SHEBOYGAN, Wis. (AP) -- Another air quality study says Wisconsin counties bordering Lake Michigan still have unhealthy levels of pollution.
The American Lung Association released its State of the Air study using data from 2010 to 2012.
The study gave Sheboygan County the lowest grade in the state. The county had the 25th worst ozone pollution in the country.
Local officials say the data may not accurately reflect air quality in Sheboygan County. The state Department of Natural Resources recently put a new air quality monitor inland from Lake Michigan where the air may be cleaner.
Officials in other eastern Wisconsin counties say the pollution comes from Chicago and other urban areas to the south.
Marathon County and other areas in central and northern Wisconsin had some of the nation's best air quality.