Scientists still divided on mercury content in seafood

WASHINGTON • For more than a decade, researcher Molly Lutcavage collected hundreds of tissue samples from bluefin tuna in the hope of settling a question that has long vexed pregnant women and the parents of young children: Should they eat the big fish, a beneficial source of protein and fatty acids? Or did mercury contamination make them too dangerous?

Dr Lutcavage hoped to test the theory that selenium, a key chemical found in tuna, prevents mercury from being transferred to the people who eat them and that, therefore, the fish are safe to eat. So she gave her hard-won samples to a colleague to analyse in his lab.

But Dr Nicholas Fisher, it seems, did not have as much interest in her selenium theory. Two years later, he produced a study focused almost exclusively on his own hypothesis: Lowering pollution emissions from power plants reduced the levels of mercury in bluefin tuna.

Said Dr Lutcavage, a researcher at the University of Massachusetts in Boston: "I feel that the paper didn't advance the issue whatsoever on this divide between scientists over methylmercury."


It simply shows that by implementing changes in mercury emissions, it could very rapidly result in changes in mercury concentrations in large fish like tuna.

DR NICHOLAS FISHER, on a study that determined lowering pollution could affect the levels of mercury in bluefin tuna.

The battle, raging for two years, sheds light on the unsettled issue of seafood safety, particularly for large, long-lived fish, such as tuna and swordfish, that tend to accumulate mercury.

Federal agencies such as the Environmental Protection Agency, the Food and Drug Administration and the National Institutes of Health urge caution for some types of fish, especially for pregnant women and young children, as high levels of mercury contamination can cause developmental disorders. But they base their recommendations on a body of research that often comes to conflicting conclusions.

Nutritionists stress that the nutrients in tuna and seafood are great for growing brains, but mercury contamination could potentially outweigh those advantages. So Dr Lutcavage's question about whether selenium could bind to mercury and protect people from its effects is a potentially important one.

But Dr Fisher, a professor of marine science at Stony Brook University on Long Island, argues that it makes more sense to try to figure out how to keep the mercury out of the fish in the first place by keeping it out of the environment.

The study had a single purpose, said Dr Fisher. "It simply shows that by implementing changes in mercury emissions, it could very rapidly result in changes in mercury concentrations in large fish like tuna."

Mercury is released into the atmosphere from coal-burning plant emissions and other pollution sources around the world, and it settles on fresh and salt waters. Microbes convert it into methylmercury, which collects in small organisms and fish. Big predators, such as tuna, accumulate higher levels of methylmercury by gobbling hundreds of smaller fish.


A version of this article appeared in the print edition of The Straits Times on March 06, 2017, with the headline 'Scientists still divided on mercury content in seafood'. Print Edition | Subscribe