September 8, 2013

Blurry issue: Blood alcohol and driving

Expert opinion varies as the question of what constitutes impaired driving is up for debate.

By TED GREGORY/Chicago Tribune

(Continued from page 1)

Push to lower legal limit of intoxication to 0.05 stirs debate
click image to enlarge

A volunteer driver takes the wheel at the University of Iowa National Advanced Driving Simulator in Coralville, Iowa, on Aug. 20.

Chuck Berman/Chicago Tribune/MCT

As to whether such a thing as responsible drinking and driving exists, some research shows that lane deviations and attention lapses occur at a BAC as low as 0.001. MADD and the National Institute on Alcohol Abuse and Alcoholism recommend no one drive after drinking.

But the American Beverage Institute, which represents restaurant and bar owners, calls the 0.05 recommendation an effort to "criminalize perfectly responsible behavior," saying that less than 1 percent of traffic fatalities in the U.S. are caused by drivers with a BAC from 0.05 to 0.08. The organization points to National Highway Traffic Safety Administration data showing that 70 percent of drunken driving deaths involve a driver with a BAC of 0.15 or higher.

In making its recommendation in May, the NTSB noted that more than 100 countries, including many in Europe, have set 0.05 as the legal limit of intoxication and experienced significant drops in traffic fatalities after doing so.

Drunken driving accounts for nearly 10,000 traffic fatalities a year in the U.S.

"The research clearly shows that drivers with a BAC above 0.05 are impaired and at a significantly greater risk of being involved in a crash where someone is killed or injured," the NTSB's Hersman said in recommending the lower level.

CONTEXT FOR RESEARCH

Sarah Longwell, managing director of the American Beverage Institute, contends the NTSB research lacks context. The significantly greater risk that the NTSB points out is no different than the risk that accompanies listening to a loud car radio or having a passenger talking to the driver, she said.

Emphasizing other countries that set their legal definition of intoxication at 0.05 is "an apples to oranges comparison" to the U.S., Longwell said. Many of those countries have "vastly different" driving, mass transit and drinking cultures, she said. In addition, the countries imposed "other draconian measures," including random breath testing, that contributed to the decline in traffic fatalities and would be unacceptable in the U.S., Longwell added.

"We're going to stand by 0.08 as the law," she said.

Clarifying alcohol's effect on the body can be tricky.

Generally speaking, the liver, brain, pancreas and stomach break down and eliminate alcohol through enzymes that convert the substance into water and carbon dioxide, the U.S. Department of Health and Human Services reports.

During that conversion, one of the enzymes metabolizes into "a highly toxic substance and known carcinogen," acetaldehyde.

That substance and an alcohol-metabolizing enzyme known as cytochrome contribute to the development of cancers in the respiratory tract, liver, colon or rectum and breast, Health and Human Services research shows.

Alcohol's effect on the brain is considered harmful but somewhat uncertain. In its 24-page "Beyond Hangovers: Understanding alcohol's impact on your health," even the National Institute on Alcohol Abuse and Alcoholism states, "There still is much we do not understand about how the brain works and how alcohol affects it."

What research does show is that alcohol can slow communication between chemical neurotransmitters that carry messages between the brain's estimated 100 billion neurons. Some research indicates that acetaldehyde may contribute to that impairment. Lab animals that received acetaldehyde exhibited impaired coordination and memory and sleepiness, according to research published in 2006 in the journal Alcohol Research & Health.

Brain regions most vulnerable to alcohol include the cerebellum, which controls motor skills; the limbic system, where memory and emotion are centered; and the cerebral cortex, which connects to the nervous system and deals with the ability to think, plan, remember, solve problems and interact socially.

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