The development of marijuana breathalyzers is making new advances. An investigation partially funded by the Justice Department has shown a possible pathway to create a low-cost, “portable” device, similar in appearance to an asthmatic inhaler. It’s made from 3-D printed plastic and can detect delta-9THC without secondary analysis.
Emanuele Alveses, a professor at Virginia Commonwealth University in Virginia (VCU), led the study that detailed results from experiments to fill the gap left by the lack of roadside tests for THC. These are similar to the ones used by police to test people who may be driving while under the influence. The study says that as more states begin to legalize cannabis, “there is a need for quick, accurate and inexpensive roadside tools.”
Colorimetric experiments using 3D printed cartridges and “Fast Blue” dye with gelatin established “foundational information” that this device could be used to “detect delta-9-THC, CBD, CBN across multiple matrix systems.”
This tool could detect cannabinoids in concentrations between 10-100nanograms, and differentiate them using color-space models. In particular, tests found “two main clusters,” and that CBN and delta-9 THC analytes could be distinguished by color from CBD analytes.
This study states: “Overall this project provided foundational information supporting the feasibility for a low-cost portable tool to detect cannabinoids by using 3D-printed carts and readily available reagents,” it says. While further field testing and validation is needed, the findings of this study provide an initial proof-of concept framework for future roadside- or point-of collection-testing technologies.
According to the Office of Justice Programs, which funded the study last month and released the results, “the author’s conclusions do not necessarily reflect official positions or policies of the Agency.”
VCU’s Alves stated that the development of breathalyzers for early detection of recent marijuana use was an important issue, given the legal status of marijuana products in the United States. To achieve this goal our first approach was to create a portable cartridge which would react selectively with cannabinoids to detect THC but not CBD.
The majority of THC breathalyzers are collection devices, which will be subject to further analysis in the laboratory. According to the same system as an alcohol breathalyzer using a THC breathalyzer could be dangerous, since it is not selective and would result in a positive test for any cannabinoids.
A patent application with a proposal design for a potential prototype has been submitted to the U.S. Patent and Trademark Office.
The device has three major components, according to the author. It looks like an inhaler for asthmatics. It has a mouthpiece that collects exhaled oxygen, an instrument with a cartridge at the other end in which delta-9 THC is “collided and then reacted” as well as a detector system.
The study concluded that “the consequences and legal sanctions for driving while under the influence of alcohol (DUI), are widely publicized.” What the public does not realize is that DUI with marijuana in conjunction or without other drugs, can be illegal.
This lack of awareness by the population, following the legalization in some parts of America of marijuana consumption has resulted in an increased risk of car accidents and fatalities caused due to drivers who are intoxicated. It is important to improve the current detection methods for marijuana because they are difficult to use and expensive. This will increase public awareness and safety.
“The outcome of this project is the fundamental chemical foundation and the initial prototype for the development of a ∆9-THC breathalyzer,” the author said. “The device developed in this project is a portable tool to increase safety on the roads and for ∆9-THC use monitoring.”
Other federal agencies have recognized the importance of THC detection technologies. The National Institute of Standards and Technology, under the U.S. Department of Commerce, organized a workshop last year to promote “an honest and open discussion” on the creation and implementation of devices that test the breath of an individual for marijuana intoxication.
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.”
In 2024, however, a DOJ researcher cast doubts on the reliability of THC as a measure of impairment. He said that states might need to “get rid” from this idea.
Scott questioned how effective it was to set “per se,” THC driving limits, as some states had done. A person could be charged for driving impaired by the amount of cannabis in their bloodstream. It may be impossible to determine impairment caused by THC, as there is with alcohol.
Scott said that there is a complication: “If you compare chronic and infrequent marijuana users, their THC levels are very different.” Scott also noted the fact that different doses correlate with 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 in 2024 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.
Researchers behind an federally-funded study also said that they had developed new methods to improve the selectivity and accuracy of popular forensic tests, which allowed better detection of delta-9THC in blood.
In a 2023 report on a Transportation, Housing and Urban Development, and Related Agencies bill, the House Appropriations Committee stated that it “continues support development of an object standard to measure cannabis impairment and related field sobriety tests to ensure highway security.”
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 (CRS) 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.
According to a different report published last year by the U.S. National Highway Traffic Safety Administration, there was “relatively less research” supporting the claim that the THC level in the blood could be used as a measure of impairment. It also called into question the laws that are in place in some states, which set limits “per se”, for cannabinoid-metabolite levels.
This report stated that “Several States have defined legal definitions for cannabis impairment per se, but there is relatively little evidence to support their relation with crash risk.” This report stated that “Unlike research consensus which shows a correlation between [blood alcohol content] “Drug concentrations in the blood do not directly correlate with driving impairment.”
Last year, at congressional hearings, members of Congress heard also from trucking representatives who called on the use of more hair-follicle test in their industry. The National Transportation Safety Board chair, meanwhile recommended that drivers receive better training.
“At time when conversations lean towards the potential reclassification of marijuana from a Schedule I to Schedule III narcotic, demonstrating that this problem is likely to only grow,” said a representative for Truckload Carriers Association, “our industry in its entirety is unable to properly employ the proper test to identify habitual users and enter them into a substance abuse program and begin the return-of-duty procedures.”
The transportation industry also advised Congress in January that if marijuana is federally rescheduled, businesses want assurances that they won’t have to forgo zero-tolerance drug policies for drivers—while stressing that a key problem for the sector is a lack of technology to detect impaired driving.
The issue of marijuana-impaired driving also arose at another recent congressional hearing, with a representative of the Governors Highway Safety Association emphasizing the importance of roadside drug testing as a tool to help combat deadly car crashes.
Last year, meanwhile, the U.S. Supreme Court ruled in favor of a trucker who sued a cannabis company after he was fired over a positive THC test that he said was caused by consuming a hemp-derived CBD product.
Separately, a Substance Abuse and Mental Health Services Administration (SAMHSA) official recently downplayed criticism from the CEO of a drug-testing company that more widespread use of saliva-based drug testing “means truckers who use cannabis will be able to do so with near impunity, as long as they avoid a drug test for a couple of days.”
Unidentified SAMHSA officials responded: “When a donation receives a call for collection, they won’t know until they get to the facility where the federal agency collects samples if it will be oral fluid or urine.” In other words, not knowing if a urine or saliva test is expected would stop drivers from stopping their marijuana use just a few weeks before the test.