Developers are marketing the devices to law enforcement and employers, but experts say they don’t actually prove impairment.
“I can understand how people like to quantify things,” says Peter Grinspoon, a physician at Massachusetts General Hospital and board member at the nonprofit Doctors for Cannabis Regulation. “And I can understand how useful it would be to have a simple machine, a thing like a breathalyzer, that would simply allow law enforcement to say, ‘you’re impaired, you’re not impaired.’ However, it just doesn’t work that way.”
In states like Colorado, if a driver has more than 5 nanograms of THC per milliliter of blood, a court can deduce that they are impaired. There’s just one problem: science doesn’t back that up. “Five nanograms is an arbitrary number,” says Halsor. “It’s what I describe as a political number.”
In a 2013 study, researchers measured blood THC above the 5-nanogram level for days after heavy users stopped smoking. And in a 2014 study comparing frequent and occasional smokers, researchers were shocked to discover that they didn’t detect THC at all in two people who smoked cannabis cigarettes right before their eyes.
Grinspoon, who jokes about being a “second generation” cannabis expert thanks to his doctor father who called for the legalization of cannabis back in the 1970s, has been working on this issue his whole life. Now, decades later, he’s skeptical that there will ever exist a formula to link the amount of THC pumping through your veins with how high you feel.
Read the article at Discover Magazine