The Environmental Protection Agency (EPA) issued regulations to improve visibility, or visual air quality, in 156 national parks and wilderness areas across the country. These areas include many of our best known and most treasured natural areas, such as the Grand Canyon, Yosemite, Yellowstone, Mount Rainier, Shenandoah, the Great Smokies, Acadia, and the Everglades. The regulations call for States to establish goals for improving visibility in national parks and wilderness areas and to develop long-term strategies for reducing emissions of air pollutants that cause visibility impairment.

• Regional Haze Rule (PDF) (61 pp, 590 K) - Federal Register - July 1, 1999

Note: the most recent revisions to the Regional Haze Rule were finalized in January 2017. 2017 Regional Haze Final Rule

• Fact Sheet (PDF)(8 pp, 130 K)