The results should help determine whether long-term monitoring is necessary, said Tamara Blett, a Denver-based National Park Service ecologist who coordinates the project.
The study focuses on national parks in the West because earlier research focused on parks in the Midwest and East.
"We really know nothing about the West. It's just a blank slate, especially for the persistent organic pollutants, such as polychlorinated biphenyls (PCBs) and DDT," Blett said.
Most of the testing is taking place at eight high-elevation or cold climate parks, including Mount Rainier and Olympic in Washington, Glacier in Montana, Rocky Mountain in Colorado, Sequoia in California and Denali in Alaska.
"It's really sort of a mystery we're trying to solve," said Dixon Landers, the lead scientist working on the Western Airborne Contaminants Assessment Project.
Landers and other scientists are trying to determine what toxic compounds and metals drop from the atmosphere into the parks, where they come from and whether their concentrations are significant enough to worry about.
PCBs were once used as coolants and lubricants in electrical transformers and capacitors. They are believed to cause learning disorders and behavioral problems in children. PCBs were banned in the United States in 1977, but they do not disintegrate over time.
In all, the scientists are looking for 85 pollutants and 49 metals, including mercury.
Scientists believe snowfall deposits most of the airborne pollution carried into the parks. But researchers also will analyze lake sediments, water, fish, lichen, willow bark and other so-called indicators, most of which are common to all of the parks under study.
Daniel Jaffe, a University of Washington atmospheric scientist, will use meteorological data to trace the origin of pollutants.
"We can't identify where every molecule came from," Jaffe said. But he expects to be able to track air currents from Southern California, Mexico and China, for example.
"Almost certainly some contamination comes from each of those places. The question becomes, how do we quantify how much from each?" Jaffe said.