The researchers analyzed regular unleaded gasoline samples from more than 200 sites in Indiana, Illinois and Michigan. They found MTBE (methyl tertiary butyl ether) in more than 70 percent of the gasoline samples, even though the additive has seen limited use because ethanol is the main oxygenate for reducing air pollution in these states, says Reynaldo D. Barreto, Ph.D., an associate professor at Purdue University North Central in Westville, Ind., and the studys lead investigator.
"MTBE is not supposed to be there," he says. The unexpectedly widespread presence of the chemical in gasoline samples suggests there is a "ticking time bomb" that could adversely affect drinking water, Barreto cautions.
MTBE has been used in increasing amounts since 1995, when amendments to the Clean Air Act mandated the use of reformulated gasoline in heavily polluted areas. By law, reformulated gasoline must contain oxygenates designed to reduce smog-causing emissions. The two most widely used oxygenates are MTBE, which is derived from natural gas, and ethanol, which is generally made from corn.
In Indiana, for which the most complete data are available, MTBE-contaminated gas samples were found in the northwestern part of the state where ethanol is used as the main oxygenate. Contaminated samples were also found in the central and eastern part of the state where reformulated gasoline is not used, according to the researcher.
Although data from Illinois and Michigan are not yet complete, gasoline samples surveyed in these areas so far indicate widespread MTBE contamination, according to Barreto. This was unexpected, given that ethanol is the predominant reformulating