The number of days in Minnesota with Air Quality Alerts is an indicator of the quality and cleanliness of the air in Minnesota. While on the majority of days the air is healthy to breathe, there may be a few days each year when air quality becomes unhealthy. Fewer of these air quality alert days is better. Many factors contribute to poor air quality, including local air pollution emissions, weather, wildfires, and emissions from sources outside of Minnesota's boundaries. Some of these are factors that simply cannot be controlled by efforts in Minnesota.
The Air Quality Index reflects air pollutants of the greatest concern in Minnesota: ozone, which causes respiratory problems, and fine particles, which cause respiratory and cardiovascular problems. When this index reaches a certain threshold, an air quality alert day is called. Air quality alert days may be called in one or more of the nine regions distributed across the state.
In 2015 there were nine air quality alert days, which is a good result by historic standards but represents an increase of the three air quality alert days in 2014. Weather conditions can greatly affect the number of air quality alert days from year to year and the Minnesota Pollution Control Agency staff attributes the fluctuations between 2014 and 2015 to such factors.
This document (.xlsx) provides the indicator data in table format.