National Emissions Inventory
The Environmental Protection Agency's (EPA) National Emissions Inventory (NEI) database contains information about sources that emit criteria air pollutants and their precursors, and hazardous air pollutants. The database includes estimates of annual air pollutant emissions from point, nonpoint, and mobile sources in the 50 states the District of Columbia, and Puerto Rico. EPA collects information about sources and releases an updated version of the NEI database every three years.
EPA compiles the NEI database from these primary sources: Emissions inventories compiled by state and local environmental agencies; Databases related to EPA's Maximum Achievable Control Technology (MACT) programs to reduce emissions of hazardous air pollutants; Toxic Release Inventory (TRI) data for electric generating units; EPA's Emission Tracking System / Continuous Emissions Monitoring data (ETS/CEM) and Department of Energy fuel use data; For onroad sources, the Federal Highway Administration's estimate of vehicle miles traveled and emission factors from EPA's MOBILE computer model ; For nonroad sources, EPA's NONROAD computer model; Previous emissions inventories, if states do not submit current data.