The past couple of decades have been good for going green. One particular type of green, at least. Within the lifetime of virtually everyone reading this article, marijuana has gone from something uniformly illegal across all 50 U.S. states to something that, well, isn’t. Today, 33 states have broad legislation in place to allow the usage of marijuana in some form.

Most people agree that these changes are for the better. But recreational marijuana use comes with a big challenge for some — namely, how do you determine whether a person is dangerously impaired under the influence of weed? It’s one thing to be in favor of a person’s right to bear spliffs; another to support someone getting behind the wheel or otherwise risking lives while getting higher than a prospective Googler’s Grade Point Average.

A growing number of research labs, law enforcement officials, and startups believe that the answer is a twist on the breathalyzer device used for assessing alcohol intoxication. Only in this case, it’s not measuring the blood alcohol content in a breath sample, but rather the amount of tetrahydrocannabinol (THC), the psychoactive compound in marijuana. This is something which hasn’t previously been possible to carry out with a portable roadside device.

“The fundamental challenge is that THC exists in breath in concentrations that are something like a billion times less than alcohol,” Dr. Mike Lynn, CEO of the startup Hound Labs, told Digital Trends. “That means you need a breathalyzer that’s literally a billion times more sensitive if you’re going to use it for marijuana. It’s like identifying 25 or 30 specific grains of sand on a beach that’s well over a mile long. That’s a pretty tough scientific [problem to solve].”

The peak impairment window

In the bad old days, things used to be easier. In a world with a zero tolerance approach, there’s technically no difference between a person stoned out of his or her gourd and a person who had a joint at a party last weekend. Evidence of marijuana use was a binary “yes” or “no” measure.

“In the past, when it was illegal, if you showed up positive on a urine screen two weeks later, you could be fired or arrested,” Lynn said. “Even if the person wasn’t impaired, it was still illegal. It’s like showing heroin or cocaine in your system today. It’s never legal to have those substances in your body.”

Old tests for marijuana looked for trace elements in things like blood, urine, and hair. But legalization changed all of this. Suddenly marijuana testing became a spectrum, with the need to delineate between the person who threw five on it a week ago, but who still has evidence of weed in their bodily fluids, and the person who’s dangerously blazed right this moment. “Unless you believe someone’s still stoned a week after smoking, those [previous] tests are basically useless in establishing potential impairment,” Lynn explained.

An emergency room doctor and reserve deputy sheriff turned entrepreneur, Lynn’s company, Hound Labs, has developed a handheld marijuana breathalyzer he says will be launching in early 2020. Aimed at law enforcement, insurance companies, and employers, this device promises a more objective measure for intoxication than the current subjective on-site measures like sobriety field tests.

Last week, it announced that it has raised an addition $30 million in funding. “It really gives us the commercialization funding so we can distribute this,” Lynn said. In total, Hound Labs has raised a massive $65 million to make its product dream a reality.

The device was subject to a recent self-funded small scale trial carried out by researchers at the University of California, San Francisco, and published in the journal Clinical Chemistry. It suggests that the device could be capable of helping determine whether a person, “has used pot very recently, and is therefore likely to be in that peak impairment window” of approximately 2-3 hours after smoking.

Others working on the problem

Hound Labs may be the first company to get a marijuana breathalyzer to market, but it’s certainly not the only group working on the problem. A Canadian startup called SannTek Labs has additionally received Y Combinator backing to develop a similar device.

Researchers from the University of Pittsburgh also showed off their own version in a recent paper published in the journal ACS Sensors. Their breathalyzer relies on nanotechnology in the form of carbon nanotubes. The THC molecules in breath bind to the surface of these tiny carbon tubes, which are some 100,000 times tinier than a human hair. In the process, it changes their electrical properties. The speed at which the electrical currents recover indicates whether or not THC is present. According to the researchers, the nanotechnology sensors can detect THC at levels superior even to mass spectrometry, the gold standard for THC detection.

“Usual methods of measuring gaseous compounds present in human breath involve using mass spectrometry techniques,” Alexander Star, a professor in the Department of Chemistry at the University of Pittsburgh, told Digital Trends. “These are laboratory-based techniques which involve sophisticated instruments and trained personnel. There has been a push to miniaturize mass spectrometry to develop field deployable instruments. However, mass spec instruments require high quality gases, vacuum pumps, and high power supplies. Our breathalyzer is based on passive electrical measurements of changes in carbon nanotube resistance and can be miniaturized to a truly portable hand-held device.”

Unlike Hound Labs’ breathalyzer, which is already rolling off production lines in small quantities for validation testing, the University of Pittsburgh’s device is still a prototype. But it may not stay that way for long. “We are hoping to commercialize the technology to develop a finished breathalyzer product,” Star said.

While further sensor chip optimization and testing are needed, the team is confident. “We are also currently working on improving machine learning models used for sensor calibration and selectivity.”

The first step on the journey

It remains to be seen how well the first marijuana breathalyzers work. More clinical trials will need to be carried out with larger sample sizes. (Although Hound Labs maintains that, “20 is a standard sample size for trials of this nature.”) This is one area where being first to market, without getting the technology 100% right, would be a major disadvantage. Everyone has their eye on the opportunity, but it’s crucial that things are executed to the letter.

Even if the technology does work as well as it’s promised to, this is still an early step. In states where marijuana is legal, there are billboards that read, “Drive high, get a DUI.” But just how high is too high? “There are no specific impairment standards related to THC in breath because no-one has had the tools to allow those studies,” Mike Lynn said. “We’re the first to be able to provide both researchers and law enforcement the tools to start to establish those levels.”

Once the tools for providing these readings have been proven reliable, the really difficult part of the work will begin. This is when lawmakers will have to agree upon the particular objective measures which determine just how much THC is too much THC in a person’s breath. For the first time, there will be weed equivalent laws to the alcohol laws made possible by the original breathalyzer. If this is carried out with rigor, it will also mean definitively proving the correlation between detection of THC in breath and impaired performance on the part of the user.

In other words, we’re still at the start of this particular story. Marijuana breathalyzers are on the way but don’t hold your breath for all the related questions to be answered overnight.

Editors' Recommendations