Mercury Levels in Fish Puzzle Scientists

RALEIGH, N.C., Oct. 6 (UPI) — In a surprise finding, U.S. researchers say fish located near coal-fired power plants have lower levels of mercury than fish that live farther away.

North Carolina State University researchers say the result may be linked to high levels of another element, selenium, found near coal-fired facilities, which can present problems of its own, a release by the school said.

“We found that fish in lakes located at least 30 kilometers (18 miles) from a coal-fired power plant had mercury levels more than three times higher than fish of the same species in lakes that are within 10 km (6 miles) of a plant,” Dana Sackett, a doctoral student at N.C. State, said. “This information will inform health and wildlife officials who make determinations about fish consumption advisories and wildlife management decisions.”

The results were unexpected since coal-fired power plants are the leading source of mercury air emissions in the world and a significant amount of that mercury is expected to settle out of the air within 6 miles of a plant’s smokestacks.

The researchers theorize lower mercury levels near power plants are likely linked to selenium levels, as fish tested within 6 miles of a plant showed selenium levels three times higher than samples taken from fish located further away. The higher the selenium level, the lower the mercury level, the researchers found.

Selenium, also emitted by coal-fired plants, is known to have an antagonistic relationship to mercury, though the specific mechanisms at work at not completely understood.

High levels of selenium pose their own risks, scientists said.

“Selenium is an important dietary element,” said Dr. Derek Aday, associate professor of biology at N.C. State. “But at high levels, it can have serious consequences — including lethal effects and an array of health problems for fish and wildlife.”

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Categorized | Coal, Consumption, Fish, Other
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