Ear defenders

Ordinary ear defenders can be modified to detect blood alcohol levels

Creativ Studio Heinemann/Getty

Forget blowing into a breathalyser – a new drink-driving test could involve putting on a pair of ear defenders.

Koji Toma at Tokyo Medical and Dental University in Japan and his colleagues have created a device that captures alcohol given off by the skin of a person’s ears. It can measure the amount of alcohol in their blood and whether they are over a legal limit.

Breathalyser tests for alcohol used by many police forces require blowing steadily into a device for several seconds, and some people can’t manage this, or claim they can’t. A skin-based test solved both issues. “They can’t cheat through their skin,” says Toma.

Toma and his team had previously investigated measuring blood alcohol using the skin of the palm, but they wondered if the ears would be better, as they have a large surface area, the skin is thin and has few sweat glands, too many of which make the results too variable. “If the signal is not stable we can’t estimate the concentration properly,” says Toma.

The researchers modified a pair of ear defenders so a stream of air could be blown into and out of them. Three men wore the device over their ears for 140 minutes while they had an alcoholic drink, and also took regular breathalyser tests. The air leaving the device was sent to an ethanol vapour sensor.

The team found that the earmuff readings showed a similar rise and fall in alcohol levels as the breathalyser, but with a 13-minute delay.

If someone wore the device for a one-off reading, such as if they were suspected of drink-driving, they would need to have the ear defenders on for 30 seconds, says Toma. Long hair would need to be pushed out of the way.

The team is now developing the idea for other medical uses where a continuous read-out of blood levels of biochemicals would be helpful, such as measuring a compound called acetone, which indicates how much fat is burned during exercise.

Journal reference: Scientific Reports, DOI: 10.1038/s41598-021-90146-1

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