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Though people have been worried about a weed breathalyzer since legalization of recreational cannabis hit Colorado and Washington State, the normalization and legalization of recreational cannabis in many states has many agreeing that it might be beneficial for public health. The trick has been producing a breathalyzer that could effectively and fairly measure inebriation. Now through a new breakthrough, scientists isolate THC vapor pressure, and are that much closer to a real cannabis breathalyzer.

Policing has been an issue: specialized training isn’t enough, and officers are relying on impairment signs that lead to their handing out DUIs to people who have never even used cannabis. Stoners have also been getting DUIs due to blood THC levels when they weren’t actually stoned at the time: THC is fat-soluble and stays in the blood for up to two weeks.

It’s time for a more reliable method that can measure THC levels and intoxication at the moment, but startups have been having a difficult time hitting the mark. Saliva tests aren’t accurate enough, and blood and urine tests on the side of the road are both difficult, and in some states, illegal.

However, scientists from National Institute of Standards and Technology (NIST) brought us one step closer to attaining that goal by measuring fundamental properties of tetrahydrocannabinol (THC), specifically the vapor pressure the compound exerts. This had not previously been accomplished due to the complex structure of molecular THC, which is far larger and more complex than ethanol.

The main challenge now is that THC has a far lower vapor pressure than ethanol, meaning it evaporates from the blood into the breath at a much lower rate. Measuring the tiny amounts of THC in the breath will be difficult, but knowing the rate at which it evaporates still brings us much closer to that reality than we have been previously.

Though it will take some time to move forward to a working breathalyzer, knowing the vapor pressure of the compound is the first step to attaining that goal. Having a reliable way to test cannabis inebriation, beyond evening the playing field in how different states determine if someone is too stoned to drive, also brings cannabis closer to the kind of legitimacy alcohol enjoys. Though no one likes the idea of getting a DUI for being high, a breathalyzer will make that process safer and fairer in the long run.