Federal scientists have found high amounts of mercury in sport fish caught in remote areas of national parks in the West and Alaska, according to a study released Thursday.
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.
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.
In two Alaskan parks, the average level of mercury in fish found bypassed the federal standard for human consumption. The amounts of mercury also exceeded healthy levels at parks in California, Colorado, Washington and Wyoming, the study found.
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.