Clearing the Air? The Effects of Gasoline Content Regulation on Air Quality

2687 Since the passage of the original Clean Air Act in 1963, US state and federal governments have implemented numerous policies designed to reduce human exposure to ground-level ozone pollution. Ozone is an odorless, colorless gas that has been linked to asthma, increased susceptibility to pneumonia and bronchitis, and damage to crops and natural vegetation. Michelle L. Bell et al. (2004) have estimated that even marginal short-term changes in ozone concentrations can have substantial human mortality impacts. While ozone is not emitted directly by any source, the two classes of chemicals that react in the atmosphere to produce ozone—volatile organic compounds (VOCs) and oxides of nitrogen (NOx)—are pollutants produced in part through human activity. Despite more than 40 years of emissions regulation, however, many areas of the US continue to experience ambient air concentrations of ozone that exceed standards set by the Environmental Protection Agency (EPA).