MAMMOTH CAVE, Ky. -- Scientists at Mammoth Cave National Park say they have documented elevated levels of mercury in bats, including one species that's at risk of extinction. Experts from the park and Western Kentucky University conducted the research, which is intended to measure the amount of the toxic metal in park wildlife, including endangered Indiana bats.
Their work is also shedding light on how pollutants become concentrated in nature. In the case of the bats, mercury from power plants and other sources falls to the ground and accumulates in microscopic plants, which in turn are eaten by tiny animals, which are eaten by insects, which, in turn, are devoured by bats. In each stage, the amount of mercury increases.
Park officials blamed the mercury contamination largely on emissions from coal-fired power plants, which utility companies say they are reducing. The utilities pointed out that some mercury in the atmosphere comes from natural sources, such as volcanoes and forest fires. So far, the park's air resource specialist, Bob Carson, and others involved in the study said they have been unable to determine whether the amount of mercury in the bats is large enough to cause harm, such as central nervous system damage or reduced reproduction. That would require a better understanding among scientists of how much mercury bats can tolerate, officials said.
But the researchers said they found mercury in bats' hair at nearly 10 parts per million -- a level beyond which detrimental effects have been detected in people and rodents. The U.S. Environmental Protection Agency's recommended limit for mercury in people is 10 times lower, at 1 part per million. "When I hear 10 parts per million, I would worry a bit," said David Evers, an expert on mercury and the environment who is the executive director of the Biodiversity Research Institute in Gorham, Maine. Evers is conducting bat studies in the Northeast that are similar to the work being done at Mammoth Cave National Park.
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