Air Pollution Impacts

Many visitors come to parks to enjoy the spectacular vistas. Unfortunately, these vistas are sometimes obscured by haze caused by fine particles in the air from vehicle exhaust, industry, power production, and fires. 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.

Visibility effects at Denali NP & Pres include:

• Reduction of the average natural visual range from about 160 miles (without the effects of pollution) to about 130 miles because of pollution at the park;
• Reduction of the visual range from about 110 miles to below 80 miles on very hazy days;
• Human-caused haze occasionally impairs scenic vistas at the park;
• Park vistas are sometimes obscured by haze resulting from the intercontinental transport of airborne contaminants across the Pacific and Arctic oceans.

(Source: IMPROVE 2010)

Explore scenic vistas through a live webcam at Denali National Park & Preserve!

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Toxic contaminants, including heavy metals like mercury, accumulate in the tissues of organisms and may alter key ecosystem processes. When mercury converts to methylmercury in the environment and enters the food web, 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 airborne contaminants of concern include pesticides, industrial by-products, and emerging chemicals. Some of these toxic contaminants are referred to as POPs (persistent organic pollutants) and are also known or suspected to cause cancer or other serious chronic health effects in humans and wildlife. Located in the far north, Alaska (including Denali NP & Pres) is particularly susceptible to the accumulation of POPs and other toxic airborne contaminants. Pesticides and other pollutants volatilize from contaminated soils at warmer temperatures in lower latitudes, then are transported to colder, high-latitude arctic and subarctic ecosystems.

Effects of mercury and airborne toxics on ecosystems at Denali NP & Pres include:

• Presence of contaminants at very low levels, including current-use pesticides, historic-use pesticides, and industrial by-products in air, snow, sediment, fish, and vegetation (Hageman et al. 2006; Landers et al. 2010; Landers et al. 2008);
• Higher than expected levels of PCBs, mercury, and dieldrin in fish (Landers et al. 2010; Landers et al. 2008). Measured contaminant levels in fish did not exceed human health thresholds adopted by the State of Alaska, nor did they exceed human health thresholds established by the EPA for consumers eating fewer than 19 meals of fish per month (Ackerman et al. 2008; Landers et al. 2010; Landers et al. 2008);
• Mercury concentrations in fish that exceed health thresholds suggested for fish-eating birds (kingfishers) and mammals (otter and mink) (Ackerman et al. 2008; Landers et al. 2010; Landers et al. 2008; Schwindt et al. 2008).

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Naturally-occurring ozone in the upper atmosphere forms a layer that absorbs the sun’s harmful ultraviolet rays and protects 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 inducing respiratory problems in people, elevated ozone exposures can injure plants. Ozone enters leaves through pores (stomata), where it can kill plant tissues, causing visible injury, or reduce photosynthesis, growth, and reproduction.

Ozone concentrations and seasonal exposures are generally low in Denali NP & Pres and unlikely to cause injury or reduced growth in plants. While ozone effects have not been documented in the park, several park species, including Salix scouleriana (Scouler’s willow) and Populus tremuloides (quaking aspen), are known to be sensitive to ozone.

Episodes of high ozone concentrations, due in part to biomass burning in Eurasia, have been documented in the park, but these episodes are relatively short in duration (Oltmans et al. In press).

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

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Nitrogen (N) and sulfur (S) emissions from local, regional, and transboundary sources deposit into ecosystems in Denali NP & Pres, where they can cause acidification and fertilization. The risk from either acidification or fertilization is considered low in the park because rates of N and S deposition are very low. Also, many park soils, streams, and lakes are rich in base cations from glacial runoff that buffer potential acidification. Certain vegetation communities in the park, including wetlands and arctic vegetation, are known to be vulnerable to excess N deposition, which can alter plant communities and reduce biodiversity. If N deposition increases significantly, these plant communities could be affected. Certain lichen species that occur in the park are known to be sensitive to air pollution, including the globally rare Erioderma pedicellatum (Nelson et al. 2009).

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