The debate heated up in March, when Carol Browner of the EPA announced plans to phase out the use of MTBE. The additive currently holds about 80 percent of the $4.5 billion market for so-called "reformulated gas," which is supposed to burn cleaner than normal gasoline. The EPA took action because MTBE (an acronym for methyl tertiary butyl ether) leaking from underground storage tanks has contaminated water supplies in 31 states. The problem is most acute in California. In some Southern California cities such as Santa Monica, 90 percent of the water supply is affected.

In April, water-well owners in 16 states filed a class-action lawsuit against some of the nation's biggest oil companies saying that they have long known that MTBE was an environmental menace.

Browner said that MTBE should be at least partly replaced with ethanol -- alcohol distilled from corn, or basically moonshine -- which she portrayed as a safer option to reduce air pollution.

If Browner's proposal is accepted, a phaseout of MTBE could begin as early as next year. If that happens, demand for ethanol, which is far more expensive than MTBE despite lavish government subsidies, will increase from about 1.3 million gallons this year to 3.2 billion gallons in 2004. Andrew Fairbanks, an energy industry analyst at Merrill Lynch, tells Salon that the cost to consumers will be an extra 3 to 5 cents per gallon at the pump.

Lawmakers from the Corn Belt, including powerful Sens. Tom Harkin, D-Iowa, and Tom Daschle, D-S.D., roundly applauded Browner's action. MTBE producers and refiners, including Lyondell Chemical, Valero and Texas Petrochemicals, were far less enthusiastic. So, too, were Republicans in Congress, who say the EPA is trying to help Vice President Al Gore's standing in Midwestern states where ethanol is largely produced. (They don't mention that George W. Bush, like Gore, is a big-time ethanol backer.)

So, what's the smart choice, MTBE or ethanol? Answer: Neither. The weight of scientific evidence shows that neither MTBE nor ethanol benefits air quality, and both inflict serious damage to the environment.

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