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A Quick Summary of EPA's Findings on National Air Quality: 2002 Status and Trends

In September 2003, EPA released a summary of the status of the Nation's air quality and emissions. EPA's findings on carbon monoxide, lead, nitrogen dioxide, ozone, particulate matter, and sulfur dioxide are

  • National air quality levels measured at thousands of monitoring stations across the country have shown improvements over the past 20 years for all six principal pollutants.


  • Of the six tracked pollutants, progress has been slowest for ground-level ozone. Over the pat 20 years, almost all geographic areas experienced some progress in lowering ozone concentrations. The Northeast and Pacific Southwest exhibited the greatest improvement. In particular, substantial progress seen in Los Angeles has continued through 2002. However, the national average ozone (8-hour) levels have been fairly constant in other metropolitan areas. An analysis to adjust 8-hour ozone levels in metropolitan areas to account for the influence of meteorological conditions shows the 10-year trend to be relatively unchanged. At the same time, for some national parks, the 8-hour ozone levels have increased. Seven monitoring sites in five of the national parks experienced statistically significant upward trends in the 8-hour ozone levels. Monitoring data for one park site showed statistically significant improvements over the period 1983-2002. For the remaining 22 parks with ozone trends data, the 8-hour ozone levels at 13 increased only slightly, while 5 showed decreasing levels and 4 were unchanged.


  • Between 1983 and 2002, NOx emissions in the United States decreased 15 percent (with a 12 percent decrease in the past 10 years).


  • Sulfates formed primarily from sulfur dioxide (SO2) emissions from coal-fired power plants are a major component of fine particles in the eastern United States. SO2 emissions decreased 33 percent from 1983 to 2002 and 31 percent from 1993 to 2002.

A summary table of the percent change in national air quality concentrations and emissions is available at this web site. A table (in pdf format) describing the peak air quality statistics for the six principle pollutants by county is provided.

For additional information about the EPA National Air Quality Status and Trends: 2002 report, please visit EPA's web page.

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