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Air Pollution Impacts

Sequoia & Kings Canyon National Parks

Natural and scenic resources in Sequoia & Kings Canyon National Parks (NPs) are susceptible to the harmful effects of air pollution. Ozone, nitrogen, pesticides, and fine particles impact natural resources such as lakes, streams, fish, 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 Sequoia & Kings Canyon NPs.

  • Ozone
  • Nitrogen & Sulfur
  • Toxics
  • Visibility

Ozone and Public Health Concerns

Ground-level ozone concentrations at the parks are among the highest recorded in national parks and frequently exceed the National Ambient Air Quality Standards set by the U.S. Environmental Protection Agency to protect public health.

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.

An ozone advisory program educates employees and park visitors about the risks of exposure to high ozone levels and precautions to reduce exposure.

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.

Effects of ozone on vegetation at Sequoia & Kings Canyon NPs include:

Photo of healthy (top) and injured from ozone exposure (bottom) ponderosa pine needles at Sequoia and Kings Canyon NPs in California
Photo of healthy (top) and ozone-injured (bottom) ponderosa pine needles at Sequoia & Kings Canyon NPs in California.
  • Injury to ponderosa pine and Jeffrey pine needles (Warner et al. 1983), with ozone injury evident on nearly 90% of Jeffrey pines in or near the Giant Forest on the west side of the parks where ozone exposure is highest (Peterson et al. 1991; Peterson and Arbaugh 1992);
  • Reduced photosynthesis and growth and premature needle drop in pines, all symptoms of reduced productivity (Peterson et al. 1987; Ewell et al. 1989;
  • Injury to Giant Sequoia seedlings, possibly affecting their long-term success (Grulke and Miller 1994; Miller and Grulke 1994 [pdf, 2.0 MB]).

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

Get Ozone Data »


How much nitrogen is too much?

Nitrogen is a fertilizer and some nitrogen is necessary for plants to grow. However, in natural ecosystems, too much nitrogen disrupts the balance of plant communities, allowing weed species to grow faster. Nitrogen deposited from air pollution may upset the balance of some high elevation lakes at Sequoia & Kings Canyon NPs. In two lakes, for example, species changed when nitrogen deposition increased in the 1960s to about 1.4 kilograms per hectare per year (kg/ha/yr). Below this critical load the lake ecosystem functioned naturally (Saros 2009 [pdf, 565 KB]). Nitrogen deposition is now about 3–4 kg/ha/yr (Sickman et al. 2001) and projects are underway to examine the effect of excess nitrogen to other resources in the park and throughout the Sierra Nevada. In Sierra Nevada forests, research suggests that the critical load for some lichen species is about 3.1 kg/ha/yr (Fenn et al. 2008). Above that level of nitrogen deposition, these lichens disappear. Critical loads for lake and forest resources can be used to establish goals for ecosystem recovery.

Nitrogen and sulfur compounds deposited from air pollution may harm lakes, streams, soils, and vegetation in Sequoia & Kings Canyon NPs. However, sulfur deposition is generally very low in California and unlikely to affect most ecosystems, while nitrogen deposition is higher and its effects are more widespread. Some high elevation ecosystems in the parks are particularly sensitive to nitrogen deposition. Not only do these systems receive more nitrogen deposition than lower elevation areas, but short growing seasons and shallow soils limit the capacity of soils and plants to absorb nitrogen.

Effects of nitrogen deposition at Sequoia & Kings Canyon NPs include:

Photo of a high elevation stream at Sequoia and Kings Canyon NPs, California.
High elevation streams at Sequoia & Kings Canyon NPs, California are sensitive to acid inputs from sulfur and nitrogen deposition.
  • Increased plant growth in lakes from excess nitrogen (i.e., eutrophication), potentially changing aquatic community dynamics (Sickman et al. 2003);
  • Replacement of certain lichen species important for wildlife food and habitat by weedy, nitrogen-loving species (Fenn et al. 2008);
  • Episodic acidification of some streams during snowmelt (Williams and Melack 1991; Stoddard 1995; Leydecker et al. 1999).

Get Nitrogen Data »


Photo of a researcher on way to sample shnow for airborne contaminants at Sequoia and Kings Canyon NPs in California.
On the way to sample snow for airborne contaminants at Sequoia & Kings Canyon NPs in California.

Toxic air pollutants include pesticides, industrial by-products, heavy metals like mercury, and flame retardants for fabrics. Certain toxic contaminants are known or suspected to cause cancer or other serious health effects in humans and wildlife, including reproductive problems, impaired growth and development, behavioral abnormalities, and reduced immune response.

Effects of airborne toxics on ecosystems at Sequoia & Kings Canyon NPs include:

  • Presence of contaminants including current-use pesticides, historic-use pesticides, and industrial by-products in snow (McConnell et al. 1998; Hageman et al. 2006; Landers et al. 2010; Landers et al. 2008);
  • Levels of dieldrin, historic-use pesticides (e.g., DDT) and/or mercury in fish that exceed safe consumption thresholds for human and wildlife health, and concentrations of current-use pesticides (e.g., endosulfans and dacthal) in fish higher than in other western U.S. national parks (Ackerman et al. 2008; Landers et al. 2010; Landers et al. 2008; Schwindt et al. 2008);
  • Pesticides likely a factor in the dramatic population declines of several frog species, including the endangered mountain yellow-legged frogs (Sparling et al. 2001; Fellers et al. 2004; Davidson and Knapp 2007);
  • Abnormalities (e.g., discoloration and thinning) in peregrine falcon eggs that contain high quantities of DDE (a breakdown product of DDT) (Jarman 1994).

Get Toxics Data »


Fine particles at Sequoia & Kings Canyon NPs and Public Health Concerns

Concentrations of fine particles in the park’s air sometimes exceed the National Ambient Air Quality Standards set by the U.S. Environmental Protection Agency to protect public health. Fine particles (smaller than 2.5 micrometers) originate from either direct emissions by a source, such as construction sites, power plants, and fires, or reactions with gases and aerosols in the atmosphere emitted from sources upwind. For example, power plants, industries, and automobiles emit gases such as sulfur dioxides and nitrogen oxides, which form particles of sulfate and nitrate in the atmosphere.

Because of their small size, fine particles can get deep into the lungs and cause serious health problems. Numerous scientific studies have linked particle pollution exposure to irritation of the airways, coughing, difficulty breathing, aggravated asthma, chronic bronchitis, heart attacks, and premature death in people with heart or lung disease.

Many visitors come to parks to enjoy the spectacular vistas. Unfortunately, these vistas are often 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. Organic compounds, soot and dust reduce visibility as well.

Images of good and poor visibility at Sequoia & Kings Canyon National Parks, California.
Air pollutants can affect visibility at Sequoia & Kings Canyon NPs, California (clear to hazy from left to right).

Visibility effects at Sequoia & Kings Canyon NPs include:

  • Reduction of the average natural visual range from about 145 miles (without the effects of pollution) to about 35 miles because of pollution at the parks;
  • Reduction of the visual range from about 110 miles to below 20 miles on high pollution days;
  • Human caused haze frequently impairs scenic vistas at the parks.

(Source: IMPROVE 2010)

Explore scenic vistas through a live webcam at Sequoia & Kings Canyon National Parks.

Get Visibility Data »


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 Sequoia & Kings Canyon NPs.

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Last Updated: December 30, 2016