On October 13, 2016, the Michigan Department of Environmental Quality (MDEQ) submitted recommendations to the United States Environmental Protection Agency (USEPA) for area designations for the October 2015 ozone 8-hour National Ambient Air Quality Standard (NAAQS). Based on certified monitoring data from 2013-2015 MDEQ has recommended that Allegan, Berrien, Muskegon, Livingston, Macomb, Monroe, Oakland, St. Clair, Washtenaw, and Wayne Counties be designated nonattainment. In Southeast Michigan, only monitors in Macomb and St. Clair Counties have design values exceeding the 70 ppb standard, but based on population, emission, and meteorological data, the remaining counties in the Detroit Metropolitan area were determined to be contributing to the violating monitors. The counties outside the Detroit Metropolitan Area are all designated as single-county nonattainment areas.
USEPA will make the final designations based on 2014-2016 data; however, MDEQ does not anticipate USEPA to make changes to the preliminary designations for these ten (10) counties. Additionally, Schoolcraft County is also tentatively recommended to be designated nonattainment due to a monitored violation using preliminary 2016 data. The "tentative" nonattainment status will become final upon certification of the 2016 monitoring data. All remaining monitors in the state are meeting the NAAQS; therefore, MDEQ has recommended the remainder of the state be designated attainment or unclassifiable.
A final designation will be made by October 1, 2017. Additional details can be found on MDEQ's website.