EPA National Emission Inventory Database
(See http://www.epa.gov/air/data/neidb.html)

EPA's National Emission Inventory (NEI) Database for Criteria and Hazardous Air Pollutants contains information about sources that emit Clean Air Act criteria air pollutants and their precursors and hazardous air pollutants.

The database includes estimates of annual air pollutant emissions from point, non-point, and mobile sources in the 50 states, the District of Columbia, Puerto Rico, and the Virgin Islands. 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 on-road sources, the Federal Highway Administration's estimate of vehicle miles traveled and emission factors from EPA's MOBILE computer model;
• For non-road sources, EPA's NONROAD computer model; and
• Previous emissions inventories, if states do not submit current data.

Four of the six criteria air pollutants are included in the NEI database – carbon monoxide, nitrogen oxides, sulfur dioxide, and particulate matter. Ozone, the fifth criteria air pollutant, is caused by photochemical reactions in the atmosphere rather than direct emissions from sources. Lead, the sixth criteria pollutant, is also a hazardous air pollutant ("lead compounds"). The NEI tracks lead emissions as a hazardous air pollutant. The NEI also includes emissions of two pollutants, volatile organic compounds and ammonia, that facilitate formation of criteria air pollutants.

The main purpose of this AirData website is to create reports and maps of air pollution data. Users choose which type of report or map to produce, and determine content by selecting options. Users start by selecting a geographic area and then selecting a report or map type. Users can use options to customize the contents. The AirData software extracts appropriate data, formats it for a report or map, and displays results in a browser. At this point, users can download data in any of several formats.