Fresh on the heels of a proof-of-concept study that showed sweat can test an individual’s ethanol level, the Halámek Lab at University of Albany has done it again—this time with marijuana use. This research furthers Jan Halámek’s mission to create an easy-to-use, reliable roadside testing kit for law enforcement.

Published in ACS Sensors, Halámek’s latest paper describes a strip that can detect a person’s marijuana use based on a small amount of perspiration that can be taken from fingerprints or any other sweat glands.

Just like the alcohol test strip debuted last month, the marijuana-use strips rely on a color change to visually confirm the presence or absence of tetrahydrocannabinol, or THC, the main psychoactive component in cannabis. The analysis works by using an antibody that quantifies the THC metabolite. Less of a color change indicates a higher amount of THC metabolite present in the sweat sample. While there is a printed legend to verify the color change, Halámek told Forensic a mobile app is currently in development, as well.

In a proof-of-concept test, Halámek and his team of graduate students surveyed eight volunteers on their recent marijuana use. Four were users; four were non-users. The group then provided their fingerprints on a plastic wrap that was cut out and subject to analysis. Results showed a clear difference in observed color change between the two groups.

The test was designed to give a Yes/No answer on the presence of marijuana as the national law is currently zero-tolerance for marijuana use when operating machinery. As recreational marijuana continues to gain approval at the state level, those laws could change. However, Halámek said the test can be modified to be quantitative. Before it gets to that level, there is a lot science still has to figure out. For example, studies have shown that marijuana can be detected in an individual’s body long after the effects of the “high” have worn off. What if the sweat test accurately shows a person used marijuana, but it was the night before and impairment is no longer an issue? Unlike a person’s blood alcohol level, marijuana “levels” are not as straightforward.

Halámek said his lab is already looking in this direction, and is seeking collaborators regarding the pharmacokinetics of THC.

“While drugs are a new topic for the Halámek lab, it is something we plan to continue diving into,” Halámek said. “Much of the fundamentals are the same as our previous research in terms of the collection, extraction, and use of sweat as a biometric.”

Photo: UAlbany forensic chemist Jan Halámek (left) and graduate student researcher Mindy Hair. Credit: Scott Freedman