EPA Air Quality System (AQS)
The EPA's national database of ambient air quality data collected from monitoring stations across the United States.
Detailed Explanation
The EPA's Air Quality System (AQS) is the comprehensive national repository for ambient air monitoring data. AQS stores data from over 4,000 monitoring stations operated by state, local, and tribal air quality agencies across the United States. These monitors continuously or periodically measure concentrations of criteria pollutants and hazardous air pollutants in the ambient air. The data collected includes hourly and daily measurements of pollutant concentrations, along with meteorological data from many stations. AQS data is used to determine whether areas meet the NAAQS, to track long-term air quality trends, to support health studies, and to inform the public through the AQI. The system makes data publicly available through the EPA's AirData website and downloadable datasets, which is the primary data source for AirHistory. AirHistory uses the "annual AQI by county" dataset, which provides annual summaries including median AQI, maximum AQI, 90th percentile AQI, the number of days in each AQI category, and the number of days each pollutant was the primary pollutant. This annual dataset spans from 1980 to the present, though AirHistory focuses on the most recent 10-year period (2014-2023) to capture current conditions and meaningful trends. All data on AirHistory is sourced directly from AQS with no modification to the underlying measurements.
Related Terms
Air Quality Index (AQI)
A standardized EPA scale from 0 to 500 that communicates daily air quality and associated health risks.
Air Quality Monitor
A device that measures pollutant concentrations in ambient air, operated by government agencies as part of the national monitoring network.
National Ambient Air Quality Standards (NAAQS)
EPA-established limits on concentrations of six criteria pollutants that must be met nationwide to protect public health and the environment.
Criteria Pollutants
The six common air pollutants regulated by the EPA under the Clean Air Act: ozone, PM2.5, PM10, CO, NO2, and SO2.
Frequently Asked Questions
The EPA's national database of ambient air quality data collected from monitoring stations across the United States.
The EPA's Air Quality System (AQS) is the comprehensive national repository for ambient air monitoring data. AQS stores data from over 4,000 monitoring stations operated by state, local, and tribal air quality agencies across the United States. These monitors continuously or periodically measure concentrations of criteria pollutants and hazardous air pollutants in the ambient air.