How are we doing?

Percentage of Good Air Quality Days (2016)

In 2016, Tucson’s air quality was rated “good” 54.9% of the time. This tied Tucson MSA with Salt Lake City for fifth out of the 12 MSAs in the percentage of good air quality days. Portland ranked first with 82.0%. Phoenix was last among the 12 western metropolitan areas, with only 7.1% of days in 2016 considered “good”. Good air quality days, according to the Air Quality Index (AQI), are 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.

Why is it important?  

Air quality is vitally important. 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, dust, smoke, and pollution from industrial factories and refineries all play a part in air quality.

How do we compare?

Tucson MSA had 98.9% of its days classified as good or moderate air quality in 2016, with 1.1% ranked unhealthy for sensitive groups, and 0% very unhealthy. Only two metropolitan areas, Phoenix and Las Vegas, had any very unhealthy days in 2016. Very unhealthy days indicate a health alert in which all residents may experience serious health effects. Phoenix had the largest percentage of unhealthy days, 19.7%, of all 12 western metropolitan areas.

What are the key trends?

Tucson moved from a third place rank in the percent of good air quality days in 2015 to fifth place in 2016. Portland, the top ranked MSA, posted the largest percentage point change, increasing their number of good air quality days by 13.8 percentage points, while Tucson had the greatest decrease at 12.5 percentage points.

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 were updated by the EPA in 2016, this update applied to all historical data.