Sulfur dioxide(SO2) is a colorless gas that is formed by combusting sulfurous compounds in fossil fuels, particularly coal. When SO2 is released, it can combine with moisture in the atmosphere to form sulfuric acid, one of the strongest acids found in nature. This acid then falls from the sky as acid rain and can lead to detrimental effects on plants, animals, and minerals. Sulfuric acid can also cause secondary damage by leaching toxic metals from the soil into the groundwater.

The National Ambient Air Quality Standard (NAAQS) for SO2 is a 24 hour average of 140 ppb (parts per billion), not to be exceeded more than once per year, and also an annual arithmetic mean of 30 ppb. This pollutant is monitored through a continuous method using electronic monitors since 1985 where before it was measured through chemical methods. ARAQMD has two sites for monitoring SO2 located in Downtown Akron and at East High School in Akron.

More in depth information about sulfur dioxide is available through the EPA including emission sources, causes of concern, health & environmental impacts, EPA efforts to reduce SO2, and other resources.