Marijuana Breathalyzer: A DUI Game Changer

As legalization of recreational and medical marijuana continues to expand throughout the U.S., so has the concern of high drivers taking to the roadways and endangering lives. Despite the fact that recreational use of marijuana is now legal in 11 states and the majority of the nation has at least decriminalized the drug, driving under the influence of cannabis remains outlawed in all 50 states – even if it’s prescribed.

While the National Highway Traffic Safety Administration reports that marijuana-impaired drivers are sometimes able to “pull themselves together” to concentrate briefly on simple tasks, driving high is by no means safe. Similar to driving under the influence of alcohol, marijuana impairs cognitive function and decision-making, putting both the driver and other patrons on the road at risk. However, unlike a breathalyzer used to detect levels of alcohol, police do not have a device that can be used in the field to determine if a driver is under the influence of marijuana. Police largely rely on field sobriety tests developed to fight drunk driving or simply observation, which leaves room for error.

Some common signs that police look out for that may indicate a driver is under the influence of marijuana are as follows:

The odor of marijuana in a car

Slurred speech

Glassy eyes

Blood shot eyes

Slow motor skills

Impaired cognitive function

Driving too slowly

Erratic driving or weaving

Police also rely on drug testing methods that examine blood, saliva, or urine; however, these can take days to yield a result. More importantly, these tests additionally can’t really tell whether a person has smoked half hour ago or eight days ago.

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Because there is no accurate and immediate measurable tool for marijuana levels, police and public health officials have been left frustrated on how to handle cannabis DUIs – until now. A team of researchers from the Department of Chemistry at the University of Pittsburgh and the Swanson School of Engineering recently developed a breathalyzer device that measures the amount of tetrahydrocannabinol (THC), the psychoactive compound in marijuana, in a user’s breath.

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How the Breathalyzer Works

The University of Pittsburgh research team developed the breathalyzer by using carbon nanotubes, tiny tubes of carbon 100,000 times smaller than a human hair. The THC molecule, along with other molecules in the breath, bind to the surface of the nanotubes and change their electrical properties. The speed at which the electrical currents recover then signals to the user whether THC is present. Nanotechnology sensors can detect THC at levels comparable to or better than mass spectrometry, which is considered to be the gold standard for THC detection by professionals.

“The semiconductor carbon nanotubes that we are using weren’t available even a few years ago,” says Sean Hwang, lead author on the paper and a doctoral candidate in chemistry at the University of Pittsburgh. “We used machine learning to ‘teach’ the breathalyzer to recognize the presence of THC based on the electrical currents recovery time, even when there are other substances, like alcohol, present in the breath.”

Hwang works in the Star Lab, led by Alexander Star, PhD, professor of chemistry with a secondary appointment in bioengineering. The group partnered with Ervin Sejdic, PhD, associate professor of electrical and computer engineering at the Swanson School of Engineering, to develop the prototype.

Creating a prototype that would work in the field was a crucial step in making this technology applicable. It took a cross-disciplinary team to turn this idea into a usable device that’s vital for keeping the roads safe. - Dr. Ervin Sejdic, Associate Professor of Electrical and Computer Engineering at the Swanson School of Engineering

The prototype looks similar to that of a hand-held alcohol breathalyzer, complete with a plastic casing, mouthpiece, and digital display. During trial runs in the lab, the breathalyzer was able to detect the THC in a breath sample that also contained components like carbon dioxide, water, ethanol, methanol, and acetone. Researchers hope that with a little more testing, the prototype will soon move to manufacturing and be available for use.

Although the breathalyzer is a true game changer for police and public health officials alike, there may still be issues on charging and convicting an individual with a marijuana DUI. There is currently no accepted standard or quantifiable number for cannabis THC impairment. Many in the industry, as well as consumers, would like to see more states settle on a science-based cut-off limit for THC impairment.

Researchers at the University of Pittsburgh agree that there needs to be a quantifiable measure of what levels of THC would amount to a DUI, but hope that the creation and implementation of their device will reduce the number of people driving under the influence of marijuana and help keep the roadways safe in the meantime.