How Clean Is the Air: Tennessee Valley Air Quality Trends. ('On the Air' Technical Notes on Important Air Quality Issues)

摘要

In July 2003, TVA produced a 29-page report entitled, 'How clean is the air. Air Quality in the Tennessee Valley Region.' This report looks back on 24 years of air quality in the east-central United States, considering trends from 1979 through 2002. In addition to examining problems associated with federal clean air standard pollutants, the report considers acid rain, hazardous (i.e., toxic) air pollution, fine particulates, indoor air quality, visibility impairment, and global climate change. Clean air 'yardsticks'--National Ambient Air Quality Standards (NAAQS)--were established by the U.S. EPA in 1971, following the 1970 Clean Air Act Amendments. There are two kinds of NAAQS: (1) 'Primary standards,' which set air quality limits protective of public health, and (2) 'Secondary standards,' which set limits protecting public welfare, including animals, crops, vegetation, materials, and visibility. Current NAAQS include six air pollutants (often referred to as 'criteria pollutants'): particulate matter, sulfur dioxide, ozone, carbon monoxide, nitrogen dioxide, and lead. In order to keep these NAAQS standards current, the U.S. EPA periodically reviews and, if warranted, updates these standards to keep in step with new findings.