Federal Study Challenges Reliability of Breath Testing for Recent Marijuana Use

A recent study that was funded by the federal government has highlighted the challenges involved in creating a breathalyzer-like device for cannabis. Despite using carefully collected samples and conducting thorough laboratory analysis, researchers from the National Institute of Standards and Technology (NIST) and the University of Colorado Boulder found that THC levels were too inconsistent to determine if someone had recently smoked marijuana.

According to results from the study which was published in the Journal of Breath Research, detecting THC in a person’s breath as a single measurement cannot reliably indicate recent cannabis use. The authors emphasized the need for further research to ensure that a cannabis breathalyzer will be able to produce accurate results. They highlighted the potential impact of a breathalyzer test on a person's life and emphasized the importance of having confidence in the accuracy of the results.

Study Method

To conduct the study, the researchers collected breath and blood samples from 18 participants in Colorado who had smoked the same type of retail marijuana containing approximately 25 percent THC. The samples were collected before and after smoking in a comfortable van parked conveniently outside the participants' homes. The analysis was conducted in a lab rather than in the field, with the aim of understanding how to accurately measure THC and related compounds in breath, rather than developing a roadside breathalyzer device.

Study Results

Out of the 14 participants who provided breath samples before and after smoking marijuana, only eight showed the expected increase in THC levels after cannabis use. The remaining results were inconsistent and inconclusive, with THC not being detected in some post-use breath samples and others showing similar or lower levels compared to baseline samples. This indicates that collecting reproducible breath aerosol samples remains a challenge.

In contrast, blood measurements of THC concentrations in plasma were found to be a more reliable indicator of recent cannabis use. The study noted that THC in breath one hour after use did not necessarily exceed baseline levels, even when THC in the blood indicated compliance with the study protocol and a significant immediate increase post-use.

Conclusion

The study, although limited in scale, emphasizes the need for further research in this area. Researchers highlighted the difficulty in differentiating between a person who regularly uses cannabis but hasn't done so recently and someone who consumed it an hour ago. A reproducible protocol for breath measurements would help answer this question and improve the accuracy of devices used for this purpose.

The study received funding from the Department of Justice's National Institute of Justice, and the research team has been awarded an additional $1.5 million to expand the study. The next phase of the study will involve 40 or more participants and over a thousand breath samples to provide more statistically significant results.

The challenges in accurately measuring cannabis in a person's system and its impact on driving ability have led to ongoing debates and discussions among policymakers. Efforts to identify drug-impaired driving and enforce the law have been emphasized, and there have been calls for reforming cannabis testing policies and developing accurate tests for impairment.

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