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PARTNERSHIP EVENTS
Partnership call: Advancing Risk Assessment: Progress and Ongoing Obstacles
4/26/12: MP3 recording available: CHE Cafe call: Designing Healthy Communities: a conversation with Richard Jackson, MD, MPH
CHE WORKING GROUP EVENTS
CHE Alaska call: Little Changes: A Discussion with Author Kristi Marsh on How to Avoid Chemicals in Food and Everyday Products:
May 30, 2012
CHE Fertility and Reproductive Health and CHE EMF working groups call: EMF and Reproductive Health Risks:
May 21, 2012
Cumulative Impacts Working Group Strategic Meeting:
May 22, 2012
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Commentary by Ted Schettler Changes in Mercury and Cadmium Concentrations and the Feeding Behaviour of Beluga (Delphinapterus Leucas) Near Somerset Island, Canada, During the 20th Century We sometimes hear assertions that the mercury content of fish is no different now than it was historically. Various studies have attempted to address that issue by comparing mercury levels in teeth of marine organisms that lived in different historical periods. Here is a recent study that also addresses the question. It examines mercury and cadmium levels in beluga whale teeth, comparing teeth from late 19th century, 1926-1947, and 1990s. Investigators took into account animal age, and using carbon and nitrogen isotopic analysis, also considered possible historical changes in diet. They conclude that the markedly increased accumulation of mercury with age is most likely explained by industrial mercury pollution, though behavioral changes (e.g, consuming in a different range or part of the marine food web) cannot entirely be ruled out as a contributing cause. It is clear from the paper that increasing anthropogenic releases of mercury are overwhelmingly likely to explain the data.
For 20 year old animals, average muscle Hg and muktuk Hg concentrations increased twofold between the late 19th century and the 1990s, and about threefold in 30 year olds (Table 3). Compared to the recommended Hg guideline for human consumption of fish flesh of 0.5 Hg/g wet wt (Health and Welfare Canada, 1979), the increase in muktuk and muscle represents a change from average historical concentrations that were below or slightly above the guideline to ones at present which are 50–400% above the guideline in beluga z20 years of age. =============== Outridge, P.M., Hobson, K.A., and Savelle, J.M. Changes in mercury and cadmium concentrations and the feeding behaviour of beluga (Delphinapterus leucas) near Somerset Island, Canada, during the 20th century. The Science of the Total Environment 350(1-3): 106-118, 2005. Notes: Beluga (Delphinapterus leucas) continues to be an important food species for Arctic communities, despite concerns about its high mercury (Hg) content. We investigated whether Hg and cadmium (Cd) concentrations had changed during the 20th century in beluga near Somerset Island in the central Canadian Arctic, using well-preserved teeth collected from historical sites (dating to the late 19th century and 1926-1947) and during subsistence hunts in the late 1990s. Mercury concentrations in both historical and modern teeth were correlated with animal age, but 1990s beluga exhibited a significantly more rapid accumulation with age than late 19th century animals, indicating that Hg concentrations or bioavailability in their food chain had increased during the last century. The geometric mean tooth Hg concentration in modern 30 year old animals was 7.7 times higher than in the late 19th century, which corresponds to threefold higher concentrations in muktuk and muscle. Teeth from 1926 to 1947 were similar in Hg content to the late 19th century, suggesting that the increase had occurred sometime after the 1940s. In contrast, tooth Cd was not correlated with animal age and decreased during the last 100 years, indicating that anthropogenic Cd was negligible in this population. Late 19th century beluga displayed a greater range of prey selection (tooth d(15)N values: 15.6-20.5 parts per thousand) than modern animals (d(15)N: 17.2-21.1 parts per thousand). To prevent this difference from confounding the temporal Hg comparison, the Hg-age relationships discussed above were based on historical animals, which overlapped isotopically with the modern group. Tooth d(13)C also changed to isotopically more depleted values in modern animals, with the most likely explanation being a significant shift to more pelagic-based feeding. Industrial Hg pollution is a plausible explanation for the recent Hg increase. However, without further investigation of the relationship between the range exploitation of modern beluga and their possible exposure to regional marine food chains with (naturally) higher Hg contents than their historical counterparts, we cannot unequivocally conclude that the increase was anthropogenically driven. |
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