Evolving Accumulation of a Complex Profile of Polychlorinated Alkanes in Canadian Polar Bears

Approximately 33 million t of polychlorinated alkanes (PCAs), also known as chlorinated paraffins, has been globally produced and used. Despite the higher bioaccumulation potential of PCAs in terrestrial ecosystems than in marine ecosystems, North American terrestrial PCA data are sparse and Arctic studies largely focus on short-chain PCAs, with minimal attention to longer-chain homologues in wildlife. This research delves into the dynamics of PCA accumulation and temporal changes across a broad spectrum of PCA homologues in polar bears (Ursus maritimus) from Hudson Bay. Subcutaneous fat samples collected over the past decade from adult male polar bears of the Western Hudson Bay (WHB) and Southern Hudson Bay (SHB) subpopulations were analyzed, identifying 109 of 545 PCA homologues, ranging from C-8 to C-26. Analysis of 37 dietary fatty acids provided insights into dietary shifts and their influence on PCA profiles. Notably, SHB bears exhibited a decrease in PCA concentrations, reflecting marine food web influences. In contrast, WHB bears displayed increasing PCA levels, likely due to the use of more terrestrial and anthropogenic food sources. This study underscores the critical yet overlooked role of longer-chain PCAs in the Arctic food web and polar bear exposure, emphasizing the variance between subpopulations and the significant impact of dietary factors.