Cannabis might be legal in some countries and some states in the United States, but that does not mean that driving while under the influence of marijuana is legal. In fact, DUIs involving cannabis is illegal in every state.
The problem is that breathalyzers that are used in determining your body’s alcohol levels are not reliable to check the amount of marijuana you have in your body.
Law enforcement is now looking to find devices to test marijuana intoxication. The problem is that THC, which is responsible for the buzz, has a very complex structure. This is especially true when you compare the molecules of ethyl alcohol to that of THC.
Researchers at the National Institute of Standards and Technology, however, may have the answer. They have found a way to measure the vapor pressure of THC, a procedure that has not been done successfully before because of THC’s chemical structure.
NIST researchers explain that vapor pressure is an indicator of how a particular compound behaves as it changes to a gas from its liquid state. Tara Lovestead, who heads the study, further explains that knowing the vapor pressure of a certain compound is a good start in determining the blood levels of a certain chemical on one’s breath.
Urine and blood testing for THC is still one of the most reliable tests for determining THC levels in the body, but this is generally frowned upon by law enforcers because it is a tedious process that is both invasive and impractical.
Not there yet
While knowing the vapor pressure of THC is a good first step, there is still a long way before the government can get a reliable device to measure cannabis intoxication.
For one, Lovestead and her team are not designing one. For another, there is still a lot of research to be done to see just how THC levels are related to blood levels and how they show up in your breath. For another, there are still no standards in place to say how much THC in your blood would make you impaired while driving.
Vapor pressure: Difference between ethyl alcohol and THC
Vapor pressure is an indicator of how much movement a certain molecule makes. Even in its solid state, molecules are in constant motion. Some of these molecules escape into the air.
Ethyl alcohol, because of its simple structure, escapes into the air quite easily. Open a bottle of alcohol and you can probably smell it even if you keep it a safe distance from your nose. THC on the other hand is larger molecules with a complicated structure. The different atoms stick together with redundant connections holding them to others. This is the reason why the vapor pressure of THC is very low and can be quite difficult to measure. Not only that, you would need to wait a considerable amount of time for the measurement to be completed.
What Lovestead and her team did was to use PLOT-cryo, a new technology that is able to capture and analyze things when they turn into vapor. The technology is very sensitive that it can analyze the few molecules that escape from THC.
A good first step
If a working and reliable breathalyzer for measuring cannabis intoxication is still far away from production, why is this study important then? Tom Bruno, an NIST researcher and co-author of Lovestead’s study, explains that “measurements are the basis for standardization.” By measuring vapor pressure accurately, the NIST can come up with standards by which cannabis breathalyzers can be calibrated to make them reliable in catching those who insist on driving even after partaking on marijuana.