The chapter summarizes the scientific literature and data on the sources, concentrations, behavior, and the fate of fuel oxygenates in ground water and surface water. We also discussed the implications for drinking water quality and aquatic life and we identified areas where the data are too limited to make definitive statements about the costs, benefits, and risks of using oxygenated gasoline in place of conventional gasoline. Recommendations for further data-base compilation, monitoring, assessment, research and reporting were made that we believe would reduce uncertainties and allow a more thorough assessment of human exposure, health risks and benefits, and environmental effects. U.S. production in 1995 was estimated to be about 9 million tons. Essentially all of the MTBE that is produced is used for fuel oxygenation.
Ethanol is the second most used oxygenate in gasoline blending.
No data are available to estimate the portion of this production used in gasoline. Releases of gasoline containing oxygenates to the subsurface from, for example, underground storage tanks, pipelines, and refueling facilities provide point sources for entry of oxygenates as well as gasoline hydrocarbons into the hydrologic cycle. Urban and industrial runoff and wastewater discharges also represent potential sources of oxygenates to the environment. In a few instances, such as in Santa Monica, California, high concentrations of MTBE have caused the shutdown of a drinking-water production wells and the source of contamination is believed to be leaking underground gasoline storage tanks. Exhaust emissions from vehicles and evaporation from gasoline stations and vehicles are sources of MTBE and other oxygenates to the atmosphere.