It is a second day in a row for ozone action days in Ottawa, Muskegon, Allegan, Kent, Mason and Oceana counties. An alert was also in effect Tuesday.
The state agency said pollutants are expected to be in the "unhealthy for sensitive groups" range, with elevated levels of ozone.
People and businesses are urged to avoid activities that lead to ozone formation. These activities include refueling vehicles or topping off gas tanks, and using gasoline-powered lawn equipment and charcoal lighter fluid.
Positive activities include car pooling, biking to work, delaying or combining errands, and using water-based paints.
It is recommended that active children and adults, and persons with respiratory diseases such as asthma, limit prolonged outdoor exertion.
For further information, visit deqmiair.org.