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 therefore, regulatory approaches to air quality issues should be 

 different. The science underlying these differences is well known and 

 includes the facts that the western atmosphere is generally dry while 

 the East is moist; the natural visibility in the East is lower than in 

 the West; sulfates are the major visibility impairing pollutant in the 

 East while nitrates and organics also play a large role in the West; 

 and ozone is a far greater threat to terrestrial ecosystems in the 

 East and far West than in the intermountain West. As an example, an 

 ambient standard for fine particles sufficient to improve visibility 

 by 10% in the West would not necessarily result in a noticeable change 

 in the East . 



Consequently, regulatory approaches in air pollution control should 

 include these and other regional considerations such as the presence 

 of fire-adapted ecosystems and the fact that small 



additions/reductions to atmospheric loadings are more critical for 

 many high elevation ecosystems that occur in the West. Generally, 

 thresholds, standards and levels of protection should be more 

 sensitive in the West to adequately protect the resource although many 

 areas in the East are already at or beyond critical levels. 



Explain the effects of air pollution on plants, animals, lands and 

 waters under the jurisdiction of the Department of Agriculture. 



While much has been learned, the effects of air pollution on the 

 National Forest System are only partially understood. A large body of 

 knowledge exists about factors that control the response of vegetation 

 to air pollutants and acidic precipitation. However, there are major 

 uncertainties which prevent a comprehensive analysis of wide scale 



