What is MTBE?

Methyl tertiary-butyl ether (MTBE) is a chemical compound added to gasoline to make it burn cleaner and more efficiently. It is one of a group of chemicals known as “oxygenates” because they raise the oxygen content of gasoline.

Following  MTBE’s approval as a gasoline component by the United States Environmental Protection Agency (EPA) in 1979, refiners began adding MTBE to gasoline to replace tetraethyl lead (TEL), which the EPA required to be phased out because it had been identified as a source of air pollution. TEL supplied much of the octane in gasoline, so a new source of octane was needed to help prevent engine knocking.

In 1990, Congress enacted amendments to the Clean Air Act that required refiners to add oxygenates to gasoline in order to combat air pollution. Adding oxygen to gasoline promotes more complete combustion of the gasoline, and cuts down on air pollution. At the time, Congress and the EPA knew that MTBE would be the primary oxygenate used given supply, transportation and other difficulties with using alternatives such as ethanol. MTBE helped reduce air pollution significantly.

Federal and state regulators have acknowledged the air quality benefits of adding MTBE and other oxygenates to gasoline. EPA has said that since the reformulated gasoline (RFG) program began in 1995, it has resulted in combined annual reductions of 105,000 tons of smog-producing emissions and at least 24,000 tons of toxic air pollutants like benzene. This is equivalent to taking 16 million cars off the road, according to the EPA. The EPA has also said that "75 million people are breathing cleaner air because of RFG."
Read more: http://epw.senate.gov/108th/Holmstead_032003.htm

The use of MTBE involves trade offs. In addition to its air cleaning benefits, MTBE can make water smell and taste bad at certain concentrations if it is spilled or handled improperly and allowed to leach into groundwater that is used for drinking water.

Related Links:

Federal Government's Knowledge of MTBE's Risks to Groundwater When the Government Required Its Use