Basic Information
Under the Clean Air Act, EPA establishes air quality standards to protect public health, including the health of "sensitive" populations such as people with asthma, children, and older adults. EPA also sets limits to protect public welfare. This includes protecting ecosystems, including plants and animals, from harm, as well as protecting against decreased visibility and damage to crops, vegetation, and buildings. View more information regarding the national standards for these pollutants.
EPA has set national air quality standards for six common air pollutants (also called the criteria pollutants):
- nitrogen dioxide (NO2),
- ozone (O3),
- sulfur dioxide (SO2),
- particulate matter (PM),
- carbon monoxide (CO), and
- lead (Pb)
Four of these pollutants (CO, Pb, NO2, and SO2) are emitted directly from a variety of sources. Ozone is not directly emitted, but is formed when oxides of nitrogen (NOx) and volatile organic compounds (VOCs) react in the presence of sunlight. PM can be directly emitted, or it can be formed when emissions of NOx, sulfur oxides (SOx), ammonia, organic compounds, and other gases react in the atmosphere.
To achieve these standards, EPA has in place regulatory and voluntary programs to reduce the amount of air pollutants emitted from a wide range of emission sources. To keep track of these emissions, the EPA maintains the National Emission Inventory (NEI), the national database of air pollutant emissions information. EPA conducts a comprehensive emissions inventory every three years. EPA also modifies the NEI at least annually to correct and augment its inventory data. Developing and updating the inventory is time-consuming, and EPA is working to reduce the amount of time it takes. While the data provided in this site are several years old, they do reflect the most recent inventory. For additional technical information about the NEI, visit the National Emission Inventory website.
This site is linked directly to AirQuest, a data warehouse that stores summary-level emissions and other air quality-related data. AirQuest obtains the emissions data for this site from the National Emissions Inventory mentioned previously.
This site groups emissions into 12 major source sectors. The table below provides more detail about which sources are included in each sector. For a more detailed description of these sectors, see the latest NEI report.
12 Major Source Sectors | Detailed Category Names |
---|---|
Fertilizer & Livestock | Livestock Waste |
Fertilizer Application | |
Electricity Generation | Fuel Combustion - Electric Utilities |
Fossil Fuel Combustion | Fuel Combustion - Industrial Boilers, Internal Combutions Engines |
Fuel Combustion - Commercial/Institutional | |
Fuel Combustion - Residential Fossil | |
Residential Wood Combustion | Fuel Combustion - Residential Fireplaces |
Fuel Combustion - Residential Woodstoves | |
Waste Disposal | Waste Disposal |
Waste Disposal - Open Burning | |
Fires | Wildfires |
Prescribed Fires | |
Agricultural Field Burning | |
Logging Slash Burning | |
Industrial Processes | Industrial Process - NEC |
Commercial Cooking | |
Industrial Process - Metals | |
Industrial Process - Chemical Manufacturing | |
Industrial Process - Storage & Transfer | |
Industrial Process - Petroleum Refineries | |
Industrial Process - Oil & Gas Production | |
Industrial Process - Pulp & Paper | |
Industrial Process - Cement Manufacturing | |
On Road Vehicles | On-Road Vehicles - Gasoline |
On-Road Vehicles - Diesel | |
Non Road Equipment | Non-Road Equipment - Gasoline |
Non-Road Equipment - Diesel | |
Planes, Trains, & Ships | |
Road Dust | Unpaved Roads |
Paved Roads | |
Solvent Use | Solvent - Non-industrial |
Surface Coating - Industrial | |
Degreasing | |
Surface Coating - Architectural | |
Graphic Arts | |
Solvent - Not Classified Elsewhere | |
Dry Cleaning | |
Miscellaneous | Agriculture - Crop Tilling & Livestock Dust |
Construction | |
Gas Stations | |
Bulk Gasoline Terminals | |
Other Miscellaneous Sources |