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With cannabis now surpassing alcohol as the most commonly used daily drug among Americans, there is an urgent need for a reliable method to detect its recent use, particularly in drivers. While developing a breath test for cannabis has proven challenging, researchers at the National Institute of Standards and Technology (NIST) and the University of Colorado Boulder are testing a new approach that could revolutionize roadside drug detection.
The Challenge of Cannabis Detection
Traditional breath tests for alcohol, which have been in use for nearly a century, work by detecting ethanol vapor exhaled from the lungs. However, detecting tetrahydrocannabinol (THC), the psychoactive component of cannabis, is far more complex. THC is present in the breath at much lower concentrations than alcohol, making it extremely difficult to measure accurately. Moreover, unlike alcohol, which is rapidly metabolized and eliminated from the body, cannabis can linger for weeks, making it challenging to differentiate between recent and past use.
Last year, researchers found that a single breath test might not be sufficient for determining recent cannabis consumption, especially among regular users who may have residual THC in their system even on days they haven’t consumed the drug. This discovery led to the consideration of a novel approach: administering two breath tests within approximately an hour of each other.
A Potential Breakthrough
“If successful, this could pave the way for on-the-spot detection of recent cannabis use by law enforcement,” said Kavita Jeerage, a materials research engineer at NIST. The idea is that a significant drop in THC levels between the two tests could indicate recent consumption, distinguishing it from past use. However, the optimal timing between the two tests remains unknown, and determining whether this method would be practical in real-world scenarios is still an open question.
The Study
The pilot study, part of a $1.5 million interagency agreement between NIST and the National Institute of Justice, involves 45 participants aged 25 to 50 from the Denver and Boulder, Colorado areas. Participants will use THC-based cannabis products in their homes before heading to a mobile pharmacology lab operated by the University of Colorado Boulder. Over two hours, they will undergo ten breath tests at set intervals, with the primary aim of identifying the ideal timing between two tests for detecting recent cannabis use.
The Road Ahead
The study, expected to take several years, also involves analyzing breath samples for THC, THC metabolites, and other cannabis-related compounds, alongside blood samples and participant questionnaires. The ultimate goal is to develop a scientifically validated breath test that can be used by law enforcement to ensure road safety while supporting fair and equitable policing practices.
Cinnamon Bidwell, associate professor and co-director of CUChange, a research center at the University of Colorado Boulder, emphasized the importance of this work: “The ultimate goal is to develop a reliable tool that supports fair law enforcement and helps keep our roads safe.”
As the study progresses, it holds the promise of providing law enforcement with a much-needed tool to detect cannabis impairment, potentially transforming how cannabis use is monitored and regulated on the road.
Further Reading
For more information, see Thomas D. Marcotte et al’s study, “Evaluation of Field Sobriety Tests for Identifying Drivers Under the Influence of Cannabis,” published in JAMA Psychiatry (2023). DOI: 10.1001/jamapsychiatry.2023.2345.
