Air Pollutant Emissions Trends Data
Current emission trends data and the documentation of estimation methods are available via the links below. The latest version of the 1970 - 2021 data show the trends for Tier 1 categories which distinguish pollutant emission contributions among major source types. The trends shown are for criteria air pollutants (CAPs) and precursors covered by the National Ambient Air Quality Standards (NAAQS), excluding lead. Lead emissions sharply declined after it was eliminated from gasoline and have remained low. As inventory methods are improved over time, for some emission sources and improved estimation method may be applied 'backwards' to previous year trend estimates.
National Tier 1 CAPS Trends (xlsx) Criteria pollutants National Tier 1 for 1970 - 2021.
State Tier 1 CAPS Trends (xlsx) Criteria pollutants State Tier 1 for 1990 - 2021.
Trends Procedural Documentation - Any changes in the data or methodologies used to estimate the emissions for a specific time period will continue to be noted in future updates.
For more information on air trends visit the National Air Quality website.