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Contact: Craig Czarnecki, DNR Air Management Outreach Coordinator or 608-250-0945  

DNR Releases 2023 Air Quality Trends Report

clear blue sky against a vibrant orange tree Wisconsin has implemented many programs that have reduced emissions of ozone-causing pollutants, but there is still more to be done. Photo credit: Wisconsin DNR

MADISON, Wis. – The Wisconsin Department of Natural Resources (DNR) today announced the release of its 2023 Air Quality Trends Report.

The annual report includes state monitoring data through 2022 for air pollutants regulated under the federal Clean Air Act, including ground-level ozone, particle pollution, sulfur dioxide, nitrogen dioxide and carbon monoxide. While concentrations of these pollutants have decreased over the last two decades, in recent years the report shows two of the most harmful pollutants – ozone and fine particulates – have decreased only modestly in recent years.

The 2023 report shows that since the early 2000s, statewide ozone concentrations have decreased 21%. With these reductions, the entire state is meeting the federal 2008 ozone standard. However, with only modest improvements, and even slight concentration increases along the Lake Michigan shoreline in recent years, the Milwaukee area and parts of Sheboygan and Kenosha counties are not meeting the more stringent 2015 ozone standard.

“Wisconsin has implemented many programs that have reduced emissions of ozone-causing pollutants from power plants, industry and transportation in the state,” said Gail Good, DNR Air Management Program Director. “However, these emission reductions have not resulted in attainment because most sources of ozone-causing emissions are outside of the state’s control.”

As part of a massive air quality research campaign, the DNR partnered with the National Oceanic and Atmospheric Administration (NOAA), National Aeronautics and Space Administration (NASA), the Environmental Protection Agency (EPA) and several universities to better understand ozone formation chemistry and emission sources driving ozone formation.

“The Wisconsin Air Management program is thrilled to be just one part of this unprecedented national air quality study to better understand the public health threat pollutants like ozone create,” said Katie Praedel, DNR’s Air Monitoring Section Chief. “These efforts will help states in the Lake Michigan region identify emission control strategies that will lead to air quality improvements and cleaner air for Wisconsin residents to breathe.”

To better illustrate the latest trends, the DNR updated the interactive StoryMap which shows Wisconsin's air quality trends for each pollutant over the last 20 years. This tool, first launched with last year’s trends report, provides a more user-friendly visual way to convey complex air quality data.

The 2023 trends report also includes updated national emissions inventory data through 2020. The data show that emissions of most directly emitted pollutants or their precursors have decreased substantially since 2002. Highlights from this data include:

  • A 72% decrease in reported emissions of nitrogen oxides (NOx) and a 28% decrease in volatile organic compounds (VOCs) – key ingredients that form ground-level ozone.
  • Emissions of sulfur dioxide (SO2) decreased by 93%, with the largest reductions coming from the electric utility fuel combustion sector.
  • Emissions of carbon monoxide (CO) decreased by 58%, with most of the reductions coming from highway vehicles and the off-highway sector.

The 2023 Air Quality Trends Report, StoryMap, and other historical reports are available on the DNR’s Air Quality webpage. Current Wisconsin air quality conditions can be found on the Wisconsin Air Quality Monitoring Data webpage.