Welfare Effects - Visibility Impairment

Air pollution also has an effect on visibility. Visibility is a measure of aesthetic value and the ability to enjoy scenic vistas, but it also can be an indicator of general air quality. Visibility degradation results when light encounters tiny pollution particles (sulfates, nitrates, organic carbon, soot, and soil dust) and some gases (nitrogen dioxide) in the air. Some light is absorbed by the particles and other light is scattered away before it reaches the observer. More pollutants mean more absorption and scattering of light, resulting in more haze. Haze obscures the clarity, color, texture, and form of what we see. Humidity magnifies the haze problem because some particles, such as sulfates, attract water and grow in size, scattering more light.

In the United States' scenic areas, the visual range has been substantially reduced by air pollution. In eastern parks, average visual range has decreased from 90 miles to 15-25 miles. In the West, average visual range has decreased from 140 miles to 35-90 miles.

More information on visibility can be found at: http://www.epa.gov/air/visibility/index.html