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Scenic views and native vegetation images from parks within Southern Colorado Plateau Network

Air Pollution Impacts

Grand Canyon National Park

Natural and scenic resources in Grand Canyon National Park (NP) are susceptible to the harmful effects of air pollution. Fine particles, nitrogen, ozone, and toxics impact scenic resources such as visibility, and can potentially harm natural resources such as surface waters, fish, and vegetation. Click on the tabs below to learn more about air pollutants and their impacts on natural and scenic resources at Grand Canyon NP.

  • Visibility
  • Nitrogen & Sulfur
  • Ozone
  • Toxics & Mercury
Three images depicting air quality impacts on visibility at Grand Canyon National Park, Arizona (clear to hazy from top to bottom).
Air pollutants can affect visibility at Grand Canyon NP, Arizona (clear to hazy from top to bottom).

Many visitors come to Grand Canyon NP to enjoy views of a mile-deep chasm into the earth and a world-renowned showplace of geology. Unfortunately, these vistas are often obscured by haze caused by fine particles in the air, primarily from coal-burning power plants, both nearby and further away. Forest fires have the potential for serious visibility impacts to the park as well. Many of the same pollutants that ultimately fall out as nitrogen and sulfur deposition contribute to this haze. Additionally, organic compounds, soot, and dust reduce visibility.

Visibility effects at Grand Canyon NP include:

  • Reduction of the average natural visual range from about 170 miles (without the effects of pollution) to about 120 miles because of pollution;
  • Reduction of the visual range from about 120 miles to below 70 miles on high pollution days;
  • Frequent impairment of scenic vistas by haze.

(Source: IMPROVE 2010)

Additional Information:

  • Explore scenic vistas through a live webcam at Grand Canyon National Park.
  • Specific sources of pollution contribute to visibility impairment at the park:
    • The MOHAVE (Measurement of Haze and Visual Effects) network was established in 1992 to help determine the contributions of the Mohave Power Plant and other sources of haze in the Southwestern US. more »
    • The Winter Haze Intensive Tracer Experiment (WHITEX) was established in 1987 to study the visibility impacts of emissions from the Navajo Generating Station. more »
    • Non-industrial sources like fire and more distant sources like large urban areas and international emissions are also large contributors to haze in the park (Eatough et al. 1997; Green 1999; Eatough et al. 2001).
  • Learn about the Grand Canyon Visibility Transport Commission (GCVTC 1996 [pdf, 1.5 MB]) and related efforts to restore visibility at Grand Canyon NP and federal lands on the Colorado Plateau. more »
  • Also, learn about efforts to address regional sources of visibility impairment at Grand Canyon NP by the State of Arizona and how the Western Regional Air Partnership (WRAP) has developed technical products in support of state plans to reduce regional haze.

Get Visibility Data »


Image of the Colorado River at the Eastern end of Grand Canyon NP in Arizona.
Surface waters and soils at Grand Canyon NP in Arizona are well-buffered against the acidification effects of nitrogen and sulfur deposition.

Nitrogen and sulfur compounds deposited from air pollution can harm surface waters, soils, and vegetation. In some ecosystems, nutrient effects from nitrogen deposition cause changes to soil nutrient cycling and the species composition of plant communities. Nitrogen and sulfur deposition can also cause acidification of soils, streams, and lakes. There are significant point sources of airborne nitrogen and sulfur near to the park. About half of the nitrogen and a third of the sulfate deposited in Grand Canyon ecosystems comes down in rain and snow, the rest is “dry deposition” of particles, dust, and droplets. Surface water chemistry data for Grand Canyon NP indicate that park surface waters are well buffered and, therefore, not likely to be acidified by atmospheric deposition. Soils are also likely to be well-buffered from acidification (Binkley et al. 1997 [pdf, 686 KB]).

However, nitrogen loading could induce unwanted fertilization of the terrestrial ecosystem. Vegetation communities in the park have evolved under low nitrogen conditions and are likely to be very sensitive to nutrient effects of nitrogen deposition. Excess nitrogen may allow more weedy, invasive plants to out-compete native species and as a result affect biodiversity (Fenn et al. 2003).

Get Nitrogen & Sulfur Data »


Photo of three-leaf sumac.
Three-leaf sumac, an ozone-sensitive plant species at Grand Canyon NP, Arizona.

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 a toxic 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 and reduced photosynthesis, growth, and reproduction.

Ozone concentrations sometimes reach levels known to be harmful to plants at Grand Canyon NP. While there are ozone-sensitive vegetation at the park including Salix scouleriana (Scouler’s willow) and Pinus ponderosa (ponderosa pine), field surveys on Ponderosa pine in 1992–93 and 2008 did not document any ozone injury (Binkley et al. 1997 [pdf, 686 KB]; NPCA 2010 [pdf, 11.8 KB]).

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

Ozone and Public Health Concern

Ground-level ozone concentrations at Grand Canyon NP sometimes exceed the National Ambient Air Quality Standards set by the U.S. Environmental Protection Agency to protect public health. Park managers have instituted an ozone advisory program to educate employees and park visitors about the risks of exposure to unhealthy ozone levels and precautions that can be taken.

Ozone is a respiratory irritant, causing coughing, sinus inflammation, chest pains, scratchy throat, lung damage, and reduced immune system functions. Children, the elderly, people with existing health problems, and active adults are most vulnerable. Park managers are optimistic that ozone air quality will improve at Grand Canyon NP because of recent air quality regulations and other related actions.

Get Ozone Data »


Photo of young humpback chub swimming in Shinumo Creek soon after release.
Humpback chub are an endangered fish at Grand Canyon NP. These sensitive populations remain at risk to environmental stressors, such as contaminants.

Airborne toxic contaminants, including heavy metals like mercury, can deposit to soils, lakes, and streams, then enter the food chain and accumulate in the tissues of wildlife and humans. Effects can include reduced reproductive success, impaired growth and development, behavioral abnormalities, reduced immune response, and decreased survival. Human activities have greatly increased the amount of mercury in the environment through processes such as burning coal for electricity and burning waste. Other toxic air contaminants that induce adverse health effects include pesticides, industrial by-products, and chemicals of emerging concern (e.g., flame retardants).

Concentrations of mercury and other metals in the Colorado River have exceeded EPA drinking water criteria at times (NPS 1996). Because the “The Grand” receives inputs from many watersheds upstream, it is likely that contaminants present in the river are a result of both point and non-point sources (e.g., atmospheric deposition). Other sources that contribute contaminants to “The Grand” include runoff and mine drainage. Such environmental toxins present a concern for natural resources as well as park visitors and locals who fish for pleasure or sustenance.


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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 Grand Canyon NP.

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Last Updated: December 30, 2016