Cannabis Breathalyzers May Not Be Possible, NIST Study Suggests

Cannabis breathalyzers may just be a pipe dream, according to a new federal study.

To see if such a device is feasible, researchers from the National Institute of Standards and Technology (NIST) and University of Colorado, Boulder, analyzed the breath of cannabis smokers before and after they smoked.

To their surprise, the research team didn’t see a conclusive uptick in THC levels in the second breath samples.

Based off their findings alone, the research team concede that a cannabis breathalyzer may not be workable idea.

The research was published in the Journal of Breath Research.

Up in smoke

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.

In an attempt to address this need, the NIST and CU Boulder researchers asked 14 participants to provide two breath samples, one before they smoked their own, legally bought cannabis product, and one after. The samples were collected in a mobile lab (dubbed “the Cannavan”) parked outside the participants’ homes. Blood samples were also collected.

The researchers then analyzed the samples using liquid chromatography with tandem mass spectrometry (LC-MS-MS). THC was identified in 36% of pre-cannabis breaths and 80% of post-use breaths. Yet only 8 of the 14 participants (57.1%) showed the anticipated increase in THC after cannabis use. THC wasn’t even detected in three post-cannabis breath samples and the remainder samples contained similar or even lower levels of THC than their pre-cannabis counterparts.

The researchers say these mixed results, on their own, don’t support the feasibility of a single-breath cannabis breathalyzer. But that doesn’t mean a cannabis breathalyzer isn’t possible.

“We don’t rule out a breathalyzer type device and one might be feasible in the future. But a lot more research is needed,” Kavita Jeerage, PhD, a materials research engineer at NIST, told Analytical Cannabis in an email.

“Our paper points out that there are only a handful of studies of THC in breath. For comparison, the alcohol breathalyzer has been studied in tens of thousands of people.”

To help bridge this research gulf and better determine the plausibility of a cannabis breathalyzer, Jeerage and her colleagues plan to conduct another study, using the same breath sampling device, with more participants, as well as other studies to test the efficacy of other breath sampling devices.

“One of our short term goals is to study different modes of cannabis use and different breath sampling devices to determine how THC and other cannabis compounds enter the breath and are carried in breath,” Jeerage said.

“NIST is currently doing a study with a different breath sampling device that includes participants who smoke and participants who vape. If we can understand the underlying science, it will provide knowledge to improve devices for the purpose of distinguishing recent use from past use.”

A YouTube video from NIST featuring Kavita Jeerage and her colleagues discussing their breathalyzer research. Video credit: NIST.

Breath or saliva?

Jeerage and her colleagues aren’t the only ones interested in developing a cannabis breathalyzer.

In light of the growing legal cannabis industry, several research groups have formed in an attempt to create a portable, viable THC-test that could match the alcohol breathalyzer. But not everyone is convinced breath is best.

According to Shalini Prasad, a professor of bioengineering at the University of Texas at Dallas, the actual THC levels present in breath are so low that such tests risk producing error-prone data, which require extensive processing to filter out other compounds. Saliva, according to Prasad, is a medium far better suited to studying THC intoxication levels, which is why her research team chose to develop their own saliva-based THC detection kit in 2020.

Jeerage and her colleagues, however, do have faith in the marijuana breathalyzer dream – despite the mixed findings from their own study – as long as filters are used.

“We consider a cannabis breathalyzer a realistic possibility – but it probably won’t operate the same way as an alcohol breathalyzer,” Tara Lovestead, a group researcher and leader at NIST, told Analytical Cannabis.

“THC is a completely different animal, chemically speaking, than ethanol. This is why the main strategy for measuring THC in breath is based on collecting breath aerosols with filters – ethanol is measured as a vapor in breath and does not need to be ‘collected’.”