Sources of PFSAs and PFCAs

The first report of an indirect source of PFCAs to the environment was the thermolysis of fluoropolymers [151, 152]. FTOHs and FSAs have also been identified as indirect sources. Degradation of FTOHs results in the production of PFCAs, under both abiotic [153-155] and biological [40,103,104,156,157] conditions. PFSAs are also observed in the biological degradation ofFSAs [158, 159], while abiotic degradation ofFSAs produces both PFCAs and PFSAs [160, 161]. 

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The origin and transport pathways of PFSAs and PFCAs in the Arctic is a topic of interest that has received considerable attention by researchers. In particular, two hypotheses have been proposed to explain the sources of PFSAs and PFCAs to the Arctic. It is important to note that proponents of both hypotheses agree that both transport routes are likely to occur simultaneously. However, the relative importance of each transport route is unknown. 

The majority of biological monitoring studies to date have focused on PFOSA, PFSAs and PFCAs. FTCAs and FTUCAs have been observed in some species, including seabirds and seals from the Canadian Arctic [107, 197], suggesting that FTOHs may be a source of the observed PFCAs. Two studies have also investigated the presence of other FSAs in biological samples. Tomy et al. [87] have observed NEtFOSA in an Eastern Arctic marine food web, while Taniyasu et al. [182] have observed NEtEOSA in beaver fiver samples. 

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