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Wisconsin's Air Quality Trends

There is a statewide network of 30 ozone monitoring sites and 18 fine particle (PM2.5) monitoring sites to measure ambient air quality in Wisconsin. In addition, the DNR monitoring network measures sulfur dioxide, nitrogen dioxide, carbon monoxide and inhalable particles (PM10). The DNR monitoring network is operated under a federally approved network plan, submitted and reviewed annually to ensure appropriate monitoring in all locations required by federal regulations.

Under the Clean Air Act (CAA), the U.S. EPA sets National Ambient Air Quality Standards for pollutants. Data from Wisconsin’s monitoring network is validated and reported to the EPA to demonstrate how well air pollution controls and programs are working to improve air quality and meet the federal standards. In addition, using continuous monitoring data, the DNR quickly informs the public when air pollution reaches unhealthy levels.

2024 Wisconsin Air Quality Trends Report

As part of its effort to communicate air quality improvements over time, the DNR released the interactive 2024 Wisconsin Air Quality Trends StoryMap. For more detailed information on Wisconsin’s historic air quality trends over the past 20 years please refer to the 2024 Wisconsin Air Quality Trends Report - data through 2023 (AM-643).

The trends shows that while most pollutants regulated under the Clean Air Act have been decreasing across the state since monitoring began, the state faces tough challenges in continued reductions. In recent years, the report shows that ozone and PM2.5 concentrations have plateaued or recorded increases in concentrations.

To view charts that show the air quality trends in each county, see the 2024 Wisconsin Air Quality Trends by County (AM-644).

We continue to work toward attainment in all counties and ensure compliance with all federal air requirements.

Previous Reports