Protocol - Air Quality Index
This protocol is based on extracting air quality data from the U.S. Environmental Protection Agency (EPA) AirData Air Quality Index Summary Report. This report displays an annual summary of Air Quality Index (AQI) values for states, counties or cities (defined by core-based statistical areas [CBSAs]). The AQI is determined using measured concentrations of carbon monoxide (CO), nitrogen dioxide (NO2), ozone (O3), particulate matter with a diameter of less than 2.5 micrometers (PM2.5), and sulfur dioxide (SO2). Standard EPA formulas convert the measured pollutant concentrations to an AQI value between 0 and 500. AQI values are associated with risk categories (e.g., good, moderate, unhealthy). The pollutant with the highest AQI is reported as the overall AQI value for the day. Each row of the AQI Summary Report lists several qualitative measures (e.g., days with "good" air quality) and descriptive statistics (e.g., median AQI value) for 1 year for one county or CBSA.
US Environmental Protection Agency Air Quality Index Report
The US Environmental Protection Agency Air Quality Index Report (https://www.epa.gov/outdoor-air-quality-data/about-air-data-reports#aqi) includes the annual summary of AQI values for counties or core based statistical areas (CBSA). The report includes the following columns.
# Days with AQI
Number of days in the year having an Air Quality Index value. This is the number of days on which measurements from any monitoring site in the county or MSA were reported to the Air Quality System (AQS) database.
# Days Good
Number of days in the year having an AQI value 0 through 50.
# Days Moderate
Number of days in the year having an AQI value 51 through 100.
# Days Unhealthy for Sensitive Groups
Number of days in the year having an AQI value 101 through 150.
# Days Unhealthy
Number of days in the year having an AQI value 151 through 200.
# Days Very Unhealthy
Number of days in the year having an AQI value 201 or higher. This includes the AQI categories very unhealthy and hazardous. Very few locations (about 0.3% of counties) have any days in the very unhealthy or hazardous categories.
The highest daily AQI value in the year.
AQI 90th %ile
90 percent of daily AQI values during the year were less than or equal to the 90th percentile value.
Half of daily AQI values during the year were less than or equal to the median value, and half equaled or exceeded it.
# Days CO
# Days NO2
# Days O3
# Days SO2
# Days PM2.5
# Days PM10
A daily index value is calculated for each air pollutant measured. The highest of those index values is the AQI value, and the pollutant responsible for the highest index value is the "Main Pollutant." These columns give the number of days each pollutant measured was the main pollutant. A blank column indicates a pollutant not measured in the county or CBSA.
US EPA Air Quality Index Ranges and Associated Categories
Unhealthy for Sensitive Groups
Personnel and Training Required
|Specialized requirements for biospecimen collection||No|
|Average time of greater than 15 minutes in an unaffected individual||No|
Mode of Administration
Secondary Data Analysis
Infant, Toddler, Child, Adolescent, Adult, Senior, Pregnancy
Not applicable; derived from publicly available data
The Environmental Protection Agency (EPA) Air Quality Index (AQI) is a standard, widely used measure that includes six National Ambient Air Quality Standard (NAAQS) pollutants. It has been maintained by the federal government for decades and is reported on a daily basis by ZIP Code.
|caDSR Common Data Elements (CDE)||Social Determinants of Health EPA Air Quality Index Assessment Score||7263162||CDE Browser|
Process and Review
The Expert Review Panel has not reviewed this measure yet.
Protocol Name from Source
Environmental Protection Agency (EPA), Air Quality Index (AQI)
U.S. Environmental Protection Agency. (n.d.). AirData. Retrieved from
AirNow. (2019). Air Quality Index (AQI) basics. Retrieved from https://airnow.gov/index.cfm?action=aqibasics.aqi
Kumari, S., & Jain, M. K. (2018). A critical review on Air Quality Index. In V. Singh, S. Yadav, & R. Yadava (Eds.), Environmental pollution. Water Science and Technology Library (vol. 77). Springer.
Rice, M. B., Ljungman, P. L., Wilker, E. H., Gold, D. R., Schwartz, J. D., Koutrakis, P., … Mittleman, M. A. (2013). Short-term exposure to air pollution and lung function in the Framingham Heart Study. American Journal of Respiratory and Critical Care Medicine, 188(11), 1351–1357.
Talbot, T. O., Haley, V. B., Dimmick, W. F., Paulu, C., Talbott, E. O., & Rager, J. (2009). Developing consistent data and methods to measure the public health impacts of ambient air quality for Environmental Public Health Tracking: Progress to date and future directions. Air Quality, Atmosphere, & Health, 2(4), 199–206.
Thach, T. Q., Tsang, H., Cao, P., & Ho, L. M. (2018). A novel method to construct an air quality index based on air pollution profiles. International Journal of Hygiene and Environmental Health, 221(1), 17–26.
Wellenius, G. A., Burger, M. R., Coull, B. A., Schwartz, J., Suh, H. H., Koutrakis, P., … Mittleman, M. A. (2012). Ambient air pollution and the risk of acute ischemic stroke. Archives of Internal Medicine, 172(3), 229–234.
|Variable Name||Variable ID||Variable Description||dbGaP Mapping|
Air Quality Index
May 11, 2020
The Air Quality Index is a location-based estimation of air pollution that can be used as a proxy for exposure (i.e., exposure risk) to air pollution.
The U.S. Environmental Protection Agency Air Quality Index includes several air pollutants that have been shown to cause respiratory disease and adverse pulmonary effects (e.g., decreased lung function, chronic bronchitis, asthma) and have been linked to cardiovascular disease (e.g., stroke onset). Additionally, long-term exposure to fine particulate matter increases premature death risk among people aged 65 or older, even when exposure is at levels below the National Ambient Air Quality Standards.
Air Quality Index, AQI, Environmental Protection Agency Air Quality Index