MTBE
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MTBE (methyl tertiary-butyl ether) is a chemical compound that is manufactured by the chemical reaction of methanol and isobutylene. MTBE is produced in very large quantities (more than 200,000 barrels per day in the United States in 1999) and is almost exclusively used as a fuel component in motor gasoline. It is one of a group of chemicals commonly known as oxygenates because they raise the oxygen content of gasoline. At room temperature, MTBE is a volatile, flammable and colorless liquid that is relatively soluble in water. MTBE has an offensive taste and odor.
MTBE has been used in U.S. gasoline at low levels since 1979 to replace tetra-ethyl lead as an octane enhancer and to help prevent engine knocking. Since 1992, MTBE has been used at higher concentrations in some gasoline to fulfill the oxygenate requirements set by Congress in Clean Air Act amendments.
In 1995 high levels of MTBE were unexpectedly discovered in the water wells of Santa Monica, California. Subsequent tests found tens of thousands of contaminated sites across the country.
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Potential health risks
Advocates of MTBE contend that it has no harmful effects on humans, although its manufacturers did not test it for its effects on human health before introducing it as an additive. As of today, researchers have limited data about what the health effects may be if a person swallows (ingests) MTBE. The Environmental Protection Agency (EPA) has concluded that available data are not adequate to estimate potential health risks of MTBE at low exposure levels in drinking water but that the data support the conclusion that MTBE is a potential human carcinogen at high doses.[1] (http://www.epa.gov/mtbe/faq.htm#concerns)
MTBE often ends up in drinking water, e.g. when oil storage tanks leak near populated areas. However, so far there are no reported cases of a person becoming sick from MTBE in drinking water. Aside from the health risks, MTBE negatively affects the taste and odor of the drinking water even at very low levels.
As an ether, MTBE acts as an emulsifier, increasing the solubility of other, harmful components of gasoline. It thus may increase the risk of contamination by other compounds. MTBE biodegrades very slowly, remaining in water for decades or more.
Alternatives
Other, safer compounds (such as ethanol) are available. Reasons for using MTBE include economical considerations, as some of the production is obtained by adding methanol to isobutylene, a toxic chemical that the industry would otherwise have to find another way to dispose of. However, most MTBE facilities have to manufacture the methanol and isobutylene required to produce MTBE.
Advocates in the United States sometimes claim that gasoline manufacturers have been forced to add MTBE to gasoline by law. However, this is incorrect, since any oxygenate would fulfill the law.
Legislation
United States
The clean-up of all MTBE in the U.S. is estimated to cost as much as $140 billion, including breaking down the compound in municipal water supplies and repairing leaky underground oil tanks. Much of the controversy centers around who will have to pay the costs of this clean-up, if such a task is required.
Recent state laws have been passed to ban MTBE in certain areas. As of 2004, more than half of all states still permit its use. However, the states of California and New York, which together accounted for 40% of U.S. MTBE consumption, banned the chemical starting January 1, 2004. (A table of state by state information is available here (http://www.eia.doe.gov/oiaf/servicerpt/mtbeban/table1.html) at the Department of Energy website.)
In 2000, the EPA drafted plans to phase out the use of MTBE nationwide over four years. Upon taking office, the Bush administration cancelled those plans.
In April of 2002, a California jury found several oil companies guilty of irresponsibly manufacturing and distributing MTBE, stating that the companies acted with malice in failing to warn customers about the dangers of MTBE contamination. There are hundreds of other lawsuits currently active regarding the compound.
Between 2000 and 2004, the top three MTBE manufacturers have donated over $1 million to the United States Republican Party and key members. An amendment to provide blanket immunity from MTBE-related lawsuits was inserted into the House version of the 2003 Energy Bill. The bill failed to pass when six Republicans voted against it, mostly because of that amendment. MTBE lawsuit immunity is likely to remain a political issue in the years to come.
The Energy Policy Act of 2005, passed on April 21, 2005, shields MTBE manufacturers from water contamination lawsuits, which means that all cost for the 80 lawsuits filed so far will be paid by the taxpayer. This provision has been a top priority of Tom DeLay and Rep. Joe Barton, chairman of the Energy and Commerce Committee. [2] (http://www.cnn.com/2005/POLITICS/04/21/energy.bill.mtbe.ap/) This bill also includes a provision that gives MTBE makers, including some of the biggest oil companies, $2 billion in transition assistance as MTBE is phased out over the next nine years. [3] (http://66.102.7.104/search?q=cache:Caya6UkgOrkJ:www.msnbc.msn.com/id/7574562/+MTBE&hl=en) The New York Times calls this "A Dirty Little Footnote to the Energy Bill." [4] (http://query.nytimes.com/gst/abstract.html?res=F50717FC3A5A0C768DDDAD0894DD404482).
Further reading
- MTBE webpage from the EPA (http://www.epa.gov/mtbe/)
- Harper's Magazine, August 2004, pp 73-64de:Methyl-tert-butylether
nl:Methyl-tert-butylether ru:Метил-трет-бутиловый эфир zh:甲基叔丁基醚