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Young Scientist May Have Found Flaw in
BAC Test

Ciara Stein, a 13 year-old scientist from County Kerry in Ireland, may have discovered a flaw in drunk-driving breathalyzer tests. Police make people blow deeply into these devices when they are stopped for possibly drinking and driving.

The breathalyzer helps determine how much alcohol is in the blood.

Ciara’s research suggests that both diabetics and those on very low-calorie diets are more likely to show false positive results because of chemical changes in their blood.

“The chemical changes in the blood are caused when levels of sugar drop too low,” Ciara told the Irish Times. “If you are diabetic or you are on a very low calorie diet, you can become hypoglycemic—your blood sugar is too low. When this happens, you get ketenes on your breath,” she said.

The simplest ketene is acetone, which can build up on the breath and is perceived by the human body as a danger. The body responds to this perceived threat by changing acetone into a form of alcohol called isopropanol. This chemical is similar to ethyl alcohol in its properties and evaporation rate. Breathalyzers cannot always tell the difference between isopropanol and drinking alcohol.

Ciara’s interest in this subject came from reading a report about a pilot from Sweden who was on a low-calorie diet and used a breathalyzer to check his breath for alcohol. The pilot found he registered almost 20 milligrams per milliliter of blood (20mg/ml), even when he didn’t drink any alcohol.

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