Visibility and Regional Haze

This Web site describes visibility impairment caused by air pollution in the United States, and EPA's activities to address the problem.

June 30, 2016 - The EPA announced the availability of and public comment period for draft guidance for the second implementation period of the regional haze rule.

Visibility and Regional Haze

One of the most basic forms of air pollution - haze - degrades visibility in many American cities and scenic areas. Haze is caused when sunlight encounters tiny pollution particles in the air, which reduce the clarity and color of what we see, and particularly during humid conditions. Since 1988 the federal government has been monitoring visibility in national parks and wilderness areas, for example, in the Great Smoky Mountains National Park as illustrated at right. In 1999, EPA announced a major effort to improve air quality in national parks and wilderness areas.

Regulatory Actions and Guidance Documents