As cannabis becomes legalized in an increasing portion of the country, law enforcement agencies are placing highway safety near the top of their priorities list-and it’s been no easy feat so far. In the eighteen states-which is far less than even half of the country-that impose a blood THC limit (in Montana, this limit is 5 ng/mL), blood testing of potentially impaired drivers is frequently criticized. This is because blood testing for THC, the psychoactive compound in cannabis, does not accurately indicate whether a driver was stoned behind the wheel or not. This method of testing only points to recent cannabis use, which could have been days or even weeks prior to the traffic incident.
Numerous startup companies have been working to create a viable breathalyzer-style testing mechanism to detect THC-impaired drivers, but nothing so far introduced has been shown to efficiently work toward that purpose. However, the National Institute of Standards and Technology (or NIST) has announced the recent findings from a study conducted that measures the vapor pressure of THC. The study was published in Forensic Chemistry, and accomplished what few, or even no, others have been able to before.
Measuring the vapor pressure of THC has been notably difficult for researchers in the past because of the size and complexity of the molecule that gets you high. In comparison, detectable alcohol molecules are significantly smaller and pass into the air more easily. This is what makes a breathalyzer so reliable in determining alcohol intoxication.
“Vapor pressure describes how a compound behaves when it transitions from a liquid to a gas. That’s what happens in your lungs when a molecule leaves the blood to be exhaled in your breath. So if you want to accurately measure blood levels based on breath, you need to know the vapor pressure,” stated Tara Lovestead. Lovestead is a NIST chemical engineer and lead author of this study.
There is still no reliable breathalyzer-style detection test for THC consumption, but the findings of Lovestead and her colleagues could be the basis for a solid invention in the near future.
Photo by SharonaGott