How are we doing?

Percentage of Good Air Quality Days (2017)

In 2017, Tucson’s air quality was rated “good” 39.7% of the time. This ranked the Tucson Metropolitan Statistical Area (MSA) eighth out of 12 western MSAs in the percent of good air quality days. Portland ranked first with 73.2%, while Phoenix ranked last with only 8.8% 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 2017 was the lowest rate reported by the AQI in the past 18 years.

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 had 98.1% of its days classified as good or moderate air quality in 2017, with 1.9% ranked unhealthy for sensitive groups, and 0% very unhealthy. Only two metropolitan areas, Phoenix and Portland, reported very unhealthy days in 2017. Very unhealthy days indicate a health alert in which all residents may experience serious health effects. Phoenix had the largest percentage of unhealthy days at 0.5%.

What are the key trends?

The percent of air quality days rated “good” for the Tucson MSA has declined substantially over the past three years, decreasing by 27.2 percentage points. Tucson moved from a third place rank among the 12 western MSAs in 2015 to eighth place in 2017. Tucson’s rate of 39.7% in 2017 is the lowest reported rate in the past 18 years. Phoenix retained its last place ranking in the percentage of “good” air quality days in 2017, but has made steady improvements since 2006.

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.