README

This directory contains data files, summaries, and documentation for the 2021 Multipollutant Platform Air Toxics Emissions and Concentrations. The following describes the subdirectories and files included in this directory:

Ambient and Exposure Concentration Summaries: This subdirectory contains ambient and exposure concentration summary excel files, organized by region. Each file covers all blocks in its region; rows are blocks, columns are pollutants, and values are the total concentration of each pollutant for that block.

Ambient and Exposure Concentrations by Pollutant: This subdirectory contains the ambient and exposure concentrations files by single pollutants. Each file contains the ambient or exposure concentration of one pollutant for the Region. Each column in those files is the source. Each row is a block.

Emission Summaries: This subdirectory contains emissions totals by pollutant and facility for the point sources, railyards, and airports in excel files. There are also emission totals by county and source group in excel files by Region.

Supplemental Data and Documentation: This subdirectory contains the Technical Support Document (TSD) that describes the methods and inputs for the 2021 Multipollutant Platform Air Toxics Emissions and Concentrations. It also includes supplemental data that supports the information in the TSD, including exposure factors and emission changes.

For questions on any of the files of documentation described here, please contact airtoxics@epa.gov.