Marijuana Breathalyzers May Be a Pipe Dream

Scientists have been working around the clock to develop a device that can detect the level of impairment resulting from marijuana intoxication. The explosion of marijuana decriminalization across the country has given a new urgency to the endeavor. We’ve been told we’re right on the cusp of a breakthrough; that at any moment now, the pot breathalyzer will be here. But a new study sheds doubt on that prospect, outlining the many challenges facing the science going forward. And in short, it's not looking good. 

The paper was recently published in Trends in Molecular Science. As the researchers note, the problem isn’t determining how much tetrahydrocannabinol (THC) is in the system, but in how it’s affecting the individual.

There are a number of factors that determine how marijuana intoxication will affect a person. These include how they consumed the cannabis, how often they typically consume cannabis, body fat, and good old genetics. Whereas alcohol leaves the bloodstream quickly, traces of THC can linger in the tissues for weeks or months. And yet the bulk of it is also eliminated from the body far more quickly than alcohol, giving law enforcement a short window to get the most accurate reading possible.

“By the time you get to the station to get your blood taken, there may not be much THC left to find,” writes Wired’s Matt Simon. And yet you could be totally stoned. Because brain is a fatty tissue, that’s where THC tends to hang out. “That’s why the effects of marijuana can last longer than THC is detectable in breath or blood.”

The reverse can also be true. Someone with ample body fat may be showing elevated levels of THC despite little or no impairment.

Hounds Labs in Oakland insists its breathalyzer will be the answer to law enforcement’s prayers. But if all its product does is provide a numerical reading, it could leave cops us with more questions than answers.

It's possible we'll have self-driving cars before we get a reliable device to spot marijuana DUIs. 

Read more about the shaky science behind marijuana intoxication testing at Live Science