Every fish tested by the U.S. Geological Survey over a seven-year period contained some mercury, according to a study appearing last year in this space, and 25 percent of those samples had levels that exceeded EPA safety standards. So, which kind of fish -- saltwater or freshwater -- is more harmful to your health?
Duke University researchers report eating saltwater fish (shark, tuna and mackerel) may be a bigger health problem than freshwater species, although mercury accumulates in far greater concentrations in the latter. Why?
Methylmercury, the most harmful form of mercury and a potent neurotoxin, degrades to a much less toxic form in dissolved organic matter (plants and animals) in freshwater when exposed to sunlight. On the other hand, the sodium in seawater binds more tightly with methylmercury, so sunlight can't break it down as easily, scientists said.
Apart from the problems related to neurological disorders, kidney dysfunction and the like, here's one more incentive to limit your exposure to methylmercury: Cutting mercury pollution by 10 percent could trim America's annual health care costs by more than $800 million, not chump change by any stretch.
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