Gasoline Additive Can Blow Breathalyzer Test

MTBE can cause a false positive reading, study says

WEDNESDAY, Dec. 26 (HealthDayNews) -- MTBE is a controversial gasoline additive designed to help reduce air pollution. It can also be absorbed through the skin or inadvertently inhaled. And that, in rare cases, could prompt police to mistakenly arrest you for driving under the influence of alcohol, a new study says.

Methyl tertiary butyl ether, a synthetic blend of the chemicals isobutylene and methanol, has been used for years as an additive for unleaded gasoline to achieve more efficient burning. And it's also used by some states to help them meet the requirements of the federal Clean Air Act.

Now researchers at Johns Hopkins University say the odiferous additive -- it smells like rotten eggs -- can create "false positive" readings, either alone or in combination with alcohol, when an individual is tested with an older type of breathalyzer.

The study was prompted by the claims of a gasoline station owner who said MTBE was responsible for his arrest for driving while intoxicated.

"He alleged he was working in his garage changing a fuel pump and had his hands immersed in fuel and then he began pumping gas. He then left the establishment, claims he had some beer and then he got stopped. His breathalyzer test was over the legal limit, and he attributed it to MTBE," says lead author Tim Buckley, an assistant professor in the department of environmental health sciences at Johns Hopkins.

The station owner's claim moved New Jersey government officials to ask Johns Hopkins to see if MTBE could skew the results of a breathalyzer test.

"So we created a simulated breath test which contained MTBE, and then later we added the equivalent of one drink of alcohol," Buckley says. "We also varied the levels of MTBE."

The researchers tested two types of breath alcohol analyzers, "an older version still in use in New Jersey, called the Breathalyzer 900A, and the Alcotest," Buckley says.

MTBE readily enters the bloodstream and can cross over into your lungs, Buckley says.

"Its chemical composition is such that it can find its way into your breath," he says. "And MTBE is somewhat famous. You may have heard of it in California and elsewhere in the country where there have been plenty of reports of MTBE contaminating water. So if it's in your water and you're in the shower, it can come in contact with your skin and be absorbed."

MTBE, either alone or in combination with alcohol, had no effect on the newer Alcotest breathalyzer, Buckley says.

And, he says, normal levels of MTBE "don't register much of a response on the older version of the breathalyzer. But it is plausible that high exposure to MTBE, such as working with gasoline, could register a false positive response on a breathalyzer over the legal threshold. But it would really have to be extreme circumstances."

"And MTBE alone would not register positive and was not over the legal threshold on the Breathalyzer 900A. But we were able to generate a positive response with a combination of MTBE and alcohol," Buckley says.

New Jersey law prohibits operating a motor vehicle "with a blood alcohol concentration of 0.10 percent or more by weight of alcohol in . . . blood," he says.

The findings were published in the current issue of Forensic Science International.

Environmentalists have been fighting to get MTBE banned since its introduction, says Barry Grossman, the president and founder of Oxybusters in Plainsboro, N.J. There's a bill before the New Jersey legislature to ban the additive, he adds.

Grossman says Oxybusters is aware of the DUI case that prompted the study. "I'm not surprised at the study's results," he says.

Says Buckley: "The solution here is that local jurisdictions should upgrade to the newer breathalyzer technology to prevent any sort of legal problems."

What to Do: For more information on MTBE and drinking water, see this Environmental Protection Agency site. For more on breathalyzers, see HowStuffWorks.

SOURCES: Interviews with Tim Buckley, Ph.D., assistant professor, department of environmental health sciences, Johns Hopkins University, Baltimore; Barry Grossman, president, Oxybusters, Plainsboro, NJ; Dec. 2001 Forensic Science International
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