TEXT BOX 5-1 Toxicological Considerations of Oxygenates in Fuels

Although this report focuses on the effects of motor-vehicle fuel composition on formation of tropospheric ozone, earlier reports dealt in considerable detail with the toxicological and health effects related to fuel composition. Two reports that focused specifically on the effects of oxygenates in fuels are Toxicological and Performance Aspects of Oxygenated Motor Fuels (NRC 1996) and Interagency Assessment of Oxygenated Fuels (NSTC 1997).

The NRC report reviewed a draft of the interagency assessment, and recommended a number of refinements and improvements in the assessment of potential human health risks associated with prolonged exposure to gasoline containing MBTE and in the assessment of the comparative risks associated with oxygenated and nonoxygenated fuels. The NRC report concluded that "until these recommendations are acted upon, no definitive statement can be made regarding these health-risk issues. Based on the available analysis, however, it does not appear that MTBE exposure resulting from the use of oxygenated fuels is likely to pose a substantial human health risk. It appears that MTBE-containing fuels do not pose health risks substantially different from those associated with nonoxygenated fuels, but this conclusion is less well established and should become the centerpiece for the government's comprehensive assessment."

The interagency assessment report concluded that "it is not likely that the health effects associated with ingestion of moderate to large quantities of ethanol would occur from inhalation of ethanol at ambient levels to which most people may be exposed from use of ethanol as a fuel oxygenate. Potential health effects from exposure to other oxygenates are not known and require investigation if their use in fuels is to become wide-spread."

In a related issue, in 1998, U.S. Senator Dianne Feinstein (California) requested an investigation possible contamination of the nation's ground-water by MTBE and sought help from EPA in dealing with potentially serious MTBE issues confronting California, namely, water contamination in the state. Moreover, Senator Barbara Boxer had requested that EPA phase out MTBE because of mounting evidence of MBTE contamination of California's drinking water. EPA announced in November 1998 that it will undertake a pilot site-remediation demonstration project in California. On March 25, 1999, California Governor Gray Davis issued Executive Order D-5-99, which requires the phase out of MTBE from California gasoline by no later than December 31, 2002.

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