The NEI is built from air emissions data stored in the Emissions Inventory System (EIS) database. EIS contains information on stationary and mobile sources that emit criteria air pollutants and their precursors as well as hazardous air pollutants.
The NEI is prepared every three years by the Environmental Protection Agency (EPA), based primarily upon emissions estimates and emissions model inputs provided by state, local, and tribal air agencies for sources in their jurisdictions. It’s supplemented by data collected by EPA.