The MPCA is responsible for understanding the condition of Minnesota's air, and there are many ways of looking at and measuring air quality. Each provides us a piece of the puzzle to understand how we are doing and where we need to focus in the future.
National air quality standards
The Clean Air Act requires the U.S. Environmental Protection Agency (EPA) to set National Ambient Air Quality Standards for pollutants that are considered harmful to public health and the environment. The EPA sets standards for six common air pollutants — ozone, fine particles, lead, nitrogen dioxide, carbon monoxide, and sulfur dioxide. The MPCA monitors air pollution across the state and compares the results to these national standards. In 2015, monitoring results in all areas of the state were better than air quality standards.
The national standards are designed to protect human health and the environment. However, studies show that health effects occur even at levels below current standards and disproportionately impact disadvantaged communities.
Minnesota’s air quality compared to National Ambient Air Quality Standards, 2015
Health benchmarks for toxic air pollutants
Air toxics are a group of over 100 air pollutants that cause or may cause cancer or other serious health effects. Nationally, there are no enforceable regulatory standards for air toxics in the environment. Minnesota relies on guidelines called health benchmarks to evaluate the health risks from exposures to toxic pollutants in the air.
Locations with air toxics concentrations above a chronic health benchmark, 2015
To protect the health of Minnesotans, we work to ensure that concentrations of all air toxic pollutants in Minnesota are below health benchmarks. We monitor air toxics at nearly 20 locations in the state, with the majority of monitors located in the Twin Cities metro area. Each of these monitors measures over 70 air toxic pollutants. In 2015, the majority of monitoring sites measured air toxics concentrations below acute (short-term exposure) and chronic (lifetime-exposure) health benchmarks. Formaldehyde continues to be found above the chronic health benchmark at monitoring sites in the urban core of Minneapolis and St. Paul.
Bad air days
On most days, air quality across Minnesota is healthy to breathe, but on several days each year pollutants such as ozone and fine particles can reach unhealthy levels. We use the Air Quality Index (AQI) to rank daily air quality. Air quality can be ranked as good, moderate, unhealthy for sensitive groups, or unhealthy for everyone. The MPCA issues an air pollution health alert when daily air quality reaches the unhealthy for sensitive groups or worse rankings.
The statewide trend in AQI days shows improvements in air quality over time. Since 2003, the number of days with good air quality has nearly doubled. In 2005, air quality was considered good in all areas of the state on less than 25 percent of all days that year. In 2015, air quality was good in all areas of the state on more than 50 percent of all days.
Despite consistent improvements in the number of good air quality days, the number of days with poor air quality varies from year to year. In 2015, across Minnesota, there were 12 bad air days. These bad air days were primarily due to elevated fine particle (PM2.5) pollution resulting from wildfire smoke transported in to Minnesota.