2020 AirToxScreen

In May 2024, EPA released the results of its 2020 Air Toxics Screening Assessment (AirToxScreen). AirToxScreen helps assess which air toxics and emission source types may pose health risks. AirToxScreen also helps EPA and other agencies determine which places may need further study to better understand risks.

EPA uses AirToxScreen results in many ways, including to:

• help communities design their own local assessments;
• improve emissions inventories; and
• learn where we can expand and improve the air toxics monitoring network.

About the 2020 Assessment

The 2020 AirToxScreen assessment includes emissions, ambient concentrations, and exposure estimates for 181 of the 188 Clean Air Act air toxics plus diesel particulate matter (diesel PM). For about 140 of these air toxics (those with health data based on long-term exposure), the assessment estimates cancer risks, the potential for noncancer health effects, or both. This includes noncancer health effects for diesel PM. We did not include several air toxics in this AirToxScreen assessment because either no emissions data were reported for them in 2020 or we couldn’t reliably make emissions or health-related estimates (radionuclides, for example). 

AirToxScreen includes four steps:

1. Compile a national inventory of air toxics emissions from outdoor sources.
2. Estimate ambient concentrations of air toxics across the United States.
3. Estimate population exposures.
4. Characterize potential public health risks due to breathing air toxics (including both cancer and noncancer effects).

EPA continues to improve AirToxScreen assessment methods, including the integration of the Community Multiscale Air Quality (CMAQ) and AERMOD models. This hybrid modeling system includes mass conservation, atmospheric chemistry, and long-range transport for over 50 air toxics.

AirToxScreen also includes an updated AirToxScreen Mapping Tool, designed to display more data at a glance. Our latest tool includes 2020 AirToxScreen results. AirToxScreen also includes a Technical Support Document (TSD). This document presents the approaches EPA used to conduct this AirToxScreen, including descriptions of how we:

• compile emissions data and prepare them for use as model inputs;
• estimate ambient concentrations of air toxics;
• estimate exposures to air toxics for different source and pollutant groups;
• characterize human health risks and hazards; and
• address the assessment’s variability and uncertainty.