Touted for its health benefits, seafood is common fare for many of us, but now a study shines new light on the relationship between global mercury emissions and the contamination of marine life, and how industrial pollution is posing a major health threat to seafood eaters worldwide.
A study conducted by The U.S. Geological Survey (USGS) explains for the first time how mercury from industrial sources contaminates seafood. The study is published in the May issue of Global Biogeochemical Cycles and presents evidence linking current atmospheric mercury deposition in the North Pacific Ocean to methylmercury, a highly toxic form of mercury that accumulates in the food chain and is absorbed in high levels by fish such as shark, swordfish and tuna. The scientists reported that mercury levels in the Pacific Ocean will rise by 50 percent within the next few decades as emissions from coal-burning power plants and other sources such as waste incineration increase. The water sampled for this study in 2006 showed that the mercury levels were already about 30 percent higher than the same samples taken in the 1990s.
Previously, some scientists had speculated that methylmercury contamination originated in the ocean and the USGS shows that it is produced in mid-depth ocean waters by processes linked to “ocean rain.” The scientists reported that dead algae “raining” down to mid-ocean depths are decomposed by bacteria, which “methylates” the industrial mercury, turning it into methylmercury, a form that can be taken up by marine life. The methylmercury then moves up the food chain, from species to species.
While the study only tested levels of mercury in ocean waters and not in fish themselves, it still helps us to understand how pollution in the air impacts the concentrations of mercury levels in marine life. The Obama administration said the USGS study proves the need to limit global mercury emissions, and the study’s authors state that it is not too late to curb the projected increase in ocean mercury. They also said the levels are likely to decrease rapidly if emissions are reduced.
About 40 percent of all human exposure to mercury in seafood in the U.S. comes from tuna harvested in the Pacific Ocean. In 2004, the Environmental Protection Agency published a guide to seafood consumption for pregnant women, women who may become pregnant and children. Other good tips about how to eat seafood safely can be found at WebMD.
Source: BecauseAction.com
