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Achieving the national visibility goal will require a substantial, long-term 

 program. 



The national visibility goal is unlikely to be achieved in a short time. The 

 committee's simple scoping calculations indicate that the application of all 

 commercially available control technology would reduce, but not eliminate, 

 visibility impairment in Class I areas. Policy makers might develop a 

 comprehensive national visibility improvement strategy as the basis for 

 further regulatory action, and establish milestones against which progress 

 toward the visibility goal could be measured. 



A long-term commitment to establishing and financially supporting monitoring 

 programs is essential. 



Monitoring programs should be able to relate visibility impairment to its 

 sources on a scale commensurate with regional haze events and the distribution 

 of major emissions sources. Monitoring networks in the East need to be 

 expanded to track visibility improvements associated with reductions in S0 2 

 emissions. Future measurement programs should devote increased attention to 

 quality assurance and control. A consensus should be developed on the 

 specific instrumentation to be used for monitoring light extinction. Greater 

 attention should be given to the implications of planned changes in airport 

 visibility monitoring for research on visibility impairment. The committee 

 recommended using high-sensitivity integrating nephelometry for routine 

 visibility monitoring. 



Current scientific knowledge is adequate and control technologies are 

 available for taking regulatory action to improve and protect visibility. 

 However, continued national progress toward this goal will require a greater 

 commitment toward atmospheric research, monitoring, and emissions control 

 research and development. 



If the nation chooses to act to improve visibility, it can do so now within a 

 rational decision framework. Visibility impairment is probably better 

 understood and more easily measured than any other air-pollution effect. The 

 relationship of visibility impairment to atmospheric composition is understood 

 at a fundamental level. The major constituents of regional haze are known, as 

 are some important categories of emissions sources. This knowledge base can 

 be used to inform judgements about the likely effects of possible initial 

 steps . 



There remain gaps and uncertainties in our knowledge. As noted above, the 

 road to the national goal of no manmade impairment is a long one, and we 

 cannot now see the way to the end. Additional atmospheric research, 

 monitoring, and emissions control R&D will be necessary to sustain cost- 



