A literature review published this month in the Journal of the Association of Official Analytical Chemists found the detection of THC or its metabolites in the blood, breath, urine, or saliva of a driver is not an indicator of driving impairment.
Scientists affiliated with the University of California at Davis also stated, similarly to other recent studies, that current methods used to detect impairment caused by cannabis consumption often indicate only the use of it, not a reduction in the driver’s ability to operate a motor vehicle.
Evidence produced in other studies has shown current detection methods produce inaccurate results. Researchers say these methods can’t distinguish between impairment and use due to the impairment window being much shorter than the amount of time cannabis can be detected in the body. Researchers believe a new approach is now necessary.
“The complex nature of cannabinoid pharmacokinetics and pharmacodynamics calls for a new approach for effectively determining recent use of cannabis within the impairment window, which cannot be established using currently available testing methods.”, wrote the author.
The study states that traffic laws adopted in some US states which criminalise drivers who test positive for trace levels of THC in their blood, (similar to those used in the UK) are “not supported by science,” and that they risk “wrongly accusing” motorists who are neither impaired nor have recently consumed cannabis.
Current methods of detection, used by law enforcement and judicial systems around the world, include mouth swabs used to detect THC in saliva, blood tests, urine analyses, and breath tests similar to those used to detect alcohol.
Researchers have developed a new method that tests kinetic changes and specific cannabinoids to more accurately determine impairment while ruling out use outside of the impairment window.
“A new testing approach has been developed based on exhaled breath and blood sampling that incorporates kinetic changes and the presence of key cannabinoids to detect recent cannabis use within the impairment window without the false-positive results seen with other methods,” the study said.
The use of more accurate methods of detection should instil a level of confidence that both authorities and the public can rely on to ensure only those who have used cannabis to a level that impairs their ability to drive are subject to the harsh penalties often handed down by courts to drivers found guilty of such offence.
“The complexity of using analytics to determine recent cannabis use and potential impairment demands a comprehensive testing approach that includes all known isomers of THC, synthetic cannabinoids, and commonly abused psychoactive drugs, both illegal and prescription, in order to ensure that suspected cases of cannabis-induced impairment are actually due to cannabis use and that test subjects used recently enough to be impaired, i.e., within the impairment window. Currently established modes of testing based on single measurements of Δ9-THC and/or its metabolites in urine, blood, oral fluid, and hair have proven to be inadequate for this purpose, basically leading to “best guess” assumptions regarding cannabis use and potential impairment.”
“A new comprehensive testing approach that involves multiple matrixes, that determines the presence of and pharmacologic changes in key compounds over time between samples, that can distinguish between the various THC isomers and analogs, and that simultaneously tests for other common psychoactive substances is needed to accurately detect recent cannabis use within the impairment window without the false-positive results seen with other methods.”
“The complexity of assessing potential cannabis impairment demands such a method so that irresponsible users can be accurately detected without falsely accusing responsible users who may unjustly suffer harsh, life-changing consequences such as lost jobs, lost livelihoods, and incarceration.”
