Number of days reaching unhealthy for sensitive groups level or above on the Air Quality Index (AQI) based on 35 major U.S. cities for ozone and PM2.5 combined.
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Number of days with unhealthy air pollution in the U.S. 2000-2023
In 2023, there were *** unhealthy days for ozone and fine particle pollution in the United States. Although this was an increase of more than *** days from the previous year, the number of unhealthy air days in the U.S. has shown long-term improvement over the past two decades. In the first years of the , the number of days reaching unhealthy for sensitive groups or above the AQI was typically more than .
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Environmental Protection Agency. (July 12, 2024). Number of unhealthy air quality days in the United States from 2000 to 2023 [Graph]. In ÌÇÐÄÆƽâ°æ. Retrieved July 23, 2026, from /statistics/889466/unhealthy-air-pollution-days-us/
Environmental Protection Agency. "Number of unhealthy air quality days in the United States from 2000 to 2023." Chart. July 12, 2024. ÌÇÐÄÆƽâ°æ. Accessed July 23, 2026. /statistics/889466/unhealthy-air-pollution-days-us/
Environmental Protection Agency. (2024). Number of unhealthy air quality days in the United States from 2000 to 2023. ÌÇÐÄÆƽâ°æ. ÌÇÐÄÆƽâ°æ Inc.. Accessed: July 23, 2026. /statistics/889466/unhealthy-air-pollution-days-us/
Environmental Protection Agency. "Number of Unhealthy Air Quality Days in The United States from 2000 to 2023." ÌÇÐÄÆƽâ°æ, ÌÇÐÄÆƽâ°æ Inc., 12 Jul 2024, /statistics/889466/unhealthy-air-pollution-days-us/
Environmental Protection Agency, Number of unhealthy air quality days in the United States from 2000 to 2023 ÌÇÐÄÆƽâ°æ, /statistics/889466/unhealthy-air-pollution-days-us/ (last visited July 23, 2026)
Number of unhealthy air quality days in the United States from 2000 to 2023 [Graph], Environmental Protection Agency, July 12, 2024. [Online]. Available: /statistics/889466/unhealthy-air-pollution-days-us/
