The Michigan Department of Natural Resources and Environment has declared Sunday as an Action Day for elevated levels of ozone in Ottawa, Allegan, Kent, Lake, Mason, Muskegon, Newaygo, Oceana and Van Buren counties.
Pollutants are expected to be in the "unhealthy for sensitive groups' range.
People and businesses are urged to avoid activities which lead to ozone formation. These activities include refueling vehicles or topping off gas tanks, using gasoline-powered lawn equipment, and using charcoal lighter fluid.