This graph shows the trend in the pounds of chemicals released to air. EPA regulates air emissions under the Clean Air Act, which requires major sources of air pollutants to obtain and comply with an operating permit.

Note: For comparability, trend graphs include only those chemicals that were reportable to TRI for all years presented.

From 2007 to 2019:

• Releases to air decreased by 57% (-756 million pounds).
  • Since 2007, hydrochloric acid, sulfuric acid, hydrogen fluoride, methanol, toluene, and xylene had the greatest reductions in releases to air.
  • The decrease was driven by electric utilities due to: decreased emissions of hydrochloric acid and sulfuric acid; a shift from coal to other fuel sources (e.g., natural gas); and the installation of pollution control technologies at coal-fired power plants.
    • Note that only those electric utilities that combust coal or oil to generate power for distribution into commerce are covered under TRI reporting requirements. Therefore, electric utilities that shift from combusting coal or oil to entirely using other fuel sources (such as natural gas) are not required to report to TRI.
• Air releases of chemicals classified as carcinogens by the Occupational Safety and Health Administration (OSHA) also decreased; see the Air Releases of OSHA Carcinogens figure.
• For trends in air releases of other chemicals of special concern, including lead and mercury, see the Chemicals of Special Concern section.

In 2019:

• The TRI chemicals released in the largest quantities were ammonia and methanol.
• Releases of TRI chemicals to air decreased by 3.7% since 2018.

This graph shows the trend in the RSEI Scores for TRI air releases.

Note: For comparability, trend graphs include only those chemicals that were reportable to TRI for all years presented.

• Stack air releases reported to TRI are considerably higher in pounds than fugitive air releases, but their relative contributions to the RSEI Score have been similar in recent years. This is because chemicals released through stacks tend to get dispersed over a wider area than fugitive air releases, resulting in lower average concentrations, and as a result, surrounding populations have a lower potential to be exposed to TRI chemicals released to air through stacks compared to fugitive emissions.
• For a complete, step-by-step description of how RSEI models and derives RSEI Scores from stack air emissions and fugitive air emissions, see “Section 5.3: Modeling Air Releases” in Chapter 5 (“Exposure and Population Modeling”) of EPA’s Risk-Screening Environmental Indicators (RSEI) Methodology, RSEI Version 2.3.8.
• For general information on how RSEI Scores are estimated, see Hazard and Potential Risk of TRI Chemicals.