- ST. LOUIS-- Once considered an environmental hero, gasoline additive MTBE
now looks tarnished. Researchers don't agree how useful the gasoline additive
really is. Worse, it's starting to show up in drinking wells and public
lakes.
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- The controversy serves as a cautionary
tale about the dangers of mandating technologies without fully understanding
their long-term impact.
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- "Politically, once you put (the
additive) in, there's inertia for people to change," says Phillip
Myers, emeritus research professor at the University of Wisconsin, Madison.
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- Since the Clean Air Act of 1990, some
17 states and Washington, D.C., have turned to methyl tertiary butyl ether
(MTBE) to help them stay within clean-air standards. When blended with
gasoline, it adds oxygen to the fuel. About a third of the gasoline in
the United States is reformulated with some kind of oxygenate. MTBE accounts
for three-quarters of the total, edging out competing substances, such
as ethanol.
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- The problem is that using oxygenates
may not help cut auto emissions anymore, several researchers say. That's
because American cars run a lot cleaner than they used to. More than a
decade ago, cars used carburetors to mix air and fuel. As the cars aged,
they tended to mix more fuel and less oxygen, so the extra oxygen from
MTBE-blended fuels helped reduce emissions.
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- But today's models use catalytic converters,
which automatically adjust the fuel-air mixture. So an MTBE-blend simply
forces the system to squirt in more fuel. As older cars head for the junkyard,
the fuel's overall impact lessens.
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- Worse, all consumers are paying to correct
a problem mostly caused by a small minority of people who drive out-of-tune
clunkers, says Douglas Lawson, an air-pollution researcher at Colorado
State University. "You get hit by a double-whammy. Not only do you
get hit with decreased fuel economy, you pay more at the pump."
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- "Typically, an oxygenated fuel costs
2 to 3 cents a gallon more even though it reduces a car's fuel economy
by 2 to 3 percent.
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- But MTBE has plenty of backers who dispute
the notion that it's outdated. "The automobile is certainly making
enormous strides," says a spokesman for the Oxygenated Fuels Association,
which backs MTBE. But "if you're going to have air quality in this
country, you're going to have the car, the gasoline, and the driver working
as a triumvirate."
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- "The air-quality benefit far outweighs
the reduction in fuel economy," adds Lori Stewart, group manager for
fuels implementation at the U.S. Environmental Protection Agency. While
the direct impact may be small, the substance allows refiners to avoid
using other, more toxic substances such as benzene.
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- The latest challenge to MTBE comes from
an unexpected source: ground water. Underground storage tanks are leaking
gasoline all over the country. California alone has some 32,400 tanks known
to be discharging fuel into the soil. While most of the toxins in the fuel
appear to dissipate over time, MTBE presents a special problem. It moves
faster and biodegrades more slowly. Thus the additive is showing up in
alarming concentrations in shallow ground water. Already, Santa Monica,
Calif., has had to close three public drinking wells, which supplied nearly
half the community's water, because of MTBE contamination. Even if low
levels of the additive pose no health threat, it can make water taste something
like turpentine.
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- MTBE supporters point out that the problem
is leaking gasoline, not just MTBE. "People should be upset if anything
is leaking from those underground storage tanks," says Martha Casey,
an EPA spokeswoman. The agency has set Dec. 22 as the deadline for replacing
leaking storage tanks in the country.
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