Airborne Contaminants Study Released

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Date: February 26, 2008
Contact: Barb Maynes - Olympic NP, 360-565-3005
Contact: Barbara Samora - Mount Rainier NP, (360) 569-2211 x3372
Contact: Kerry Olsen - North Cascades NP, (360) 854-7365 x13

A study released today by the Western Airborne Contaminants Assessment Project (WACAP), shows that airborne contaminants, including heavy metals and both current-use and North American historic-use pesticides, have been detected at measurable levels in ecosystems at twenty western U.S. and Alaska national parks from the Arctic to the Mexican border, including Mount Rainier, North Cascades and Olympic National Parks.

Eight “core” park areas were studied, including Mount Rainier and Olympic National Parks in Washington State, along with Rocky Mountain, Sequoia & Kings Canyon, Denali, Glacier, Gates of the Arctic, and Noatak. North Cascades National Park was one of twelve “secondary” parks which received more limited examination. The study was funded primarily by the National Park Service (NPS) to evaluate the potential threats to park ecosystems and likely sources of these contaminants.

Findings from the six-year, multi-agency study indicate that organic contaminants were found at detectable levels in snow, water, vegetation, lake sediment, and fish. Key findings from Washington’s three national parks are outlined below.

Snow in Olympic National Park contained unexpectedly high concentrations of mercury. Mercury levels in snow at Mount Rainier were also relatively high in comparison to the other parks studied. Mercury is a naturally occurring element, but is also produced during coal and hazardous material combustion. A three-year follow-up program to collect and analyze snow samples in the parks recently concluded and results are pending.

In fish, concentrations of current and historic use pesticides were low in Olympic and generally mid-range at Mount Rainier when compared to the other parks studied. Mercury compounds in fish at Olympic were among the highest of all parks and were also high at Mount Rainier. All fish from both parks exceeded health thresholds for one or more species of fish-eating wildlife; some individual fish exceeded health thresholds for humans. All fish appeared reproductively normal.

A recent study of fish in lakes in the three parks was conducted by the U.S. Geological Survey. It examined similar compounds, but used different methodology from the WACAP study and found generally low contaminant levels.

While the extent of the effects on wildlife depending upon fish for survival is unknown, the risk to people is considered low and varies given location, frequency and type of fish consumption. Most people are not likely to eat enough of the contaminated fish to be at risk. Guidelines for safe consumption of recreationally caught fish are available at the Washington Department of Health website ( In the absence of specific local guidelines, the Environmental Protection Agency recommends consuming no more than six ounces of recreationally caught fish per week.

Pesticides were also found in vegetation samples from all three parks and mercury was detected at Mount Rainier and Olympic. (The presence of mercury was not analyzed at North Cascades.) Levels of these contaminants were in the mid to upper ranges when compared to other parks studied.

The relatively high levels of pesticides and mercury in vegetation reflect the ability of both lichens and evergreen trees to scrub contaminants from the air. Because of the density and rapid growth rates of forests in Washington’s parks, contaminants scrubbed from the air could contribute significant contaminant levels to soils when lichens and evergreen needles fall to the ground. Scientists estimate the resulting contaminant levels in the soil are comparable to some agricultural application rates.

Evidence suggests that the contaminants found in this study are carried in air masses from sources as far away as Europe and Asia, and as near as the local county.

National Park Service resource managers worked with scientists from the U.S. Environmental Protection Agency, the U.S. Geological Survey, the U.S. Forest Service, Oregon State University and the University of Washington to plan and conduct the WACAP study. More information about WACAP, including the full report, is available online.

Last updated: February 28, 2015

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