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USDA Forest Service
1400 Independence Avenue SW
Washington, D.C.
(202) 205-8333

Sources and Effects of Air Pollution

Above: California's John Muir Wilderness


Many challenges face the Forest Service in fulfilling the responsibilities of the Clean Air Act. Forest managers must work to protect national forests and grasslands from the adverse effects of air pollution to air quality and resources such as visibility, water quality, soils, aquatic organisms and forest vegetation. Often this air pollution comes from sources outside the boundaries and control of the Forest Service. To fulfill the responsibilities, Forest Service managers work closely with state, local and federal regulators as well as other land managers, industry and other stakeholders to protect sensitive resources on national forests and grasslands.

On the other hand, some activities conducted or permitted by the Forest Service, such as prescribed fire, can adversely impact air quality. The Forest Service has to balance the use of management tools such as prescribed fire to promote ecosystem health and minimize the risk of catastrophic wildfire with the need to minimize the possible impacts of smoke to human health and resources such as visibility.

Air pollutants affecting our National Forests can be divided into two groups: primary and secondary pollutants. Primary pollutants come directly from sources such as industrial facilities, automobiles and forest fires. These include sulfur and nitrogen compounds, particulate matter, volatile organic compounds such as paint fumes and solvents, and toxic metals such as mercury. Secondary pollutants, such as ozone, are formed when primary pollutants undergo chemical reactions in the atmosphere. Most pollutants can be transported great distances from their source to impact distant lands.

[graphic] USDA logo, which links to the department's national site. [graphic] Forest Service logo, which links to the agency's national site. [graphic] A link to the US Forest Service home page.