Air Quality Index: facts & figures

The AQI reports daily air quality

In Minnesota, the Air Quality Index (AQI) is based on measurements of four pollutants: fine particles (PM2.5), ozone, sulfur dioxide, and carbon monoxide. Each hour, the Minnesota Pollution Control Agency (MPCA) converts measurements to an AQI value based on health standards established by the US Environmental Protection Agency.

In 2015, the MPCA reported the AQI in 10 regions across the state: Brainerd, Detroit Lakes, Duluth, Ely, Grand Portage, Marshall, Rochester, St Cloud, the Twin Cities, and Virginia. See current air quality conditions in Minnesota

Air alerts are issued as health warnings

Since air quality affects health, the AQI can help people prevent the health effects of exposures to air pollution. On days with "moderate" air quality (yellow), air pollution levels are elevated and may cause health effects for people who are vulnerable to air pollution.

The MPCA issues an air quality alert on days when the AQI is above 100 ("unhealthy for sensitive groups"). On these days, air pollution levels may cause adverse health effects for people with cardiovascular disease, lung disease, older adults, children, and even healthy people doing vigorous activity. 


Air Quality Index by region in Minnesota

Number and type of air alert days by region, 2015.
Color AQI Category AQI
Good 0-50
Moderate 51-100
Unhealthy for sensitive groups 101-150
Unhealthy 151-200

Data not available for all days at each monitor, because monitors may go down or record invalid data. Source: Minnesota Pollution Control Agency.

In 2015, the number of air quality alerts issued was low. Across all areas of the state, most days were rated "good" for air quality. Ely experienced the highest number of good air quality days (343). The Twin Cities had the lowest number of good days (211).

Because most air quality alerts in Minnesota are driven by weather, year to year changes in the weather can impact the number of air quality alerts each year.


Air alert days are declining over time

Number of air alert days by region, 2005-2015
The health standards used to calculate the AQI and air alert days have changed over time. AQI results from past years have been adjusted to reflect what would have been air alert days using the current air quality standards. Source: MPCA.

In Minnesota, the number of air alert days each year has generally been declining over time. The slight increase noted for 2015 was primarily due to increased wildfire activity. The primary pollutants causing air alerts are fine particles and ground-level ozone.

On most days, air quality across Minnesota is healthy to breathe, but on some days each year the air can reach unhealthy levels. The amount of pollution in the air varies by how much pollution is emitted within an area, how much pollution is blown in from other areas, and the weather. Because most air quality alerts in Minnesota are driven by weather, year to year changes in the weather can impact the number of air quality alerts each year.

More information about the AQI

For additional ways to keep track of air quality:

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