Currently, there are no roadside breath tests when marijuana-influenced driving impairment is suspected. Canada recently approved use of a roadside test using saliva, but a sensitive test using breath has yet to be available.

Dr. Tara Lovestead, a research chemical engineer for the National Institute of Standards and Technology in the U.S., described one of the problems with this goal, "Picture cutting a raisin into a trillion parts and trying to detect one of them."

Dr. Lovestead has been working on vapor detection for over 10 years. She expresses concern, because the ingredient in marijuana causing psychoactive impairment, THC, has a much lower vapor pressure than the ethanol in alcohol, which makes it much more challenging to detect.

"Not only is the vapor pressure of THC really low, it is predicted to be approximately 100 million times less than ethanol’s vapor pressure," says Lovestead. "Thus, a breathalyzer designed to detect THC will have to be extremely sensitive, able to capture a needle in a haystack."

Even with the challenges, there are companies working to bring a marijuana breathalyzer to market. One with a talented marketing team that is also frequently discussed in the media is HoundLabs.

This breathalyzer reports to have the ability to measure any form of consumed marijuana, including any in edibles. Further, the technology measures both alcohol and THC.

Several patents have been issued relative to the HoundLab technology. The company had one science abstract in the form of a poster at PittCon 2018. Researchers from Triple Ring Technologies; the University of California, Berkeley; and University of California, San Francisco contributed to the science.

Cannabix Technologies is another breathalyzer under development. Advising the company in the development of the product is Dr. Marilyn Huestis, who has pioneered aspects of detecting marijuana in biologic samples. The company has a relationship with the University of Florida and there are agreements regarding patents and patent applications.

Neither the HoundLab or Cannabix breathalyzers are close to being available for roadside use by law enforcement. But those aren’t the only two companies diligently pursuing the development of a marijuana breathalyzer.

Giner Inc. has received two separate federal grants under the Small Business Innovation Research (SBIR) program. The first was through the National Institutes of Health, and the second from the Department of Transportation.

Both funded projects were considered Phase I in product development, but the breathalyzer has yet to be moved out of the laboratory onto the streets for roadside use. Other companies receiving federal funding under the SBIR program to develop marijuana breathalyzers include N2 Biomedical, LLC and BreviTest Technologies, LLC; funded by the Department of Transportation and National Institutes of Health, respectively.

One group from Washington State University had previously demonstrated efficacy with its prototypes. It had state funding from Washington and had demonstrated that the technology worked.

The group had numerous abstracts, including those at The International Society for Ion Mobility Spectrometry. However, the research has been abandoned due to federal political concerns and funding.

Given barriers to research and limited resources, it is unlikely that law enforcement will have a reliable breathalyzer for the detection of marijuana anytime soon.