Protocol - Air Quality Index

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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.

Specific Instructions



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.

AQI Median

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




Very Unhealthy





Personnel and Training Required


Equipment Needs


Requirement CategoryRequired
Major equipment No
Specialized training No
Specialized requirements for biospecimen collection No
Average time of greater than 15 minutes in an unaffected individual No
Mode of Administration

Secondary Data Analysis

Life Stage

Infant, Toddler, Child, Adolescent, Adult, Senior, Pregnancy


Not applicable; derived from publicly available data

Selection Rationale

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
Derived Variables


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


General References

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.

Protocol ID


Export Variables
Variable Name Variable IDVariable DescriptiondbGaP Mapping
Social Determinants of Health
Measure Name

Air Quality Index

Release Date

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