A federal agency this spring will convene government officials, forensics experts, academics, industry representatives, law enforcement and standards organizations for what it describes as “an open and candid discussion” about “the path forward to realize meaningful cannabis breathalyzer technology and implementation.”
The two-day event, hosted by the National Institute of Standards and Technology (NIST), which is part of the U.S. Department of Commerce, is scheduled to be held in Boulder, Colorado, on April 16 and 17.
According to a preliminary agenda sent to Marijuana Moment by a NIST representative, topics to be discussed will include challenges facing marijuana breathalyzer design and development, obstacles to prosecutors handling drugged-driving cases and how NIST and others might partner to advance the technology.
Findings of the workshop, “Building a Path Forward for Meaningful Cannabis Breathalyzer Realization,” are set to be compiled into a NIST internal report that the agency has said will be publicly available.
Further information about the event is forthcoming, the NIST representative said.
Unlike with alcohol, there’s currently no widely accepted field test to determine whether someone is under the influence of marijuana.
In 2023, a federally funded report by researchers at NIST and the University of Colorado Boulder concluded that evidence does “not support the idea that detecting THC in breath as a single measurement could reliably indicate recent cannabis use.”
“A lot more research is needed to show that a cannabis breathalyzer can produce useful results,” Kavita Jeerage, a NIST materials research engineer and co-author of the report, said at the time. “A breathalyzer test can have a huge impact on a person’s life, so people should have confidence that the results are accurate.”
More recently, a U.S. Department of Justice researcher cast doubt on whether a person’s THC levels are even a reliable indicator of impairment.
States may need to “get away from that idea,” Frances Scott, a physical scientist at the National Institute of Justice (NIJ) Office of Investigative and Forensic Sciences under DOJ, said on a podcast early last year.
Scott questioned the efficacy of setting “per se” THC limits for driving that some states have enacted, making it so a person can be charged with driving while impaired based on the concentration of cannabis components in their system. Ultimately, there may not be a way to assess impairment from THC like we do for alcohol, she said.
One complication is that “if you have chronic users versus infrequent users, they have very different concentrations correlated to different effects,” Scott said. “So the same effect level, if you will, will be correlated with a very different concentration of THC in the blood of a chronic user versus an infrequent user.”
That issue was also examined in a federally funded study last year that identified two different methods of more accurately testing for recent THC use that accounts for the fact that metabolites of the cannabinoid can stay present in a person’s system for weeks or months after consumption.
The THC impairment question has nevertheless been a major focus for lawmakers and the research community, particularly as it concerns driving laws.
Last October, a study preprint posted on The Lancet by an eight-author team representing Canada’s Centre for Addiction and Mental Health, Health Canada and Thomas Jefferson University in Philadelphia identified and assessed a dozen peer-reviewed studies measuring “the strength of the linear relationship between driving outcomes and blood THC” published through September 2023.
“The consensus is that there is no linear relationship of blood THC to driving,” the paper concluded. “This is surprising given that blood THC is used to detect cannabis-impaired driving.”
Most states where cannabis is legal measure THC intoxication by whether or not someone’s blood THC levels are below a certain cutoff. The study’s findings suggest that relying on blood levels alone may not accurately reflect whether someone’s driving is impaired.
“Of the 12 papers included in the present review,” authors wrote, “ten found no correlation between blood THC and any measure of driving, including [standard deviation of lateral position (SDLP)], speed, car following, reaction time, or overall driving performance. The two papers that did find a significant association were from the same study and found significant relationship with blood THC and SDLP, speed and following distance.”
Earlier last year, researchers behind a federally funded study said they’d developed new procedures to enhance the selectivity of a popular forensic testing method, allowing better detection of delta-9 THC and its metabolites in blood.
A 2023 congressional report for a Transportation, Housing and Urban Development, and Related Agencies (THUD) bill said that the House Appropriations Committee “continues to support the development of an objective standard to measure marijuana impairment and a related field sobriety test to ensure highway safety.”
A year earlier Sen. John Hickenlooper (D) of Colorado sent a letter to the Department of Transportation (DOT) seeking an update on that status of a federal report into research barriers that are inhibiting the development of a standardized test for marijuana impairment on the roads. The department was required to complete the report under a large-scale infrastructure bill that President Joe Biden signed, but it missed its reporting deadline.
A study published in 2019 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.
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 study from 2022 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.
Evan as far back as 2015, a U.S. National Highway Traffic Safety Administration (NHTSA) concluded that it’s “difficult to establish a relationship between a person’s THC blood or plasma concentration and performance impairing effects,” adding that “it is inadvisable to try and predict effects based on blood THC concentrations alone.”
In a separate report last year, NHTSA said there’s “relatively little research” backing the idea that THC concentration in the blood can be used to determine impairment, again calling into question laws in several states that set “per se” limits for cannabinoid metabolites.
“Several states have determined legal per se definitions of cannabis impairment, but relatively little research supports their relationship to crash risk,” that report said. “Unlike the research consensus that establishes a clear correlation between [blood alcohol content] and crash risk, drug concentration in blood does not correlate to driving impairment.”
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Photo courtesy of Mike Latimer.
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