Air Quality

On October 1, 2015, the U.S. Environmental Protection Agency (USEPA) finalized the 2015 eight-hour ozone national ambient air quality standard (NAAQS) of 70 parts per billion. Based on recently certified 2016 data, several air quality monitors in the Southeastern Wisconsin Region violate the new 2015 ozone standard.

During the 1st quarter of 2017, the Wisconsin Department of Natural Resources (WDNR) convened a subgroup of the State Air Management Study Group (AMSG) to explore potential recommendations related to nonattainment area boundaries for this standard. The Commission staff served on both the AMSG and this subgroup. This group reviewed the scientific analysis compiled and included by WDNR in its April 20, 2017, submittal of a technical support document in support of Governor Walker’s recommendation. This technical document identified several key conclusions based on observed data:

  • Elevated ozone levels are confined to an extremely narrow band that follows Wisconsin’s shoreline, with air quality improving dramatically just a few miles inland;
  • Ozone concentrations measuring above the level of the 2015 ozone NAAQS at the state’s lakeshore monitors occur almost exclusively when the wind is coming from over the lake, not from over Wisconsin;
  • Ozone concentrations at Wisconsin’s lakeshore monitors are primarily due to emissions originating from outside the State;
  • Additional emissions reductions from the areas around Wisconsin’s shoreline monitors, including the State’s most populous areas, would not meaningfully change the design values at those monitors. In fact, in some cases such reductions would actually increase ozone concentrations.

On November 6, 2017, USEPA designated a majority of the country as being in attainment/unclassifiable for the 2015 Ozone NAAQS, consistent with State and Tribal recommendations, but temporarily left other areas of the country undesignated. Within Wisconsin, the undesignated areas included the following 16 counties: Kenosha, Racine, Milwaukee, Washington, Ozaukee, Waukesha, Sheboygan, Manitowoc, Kewaunee, Door, Brown, Calumet, Dodge, Fond du lac, Jefferson, and Walworth. Subsequently, on December 20, 2017 USEPA sent Governor Walker a letter including Washington county as being in nonattainment of the 2015 Ozone NAAQS.

Wisconsin now has until February 28, 2018, to submit any additional information for USEPA to consider. The Commission will be working with WDNR to provide  information in regard to the State’s reaction and next steps regarding USEPA’s proposed nonattainment area designations. The State’s recommendations and USEPA’s response can be found by following the link:

For more specific information about what ozone standards are, and how they are developed and reviewed, please visit the following website:

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