The air in Denali National Park is exceptionally clean, allowing spectacular views of the Alaska Range when the mountains are free of clouds. National Park Service air quality monitoring has shown that Denali consistently has some of the best visibility and cleanest air measured in the country, although parks in the Pacific Northwest often record lower annual ozone values, and western desert parks sometimes have fewer visibility-degrading particles in the air. It is not surprising to discover that Alaska has such clean air, considering the low population density and relatively sparse industrial activity in the state.
What may be surprising, however, is the presence of airborne contaminants in Denali that travel halfway around the world before reaching the park. Each year, small but measurable amounts of pollution arrive in Denali from Europe and Asia. These persistent pollutants come from power plants, metal smelters, and other industrial sources, and are transported over the North Pole and throughout the arctic regions in a phenomenon called arctic haze. Desert dust and agricultural contaminants can travel directly across the Pacific Ocean to reach the park. Airborne contaminants from other continents will likely increase over time as the source areas grow and develop. Denali’s clean air may eventually depend more on international treaties and the environmental policies of other countries than on U.S. laws designed to protect air quality.
Under the U.S. Clean Air Act, Denali receives the strongest protection possible as a designated Class I area. The National Park Service carries out its responsibility to protect park air quality in the following ways: