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New Breathalyzers Can Detect THC “Better Than Mass Spec”

By Leo Bear-McGuinness

Published: Aug 28, 2019   
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As more US states legalize cannabis, there’s a growing concern that “high drivers” could become a greater danger to the public.

But while alcohol breathalyzers can provide a quick and non-invasive test of a driver’s sobriety, there has never been a comparable device to measure THC levels – until now.

Researchers from the University of Pittsburgh announced yesterday that they have developed a “cannabis breathalyzer” that can measure the amount of THC in a user's breath.

The news coincided with an announcement from a Californian start-up, which has raised $30 million to bring its own THC breathalyzer technology to market.

Take a deep breath

Current cannabis testing methods rely on the invasive provision of blood, urine, or hair samples from the suspected individual. These are then typically put through a mass spectrometer machine, which breaks the samples down into their atoms to precisely identify which chemicals they harbor.

While accurate, these tests have only ever revealed the presence of THC in the suspect’s system and not whether they are still under its influence, which is usually within the first three hours after consumption.  

But now the two teams of researchers claim to have produced breathalyzers that can do just that and “detect THC at levels comparable to or better than mass spectrometry.”

The University of Pittsburgh’s prototype uses carbon nanotubes, 100,000 times smaller than a human hair. According to breathalyzer’s designers, any THC molecules in a driver’s breath will bind to the surface of these fibers and change their ability to conduct electricity. This change in the electrical currents’ speed then signals that THC is present.

“The semiconductor carbon nanotubes that we are using weren’t available even a few years ago,” Sean Hwang, lead author on the paper published in ACS Sensors, wrote in a press statement.

“We used machine learning to ‘teach’ the breathalyzer to recognize the presence of THC based on the electrical currents recovery time, even when there are other substances, like alcohol, present in the breath.”

In contrast, the breathalyzer developed by the Californian company Hound Labs contains a special salt that can bind to any THC present. This binding forms a new chemical, which can then be detected by its fluorescence.

In a study published earlier this year, researchers found that Hound Labs’ device reliably detected THC throughout the three-hour impairment window. The study involved 20 participants and was paid for by Hound.

High and drive

So how dangerous is driving under the influence of cannabis? Well, there doesn’t appear to be a conclusive answer.

One extensive review of 60 studies found that marijuana affected all areas relevant to safe driving, including psycho-motor skills, continued attention, visual function, and reaction time. But another study found that, when compared to drunk drivers, high drivers had an increased awareness that they were impaired and were often able to compensate for their intoxication.

“Marijuana smokers tend to compensate effectively for their impairment by utilizing a variety of behavioral strategies such as driving more slowly, passing less, and leaving more space between themselves and cars in front of them,” the authors summarized in their conclusion.

But regardless how severe marijuana’s intoxication can be, the designers of the new THC breathalyzers believe their devices will be still be needed when clearer regulations come into effect.

“In legal states, you’ll see road signs that say “Drive High, Get a DUI,’ but there has not been a reliable and practical way to enforce that,” said Alexander Star, a co-designer of the Pittsburgh breathalyzer. “There are debates in the legal community about what levels of THC would amount to a DUI, but creating such a device is an important first step toward making sure people don’t partake and drive.”

Leo Bear-McGuinness

Science Writer & Editor

Leo joined Analytical Cannabis in 2019. From research to regulations and analysis to agriculture, his writing covers all the need-to-know news for the cannabis industry. He holds a Bachelor's in Biology from Newcastle University and a Master's in Science Communication from the University of Edinburgh.


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