Environment Canada researchers, in collaboration with Danish colleagues, investigated the comparative accumulation of perfluoroalkyl acids (PFAA) contaminants in eight brain regions of 19 polar bears (Ursus maritimus) collected in 2006 from Scoresby Sound, East Greenland. They found that PFAA contaminants accumulated differently depending on the region of the brain. PFAA exposure in the polar bear brain is of toxicological concern.

PFAAs studied were perfluorinated carboxylates (PFCAs; C₆-C₁₅ chain lengths) and sulfonates (C₄, C₆, C₈ and C₁₀ chain lengths), and selected precursors including perfluorooctane sulfonamide. On a wet weight basis, blood-brain barrier transport of these PFAAs occurred for all brain regions, although inner regions of the brain closer to incoming blood flow, the pons/medulla, thalamus and hypothalamus, contained consistently higher PFAA concentrations compared to outer brain regions (cerebellum, striatum, and frontal, occipital and temporal cortices). For pons/medulla, thalamus and hypothalamus, the most concentrated PFAAs were perfluorooctane sulfonate (PFOS) and perfluorotridecanoic acid. However, perfluorooctane sulfonate and the longer chain PFCAs (C₁₀-C₁₅) were significantly positively correlated with lipid content for all brain regions. Lipid normalized perfluorooctane sulfonate and PFCA (C₁₀-C₁₅) concentrations were not significantly different among brain regions.

Source: Greaves, A.K., R.J. Letcher, C. Sonne and R. Dietz. 2012. Brain region distribution and patterns of bioaccumulative perfluoroalkyl carboxylic and sulfonic acids in highly exposed East Greenland polar bears (Ursus maritimus). Environ. Toxicol. Chem. Accepted June 2012.

Contact: Dr. Robert Letcher, 613-998-6696, Ecotoxicology and Wildlife Health Division, Wildlife and Landscape Science Directorate