Federal researchers at the National Institute of Standards and Technology (NIST) say they’ve made the first-ever detection of THC in human breath following the consumption of infused edibles—a possible step forward in terms of field testing for cannabis impairment.
They add that more research is needed, and they point out the “incertitude of breath measurements”, as well as the need for further analysis of the detectability cannabinoids in longer periods of time.
Jennifer Berry said, “This is a significant step forward. We can detect THC in breath increases after ingestion of marijuana,” in a release from the agency about the new results, published in the Journal of Analytical Toxicology this past month.
This project is a joint effort between NIST, University of Colorado Anschutz Medical and three NIST scientists. The report calls it a “proof of concept study.” This project falls under the agency’s larger research on driving and cannabis.
Before and after eating a THC infused edible that the subjects brought themselves, 29 participants’ breath samples were collected. Five milligrams of THC to 100 mg were found in the products, although the report states that the quantities weren’t independently verified.
NIST and University of Colorado Anschutz, with their partners have measured the first tetrahydrocannabinol level (THC), in breath taken from edible marijuana.
Two different collection devices were used, the first described as aerosol and second as condensate. The samples were taken at the time of ingestion as well as three times afterward, approximately 47 minutes later, 92 and 180.
Although participants were told to refrain from eating edible cannabis and inhaling marijuana for at least 8 hours before the study, nearly all samples detected THC prior to the edibles.
The report states that “THC has been detected in the breath samples of 27 out of 29 participants, with levels ranging between a trace (ten participants) and greater than 0.4ng/device”, noting similar findings in previous studies.
Authors wrote that the finding of quantifiable and/or detectable THC in the air before cannabis consumption “shows just how challenging it can be to interpret one THC measurement when there is no baseline information available.”
They added that “the high detection rate for THC after eight hours of abstinence requested” shows the difficulty of detecting recent use with a single measure.
After ingesting the edibles, measured THC levels in the breath of most participants—but not all—rose over time.
According to the study, “of 29 participants who participated in the study, 19 of them showed an increase in THC after eating edibles (at either one or all three time points post-use), while 4 others showed no difference and 6 displayed a decrease in THC after edible use.”
The study points out that the THC level of those people who experienced a drop in THC was also higher before they took the edibles.
Authors asserted that the breath test can be used to detect recent cannabis consumption in those who had THC levels rise or remain stable.
The researchers wrote that “THC levels in the breath of two thirds of participants showed an increased concentration following cannabis consumption.” However, the results of the other one-third did not contradict the idea that cannabis can be detected on the breath regardless of how it was used.
It is notable that the measured THC levels and those of some cannabinoids change similarly. THC levels and CBD did not always correlate.
According to the study, CBD and THC were found in different amounts at times, suggesting that there are differences between biological processes or clearance.
Tara Lovestead is a chemical engineering on the NIST breath research project. She said that the study supports the idea of using multiple breath measurements for a long period to be able to use a breathealyzer in order to detect marijuana use regardless of the way it was ingested.
Scientists added that, “but, devices will still require standards in order to be accurate and used properly, standards which do not exist yet.”
In its press release, NIST states that it is not working on a device to test for cannabis in the breath. NIST is instead responsible for ensuring that the measurements of marijuana in breath are accurate and reliable, with scientifically-sound standards.
We can also analyze the data from breathalyzers to find out the answers we need. Kavita Jeerage is a NIST chemical research engineer and the head of cannabis breath research.
In September, the agency will host a workshop for device manufacturers.
The event was originally scheduled to be held in Boulder, Colorado, in April, but a month ahead of the originally scheduled event, it was abruptly postponed.
NIST sent a draft agenda to MEDCAN24 earlier this year. Topics to be covered include the challenges of designing and developing marijuana breathalyzers, obstacles for prosecutors to handle drugged driving cases, and ways NIST and other organizations could partner in order to advance technology.
The findings of the workshop “Building A Path Forward For Meaningful Cannabis Breathalyzer Reality” will be included in a NIST report, which the agency says it plans to make public.
There is no universally accepted test for determining if someone has been under the influence.
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.”
Jeerage, a NIST employee at the time, said that “a lot more research was needed” to prove that a marijuana breathalyzer could produce useful results. The results of a breathalyzer can be a life-changing event for a person, and they should feel confident that the test is 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.
Frances Scott of the National Institute of Justice Office of Investigative and Forensic Sciences (NIJ), under DOJ said that “states may need to get away from this idea” on a recent podcast.
Scott has questioned whether the “per se”, THC-based limits that have been set by some states for drivers are effective. This allows a driver to be accused of driving under the influence if they exceed the THC limit. It may be impossible to determine impairment caused by THC, as there is with alcohol.
Scott explained that one complication was “if you had chronic users and infrequent users they would have different concentrations which correlate to different effects.” The same level of effect, if that’s what you want to call it, would be associated with very different THC concentrations in blood between chronic users and infrequent users.
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.
THC impairment has been an important topic for legislators and researchers, especially when it comes to 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.
This paper concludes that “the consensus is there is no linear relation between blood THC and driving”, the conclusion. This is surprising, given that blood THC can be used to detect driving while impaired by cannabis.
The majority of states with legal cannabis measure THC intoxication based on whether someone’s THC blood levels fall below a specific cutoff. Findings from the study suggest that blood levels are not a reliable indicator of driving impairment.
Ten of the twelve papers reviewed in this review found that there was no relationship between the blood THC level and driving performance, or other measures. [standard deviation of lateral position (SDLP)]The two papers that did find a significant association were from the same study and found significant relationship with blood THC, SDLP, speed and following distance. Two papers found a significant link between SDLP (serum THC) and blood, as well speed and 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.
According to a congressional report from 2023 for the Transportation, Housing and Urban Development, and Related Agencies Bill (THUD), the House Appropriations Committee continues to “support the development of a standard objective to measure impairment by marijuana and an associated field sobriety to ensure road 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.
This report stated that “Relatively little research has been done to support the relationship between cannabis impairment and crash risk” in several states. This report stated that “there is no research consensus which shows a correlation between cannabis and crash risk.” [blood alcohol content] The drug level in blood is not correlated with impaired driving.”
A Rutgers University professor wrote a commentary earlier this month arguing that the roadside tests used by many police departments in America to determine marijuana impairment are “inadequate.” He urged policymakers to adopt a robust, evidence-based approach to transport safety, while not relying on their ostensible expert knowledge.
The paper, by William J. McNichol of Rutgers University’s Camden School of Law, asserts that current approaches to detecting cannabis impairment “either merely imitate tools used to identify alcohol based impairment without taking into account important differences between the effects of these molecules or they are pseudoscientific ‘police science.'”