Good Air Quality
Air quality conditions with an AQI of 0-50, posing little or no health risk for any population group.
Detailed Explanation
An AQI reading of 0-50 is classified as "Good" by the EPA, represented by the color green. At this level, air pollution poses little or no risk, and no precautions are necessary for any population group, including children, the elderly, and people with respiratory or cardiovascular conditions. Cities with consistently good air quality, meaning a median annual AQI in the good range, are relatively uncommon in the United States. Based on AirHistory's analysis of 10 years of EPA data, cities that maintain median AQI values below 50 tend to be located in areas with low population density, minimal industrial activity, and favorable geography that allows air to disperse. Examples include cities in northern New England, the upper Midwest, and parts of the Pacific Northwest away from wildfire-affected zones. Even in cities with overall "Good" air quality, individual days may spike into higher categories due to weather events, nearby wildfires, or temperature inversions. The AirHistory Air Quality Grade assigns the highest scores to cities that maintain "Good" AQI readings consistently over the full 10-year period rather than just in recent years, because consistency is a better predictor of long-term health outcomes than any single year's readings.
Related Terms
Air Quality Index (AQI)
A standardized EPA scale from 0 to 500 that communicates daily air quality and associated health risks.
AQI Categories
The six color-coded health concern levels, Good, Moderate, Unhealthy for Sensitive Groups, Unhealthy, Very Unhealthy, and Hazardous, used by the EPA to describe air quality.
Air Quality Grade
AirHistory's proprietary A-F scoring system that rates cities based on average AQI, trend direction, unhealthy days, and dominant pollutant.
Unhealthy Air Days
Days when the AQI exceeds 100, meaning air quality may pose health risks for sensitive groups or the general population.
Frequently Asked Questions
Air quality conditions with an AQI of 0-50, posing little or no health risk for any population group.
An AQI reading of 0-50 is classified as "Good" by the EPA, represented by the color green. At this level, air pollution poses little or no risk, and no precautions are necessary for any population group, including children, the elderly, and people with respiratory or cardiovascular conditions. Cities with consistently good air quality, meaning a median annual AQI in the good range, are relatively uncommon in the United States.
this entity is one of the U.S. air quality and pollution monitoring concepts that recurs across this site. The definition above is the technical answer; the paragraphs below add the practical context for how the concept connects to the the EPA Air Quality System (AQS) data behind every per-entity page on the site.
In the the EPA Air Quality System (AQS) data, this concept shapes one or more of the fields that drive the per-entity grades and rankings on this site. The methodology page describes which fields feed into which output; this glossary entry documents the underlying term.