State regulators largely blamed Holland's readings on pollution carried over Lake Michigan from upwind states.
Ozone levels across most of Michigan stayed at or below federal air quality standards during the 2026 ozone season, the Michigan Department of Environment, Great Lakes, and Energy (EGLE) said. That held true even when wildfire smoke affected air quality. EGLE based the results on data from the state's air monitoring network. It released them Nov. 6, when it announced the official close of the season.
Holland remained the exception. It recorded the highest ozone concentrations in the state this season, EGLE said. The agency said this was largely due to pollution from states upwind that crosses Lake Michigan. Every other monitoring site in Michigan met the federal ozone standard, including those in the Detroit area, EGLE reported.
Those results fit a long-term trend of cleaner air in southeast Michigan, the agency said. EGLE credited decades of lower emissions from cleaner fuels and vehicles. It also pointed to up-to-date pollution controls and other investments in the environment.
Michigan's ozone season runs from March through October. Those are the months when weather con...