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Air Pollution Impacts

Glacier National Park

Natural and scenic resources in Glacier National Park (NP) are susceptible to the harmful effects of air pollution. Mercury, nitrogen, sulfur, ozone, and fine particles impact natural resources such as wildlife, surface waters, and vegetation, and scenic resources such as visibility. Click on the tabs below to learn more about air pollutants and their impacts on natural and scenic resources at Glacier NP.

  • Toxics & Mercury
  • Nitrogen & Sulfur
  • Ozone
  • Visibility
Photo of a bull trout at Glacier NP, Montana.
Mercury levels in fish exceed safe consumption thresholds at numerous lakes in Glacier National Park, Montana.

Toxics, including heavy metals like mercury, accumulate in the tissue of organisms. When mercury converts to methylmercury in the environment and enters the food chain, effects can include reduced reproductive success, impaired growth and development, and decreased survival. Other toxic air contaminants of concern include pesticides, industrial by-products, and emerging chemicals such as flame retardants for fabrics, some of which are also known or suspected to cause cancer or other serious health effects in humans and wildlife.

Effects of mercury and toxics at Glacier NP include:

  • Presence of contaminants including current- and historic-use pesticides, mercury, and industrial by-products in snow, fish, water, and lake sediment (Downs and Stafford 2009; Hageman et al. 2006; Ingersoll et al. 2007; Krabbenhoft et al. 2002; Landers et al. 2010; Landers et al. 2008; Mast et al. 2006 [pdf, 4.4 MB]; Watras et al. 1995);
  • Concentrations of a combustion by-product, PAHs, in snow, lichens, and sediment 3.6 to 60,000 times greater in the park’s Snyder Lake watershed than in watersheds from other western and Alaskan national parks; levels attributable to emissions from a local aluminum smelter. Although the smelter is now closed, PAHs deposited from its emissions persist in the park’s ecosystems (Usenko et al. 2010);
  • Levels of historic-use pesticides dieldrin and DDT in fish that exceed safe consumption thresholds for human and wildlife health, and concentrations of current-use pesticides (e.g., endosulfans, dacthal) in fish higher than in other western U.S. national parks (Ackerman et al. 2008; Landers et al. 2010; Landers et al. 2008);
  • Concentrations of mercury in fish from numerous lakes in the park that exceed safe consumption thresholds for human and wildlife health (Downs and Stafford 2009; Downs et al. 2011), prompting guidelines for fish consumption (GNP 2009 [pdf, 330 KB]). Mercury levels are also associated with tissue damage in fish kidney and spleen (Schwindt et al. 2008);
  • Male “intersex” fish (the presence of both male and female reproductive structures in the same fish) found in the park, a response that often indicates exposure to contaminants (Schwindt et al. 2009).

Get Toxics & Mercury Data »


Photo of a scientist using a grid plot to monitor alpine vegetation at Logan Pass in Glacier NP, Montana.
A scientist uses a grid plot to monitor nitrogen-sensitive alpine vegetation at Logan Pass in Glacier NP, Montana.

Nitrogen and sulfur compounds deposited from air pollution can harm surface waters, soils, and vegetation. While nitrogen and sulfur deposition is generally low at Glacier National Park, concentrations of ammonium in wet deposition, a contributor to nitrogen deposition that often indicates the influence of nearby agriculture, are elevated and increasing (Clow et al. 2003; Ingersoll et al. 2007; NPS 2010 [pdf, 2.8 MB]). High elevation ecosystems in the park are particularly sensitive to nitrogen deposition. Not only do these systems receive more nitrogen deposition than lower elevation areas because of greater amounts of snow and rain, but short growing seasons and shallow soils limit the capacity of soils and plants to absorb nitrogen. Dilute surface waters in some park watersheds are also very sensitive to acidification from sulfur and nitrogen deposition. Other watersheds in the park, especially those that receive glacial runoff, are less sensitive to acid deposition due to buffering minerals like calcium in the runoff (Ellis et al. 1992; Clow et al. 2002; Nanus et al. 2009; Peterson et al. 1998 [pdf, 1.1 MB]; Sullivan et al. 2011a; Sullivan et al. 2011b [pdf, 11.1 MB]).

Beyond the possible effects of acidification, excess nitrogen loading can contribute to overenrichment, causing changes to the species composition of sensitive terrestrial and aquatic communities. Certain vegetation communities including alpine and wetland are at high risk from nitrogen enrichment (Bowman 2009; Sullivan et al. 2011a; Sullivan et al. 2011b [pdf, 11.1 MB]). Recent research in the park’s Snyder and Oldman Lakes indicates that aquatic communities appear undisturbed by nitrogen deposition to that area, suggesting that these lakes, like many in the area, are phosphorus-limited (Ellis et al. 1992; Saros 2009).

Get Nitrogen & Sulfur Data  »


Photo of Populus tremuloides (Quaking aspen).
While ground-level ozone concentrations are generally low at Glacier NP, Montana, there are a few ozone-sensitive species present in the park, such as Populus tremuloides (quaking aspen).

Naturally-occurring ozone in the upper atmosphere absorbs the sun’s harmful ultraviolet rays and helps to protect all life on earth. However, in the lower atmosphere, ozone is an air pollutant, forming when nitrogen oxides from vehicles, power plants and other sources combine with volatile organic compounds from gasoline, solvents, and vegetation in the presence of sunlight. In addition to causing respiratory problems in people, ozone can injure plants. Ozone enters leaves through pores (stomata), where it can kill plant tissues, causing visible injury, or reduce photosynthesis, growth, and reproduction.

There are a few ozone-sensitive plants in Glacier NP including Populus tremuloides (quaking aspen) and Salix scouleriana (Scouler’s willow). The low levels of ozone exposure at Glacier NP make the risk of foliar ozone injury to plants low (Kohut 2004 [pdf, 145 KB]).

Search the list of ozone-sensitive plant species (pdf, 184 KB) found at each national park.

Get Ozone Data  »


Images of good and poor visibility at Glacier National Park, Montana
Air pollutants can affect visibility at Glacier NP, Montana (clear to hazy from top to bottom).

Visitors come to Glacier NP to enjoy spectacular views of active glaciers and the work of colossal glaciers in the past, creating rugged topography and stunning lakes and streams. Unfortunately, park vistas of such spectacular scenery are sometimes obscured by haze caused by fine particles in the air. Many of the same pollutants that ultimately fall out as nitrogen and sulfur deposition contribute to this haze and visibility impairment. Additionally, organic compounds, soot, and dust reduce visibility; as does smoke from nearby forest fires.

Visibility effects at Glacier NP include:

  • Reduced visibility sometimes due to human-caused haze and fine particles of air pollution;
  • Reduction of the average natural visual range from about 140 miles (without the effects of pollution) to about 50 miles because of pollution at the park;
  • Reduction of the visual range to below 25 miles on high pollution days.
  • (Source: IMPROVE 2010)

Explore scenic vistas through live webcams at Glacier National Park.

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Featured Content

Studies and Monitoring icon

Studies and monitoring help the NPS understand the environmental impacts of air pollution. Access air quality data and see what is happening with Studies and Monitoring at Glacier NP.

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Last Updated: January 03, 2017