implementation of virtual elimination of PFOS and its salts under subsection 65(3) of CEPA 1999.

^a Due to a lack of empirical data characterizing PFOS and its precursors in Canadian water, data from the United States were used as a surrogate for Canadian data. The highest relevant water concentration found was 2.93 µg/L in quiet water (pond) close to Port St. Lucie, Florida. The site was considered a reference site, since PFOS is not manufactured there. A dilution factor was not used to calculate the EEV, since PFOS has been determined to be persistent and bioaccumulative.
^b US EPA OPPT AR226-1030a042 on bluegill (Lepomis macrochirus).
^c AF (application factors): 10 applied for extrapolation from laboratory to field conditions and for intraspecies and interspecies variations in sensitivity; 10 applied because PFOS and its precursors are bioaccumulative and persistent.
^d The highest level of PFOS in liver of wild birds was 0.65 mg/kg liver (650 µg/kg liver) in common cormorant in Japan. This value was considered an appropriate surrogate given the limited information for PFOS in liver of Canadian birds. It is noted that risk quotients for a range of fish-eating birds worldwide ranged from < 1.18 in albatross in the mid-Pacific (EEV < 0.035 mg/kg liver) to 15.5 in brown pelican in Mississippi (EEV 0.46 mg/kg liver).
^e LOEC of 29.7 mg/kg (29.7 µg/g) liver wet weight for effects on body weight gain in mallard feeding study (US EPA OPPT AR226-1030a049).
^f AF (application factors): 10 applied for extrapolation from laboratory to field conditions and for intraspecies and interspecies variations in sensitivity; 10 applied because PFOS, its salts and its precursors are bioaccumulative and persistent; an additional 10 applied to extrapolate from LOEC to a chronic NOEC.
^g The highest level of PFOS measured in wildlife in serum or plasma was reported in bald eagle from Michigan, Wisconsin and Minnesota at a maximum concentration of 2220 µg/L or 2.22 mg/L (US EPA OPPT AR226-1030a159).
^h As no data exist on concentrations of PFOS in bird serum for specific toxicological endpoints, levels of PFOS in serum of rats for known toxicological effects were used as surrogates.
ⁱ In Canada, the highest PFOS concentration was found in polar bear liver (maximum >4.0 mg/kg liver) (Martin et al. 2004). The PFOS concentrations in polar bear liver were higher than any other previously reported concentrations of persistent organochlorine chemicals (e.g., PCBs, chlordane or hexachlorocyclohexane) in polar bear fat. It is noted that using the highest tissue concentration (4.87 mg/kg liver) found in the livers of mink in the Midwestern United States would yield a risk quotient (119) of the same order of magnitude, which could also be considered relevant to Canadian wildlife in mid-latitudes. The polar bear data were selected given that they are more recent and are Canadian.
^j As no wild mammal studies were found, laboratory mammal studies were used as surrogates. The CTV for mammals was selected from a 2-year dietary rat study in which histopathological effects in the liver were seen in males and females at intakes as low as 0.06-0.23 mg PFOS/kg bw per day and 0.07-0.21 mg PFOS/kg bw per day, respectively (Covance Laboratories, Inc. 2002). Average values were determined for males and females, to establish LOELs of 40.8 µg/g in liver and 13.9 mg/L in serum.