Noting the current lack of an accurate cannabis breathalyzer, researchers in a protocol development study analyzed levels of THC before and after participants smoked cannabis.
Earlier this month, researchers from the University of Colorado Boulder and the National Institute of Standards and Technology (NIST) published an open access article in the Journal of Breath Research on testing tetrahydrocannabinol (THC) amounts in breath samples (1). “The goal of this study was to begin developing a protocol that yields reproducible results—a necessary step toward a reliable, validated field-based method,” a news article from NIST stated (1). NIST is part of the US. Department of Commerce and is one of the US’s oldest physical science laboratories (1).
The study, titled “THC in breath aerosols collected with an impaction filter device before and after legal-market product inhalation—a pilot study,” collected breath and blood samples from 18 participants before and after smoking high-THC cannabis and measured the amounts of THC using liquid chromatography with tandem mass spectrometry (1,2).
“Simply translating what is known about alcohol breathalyzers is insufficient because ethanol is detected as a vapor,” the abstract of the study stated, noting that THC is hypothesized to be carried by aerosol particles in the breath (2). A handheld breathalyzer was not used in this experiment (1).
“The concentrations of THC in a person’s breath is very low,” Cheryle Buening, research chemist at NIST and study co-author said in a video explaining the study (3). “We’re talking nanograms to picograms per mil, and each person provides 12 breaths just to get to that concentration.”
“Of the 14 participants who provided two samples during the experimental session, eight participants showed the anticipated increase in THC after cannabis use,” the results stated (2). “THC was not detected in three post-use breath extracts and the remainder of post-use extracts were similar to or lower than baseline extracts. THC quantities, when detected and with one exception, were similar in baseline and post-use extracts.”
“We expected to see higher THC concentrations in the breath samples collected an hour after people used,” said NIST supervisory chemical engineer and study coauthor Tara Lovestead (1). “In many cases, we would not have been able to tell whether the person smoked within the last hour based on the concentration of THC in their breath.”
“A lot more research is needed to show that a cannabis breathalyzer can produce useful results,” said NIST materials research engineer and co-author Kavita Jeerage (1). “A breathalyzer test can have a huge impact on a person’s life, so people should have confidence that the results are accurate.”
The researchers also examined other similar pilot studies and recommendations for future research on this subject. “Our results do not support the idea that detecting THC in breath as a single measurement could reliably indicate recent cannabis use,” the researchers concluded in this study (1). The study was funded by a grant from the National Institute of Justice, which also awarded the researchers $1.5 million over three years to continue the research with a greater number of participants (1).