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Six Principal Pollutants

Note: EPA no longer updates this information, but it may be useful as a reference or resource.

Please see www.epa.gov/airtrends for the latest information on Air Quality Trends.

For the past 24 years, EPA has examined air pollution trends in concentrations and emissions of each of the six principal pollutants in this country. EPA examines changes in air pollution levels over time and summarizes the current air pollution status annually in two comprehensive technical documents titled National Air Quality and Emissions Trends Report and National Air Pollutant Emissions Trends. The following sections summarize trends in air quality and emissions during the last 10 years.

Long-Term Emissions Trends
New Ozone and Particulate Matter Standards
Summary of Air Quality Emissions Trends
Carbon Monoxide (CO)
Lead (Pb)
Nitrogen Dioxide (NO2)
Ozone (O3)
Particulate Matter (PM)
Sulfur Dioxide (SO2)


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