The federal government will spend more than $1.4 million to study how the concentration of marijuana compounds in people’s breath changes over time after consuming it, part of an ongoing effort to create a reliable roadside test to screen drivers for recent cannabis use.
In a brief “sources sought” notice posted last week, the National Institute of Science and Technology (NIST), a nonregulatory agency of the U.S. government, said it’s looking for an vendor capable of helping to conduct a study that would collect breath and blood samples, then test those samples for evidence of acute cannabis use—things like delta-9 THC, other cannabinoids and their metabolites.
“NIST intends to seek a contractor that will recruit participants to the study, collect breath samples from them after they use their own legal-market marijuana, and send those samples to NIST for laboratory analysis,” Richard Press, the agency’s acting director of media relations, told Marijuana Moment in an email. “The sources sought notice is to inform potential vendors of the requirements.”
Despite numerous efforts in the past decade to design and manufacture a device that works like a breathalyzer does for alcohol, there still exists no broadly accepted method to detect acute cannabis use in the field.
“As cannabis/marijuana use is legalized across the country, and knowing that its use can impair executive functions needed for driving, the need for a roadside technology to detect impairment from marijuana in drivers is critical.”
The upcoming study, dubbed Breath Measurements of Acute Cannabis Elimination, or BACE, “will look at how the concentration of cannabis compounds on a person’s breath changes in the hours after using marijuana,” Press said. “The study will not measure impairment, just concentrations of compounds in breath.”
The notice says the study will entail taking both baseline and experimental samples from subjects, both before and periodically after consuming cannabis. The measurements are aimed to account for the fact that cannabis users sometimes retain THC in their breath even after periods of abstinence.
“To resolve the challenges of determining recent cannabis use from a single breath sample, we propose a paradigm shift: two breath samples spaced a short interval apart,” says the project’s funding description. “Recent cannabis use would be distinguished from abstinence by a slope consistent with acute cannabis elimination.”
NIST will use the data “to investigate the feasibility of a two-point measurement that could be implemented at the roadside,” the funding description says. “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.”
The description adds that “currently, 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.”
“We propose to collect breath samples from occasional and frequent cannabis users at 10-minute intervals during acute cannabis elimination, similar to the previous work, and during periods of abstinence, which has not been examined. The proposed paradigm shift depends on consistency in the collection of breath samples, therefore numerical modeling will characterize the influence of human (e.g. flowrate and volume) and device factors to improve the reproducibility of aerosol particle collection. We will analyze breath samples for Δ9THC, its metabolites, and other cannabinoids with high sensitivity analytical methods. We will employ urine analysis to classify users into occasional and frequent use populations and blood analysis to verify compliance with study protocols. Comprehensive statistical analyses will compare elimination profiles and abstinence profiles with different intervals (e.g., 10 minutes vs. 20 minutes) and will examine the multivariate response.”
A federal grant of $1.45 million will pay for the research. That money was approved as part of a part of a $14.4 million forensic-science spending package announced late last year.
Elected officials on the U.S. House Appropriations Committee said in June that they remain concerned about people driving under the influence of substances. They urged regulators to continue “efforts to ensure stakeholders can identify drug-impaired driving and enforce the law.”
In May, U.S. Rep. Earl Blumenauer (D-OR) urged the Department of Transportation to reform its cannabis testing policies in light of the difficulty of determining recent use. He cited agency data showing that tens of thousands of truckers and other commercial drivers are penalized for using cannabis and noted that there’s no way to tell whether that use was days or weeks ahead of when they were tested.
The congressman told Transportation Secretary Pete Buttigieg that his department “should rapidly reform requirements for testing drivers and returning them to service, as well as develop an accurate test for impairment.”
Data on highway safety and cannabis legalization is highly contentious, in large part because of the difficulty of accurately measuring the amount of cannabis in a person’s system as well as its impact on driving ability.
A study published in 2019, for example, concluded that those who drive at the legal THC limit—which is typically between two to five nanograms of THC per milliliter of blood—were not statistically more likely to be involved in an accident compared to people who haven’t used marijuana. But other studies have indicated possible increases in highway road deaths following adult-use legalization.
Yet other research has suggested that impaired driving actually goes down after legalization, at least according to self-reported surveys. A report published in April by the research nonprofit RTI International found that people were less likely to drive within three hours of consuming cannabis in states where some form of cannabis was legal.
Another study this year found that auto-insurance premiums decreased in states that legalized medical marijuana.
President Joe Biden, meanwhile, signed a large-scale infrastructure bill late last year that included an amendment encouraging states that have enacted legalization laws—and only those states—to educate people about impaired driving. That measure was criticized by advocates who similarly want to discourage driving under the influence of cannabis but who also feel that any public education campaigns on the issue should be holistic, rather than singling out states that have legalized.
Officials have sometimes struggled to message their concerns about impaired driving. Last year the National Highway Traffic Safety Administration (NHTSA) put out a PSA that featured a confusingly cool-looking cheetah smoking a joint while driving in what critics called a questionable effort to deter such activity.
In 2020, NHTSA and the Ad Council teamed up with Vox Creative for another ad that essentially told consumers that they shouldn’t drive while impaired—even if they’re being chased by a psychopathic axe murderer.
Experts and advocates have emphasized that evidence isn’t clear on the relationship between THC concentrations in blood and impairment.
Separately, the Congressional Research Service in 2019 determined that while “marijuana consumption can affect a person’s response times and motor performance…studies of the impact of marijuana consumption on a driver’s risk of being involved in a crash have produced conflicting results, with some studies finding little or no increased risk of a crash from marijuana usage.”
Another recent study found that smoking CBD-rich marijuana had “no significant impact” on driving ability, despite the fact that all study participants exceeded the per se limit for THC in their blood.
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