Crater Lake, Mount Rainier and Olympic national parks are among wilderness areas in the Western U.S. in which scientists have found evidence of airborne contamination, including mercury, agricultural pesticides and banned substances such as DDT.

A sweeping, six-year federal study by the Environmental Protection Agency and Oregon State University was released Tuesday. The study found evidence of 70 contaminants in 20 national parks and monuments.

The findings revealed that some of the earth’s most pristine wilderness is still within reach of the toxic byproducts of the industrial age.

“Contaminants are everywhere. You can’t get more remote than these northern parts of Alaska and the high Rockies,” said Michael Kent, an OSU fish researcher who co-authored the study results.

The substances ranged from mercury produced by power plants and industrial chemicals such as PCBs to the banned insecticides dieldrin and DDT. Those can cause health problems in humans including nervous system damage, dampened immune system responses and lowered reproductive success.

Other than Crater Lake, Mount Rainier and Olympic parks, scientist focused on primarily on these six: Sequoia and Kings Canyon in California, Glacier in Montana, Rocky Mountain in Colorado, plus Gates of the Arctic, Denali national parks and Noatak National Preserve in Alaska.

The parks were most affected by contaminants from nearby or regional sources, scientists said. For example, concentrations of pesticides were highest in parks closest to agricultural areas.

The study released this week was not the first scientific report to emerge from the Western Airborne Contamination Project, which was completed last year.

In May 2006, chemists announced that winter snow falling on Mount Rainier and other high-elevation parks in the Western states is contaminated with minute amounts of agricultural pesticides.

Researchers uncovered a correlation between regional farm practices and contaminated snow at Mount Rainier and three national parks in California and Montana.

When scientists initiated the study, they believed airborne contaminants tainting Western national parks came from Europe and Asia and traveled across the Pacific Ocean before settling in the parks. But by tracking the pollutants to their sources, they found that results contradicted their hypotheses and that regional sources contribute more to park pollution than so-called trans-Pacific pollution does.

At Mount Rainier, scientists found higher concentrations of pollutants and mercury in vegetation than in other parks. Scientists also discovered high levels of flame retardants in one of two lakes sampled there. The concentrations of mercury found in both lakes were higher than scientists believe is healthy for birds, such as kingfishers. Also, mercury levels found in some fish were too high for people to safely eat them.

EPA senior researcher Dixon Landers says Yosemite National Park and Crater Lake National Park both tested very high.

Landers says researchers found chemicals in the plants and air around Crater Lake.

“We are seeing concentrations here that are elevated above the average, you might say, of the parks we’ve looked at. I certainly do hope this information will influence decision-makers,” Landers said.

Landers says current research shows a correlation between pesticides used on a nearby farms and pesticides found in National Park air and water.

The study also found contaminated fish in national park lakes, though they didn’t test the water in Crater Lake.

University of Washington atmospheric researcher Daniel Jaffe said scientists previously thought banning substances like DDT and dieldrin would lessen the persistence of chemicals in the environment.

“We replaced them with pesticides with much shorter lifetimes in the environment,” Jaffe said. “But in places like the Central Valley of California, we are applying many, many tons of these every year… We now know they can move substantial distances.”

A parks advocacy group called the federal report “a wake-up call” that should mobilize Congress to take a tougher stance on air pollution.

“We can take steps to reduce mercury emissions from power plants, steps to reduce carbon dioxide emissions that cause global warming,” said Will Hammerquist with the National Parks Conservation Association.

The $6 million study is the most comprehensive to date on the distribution and concentration of contaminants outside developed areas, according to Landers.

Release of the study, which was coordinated by the National Park Service, came after a delay of several months. Park Service spokeswoman Colleen Flanagan said the delay was caused by the time needed to analyze the vast volumes of data collected between 2002 and 2007.

The study also included researchers from the U.S. Geological Survey and the U.S. Forest Service.

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