Cannabis has gained increased use in the United States, outpacing alcohol as Americans' daily recreational drug of choice. Nearly 20 percent of cannabis users have admitted to driving after using the drug. However, unlike for alcohol, reliable roadside tests for cannabis don't 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 tetrahydrocannabinol (THC) shows up in breath after smoking, but what about edibles? Would those show up in breath too?
The answer is yes; they do. In a study published in the Journal of Analytical Toxicology, researchers at the National Institute of Standards and Technology (NIST) and their colleagues made the first cannabinoid measurements in breath after study participants ingested cannabis-infused edibles.
"This is an important step forward, that we can detect THC increases in breath after the ingestion of cannabis," said Jennifer Berry, NIST research chemist and lead author on the paper.
Making a breathalyzer for cannabis is harder than making a breathalyzer 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 milligrams 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. That wasn't surprising. 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. Many of them exhibited 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.
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. 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, Berry said. This matches something else that stood out to the NIST team, 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."
This study provides just the first steps of understanding how edible cannabis shows up in breath, said Kavita Jeerage, a NIST research chemical engineer leading the cannabis breath research. 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.
It will be up to toxicologists to determine what those measurements say about impairment, she said, work that NIST's research partners are already pursuing.
"Our partners at Anschutz conducted a variety of assessments to probe impairment after participants ingested their cannabis gummies, including observing participants' driving abilities with a driving simulator. The breath samples were a bonus that allowed us to gather first-ever data to explore whether THC increases in breath after edible ingestion," Jeerage said. "Looking forward, we can now tackle the question of when THC increases after edible ingestion, when it goes back to baseline, and how to analyze breathalyzer data to get the information needed."
"This study supports the idea that multiple breath measurements over a period of time could be a way to use a breathalyzer to detect cannabis use, regardless of how it's ingested," said Tara Lovestead, a NIST chemical engineer on the cannabis breath research project. "However, devices will still need standards to ensure that they are accurate and used correctly, standards that don't yet exist."
NIST itself is not developing a cannabis breathalyzer, Lovestead added. Instead, NIST's role is to help ensure that measurements of cannabis in breath can be accurate, reliable and have scientifically sound standards behind them. NIST will be hosting a workshop with device developers in September to discuss a path forward.
Paper: Jennifer L. Berry, Ashley Brooks-Russell, Tara M. Lovestead and Kavita M. Jeerage. The detection of cannabinoids in breath after ingestion of cannabis-infused edibles. Journal of Analytical Toxicology. Published online July 10, 2025. DOI: 10.1093/jat/bkaf063
