Why seafood collects more mercury

Duke researchers show how the chemistry of sunlight and saltwater makes marine fish more dangerous to eat.

By Ilana Yurkiewicz
ilanay@nando.com

Posted: Sunday, Jul. 04, 2010

Seafood, like this bluefin tuna caught off Morehead City, tends to collect more mercury than freshwater fish. OBSERVER FILE PHOTO

Scientists have known for years that mercury in seafood poses a bigger health hazard than in freshwater fish, but only now do we know why: chemistry.

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The mercury risk first captured public attention in 2004, when the federal government issued a consumer advisory for what’s safe to eat. Large ocean fish, including shark, swordfish and king mackerel, accumulate the most methyl mercury, and the federal agencies have recommended against eating them. Smaller fish such as tuna should be limited to about two meals a week.

The recommendations are especially important for pregnant women, nursing mothers and young children, because methyl mercury exposure poses the greatest risk to developing fetuses and children.

Hsu-Kim and lead author Tong Zhang, a doctoral candidate in environmental engineering, focused on how nature breaks down methyl mercury.

Two forces are at play: sunlight and microbes such as bacteria.

Read more: http://www.charlotteobserver.com/2010/07/04/1544304/why-seafood-collects-more-mercury.html#ixzz0sqYSrjur