A photo of a woman wearing blue gloves holding a small red and yellow object in her hands.
With funding from the Justice Department, Emanuele Alves, Ph.D., an assistant professor in the Department of Forensic Science, is developing a breathalyzer that can differentiate between THC and CBD, leading to fewer false-positive results for THC. (Tom Kojcsich, Enterprise Marketing and Communications)

VCU forensic science professor hopes a better THC breathalyzer will increase road safety

Emanuele Alves, Ph.D., is developing a device that could offer results within minutes and reduce false positives.

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With a goal of increasing road safety, a Virginia Commonwealth University professor is working to develop a faster, more effective breathalyzer for THC, the component of cannabis most associated with its psychoactive effects.

While alcohol breathalyzers offer results within minutes, the THC breathalyzers now on the market have to be sent to a lab for testing, which can take hours. With funding from the Justice Department, a team led by Emanuele Alves, Ph.D., an assistant professor in the Department of Forensic Science at VCU’s College of Humanities and Sciences, hopes to create a device that allows testing in the moment – it would yield results within minutes, and it could differentiate between THC and CBD, leading to fewer false-positive results for THC.

“With this approach, we could reduce the number of accidents caused by impaired drivers, making roads safer for all of us,” Alves said. “When a device like this is public, drivers know that they can be caught using marijuana, and this could act as a deterrent for people considering using marijuana before getting behind the wheel. This is a similar effect to alcohol breathalyzers, which have been shown to deter drunk driving.”

Alves, principal investigator for the “Development of a Colorimetric Breath Analyzer for THC” project, first saw the importance of impairment monitoring systems in her earlier work for a variety of entities and agencies, including the Rio de Janeiro State Police in Brazil. As a forensic toxicologist, she conducted testing to identify drugs, chemicals and toxins to determine their potential effect on an individual’s death, illness or mental or physical impairment.

“I kept thinking about how many lives were lost due to driving under the influence of drugs,” Alves said. “Alcohol was the main reason for many years. I have several projects in my lab at VCU dedicated to opioids – my main research substance group – but it was impossible for me to ignore the increasing presence of marijuana cases. It started to call my attention to, how could we try to make the roads safer?”

Alves and her team began studying current THC detection devices and found that they don’t provide a readout of how much THC is in someone’s system. Instead, they are collection devices that need to be sent to a lab for analysis. That’s when she got to thinking about breathalyzers.

“Breathalyzers are a fast, practical and reliable tool for impairment monitoring on the road,” Alves said.

A photo of a woman and a man wearing lab coats and blue gloves sitting at a table with testing materials.
Emanuele Alves, Ph.D., (right) an assistant professor in the Department of Forensic Science, uses a pipette to demonstrate how her testing device would work, while Wagner Pacheco, Ph.D., (left) a postdoctoral fellow and researcher in her lab, looks on. (Tom Kojcsich, Enterprise Marketing and Communications)

In addition, the legal implications of a THC breathalyzer, especially in cases of drivers caught under the influence, could make a major impact, she said. “Breathalyzer results are admissible in court and could make it easier to prosecute offenders.”

As states, including Virginia, decriminalize and legalize marijuana, “it is imperative to create ways to detect short-time use, especially by drivers,” Alves said.

Alcohol breathalyzers use electrochemical reactions to detect alcohol on the breath when a person exhales. Other researchers are exploring how to use this method to detect cannabis use faster. The challenge, however, is that the electrochemical reaction that occurs in this method isn’t specific to THC. An electrochemical reaction would simply detect the presence of cannabis – it can’t tell whether the substance is CBD or its psychoactive cousin, THC.

“Our idea is to create a colorimetric-based device where the reaction between THC and a specific dye occurs inside the device, leading to the formation of intense color,” Alves said. “Due to the nature of these reactions, the color intensity is directly proportional to the concentration of the substance we’re looking for – in this case, THC.”

With Alves’ test, people who are using CBD, which is legal in many states, wouldn’t blow a false positive for THC like they might with a device that’s based on an alcohol breathalyzer. For the device she envisions, the colorimetric test – similar to those used in some at-home COVID-19 tests – would only change color if THC is present.

Alves is collaborating with Wagner Pacheco, Ph.D., from the Universidade Federal Fluminense in Rio de Janeiro who is currently a postdoctoral fellow and researcher in her laboratory at VCU. They hope to have a prototype in 2025. This project received funding through the Justice Department’s Research and Development in Forensic Sciences for Criminal Justice Purposes program.