High On The Highway: Scientists Try To Build A Marijuana Breathalyzer

A quartet of Western states and the District of Columbia have legalized recreational marijuana, and voters in half a dozen more states may vote on pot legalization in 2016. That’s leading law enforcement officials and entrepreneurs to try to come up with better ways of testing for driving while stoned.

Police usually spot impaired drivers by noting driving behavior, coordination, mannerisms and physical cues. But while a handheld breath test can quickly determine whether someone is legally drunk based on ethanol in the breath, there’s no instant test for marijuana intoxication.

In Washington state, which is one of 18 states that has set limits on marijuana intoxication while driving, law enforcement can seek a warrant for a blood draw to test for THC, the main active ingredient in marijuana. But it can take weeks for results to come back from the toxicology lab.

With more Washington state drivers being arrested with marijuana in their systems since the state legalized recreational marijuana, there’s growing need for a fast way to identify impaired drivers and get them off the road.

Herb Hill, a chemistry professor at Washington State University in Pullman, Wash., heard about the challenges of nailing drug-impaired drivers from a colleague who was a political science professor. “I said, ‘Why don’t we have a Breathalyzer for that?’ He said none exists,” Hill said. “I said, “We can probably make one.’ ”

So Hill and his colleagues are trying to develop a hand-held device that police officers can use to detect THC in breath. Preliminary field testing with 30 human subjects this spring established that the device can detect THC in breath, Hill said. Much more testing is ahead to look at potential variations among gender, race, body types and amount of use.

Hill’s team recruits volunteers who buy their own weed, smoke it at their homes and then blow into the prototype.

“We had to go through institutional board review,” Hill said, referring to federal restrictions on research involving marijuana. “It took us almost a year to get permission to do this.”

“It wasn’t very hard to find the volunteers,” Hill added. “We have a waiting list of volunteers.”

The human guinea pigs get paid just over minimum wage to smoke their pot.

Hill said the portable device may look like an alcohol Breathalyzer, but works differently inside. His team is modifying existing sniffers used at airports to detect explosives and by the military to alert to the presence of chemical warfare agents. The technology is called ion mobility spectrometry.

“In the beginning at least this would not be used as evidential information,” Hill explained. “It would be used as screening information to help the officer say he should take a blood sample now.”

Jake Yancey, a police officer in Tumwater, Wash., said he would be “super excited” to get a detector that he hopes could “drastically speed up” the process of confirming or ruling out a person’s possible marijuana impairment. But a pot breath test must prove itself highly accurate before Washington state would adopt it, according to Lt. Rob Sharpe, head of the impaired driving section at the Washington State Patrol.

“Even if it is a preliminary device, we still need that level of accuracy and reliability for trust and confidence,” Sharpe said. “Regardless where it comes into play in that arrest decision, we’re talking about people’s rights, their liberties and freedoms. We need to be accurate.”

All of which points to it being several years at the earliest before you’d see a roadside breath test to identify stoned drivers.

Sharpe said a pot breath test might not even be the chosen answer. He said other companies and research teams are working on alternatives, including cheek swabs or a saliva test, a smartphone-based eye scan or analyzing sweat on a person’s skin.

Since legalizing marijuana use for adults, Washington and Colorado have both set legal limits for THC intoxication at five nanograms per milliliter of blood. Oregon and Alaska have not established a legal THC limit beyond which a driver is presumed to be impaired.

Some marijuana activists have expressed fears this technology could lead to unimpaired drivers getting unfairly arrested. They point out that THC persists in the body long after the high has worn off. The effects of weed are also different in different people, including between infrequent versus chronic smokers.

Indeed, there is no universal agreement on how much THC is impairing, with countries in Europe setting legal limits at 2 to 7 nanograms.

As part of the next rounds of human testing of the marijuana breath tester, the Washington State researchers want to correlate breath readings of THC with simultaneous blood draws and measurements. This could help to establish how long THC lingers in the breath after initial consumption.

Early on, the WSU professors took their idea to Chemring, a Falls Church, Va., instrument maker that agreed to pay for the R&D and will have the commercialization rights.

The Chemring-WSU team is by no means alone in trying to perfect a marijuana breath test. Competitors include Lifeloc Technologies of Colorado, which already makes alcohol testers, and Cannabix Technologies Inc. of Vancouver, Canada, has shown off an initial prototype at conferences. There are reportedly several research teams at work in Europe as well.

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