ABSTRACT
The 1990 Amendments to the federal Clean Air Act (1990 CAA) mandated the addition of oxygenates to gasoline in regions that failed to meet federal air quality standards. MTBE and ethanol are currently the two gasoline oxygenates most commonly used in the U.S. to reduce carbon monoxide (CO) and ozone (O3) motor vehicle emissions, though MTBE is by far the more commonly used additive. U.S. production of MTBE in 1995 totaled 8.0 billion kilograms, roughly double that of ethanol in the previous year.1 Because MTBE not only reduces CO emissions by approximately 10%, but also serves as an octane enhancer in gasoline, the additive seemed to provide an answer to the oil industry’s drive toward better fuel efficiency and environmentalists’ concerns about increasingly disastrous air quality standards in major urban areas. The fact that MTBE is manufactured from chemicals that were previously refinery byproducts made it even more attractive to the petrochemical industry.
