Found 10489 publications. Showing page 296 of 420:
Contaminants in Atlantic walruses Part 2: Relationships with endocrine and immune systems
Marine mammals in the Barents Sea region have among the highest levels of contaminants recorded in the Arctic and the Atlantic walrus (<i>Odobenus rosmarus rosmarus</i>) is one of the most contaminated species within this region. We therefore investigated the relationships bewteen blubber concentrations of lipophilic persistent organic pollutants (POPs) and plasma concentrations of perfluoroalkyl substances (PFASs) and markers of endocrine and immune functions in adult male Atlantic walruses (n = 38) from Svalbard, Norway. To do so, we assessed plasma concentrations of five forms of thyroid hormones and transcript levels of genes related to the endocrine and immune systems as endpoints; transcript levels of seven genes in blubber and 23 genes in blood cells were studied. Results indicated that plasma total thyroxine (TT4) concentrations decreased with increasing blubber concentrations of lipophilic POPs. Blood cell transcript levels of genes involved in the function of T and B cells (FC like receptors 2 and 5, cytotoxic T-lymphocyte associated protein 4 and protein tyrosine phosphatase non-receptor type 22) were increased with plasma PFAS concentrations. These results suggest that changes in thyroid and immune systems in adult male walruses are linked to current levels of contaminant exposure.
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Plastic litter in the European Arctic: What do we know?
Despite an exponential increase in available data on marine plastic debris globally, information on levels and trends of plastic pollution and especially microplastics in the Arctic remains scarce. The few available peer-reviewed scientific works, however, point to a ubiquitous distribution of plastic particles in all environmental compartments, including sea ice. Here, we review the current state of knowledge on the sources, distribution, transport pathways and fate of meso- and microplastics with a focus on the European Arctic and discuss observed and projected impacts on biota and ecosystems.
2019
Levels and trends of poly- and perfluoroalkyl substances in the Arctic environment – An update
Poly- and perfluoroalkyl substances (PFASs) are important environmental contaminants globally and in the early 2000s they were shown to be ubiquitous contaminants in Arctic wildlife. Previous reviews by Butt et al. and Letcher et al. have covered studies on levels and trends of PFASs in the Arctic that were available to 2009. The purpose of this review is to focus on more recent work, generally published between 2009 and 2018, with emphasis on PFASs of emerging concern such as perfluoroalkyl carboxylates (PFCAs) and short-chain perfluoroalkyl sulfonates (PFSAs) and their precursors. Atmospheric measurements over the period 2006–2014 have shown that fluorotelomer alcohols (FTOHs) as well as perfluorobutanoic acid (PFBA) and perfluoroctanoic acid (PFOA) are the most prominent PFASs in the arctic atmosphere, all with increasing concentrations at Alert although PFOA concentrations declined at the Zeppelin Station (Svalbard). Results from ice cores show generally increasing deposition of PFCAs on the Devon Ice cap in the Canadian arctic while declining fluxes were found in a glacier on Svalbard. An extensive dataset exists for long-term trends of long-chain PFCAs that have been reported in Arctic biota with some datasets including archived samples from the 1970s and 1980s. Trends in PFCAs over time vary among the same species across the North American Arctic, East and West Greenland, and Svalbard. Most long term time series show a decline from higher concentrations in the early 2000s. However there have been recent (post 2010) increasing trends of PFCAs in ringed seals in the Canadian Arctic, East Greenland polar bears and in arctic foxes in Svalbard. Annual biological sampling is helping to determine these relatively short term changes. Rising levels of some PFCAs have been explained by continued emissions of long-chain PFCAs and/or their precursors and inflows to the Arctic Ocean, especially from the North Atlantic. While the effectiveness of biological sampling for temporal trends in long-chain PFCAs and PFSAs has been demonstrated, this does not apply to the C4–C8–PFCAs, perfluorobutane sulfonamide (FBSA), or perfluorobutane sulfonate (PFBS) which are generally present at low concentrations in biota. In addition to air sampling, sampling abiotic media such as glacial cores, and annual sampling of lake waters and seawater would appear to be the best approaches for investigating trends in the less bioaccumulative PFASs.
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