The amount and density of pollutants in the air are converted into an Air Quality Index, or AQI. The Wisconsin Department of Natural Resources’ statewide monitoring network is operated following a federally approved plan. The DNR statewide network includes 30 ozone and 18 fine particle, or PM2.5, monitoring sites. PM2.5 describes particles with diameters that are generally 2.5 micrometers or smaller and thus inhalable.
Under the Clean Air Act, the Environment Protection Agency sets National Ambient Air Quality Standards for pollutants.
The DNR monitoring network is operated under a federally approved network plan, reviewed annually to ensure appropriate monitoring in all locations as required by federal regulations.
Continuous monitoring enables the determination of trends in air quality, which demonstrates how well air pollution controls and programs are working to improve our air quality. The monitoring also enables the DNR to rapidly inform the public when air pollution reaches unhealthy levels.
The data indicate that the concentrations of most pollutants regulated under the Clean Air Act have been decreasing across the state since the early 2000s, an indication that air quality is improving. However, in the most recent years, their report shows that ozone and PM2.5 concentrations have leveled off or recorded increases in concentrations.
The Endangerment Finding, established by the EPA in 2009, authorizes regulation of emissions from various sources, including vehicles and power plants. Without the Endangerment Finding, the U.S. would have fewer tools to curb emissions linked to greenhouse gases and poor air quality.
Recently, under the Trump administration, the EPA rescinded the Endangerment Finding, which could reduce regulatory oversight and worsen air quality. It will be important to continue collecting data on air quality to determine future impacts of this regulatory change.
Steve Ackerman and Jonathan Martin, professors in the UW-Madison department of atmospheric and oceanic sciences, are guests on WHA radio (970 AM) at noon the last Monday of each month. Send them your questions at stevea@ssec.wisc.edu or jemarti1@wisc.edu.
