Haziest Day in Tucson

Federal standards set by the Environmental Protection Agency (EPA) state that levels should not top 70 ppb over an 8 hour period. In 2017, Pima County hit 70 ppb during summer wildfires, and again in 2020 with 72 ppb. In 2021, there was an hourly spike of over 90 ppb recorded on August 27.

2020 was a poor year for air quality in Pima County. Only 42.1% of days in 2020 ranked “good” on the air quality scale according to the EPA. In 2021, this dropped to 39.2%.

To date, the highest levels of particulate matter (PM10) ever monitored in Pima County occurred on July 22, 2009. The PM10 reading at the Pima Department of Environmental Quality’s (PDEQ) Orange Grove monitoring site was 270 micrograms/cubic meter of air over 24 hours. The EPA’s health standard is 150 micrograms/cubic meter over a 24 hour period. A healthy average yearly standard is only 15 micrograms. Unhealthy levels of particulates in our air typically occur in Pima County when there are high winds and/or forest fires.

Exposure to particulate matter has been linked to increased respiratory symptoms, such as:

  • irritation of the airways
  • coughing, or difficulty breathing
  • decreased lung function
  • aggravated asthma
  • irregular heartbeat
  • nonfatal heart attacks
  • premature death in people with heart or lung disease

Pima County Department of Environmental Quality (PDEQ) monitors local air quality and provides information about current air quality readings at Air Monitoring. PDEQ can be reached by phone at 520-724-7400.

Another source for air quality information is the EPA's AirNow Interactive Map.


“Hazy Wednesday last week set record of particulate level.” Arizona Daily Star. July 30, 2009. Page A13.

Davis, Tony. "Tucson-area air quality the worst in five years." Arizona Daily Star. June 22, 2017.

“Tucson’s Health: MAP dashboard.” Arizona Daily Star. July 5, 2021.

Air Quality: How are we doing?” | Making Action Possible for Southern Arizona.

“Air quality statistics by city, 2020.” Air quality – Cities and Counties. United States Environmental Protection Agency.

Air Monitoring | Pima County Department of Environmental Quality

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