In much of the world's oceans, levels of the metal mercury are double to triple what they were before the industrial revolution, a new study says. Researchers found there's more mercury from human sources — mostly burning fossil fuels and mining for gold — than scientists had thought. The study assessed inorganic mercury, which in the ocean gets converted into the toxic methylmercury found in seafood.
The study, published Wednesday in the journal Nature, found that mercury concentration varied by depth, generally higher at the surface and mid-level depths than in deep water. But in the North Atlantic, high concentrations reached even deeper than 3,300 feet. In general, mercury levels between the surface and 330 feet deep were more than triple pre-industrial times levels, according to the study team headed by Carl Lamborg of the Woods Hole Oceanographic Institute. Between 330 and 3,300 feet deep, they were about 150 percent greater than the levels from more than a century ago. But they were only about 10 percent higher at depths greater than 3,300 feet, except for the North Atlantic.
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— The Associated Press