We've told you about the dangers of eating mercury-contaminated fish. Today, the US Geological Survey released a comprehensive study linking the mercury emissions from smokestacks here in the US and abroad, and the contamination of fish like tuna and other marine life in the Pacific Ocean. According to the NY Times and Greenwire:

The study documents the formation in the North Pacific of methylmercury, a highly toxic form of mercury that rapidly accumulates in the food chain to levels that can cause serious health concerns for people who consume seafood. Scientists have known for some time that mercury deposited from the atmosphere can be transformed into methylmercury, but the study focuses on how that transformation occurs.

USGS showed that methylmercury is produced in mid-depth ocean waters by processes linked to "ocean rain." Algae, which are produced in sunlit waters near the surface, die quickly and rain downward to greater water depths. The settling algae are decomposed by bacteria and the interaction of this decomposition process in the presence of mercury results in the formation of methylmercury.

Many steps up the food chain later, predators like tuna receive methylmercury from the fish they consume, the study shows.

EPA Administrator Lisa Jackson said, "This study gives us a better understanding of how dangerous levels of mercury move into our air, our water, and the food we eat, and shines new light on a major health threat to Americans and people all across the world."

Just last week, the EPA proposed significant cuts in cement kiln mercury emissions (up to 16,000 pounds a year), and we’re hopeful they will continue this leadership when they work to cut mercury from coal-fired power plants sometime in the future.

Mercury is a neurotoxin especially dangerous to young and unborn children, and women of childbearing age are often warned to limit their consumption of contaminated fish (like tuna, shark, walleye, or wild striped bass).