Air Quality

How are we doing?

Percentage of Good Air Quality Days (2020)

Air Quality Fuel 2020


In 2020, Tucson’s air quality was rated “good” 42.1% of the time. This ranked the Tucson Metropolitan Statistical Area (MSA) sixth out of 12 western MSAs in the percent of good air quality days. Portland ranked first with 78.1%, while Phoenix ranked last with only 3.0% of days considered “good”. According to the Air Quality Index (AQI), good air quality days occur when air quality is satisfactory and air pollution poses little or no threat. The AQI has six rankings:  good, moderate, unhealthy for sensitive groups, unhealthy, very unhealthy, and hazardous. Tucson’s percentage of good air quality days in 2020 was a decline of almost 20 percentage points from last year’s rate of 61.6%. The prolonged smoke during fires in the Tucson MSA region contributed to the decline in air quality.

Why is it important?  

Air quality is vitally important to the well-being of a region’s residents. It is a particularly important health concern to those who have sensitivity to air pollution due to respiratory or other conditions. Air pollution can cause loss of productivity due to illness, as well as damage to buildings and crops, making it a hazard not only to the environment but also to the economy. Traffic congestion, smoke, and pollution from industrial factories and refineries all play a part in air quality.

How do we compare?

The Tucson MSA posted 96.4% of days classified as good or moderate air quality in 2020, with 3.3% ranked unhealthy for sensitive groups, and 0.3% very unhealthy. Of the western MSAs, Phoenix reported the highest rate of very unhealthy days in 2020 at 20.8%. According to a report by the American Lung Association, Phoenix has a high level of Ozone which is brought on by warm temperatures. Very unhealthy days indicate a health alert in which all residents may experience serious health effects.

What are the key trends?

The percentage of air quality days rated “good” for the Tucson MSA has been volatile in recent years, reaching a peak of 67.4% in 2015 then sharply decreasing to a 20 year low of 39.7% in 2017. The percentage of good air quality days showed improvement in 2018 and 2019 but declined to just above the 20 year low in 2020. Tucson moved from a fourth-place rank among the 12 western MSAs in 2019 to sixth place in 2020. Phoenix retained its last-place ranking among the 12 MSAs tracked on the MAP in the percentage of good air quality days in 2020 and also continues to struggle nationally.  

How is it measured?

Air quality data come from the U.S. Environmental Protection Agency’s Air Quality Index Report, which is an annual summary of AQI values for four major air pollutants, though many areas do not have monitoring stations for all pollutants. The AQI has a range of 0-500 broken down into six levels: good (0-50), moderate (51-100), unhealthy for sensitive groups (101-150), unhealthy (151-200), very unhealthy (201-300), and hazardous (301-500).  The AQI for ozone was updated by the EPA in 2016, this update applied to all historical data.