Description

The Regional Haze rule addresses visibility impairment in 156 Federal Class I areas. The goal of the rule is to remove all anthropogenic air pollution from the National Parks and Wilderness areas. Determining natural visibility conditions is an interesting and complicated problem. There is a large archive of pre- and early-settlement narratives, landscape paintings, and photographs that could be used as part of a weight-of-evidence demonstration in regional haze State implementation plans (SIPs), especially for Western States. With an understanding of inherent limits, these materials could be used for qualitative evaluation of the early American atmosphere. Despite large uncertainties and with knowledge of film properties, application of quantitative analysis of contrast in photographs is possible and could provide estimates of visual range. These issues are introduced here as a theoretical treatment with some reference material for further investigation and practical application.