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aside for protection. It can shroud breathtaking vistas, acidify 

 pure mountain streams, damage vegetation and soils, reduce the 

 diversity of plant and animal life, efface national monuments, and 

 affect the health of visitors. Air pollution can come from sources 

 of all sizes and types — for example, power plants, refineries, 

 smelters, dry cleaners, wood stoves, cars and trucks — located 

 nearby or hundreds, even thousands, of miles away. Perhaps more 

 obviously than in other areas of ecosystem management, the 

 protection of park and wilderness resources from air pollution 

 necessitates the involvement of many outside the boundaries whose 

 actions largely determine the quality of the air within. 



Recognizing this necessity, Congress included provisions in the 

 1977 amendments to the Clean Air Act "to preserve, protect, and 

 enhance the air quality in national parks, national wilderness 

 areas,... and other areas of special. . .value. " In particular, 

 Congress established the Prevention of Significant Deterioration 

 (PSD) program and the Visibility Protection program, and focused 

 the strongest measures of protection on Class I areas, i.e. , the 

 larger national park and wilderness areas in existence in 1977. 

 The National Park Service manages 48 Class I areas, and the U.S. 

 Fish and Wildlife Service manages 21 Class I areas. 



In the 1990 amendments to the Clean Air Act, Congress confronted 

 the lack of progress being made toward the protection goals set in 

 1977 for Class I areas, and passed amendments to facilitate 



