How much air pollution comes from motor vehicles?

Motor vehicles account for over 1/5 of atmospheric pollution worldwide. Cars and trucks contribute over 1/3 of the nitrogen oxides and carbon monoxide in the air. By some accounts, cars account for 3/4 of carbon monoxide pollution in the United States.

Cars do not just contribute to air pollution in normal operation; they also contribute when they are

created or destroyed as well as when they are refueled. Particles released from cars can become smog. Cars release other harmful pollutants such as hydrocarbons, sulfur and nitrogen oxides, carbon monoxide and toxins. They also produce greenhouse gases, worsening the effects of global warming.