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Could a Roadside Test Move the U.S. Closer to Cannabis Legalization?

If the research and development efforts of the National Institute of Standards and Technology (NIST) pan out, the U.S. could soon have a roadside test for the chemical determination of recent cannabis use.

On July 27, the NIST posted a notice seeking information from vendors capable of measuring a person’s breath for cannabis. The action is a first step in the Breath Measurements of Acute Cannabis Elimination (BACE) program for which NIST was awarded $1.4 million from the U.S. National Institute of Justice (NIJ) as a part of its forensic science research and development grant awards. The basis of the BACE program is the use of a two-stage, roadside test for cannabis impairment.

The NIST description explained that although cannabis use induces executive function deficits that make drivers more likely to be involved in crashes than unimpaired drivers, there is currently no means to chemically detect impairment at the roadside. Specifically, “it is impossible to draw a correlation between driving impairment and delta-9-terahydrocannabinol (Δ9THC) concentration in blood, which is the most reliable matrix with which to determine recent cannabis use.”

While breath-based detection of recent cannabis use, similar to that of alcohol-use testing, has been proposed, the two are not comparable because Δ9THC can stay in the breath well past usage. So NIST proposed detection of “acute cannabis elimination” through the taking of two breath samples spaced a short interval apart to show the slope of elimination. Based on the preliminary work of Lynch et al. which showed a decline in Δ9THC in breath samples collected at 15-minute intervals over three hours for both occasional and frequent users, NIST’s first step is to determine the feasibility of a two-point measurement that could be implemented at roadside – for which it issued the information request.

NIST’s research goal is to collect breath samples from occasional and frequent cannabis users at 10-minute intervals during acute cannabis elimination and during periods of abstinence (which it says has not been examined). Understanding that accuracy depends on consistency in the collection of breath samples, NIST will use numerical modeling to characterize the influence of human (e.g., flowrate and volume) and device factors to improve the reproducibility of aerosol particle collection, then will analyze breath samples for Δ9THC, its metabolites, and other cannabinoids with high sensitivity analytical methods.

The research will also include urine analysis to classify users into occasional and frequent use populations and blood analysis to verify compliance with study protocols, the comparison of elimination profiles and abstinence profiles with different intervals (e.g., 10 minutes vs. 20 minutes), and examination of the multivariate response.

From the data gathered through the informational request, NIST anticipates issuing a Request for Quotation by the fourth quarter of FY2022 and awarding a contract no later than the fourth quarter of FY2022.

With the inability to test drivers for cannabis usage being a strong argument by some who oppose its national legalization, the successful outcome of this research and the development of an effective roadside test could take at least one challenge out of the picture. Whose, and how many, opinions this would be enough to sway is a different issue, but as NIST stated in its proposal, “The positive impact of this research on public safety will be a practical path towards a method that could be implemented at the roadside to chemically determine recent cannabis use.”


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