FRESNO, CALIF. -- Federal scientists have found elevated amounts of mercury in fish caught in remote areas of national parks in Alaska and the West, according to a study released Wednesday.
Researchers for the U.S. Geological Survey and National Park Service said that most fish they caught had acceptable levels of mercury, but 4 percent exceeded healthy levels.
Mercury occurs naturally, but scientists say its presence in national parks, which are supposed to leave wildlife unimpaired for future generations, was cause for concern.
Among the most widespread contaminants in the world, mercury can damage the brain, kidneys and a developing fetus. Fish and the birds and other animals that feed on them are also at risk, the report said.
In two Alaska parks, the average level of mercury found in fish surpassed the federal standard for some human consumption. The amounts of mercury also exceeded healthy levels at parks in California, Colorado, Washington and Wyoming, the study found. One individual fish from Yosemite National Park had a muscle concentration of mercury so high that no human consumption was advised.
In Alaska, fish with higher mercury levels were found at Copper Lake and Tanada Lake in Wrangell-St. Elias National Park and at Lake Clark and Lake Kontrashibuna at Lake Clark National Park.
Lake trout and some of the grayling at the parks had too much mercury for human consumption by women and children, according to state standards. But the kokanee, rainbow trout, and most of the grayling are safe to eat in unlimited quantities, according to a flyer put out Thursday by the Alaska Department of Health and Social Services, the National Park Service and the state Department of Environmental Conservation.
Researchers also studied a variety of fish including northern pike and Dolly Varden from Denali National Park and Glacier Bay National Park. At Denali, researchers observed some of the lowest mercury concentrations compared to other sites. At Glacier Bay, mercury levels were slightly above the global mean, the study said.
The two agencies behind the study don't regulate health guidelines, but the National Park Service said it is working with officials in the 10 states studied on possible fish consumption advisories.
"For us this is a wakeup call," said Jeffrey Olson of the National Parks, the agency that protects animals found in the wild. "We're charged with keeping their habitat in good condition so generations to come visiting these parks can see what these landscapes look like."
In the study, researchers caught 1,400 fish between 2008 and 2012 at 86 lakes and rivers in places such Yosemite National Park in California, Mount Rainier National Park in Washington and Yellowstone National Park in Wyoming.
Mercury occurs naturally from sources such as volcano eruptions, but pollution from burning fossil fuels is the leading contributor, the study said.
The results are not surprising because pollution in the atmosphere is a global problem, said Olson, adding that these findings call for a better understanding of how mercury is introduced into the remote corners of nature and the risks.
Tegan Hanlon of the Daily News contributed to this story.
By SCOTT SMITH