Pollutants are expected to be in the "unhealthy for sensitive groups" range.
The action day is in effect for Ottawa, Allegan, Kent and Muskegon counties.
People and businesses are urged to avoid activities today that lead to ozone formation. These activities include refueling vehicles or topping off gas tanks, using gas-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 also recommended that active children and adults, and people with respiratory diseases such as asthma, limit prolonged outdoor exertion today.
For more information, visit www.deqmiair.org.