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Effects of Acid Rain - Visibility

 Image: Aerial view of mountain range in Shenandoah National Park

Sulfates and nitrates that form in the atmosphere from sulfur dioxide (SO2) and nitrogen oxides (NOx) emissions contribute to visibility impairment, meaning we cannot see as far or as clearly through the air. Sulfate particles account for 50 to 70 percent of the visibility reduction in the eastern part of the U.S., affecting our enjoyment of national parks, such as the Shenandoah and the Great Smoky Mountains. The Acid Rain Program is expected to improve the visual range in the eastern U.S. by 30 percent. Based on a study of the value national park visitors place on visibility, the visual range improvements expected at national parks of the eastern United States due to the Acid Rain Program's SO2 reductions will be worth over a billion dollars annually by the year 2010. In the western part of the U.S., nitrates and carbon also play roles, but sulfates have been implicated as an important source of visibility impairment in many of the Colorado River Plateau national parks, including the Grand Canyon, Canyonlands, and Bryce Canyon.

For more information on visibility and regional haze, visit EPA’s Visability Web site.

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