Washington State University researchers are working to develop a roadside test that would detect marijuana in a person’s breath.
Studies began last month on a prototype that tests breath for THC, the chemical responsible for most of marijuana’s psychological effects.
Public interest in the research is high, though “we have a long way to go before we have a dependable test for THC,” said Herbert Hill, a WSU chemistry professor, who spoke at a medicinal plants conference last week in Spokane.
Law enforcement officials want a quick, reliable method to test for THC in drivers who fail voluntary sobriety tests, similar to breath tests for alcohol, said Lt. Rob Sharpe of the Washington State Patrol.
When officers suspect that a driver is stoned, they have to get a search warrant from a judge for a blood test or call in a specially trained drug recognition expert. Either of those steps can take an hour or more, Sharpe said.
But if officers could administer a roadside breath test for THC, they would quickly know whether a follow-up blood test was needed, he said.
The number of people driving under the influence of marijuana is increasing in Washington. Last year, 28 percent of blood samples taken from drivers tested positive for active THC, according to the Washington State Toxicology Lab.
In Washington, people are legally impaired if they have a THC concentration of 5 nanograms per milliliter or higher in their blood within two hours of driving.
Hill said the prototype uses existing technology called ion mobility spectrometry, which tests for the explosives at airports and narcotics at border crossings. A Swedish researcher was the first to detect THC in breath through the use of ion mobility spectrometry.
In the WSU experiments, people have their breath tested before they smoke a joint and again when they are “midway through their experience,” Hill said. The testing is not done on WSU’s campus and no public money is used to purchase the marijuana, he said.
“We’re only looking at smoking, not edibles or oils,” said Hill, who is working on the research with graduate student Jessica Tufariello.
Chemring Detection Services is funding part of the WSU research. The North Carolina company makes other devices that detect for drugs, explosives and biological threats, and it’s interested in bringing a THC breath test to market, Hill said.
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