Cannabis detected in breath from edibles

Researchers at the US National Institute of Standards and Technology (NIST) and their partners say they have made the first measurement of tetrahydrocannabinol (THC) in breath from edible cannabis, in a breakthrough that supports public safety and law enforcement as consumption of cannabis rises across the US. Their work has been published in the Journal of Analytical Toxicology.

With cannabis now outpacing alcohol as Americans’ daily recreational drug of choice, nearly 20% of users admit to driving after using the drug. But reliable roadside tests for cannabis do not exist — even blood tests can’t determine when a person used cannabis, leaving law enforcement without a way to determine a person’s recent use, much less how intoxicated they are.

To make things more complicated, there are multiple ways to consume cannabis, such as smoking, vaping, ingestion and dabbing (inhaling a concentrated form of cannabis extracts). Scientists know that the psychoactive component THC shows up in breath after smoking, but now they have shown that it can also be measured after the consumption of edibles.

Making a breathalyser for cannabis is harder than making a breathalyser for alcohol. Alcohol is a relatively simple and highly volatile molecule: it easily travels through the lungs and evaporates when it contacts air. But THC is a larger, more complicated molecule with very low volatility, and consumption is typically hundreds of times less than alcohol. It shows up in very small concentrations in breath, making THC detection much more challenging. Regular users of cannabis can have THC in their breath for at least eight hours and in their blood for potentially weeks after stopping use, meaning that a single measurement is insufficient to learn when a person last used it.

In the new study, NIST’s partners at the University of Colorado Anschutz Medical Campus observed 29 participants who each brought a cannabis-infused gummy to the lab with them; the edibles contained anywhere from 5 to 100 mg of THC. Researchers first took a breath sample from the participants before they ingested the product. Then they observed each participant for three hours, obtaining breath samples approximately every hour.

NIST researchers measured the concentration of THC and other cannabinoids in breath at those intervals. They detected THC in most of the participants before they took the edible, even though they had been asked to abstain for eight hours before the study. This wasn’t considered surprising, as our bodies process cannabinoids slowly — taking weeks to get them out of our systems compared with hours for alcohol.

The researchers found that 19 of the participants showed significant increases in THC in the three-hour period after ingesting the edible, with many exhibiting a peak and then a decline in THC concentration during that time. Four of the participants did not show any change in THC, and six showed only a decrease from their first breath sample. However, it is possible that the measurements may have missed the time window in which a jump in THC could have occurred.

“This is an important step forward; that we can detect THC increases in breath after the ingestion of cannabis,” said lead author Jennifer Berry, a research chemist at NIST.

The observed spikes and dips in THC levels clear up some questions about how cannabinoids distribute in our bodies and leave our systems after use. There is a common misconception that THC in breath is from leftover smoke in the lungs after smoking cannabis, but Berry said this study shows that THC that is swallowed in edibles can make it through the digestive system and be exhaled back out through the lungs. This matches something else that stood out to the NIST team: the fact that edible cannabis takes time to show up in breath.

“Edibles aren’t that different from smoked cannabis and alcohol in that way,” Berry said. “Whether you inhale it or ingest it, it will show up in breath, but it may take some time before doing so.”

According to Kavita Jeerage, a NIST research chemical engineer leading the cannabis breath research, this study provides just the first steps of understanding how edible cannabis shows up in breath. But this first detection of THC from edibles in breath provides encouraging signs that future instruments will be able to measure THC from ingested cannabis — with toxicologists set to determine what those measurements say about impairment.

“Our partners at Anschutz [have] conducted a variety of assessments to probe impairment after participants ingested their cannabis gummies, including observing participants’ driving abilities with a driving simulator,” Jeerage said. “The breath samples were a bonus that allowed us to gather first-ever data to explore whether THC increases in breath after edible ingestion.

“Looking forward, we can now tackle the question of when THC increases after edible ingestion, when it goes back to baseline, and how to analyse breathalyser data to get the information needed.”

Tara Lovestead, a NIST chemical engineer on the cannabis breath research project, concluded, “This study supports the idea that multiple breath measurements over a period of time could be a way to use a breathalyser to detect cannabis use, regardless of how it’s ingested. However, devices will still need standards to ensure that they are accurate and used correctly — standards that don’t yet exist.”

Image credit: iStock.com/Stefan Tomic