An illustration showing a researcher analyzing breath samples in the lab. Credit: NIST With cannabis now outpacing alcohol as Americans’ daily drug of choice, there is a critical need for a scientifically validated breath test to detect the recent use of the substance in drivers.
But developing such a breath test has proved a significant challenge.
Last year, researchers at the National Institute of Standards and Technology (NIST) and the University of Colorado Boulder found that a single breath test may not be reliable in detecting recent cannabis use because cannabis can linger in the body for weeks, making it difficult to distinguish between past and present use.
Now, these researchers are considering a new approach: two breath tests administered within roughly an hour of each other. If their research is successful, it could lead to a roadside test for cannabis use that involves two breath tests given at a specified interval apart.
"This is potentially paradigm-changing," said NIST materials research engineer Kavita Jeerage. "If successful, it could pave the way for on-the-spot detection of recent cannabis use by law enforcement."
Breath tests for alcohol have been around for nearly a century. They detect ethanol, which is exhaled in a gaseous vapor and correlates with the amount of ethanol in the blood.
But tetrahydrocannabinol (THC), the main psychoactive ingredient in cannabis, is present in the breath at a much smaller concentration than ethanol. NIST chemical engineer Tara Lovestead has likened detecting it to "looking for a needle in a haystack."
In addition, the body breaks down and eliminates cannabis much more slowly than ethanol. NIST and University of Colorado researchers have found that the amount of THC in regular cannabis users’ breath on days they don’t smoke can sometimes be similar to the amount an hour after they’ve used cannabis. This makes it challenging to distinguish recent and past cannabis consumption among regular users.
Currently, when police pull over a driver they suspect of cannabis impairment, they typically use a battery of roadside tests such as heel-to-toe walking or repeating a sentence correctly. But field sobriety tests, as they are called, can be imprecise, weren’t designed for […]
Researchers to test new approach for detecting cannabis in breath
