How much pollution comes from vehicles?
Unlike other pollutants, ozone is not emitted directly into the air. Rather, it is formed in the presence of sunlight through chemical reactions between nitrogen oxides (NOX) and volatile organic compounds (VOCs). In southeastern Wisconsin, vehicles emit about one-third of these ozone-forming pollutants – which the rest emitted by industry and other smaller sources, such as lawn and garden equipment, paints, motorboats, and some businesses.
