Ethanol, also known as "ethanol" or "grade alcohol," is a flammable, colorless compound that is one of the most common alcohols in alcoholic beverages. It is often referred to as alcohol for short. Its molecular formula is C2H6O, variously expressed as EtOH or C2H5OH. Bioethanol and ethanol are chemically identical, and the properties of bioethanol and ethanol do not differ much in parameters. The properties of bioethanol are shown in Table 5.1 and compared with those of gasoline. Ethanol was found to have a higher octane rating than conventional gasoline. Ethanol is also increasingly used as an oxygen-containing additive in standard gasoline to replace methyl tert-butyl ether (MTBE) to enhance its octane number. Because MTBE is toxic and causes significant groundwater and soil pollution, MTBE is increasingly replaced by ethyl tert-butyl ether produced from bioethanol. Because ethanol has a lower energy yield than gasoline, it is recommended to use bioethanol to produce biodiesel rather than replace conventional gasoline.
No EPA toxicity values were established for cancer (cancer slope factor) or non-cancer (RfD or RfC) health endpoints of ethanol. There are no safe drinking water standards for ethanol. The lack of ethanol toxicity values for various exposure pathways and the lack of exposure information in various exposure media due to ethanol cycling in the environment makes it impossible to quantitatively estimate the public health risks of exposure to ethanol under different exposure conditions related to its widespread use in gasoline. This analysis should include not only ethanol, but also all environmental degradation products of ethanol, and an analysis of the health risks and benefits of multimedia exposure is essential to not repeat the history of MTBE events.
In the United States, production of ethanol-fueled vehicles is increasing, thanks to support from corn-growing states and the U.S. Department of Energy and Agriculture. Automakers began producing cars and pickup trucks that can run on ethanol or gasoline in 1997.
