21 



lation growth in the West is projected to continue during the com- 

 ing decades, bringing with it the potential for increases in many of 

 these categories. 



Achieving the national visibility goal will require a substantial 

 long-term program. The committee's simple scoping calculations in- 

 dicate that the application of all commercially available control 

 technology would reduce but not eliminate visibility impairment in 

 class I areas. This means that a long-term commitment to estab- 

 lishing and financially supporting monitoring programs is essen- 

 tial. 



Current scientific knowledge is adequate, and control tech- 

 nologies are available for taking regulatory action to improve and 

 protect visibility. Visibility impairment is probably better under- 

 stood and more easily measured than any other air pollution effect. 

 However, continued cost-effective national progress toward this 

 goal will require a greater commitment toward atmospheric re- 

 search, monitoring, and emissions control R&D. 



The committee felt that the slowness of progress to date has been 

 due largely to a lack of commitment to an adequate government ef- 

 fort to protect and improve visibility and to sponsor the research 

 and monitoring needed to better characterize the nature and origin 

 of haze in various areas. The Federal Government has accorded the 

 national visibility goal less priority than other clean air objectives. 

 Even to the extent that Congress has acted, EPA, the Department 

 of Interior, and the Department of Agriculture have been slow to 

 carry out their regulatory responsibilities or to seek resources for 

 research. Visibility research would benefit from increased integra- 

 tion with other air quality research and from wider participation 

 by the scientific community. 



Visibility impairment can be attributed to emission sources on a 

 regional scale through the use of several kinds of models. In gen- 

 eral, the best approach for evaluating emission sources is a nested 

 progression from simpler and more direct models to more complex 

 and detailed models. The simpler models are available today and 

 could be used as the basis for designing regional visibility pro- 

 grams. The more complex models could be used to refine these pro- 

 grams over time. 



Reducing emissions for visibility improvement could help allevi- 

 ate other air quality problems, just as other types of air quality im- 

 provements could help visibility. Emissions that contribute to re- 

 gional haze also contribute to a variety of other undesirable effects 

 on the environment and human health. 



In summary, any effective visibility protection program must be 

 aimed at preventing and reducing regional haze. An effective pro- 

 gram must therefore control a broad array of sources over a large 

 geographic area. Such a program would mark a considerable break 

 from the present approach of focusing on visible plumes from near- 

 by sources and of attempting to determine the effects of individual 

 sources on visibility impairment. 



Although visibility impairment is as well understood as any 

 other air pollution effect, gaps in knowledge remain. Filling these 

 gaps will require an increased national commitment to visibility 

 protection research. With major shifts projected in present patterns 

 of pollutant emissions, the committee believes that the time has 



