Federal Scientists Detect THC in Human Breath After Edible Use for First Time
WASHINGTON, D.C. — In a breakthrough for cannabis research, federal scientists have, for the first time, successfully detected tetrahydrocannabinol (THC)—the psychoactive compound in marijuana—in human breath after the consumption of edible cannabis products. This milestone, achieved by the National Institute of Standards and Technology (NIST), opens the door for future roadside breathalyzer-style tests for cannabis use. But scientists caution: we’re not there yet.
“This is an important step forward,” said Jennifer Berry, lead author of the study and a research chemist at NIST. “We can now detect THC increases in breath after cannabis is ingested, but interpreting those results remains a major scientific challenge.”
The findings were published this month in the Journal of Analytical Toxicology, positioning them as a proof-of-concept in the growing field of cannabis impairment research—especially as more states legalize recreational marijuana use.
The Study: THC in Breath After Edibles
Researchers collected breath samples from 29 volunteers before and after they consumed cannabis-infused edibles. Participants brought their own products, which varied widely in THC content (5 mg to 100 mg), though the potency was not independently verified.
Samples were taken at three time intervals—around 47, 92, and 180 minutes after ingestion—using two types of breath collection devices. Despite instructions to abstain from cannabis for at least 8–12 hours before the study, THC was already detectable in 27 of the 29 participants before the test even began.
That’s a key complication: “Residual THC” makes it hard to determine whether someone is currently impaired or just a regular user.
Mixed Signals: What the Breath Data Revealed
Post-edible breath samples showed:
- 19 participants had a significant increase in THC levels.
- 4 participants showed no change.
- 6 participants had a decrease in THC levels—though these individuals started with the highest pre-edible THC levels.
In about two-thirds of the cases, breath THC concentrations rose after ingestion. Researchers said this supports the idea that recent cannabis use can, in theory, be detected via breath.
But the inconsistent patterns—such as high THC levels before consumption and some users showing decreased levels afterward—underscore how difficult it is to pinpoint impairment based on a single breath measurement.
Not Just THC: Cannabinoids Behave Differently
Interestingly, other cannabinoids tracked differently. Cannabinol (CBN) and cannabigerol (CBG) mostly followed THC trends, while cannabidiol (CBD) levels did not always align—hinting at differences in how the body processes these compounds.
The Road Ahead: No Breathalyzer Yet
Tara Lovestead, a chemical engineer on the project, emphasized that more research is needed before breath tests can be reliable tools for law enforcement.
“Multiple breath measurements over time may be the key,” she said. “But we still lack the standards and calibration protocols to make these devices accurate.”
NIST clarified that it is not building a cannabis breathalyzer. Instead, its role is to ensure scientific rigor behind future detection methods, so that any future devices are based on solid data—not guesswork.
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