We are concerned that the weight of evidence and the emphasis on biomagnification in aquatic species played a significant role in the final decision of bioaccumulation for PFOA despite the availability of evidence of PFOA in higher tropic levels (mammals and terrestrial animals).
We are uncertain if the low levels of PFOA detected in various species of fish were the primary reasons for concluding that PFOA is not bioaccumulative as prescribed by the bioaccumulation criteria in the Persistence and Bioaccumulation Regulations, CEPA 1999.
|The numeric criteria for bioaccumulation, outlined in the Persistence and Bioaccumulation Regulations of CEPA 1999, are based on bioaccumulation data for freshwater aquatic species (i.e. fish) only as well as for substances that preferentially partition to lipids. As a result, the criteria are of uncertain relevance as indicators of the bioaccumulation potential of PFOA which preferentially partitions in the proteins of liver, blood and kidney in terrestrial and marine mammals. The bioaccumulation potential of PFOA in fish may be low. However, PFOA is considered to accumulate and biomagnify in terrestrial and marine mammals as BMFs ranged from 0.03 to 125 (polar bears) and TMFs ranged from 0.1 – 3.28 (beluga whales).|
|Was the weight of evidence approach applied by the assessors adequate to include careful consideration of all degradation or breakdown products, metabolism, and potential synergistic effects of other substances similar to long chain PFCAs or PFOAs, their salts and their precursors?||The key issue considered in this assessment is the bioaccumulation potential of PFOA, rather than the accumulation of individual precursors. While the full range of precursors is less well characterized than PFOA itself, precursors were included as they are expected over time to degrade to PFOA, thereby ultimately contributing to the environmental loading for PFOA. Precursors may also play a key role in the long-range transport and subsequent degradation to PFOA in remote areas.|
|We encourage the government to initiate a review of the Persistence and Bioaccumulation Regulations, with an aim to strengthen the criteria applied for persistence and include the consideration of bioaccumulation in terrestrial animals and mammals. The government should acknowledge that certain substances such as those that are ionizable may not exhibit the bioaccumulative potential as required under the Persistence and Bioaccumulation Regulations. The Persistence and Bioaccumulation Regulations should be more encompassing and ensure that the determination of bioaccumulation potential for these types of substances can be undertaken.||In the published assessments for perfluorinated substances such as PFOS, PFOA and the long-chain PFCAs, the Government of Canada has acknowledged that the criteria for bioaccumulation as stated in the Persistence and Bioaccumulation Regulations may not fully account for accumulation of substances that partition to non-lipid tissues. The appropriateness of revisions to the Persistence and Bioaccumulation Regulations will be further considered.|
|While the screening assessment noted that the measures for TMFs and BMFs may note the differences found in the food webs of these organisms, they may not determine the bioaccumulation potential for PFOA. Nevertheless, we note the importance of using these measures to inform the decisions by government on bioaccumulation for PFOA.||There are various uncertainties associated with the bioaccumulation of perfluorinated compounds, such as PFOA, and these are recognized and described in the screening assessment. However, if substances have been shown in field studies to biomagnify through the food web (through measures such as BMFs and TMFs), it is considered that this provides weight of evidence that the substance can significantly accumulate in biota.|
|We have great concern as there is limited information on the toxicology of PFOA precursors, the potential for combined or synergistic effects with PFOA, and the toxicology and potential for combined or synergistic effects of PFOA with other perfluoroalkyl acids. With variability in analytical results between individual laboratories, this raises more concern as to the confidence level in the data collected.||It is recognized that other perfluoroalkyl compounds and precursors to PFOA may contribute to the overall additive or synergistic impact of PFOA and that precursors contribute to the ultimate loadings of PFOA. However, the assessment did not consider the combined effects of PFOA, all its precursors and other perfluorinated compounds. The key issue considered is the bioaccumulation potential of PFOA, rather than the accumulation of individual compounds. However, the screening assessment does recognize the various uncertainties and data gaps associated with the evaluation of ecological risks of perfluorinated compounds, such as PFOA.|
|It is not scientifically appropriate to ascribe causation to PFOA for potential observed effects where a causative relationship has not been established (even if a statistical association has been observed).||Causation to PFOA was not stated for potential observed effects if a causative relationship was not clearly established for studies described in the screening assessment. For example, causation to PFOA was not stated for the study on liver lesions in East Greenland polar bears and for the study on inflammation and immunity parameters in bottlenose dolphin.|
|The ecological exposure, effects and risk assessments do not focus on exposure concentrations to the same extent, but rather seems to infer the importance of potential exposure concentrations based solely on the persistence of PFOA and detection of PFOA at typically very low concentrations.||The exposure and risk characterization of PFOA is based on the available data in Canada. The risk quotients for some types of fish indicate a low likelihood of risk from exposures at current concentrations in the environment.|
|There are no studies using environmental samples collected since 2000 that suggest that there is an on-going, increasing trend in PFOA concentrations in any species.||The Government of Canada identified three studies showing temporal trends of PFOA up to 2002 and 2006 (i.e, 1972–2002, 1984–2006, and 1992–2002) for polar bears and sea otters.|
|The evaluation of “biomagnification” (and perhaps bioaccumulation) based on extrapolations from liver residues in one organism to liver residues in another organism at the next higher position in the food chain is inappropriate because it assumes undemonstrated similarities in uptake processes and organism physiology.||From a physiological perspective, it is the concentration of a substance at the site of toxic action within the organism that determines whether a response is observed, regardless of the external concentration. In the case of PFOA, the site of toxic action is often considered to be the liver. However, when the potential for toxicity in consumer organisms is being determined, it is the concentration in the whole body of a prey item that is of interest, since the prey is often completely consumed by the predator (including individual tissues and organs, such as the liver and blood). Since perfluorinated substances partition to liver and blood, most field measurements for these substances have been performed on those individual organs and tissues. This is especially true for organisms at the higher trophic levels (e.g., polar bear), where whole-body analysis is not feasible. Thus, from a toxicological perspective, BCFs, BAFs and BMFs based on concentrations in individual organs, such as the liver, may be more relevant when the potential for direct organ-specific toxicity (i.e., liver toxicity) is being predicted.|