Known for its use in thermometers and some light bulbs, mercury is a liquid metal that can harm the brain, heart, kidneys, lungs and immune system. It’s particularly harmful for pregnant women and children, according to the Environmental Protection Agency.
Mercury’s entry into an environment is incredibly complex, said Eagles-Smith. So in order to work toward developing a map of mercury’s journey to the fish, researchers need to know how much is there in the first place.
“It’s a matter of getting a better understanding of how mercury is distributed across all the sites within parks,” he said.
Jeff Olson, a National Park Service spokesman, said that while the study reveals no specific source for the elevated mercury levels in these remote places, human activities have taken their toll.
“We believe that most of the mercury that affects parks comes from burning fossil fuels like coal in power plants,” he said.
According to the study, mercury levels in Earth’s atmosphere have tripled over the last 150 years.
Paul Gremillion, an assistant professor of environmental engineering at Northern Arizona University, has worked with the Arizona Department of Environmental Quality to examine Arizona reservoirs known for higher mercury levels.
Most mercury doesn’t enter an environment in the liquid-silver-blob form it’s known for, Gremillion said. Instead, it’s a vapor that can blow across continents and reach Earth’s surface via rain.
That’s why there’s no simple way to discover the mercury’s origins, he said — because it’s such a world traveler in its atmospheric form.
“There’s not an easy way to figure where this came from. You have to piece together a lot of different elements of evidence,” he said.
Vaporized mercury from coal burned at power plants as far away as China can find its way into America’s water systems, he said.