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 23 years, EPA has examined air pollution trends 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 Emission Trends. The following sections summarize trends in air quality and emissions during the last 10 years.

Long-Term Emissions Trends
Summary of Air Quality Emissions Trends
Carbon Monoxide (CO)
Lead (Pb)
Nitrogen Dioxide (NO₂)
Ozone (O₃)
Particulate Matter (PM-10)
Sulfur Dioxide (SO₂)

This document is provided for historical purposes only. The most recent version can be found at AIRTrends

Six Principal Pollutants

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