2020 AirToxScreen: Assessment Results
On this page:
- About the 2020 Assessment
- 2020 AirToxScreen Emissions
- 2020 Modeled Ambient Concentrations, Exposures and Risks
About the 2020 Assessment
This page provides the emissions data, ambient concentrations and health-effect results for the 2020 Air Toxics Screening Assessment, or AirToxScreen. You can also find links to supporting files and web pages with more information about these results.
EPA developed AirToxScreen as a screening tool for State, Local and Tribal air agencies. AirToxScreen’s results help these agencies identify which pollutants, emission sources and places they may wish to study further to better understand any possible risks to public health from air toxics. Often, more localized studies are needed to better characterize local-level risk. The localized studies often include air monitoring and more detailed modeling.
The following files will help you navigate the AirToxScreen results:
- AirToxScreen Technical Support Document provides technical information on the assessment, including and emissions, modeling, and risk calculations.
- 2020 AirToxScreen: Emissions Update Document lists some of the known issues and updates that were not addressed during the review of the 2020 assessment, including information on some facilities about which EPA is aware that have reduced emissions of certain air toxics since 2020.
2020 AirToxScreen Emissions
The 2020 AirToxScreen used the 2020 National Emissions Inventory (NEI) as a starting point. The NEI is EPA’s comprehensive estimate of air pollution emissions from sources across the country. NEI supports air quality modeling and other activities within EPA’s Air Toxics Program. We updated these data for 2020 from comments provided by state, local and tribal agencies during the AirToxScreen review. The resulting emission files, accessed below, reflect the emissions used in AirToxScreen.
- 2020 NEI Technical Support Document provides more details on the 2020 NEI.
NOTE: Emission inventories submitted by State, Local and Tribal agencies vary in the level of detail and completeness. For this reason, you should not compare AirToxScreen risk estimates between states or regions without considering these inventory differences.
- 2020 AirToxScreen emissions by facility (xlsx)
- 2020 AirToxScreen emissions by railyard (xlsx)
- 2020 AirToxScreen emissions by airport runway (xlsx)
- 2020 AirToxScreen emissions by airport non-runway (xlsx)
- 2020 AirToxScreen emissions by county (zip)
2020 Modeled Ambient Concentrations, Exposures and Risks
The following links provide the EPA's 2020 AirToxScreen ambient concentration, exposure concentration and risk estimates across all 50 U.S. states, Puerto Rico, the Virgin Islands, and the District of Columbia.
We show total risks, then break out the contribution for each AirToxScreen source type (for example, stationary point sources, on-road gasoline vehicles, etc.) in the source type files or by pollutant in the pollutant files.
In the 2020 AirToxScreen results, results for stationary sources are broken into two groups: “point” and “nonpoint” sources. This reflects the way we modeled each source.
Each point source’s exact latitude and longitude coordinate is in the AirToxScreen source inventory. We used these locations in modeling. Large industrial complexes often have many individual point sources. We also modeled some smaller sources, such as dry cleaners, as point sources.
For other smaller sources, we may not have an exact location in the AirToxScreen inventory. We modeled these as nonpoint sources. Emissions from homes, such as wood-burning stoves and fireplaces or solvent emissions, are examples of nonpoint sources.
We usually inventory nonpoint sources by county. But a more precise location gives better modeling results. So we divided each county into smaller, square “grid cells,” then assign nonpoint emissions to each cell using population or another method that realistically distributes the emissions across the county (these are called “surrogates;” see the AirToxScreen Technical Support Document for more details).
We used a similar approach to assign most mobile source emissions. An exception is for airports, included as a nonroad source type under mobile sources. We modeled airports using their actual locations.
Result Files
2020 Nationwide Cancer Risk Results
- Block-level cancer risk by region and source group
- Block-level cancer risk by region and pollutant
- County average cancer risk by source group (xlsx)
- County average cancer risk by pollutant (xlsx)
- State average cancer risk by source group (xlsx)
- State average cancer risk by pollutant (xlsx)
2020 National Concentration Summaries
2020 National Concentration Summaries by Region
2020 Pollutant-Specific Results