MTBE Gasoline Additive
Threatens US Ground Water

WASHINGTON (Reuters) - A widely used additive to make cleaner-burning gasoline, but which may cause cancer in humans, may be leaking into as many as 9,000 community water wells in 31 states from underground storage tanks, a study released on Monday found.
The chemical known as MTBE -- which stands for methyl tertiary butyl ether -- was first added to gasoline to enhance octane and later in much larger amounts to cut air pollution.
But the foul-tasting and smelling oxygenate has been found in ground water all over the United States, researchers wrote in the March 23 Web edition of the journal Environmental Science & Technology.
The study will likely underscore efforts already under way by the Clinton administration to end the use of the oxygenate, which is added to 85 percent of the cleaner-burning gasoline required in U.S. areas with the worst air pollution problems.
``Very large amounts of MTBE have been used in gasoline during the past 20 years and perhaps 250,000 leaking underground storage tank releases have contained MTBE,'' said John Zogorski, a scientist at the U.S. Geological Survey and one of the study's authors.
On Monday, the Clinton administration said it would try to ease concerns about contaminated water by seeking legislation to require that at least 1.2 percent of gasoline supplies come from renewable fuels, such as ethanol made from corn.
Environmental Protection Agency administrator Carol Browner also said she would ask Congress for more authority to phase out or reduce MTBE. Phasing out MTBE will have only a ``minimal effect'' on U.S. gasoline prices if done properly, she said.
Zogorski said many leaking underground storage tanks are ''likely to have caused significant ground water contamination'' and called for speedy and detailed assessments of the community wells since MTBE also tended to migrate long distances.
An estimated 90 million people in the United States obtain a portion of their drinking water from community water wells.
The 9,000 wells identified in the study represent one-third of the wells in states where data was suitable for analysis. In their study, the scientists combined data about the locations of leaking underground storage tanks and drinking water wells with information about the behavior of MTBE.
Zogorski said past MTBE releases would continue to threaten wells until 2010 because MTBE degrades slowly in ground water.
Several states already plan to halt or reduce MTBE use.
California, the only state permitted by the Clean Air Act to make its own regulatory decisions about MTBE, plans to ban the oxygenate in 2003. Maine has EPA approval to quit using MTBE if it can find other ways to meet air quality goals, while New Jersey can stop using extra MTBE during winter months.
About 21 billion gallons of MTBE were produced for use in gasoline in the United States between 1970 and 1998.
The report will also appear in the May 1 print edition of the journal Environmental Science & Technology, which is published by the American Chemical Society, the world's largest scientific society.


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