The Race to Build a Weed Breathalyzer

By Daniel Oberhaus on April 20, 2017

Late last year, a few dozen California drivers suspected of driving under the influence of cannabis were treated to a surprise when the officer who pulled them over asked them an unexpected question: Would you care to submit to a breathalyzer test?

None of the individuals who assented to the test were arrested. Rather, they became live test subjects in the development of the world’s first weed breathalyzer, designed to take real-time measurements of THC concentrations in a driver’s breath, and were escorted home after the test. The breathalyzer used during this test run was designed by Hound Labs, a company run by Mike Lynn, a deputy sheriff turned physician turned venture capitalist. And if Lynn has his way, this device will be making its way into the hands of law enforcement officers around the country by the end of this year.

Yet Hound Labs is not alone in its quest to develop a weed breathalyzer. Indeed, there is a full-blown race to develop a reliable “potalyzer” now that more than half of the United States has legalized medical and/or recreational cannabis. The first company to do so will have a monopoly over road-side THC testing, and with nearly 18,000 police agencies in the U.S., and an estimated price of just under $1,000 per breathalyzer, there is some serious money to be made.

Hound Labs’ main competition in this race to develop a weed breathalyzer is a Vancouver-based company called Cannabix Technologies. Both companies have developed breathalyzers that use ion mass spectrometry to detect THC molecules in a person’s breath. Ion mass spectrometry is basically a fancy way of describing a process where a system can detect small amounts of organic compounds (in this case, THC) by filtering out ions (charged atoms and molecules) in a breath sample based on the ions’ size, shape and charge. The THC molecules are then "tagged," and the total quantity is measured in a ratio of THC molecules to other compounds to determine how intoxicated a user is.

The devices were each developed in tandem with university research teams (Hound Labs worked with researchers at UC Berkeley, whereas Cannabix partnered with the University of Florida). So far, Hound Labs has a large lead over Cannabix in terms of actually having a product ready for deployment, although Cannabix recently wrote a press release saying it planned to begin “pre-trial live subject testing” later this month.

Other methods of testing THC quantities in a driver exist, such as Stanford’s potalyzer, which repurposed a cancer-screening technology to measure THC quantities based on a saliva sample in under three minutes. Unfortunately for devices that rely on testing THC-levels in body fluids, a 2016 Supreme Court decision that prohibits warrantless blood tests may also extend to other body fluids as well, which would render saliva-based tests less practical than using a breathalyzer.

There’s also the issue that many compounds found in cannabis can stay in the body for days after a person smoked, even if that person is perfectly sober at the time of testing. This often leads to false positives, and it is the reason it is notoriously hard to prosecute people for stoned driving. However, the faint traces of THC in the breath only last for two to three hours, meaning they are a more reliable indicator of whether that person has recently consumed cannabis.

“Use is different than intoxication,” Dale Grieringer, the director of the California chapter of NORML, told PRØHBTD. “Blood and oral fluid levels of THC soar in the first few minutes after taking a toke, but that doesn’t mean the users are intoxicated. It takes time for the THC in the blood to distribute itself in the body, and most of it never reaches the brain.”

Indeed, as Grieringer alluded to, the main problem barring the way to the deployment of breathalyzers is a lack of consensus as to what actually counts as intoxication when it comes to cannabis. Following the legalization of medical and/or recreational cannabis, a number of states sought to set a limit as to what the legal limit should be for stoned driving. Only a handful of states actually managed to pass legislation on this front, mostly due to the lack of any sort of scientific consensus on the matter. Now states like Colorado, Washington and Montana have limits of 5 nanograms of THC per milliliter of blood.

Is that actually enough to consider a person stoned? The answer is both yes and no, and that’s the problem.

For a heavy smoker, THC in that concentration is unlikely to produce much of an effect, whereas a novice could be stoned out of his or her mind. According to Grieringer, the concentration of THC in a person’s blood is not a reliable indicator of how much THC is in a person’s brain due to the way cannabinoids interact with the blood-brain barrier, which shields the cannabinoid receptors that supply cannabis with its psychoactive properties from the rest of the body. This is very different from alcohol, which has a high solubility, meaning that its presence in your blood is about the same as its presence in your brain, meaning a blood-test is a pretty good indicator of how fucked up you are.

“Breathalyzers are just another dead end in a futile effort to detect cannabis impairment by chemical means,” Grieringer said. “It is impossible to accurately assess marijuana’s action in the brain by measuring its presence elsewhere in the body.”

Despite the pushback from cannabis advocates and the scientific community, the plans to develop and deploy a cannabis breathalyzer are forging full steam ahead. Although it is significantly less dangerous to drive stoned than drunk (although both are more dangerous than driving sober), cannabis connoisseurs would be well-advised to start thinking twice before smoking and driving in the coming months.


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