Bioaccumulation and biomagnification of perfluoroalkyl acids and precursors in East Greenland polar bears and their ringed seal prey

Abstract

The bioaccumulation and biomagnification of 22 major perfluoroalkyl substances (PFAS) were investigated in tissues of polar bears (Ursus maritimus) and their major prey species, the ringed seal (Pusa hispida), from the Scoresby Sound region of East Greenland. In polar bear liver the mean Σ₄PFSA (perfluoroalkyl sulfonic acid) concentration (C₄, C₆, C₈ and C₁₀) was 2611 ± 202 ng/g wet weight (ww; 99% perfluorooctane sulfonate (PFOS)) and two orders of magnitude higher than the 20 ± 3 ng/g ww (89% PFOS) concentration in fat. The mean Σ₄PFSAs in seal liver was 111 ± 5 ng/g ww (98% PFOS) and three orders of magnitude higher relative to the 0.05 ± 0.01 ng/g ww concentration in blubber (100% perfluorohexane sulfonate). Perfluoro-1-octane sulfonamide (FOSA) was quantifiable in bear (mean 10 ± 1.4 ng/g ww) and seal (mean 0.6 ± 0.1 ng/g ww) liver but not in fat or blubber. The mean Σ₁₃PFCAs (C₄-C₁₈; perfluoroalkyl carboxylic acids) in bear liver (924 ± 71 ng/g ww) was much greater than in seal liver (74 ± 6 ng/g ww). In bear fat and seal blubber, the mean Σ₁₃PFCAs were 15 ± 1.9 and 0.9 ± 0.1 ng/g ww, respectively. Longer chain C₁₁ to C₁₄ PFCAs dominated in bear fat and seal blubber (60-80% of Σ₁₃PFCA), whereas shorter-chain C₉ to C₁₁ PFCAs dominated in the liver (85-90% of Σ₁₃PFCA). Biomagnification factors (BMFs) were orders of magnitude greater for PFHxS and C₉ to C₁₃ PFCAs when based on bear liver to seal blubber rather than bear liver to seal liver, and PFCA (C₉ to C₁₃) BMFs decreased with increasing chain length. Seal blubber to bear liver BMFs better reflects the dietary exposure relationship of PFAS between bears and seals.

Keywords: Bioaccumulation; East Greenland; PFOS; Perfluorinated acids; Polar bear; Ringed seal.