The U.S. Environmental Protection Agency says Michigan and 19 other states have complied with a 2008 rule to reduce their pollution that was drifting into other states. But air quality experts say there's much more to be done.
Ozone is a harmful gas created when sunshine, heat and pollutants like nitrogen oxides and volatile organic compounds interact. Those pollutants, which come from power plants, manufacturing, and vehicles, can drift from one state to another.
Janice Nolen is with the American Lung Association.