Air Quality System Sites

This layer displays the locations of air quality monitoring stations in the United States. The Air Quality System (AQS) contains ambient air pollution data collected by EPA, state, Local, and tribal air pollution control agencies from thousands of monitoring stations. AQS also contains meteorological data, descriptive information about each monitoring station (including its geographic location and its operator), and data quality assurance/quality control information. For more information, please visit the EPA Air Quality System web page.

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Air Facility System Sites

This layer displays the locations of regulated facilities that discharge air pollutants in the United States. The Air Facility System (AFS) contains compliance and permit data for stationary sources of air pollution (such as electric power plants, steel mills, factories, and universities) regulated by EPA, state and local air pollution agencies. The information in AFS is used by the states to prepare State Implementation Plans (SIPs) and to track the compliance status of point sources with various regulatory programs under Clean Air Act. For more information, please visit the EPA Air Facility System web page.

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Toxic Release Inventory by County

This layer displays the amount of toxic releases based on the Environmental Protection Agency (EPA) Toxics Release Inventory (TRI), a national program which tracks the management of over 650 toxic chemicals that pose a threat to human health and the environment. Facilities must report how each chemical is managed through recycling, energy recovery, treatment, and releases to the environment. A “release” of a chemical means that it is emitted to the air or water, or placed in some type of land disposal. The information submitted by facilities to the EPA and states is compiled annually as the Toxics Release Inventory or TRI, and is stored in a publicly accessible database ( Envirofacts. For more information, please visit the EPA Toxics Release Inventory web page.

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