THC breathalyzer science is complicated because vapor pressure after marijuana consumption is different than alcohol. Scientists also have to take into account that just because a breathalyzer is indicating that there is THC in a person’s system, that does not necessarily mean that they are not sober at that moment. A breathalyzer that could effectively determine insobriety in drivers, heavy machinery workers or any sensitive profession that requires the worker to have all of their faculties working for them, would be very helpful.
A report out of Michigan recently suggested that employers were overlooking failed drug tests or were not bothering to test at all because they would have to turn away too many people that would leave them deficient for their necessary workforce. If technology and science could create an easy and fast way to determine an employee’s sobriety at the moment they come into work, this is a potential solution that allows medical patients or recreational users of marijuana to ingest THC when not at work, which is likely to have them test positive on most drug tests that are currently in use, but become sober before they come to work. Would you argue that sobriety while working for an employer is important?
Federal researchers at a Colorado lab of the National Institute of Standards and Technology (NIST) have figured out how to measure the vapor pressure of THC, one of the main psychoactive chemicals in cannabis. The discovery means law enforcement officers could someday test for cannabis impairment based on a person’s breath.
The traditional tests for cannabis use — blood draws and urine samples — do an adequate job of detecting the past THC usage. But they aren’t very good at figuring out whether someone is currently impaired by THC. Some states, like Washington, allow police officers to test drivers for a cannabis-related DUI by drawing their blood. But traces of THC can stay in the bloodstream of regular consumers for up to seven days, according to the National Organization for the Reform of Marijuana Laws.
Employers have run into a similar dilemma. Out of fear of workplace accidents, rejected insurance claims and lawsuits, many businesses in legal states continue to screen their employees for marijuana use. But testing positive for THC isn’t the same as being impaired; conflating the two raises privacy questions. So long as nurses and forklift operators shows up to work sober, should their employers have a say over what they do in their free time?
“The quest for a reliable means to detect cannabis intoxication with a breathalyzer is ongoing,” the researchers, Tara Lovestead and Thomas Bruno, wrote. “Breath sampling is attractive because it is non-invasive, can be portable, and has been shown to indicate recent use within [thirty minutes to two hours].”
When asked why they decided to study THC molecules, Lovestead told Leafly, “Well, I’m in Colorado.” She’s been working on this project for about three years. The idea was initially inspired by the state’s legalization of marijuana use, in 2012. After getting approval from the DEA — a process that took about nine months — Lovestead got to work.
To explain the science, she gave the example of a closed, partially finished liquor bottle. Some of the ethanol is in liquid form. There’s also gaseous ethanol molecules trapped in the enclosed air space above.
If you know how much pressure is produced by ethanol vapor, you can figure out how much ethanol is left in the bottle based on properties of those gases. The same logic applies for THC leaving a human body in exhaled breath. This chemistry can be used to create an ethanol breathalyzer. But scientists have previously struggled to figure out the vapor pressure of THC, which is a relatively complex molecule.