Air pollution has become a major environmental health problem affecting both developed and developing countries throughout the world (Nadakavukaren, 2006). The consequence has been that air pollution is causing human health problems as well as damage to vegetation, crops, wildlife, materials, buildings and even the climate. In the U.S., the largest sources of air pollution, in order of importance, are: 1) transportation, mainly automobiles and trucks. 2) electric power plants that bum coal or oil. and 3) industry, for which the major sources include steel mills, metal smelters, oil refineries, and paper mills (Nadakavukaren, 2006). The most common air pollution problem resulting from these emission sources is ground-level ozone (O3), According to the United States Environmental Protection Agency (EPA), non-attainment of EPA requirements for O3 is the most common air pollution problem facing large cities in the U.S (Crpc-La.org, 2011). It is estimated that 160 million people in the U.S. lived in areas that are in non-attainment of healthful O3 levels (Organization for Economic Co-operation and Development [OECD], 2005).
In the past, efforts to reduce air pollution have consisted primarily of "command and control" programs that involve enforcement of government regulations designed to reduce toxic emissions. Such programs have proven highly effective in reducing industrial, point source pollution and causing auto manufacturers to produce cleaner-burning automobiles (Environmental Protection Agency [EPA], 2011a). While these government controls continue to effectively lower industrial emissions and reduce pollutants emitted from vehicles, O3 precursor, NOx, continues to be emitted into the air at increasing levels. Problems underlying ever-increasing auto emissions of NOx and subsequent development of ground-level ozone air pollution are complex and multifaceted, requiring solutions that are more complex and wider in scope than traditional command and control methods.