Produced by burning coal, most notably in power plants. Major contributor to smog and acid rain. Synthesized and concentrated. Many released from burning fuel, such as gasoline, wood, coal, natural gas and from solvents, paints, glues, and other products. Better Cars, More Driving v Emissions from vehicles have been reduced by a factor of 8 times since the late 1960s through legislative effort.
Emission controls are part of it, improved gas mileage is another.
Annual vehicle miles traveled have increased by 50 percent since 1970, while population has increased only 15 percent. In other words, much of the gains in fuel efficiency have been offset by increased use of vehicles over that time. In addition, recent shifts towards light trucks and SUVs have resulted in a net decline in fuel efficiency in the last decade. Between 1994 and 1997, SO 2 emissions were reduced by 30 percent. Some inspections but insufficient to completely monitor.