Mercury Emissions in Seafood – It's Worse Than We Thought

A federal study just released documents a serious link between global emissions of mercury and seafood contamination.

The U.S. Geological Survey study(pdf) outlines the formation in the north Pacific Ocean of methylmercury, a highly toxic form of mercury that rapidly accumulates in the food chain to levels that can create serious health issues for people who eat seafood.

Scientists have known about the link between mercury deposited in the atmosphere and methylmercury, but this study shows how the it actually happens.

The study shows that methylmercury is produced in mid-depth ocean waters by processes linked to “ocean rain.” Algae, produced in sunlit waters near the surface, die quickly and “rain” downward to deeper water.  Bacteria decomposes the settling algae.  The interaction of this decomposition process in the presence of mercury results in methylmercury.

The study shows that, later in the process, predators like tuna ingest methylmercury from the fish they consume.

Also, the study shows the long-range movement of mercury in the ocean that originates in the western Pacific Ocean, off the Asian coast.

Mercury researchers typically look skyward to find a mercury source from the atmosphere due to emissions from land-based combustion facilities,” said USGS scientist and co-author David Krabbenhoft.

However, this study shows the pathway of the mercury was different. “It appears the recent mercury enrichment of the sampled Pacific Ocean waters is caused by emissions originating from fallout near the Asian coasts. The mercury-enriched waters then enter a long-range eastward transport by large ocean circulation currents,” Krabbenhoft said.

In a released statement, Interior Secretary Ken Salazar said “This unprecedented USGS study is critically important to the health and safety of the American people and our wildlife because it helps us understand the relationship between atmospheric emissions of mercury and concentrations of mercury in marine fish.”

“This study gives us a better understanding of how dangerous levels of mercury move into our air, our water, and the food we eat, (shining) new light on a major health threat to Americans and people all across the world,” EPA Administrator Lisa Jackson added. “With this information, plus our own mercury efforts, we have an even greater opportunity to continue working with our international partners to significantly cut mercury pollution in the years ahead and protect the health of millions of people.”

One wonders if this new information will be used for positive action rather than merely the usual political rhetoric.

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