Law enforcement has long been struggling to come up with a device that can accurately measure marijuana intoxication in the field.
While testing for alcohol levels is as simple as having a person blow into a breathalyzer, deciphering marijuana’s influence is far more complex.
Now, scientists may be closer to a solution.
Researchers from the University of Pittsburgh have unveiled a breathalyzer device they say can measure levels of THC – weed’s dominant psychoactive compound – in the breath.
While testing for alcohol levels is as simple as having a person blow into a breathalyzer, deciphering marijuana’s influence is far more complex. Now, scientists may be closer to a solution. Stock image
Currently, testing for marijuana levels is done using blood, urine or hair samples. But, this doesn’t tell much about whether a person is currently under the influence.
The new device uses carbon nanotubes, which bind with the THC molecules to detect the compound with a higher degree of precision.
‘The semiconductor carbon nanotubes that we are using weren’t available even a few years ago,’ says lead author Sean Hwang.
‘We used machine learning to “teach” the breathalyzer to recognize the presence of THB based on the electrical currents’ recovery time, even when there are other substances, like alcohol, present in the breath.’
According to the team, the system is about as good – or possibly better – than mass spectrometry, which is right now considered to be the best method of THC detection.
The prototype looks much like a standard breathalyzer, and tests showed it could not only detect THC in the breath, but distinguish it from compounds such as carbon dioxide, water, ethanol, methanol, and acetone.
‘Creating a prototype that would work in the field was a crucial step in making this technology applicable,’ says Ervin Sejdic, PhD.
The prototype looks much like a standard breathalyzer, and tests showed it could not only detect THC in the breath, but distinguish it from compounds such as carbon dioxide, water, ethanol, methanol, and acetone. Above, the researchers are shown holding their device
‘It took a cross-disciplinary team to turn this idea into a usable device that’s vital for keeping the roads safe.’
While it isn’t a perfect system yet, the researchers say it’s a step in the right direction.
‘In legal states, you’ll see road signs that say “Drive High, Get a DUI,” but there has not been a reliable and practical way to enforce that,’ says Alexander Star, PhD, who leads the Star Lab.
‘There are debates in the legal community about what levels of THC would amount to a DUI, but creating such a device is an important first step toward making sure people don’t partake and drive.’
WHY IS IT DIFFICULT TO DEVELOP SOBRIETY TESTS FOR MARIJUANA?
Determining when someone is too high to drive is a problem that has evaded the chemists, psychiatrists, law enforcement agents and public policy makers.
Scientists explained to Daily Mail Online why the most scientific tests may not be the best way to determine how high is too high and the unique chemistry that makes marijuana a drug-screening enigma.
Some are unique to the drug, but one is true of just about any substance: tolerance.
Depending on how often and in what doses someone uses any substance, the amount it takes to for the drink or drug to have an effect varies drastically.
So, people with medical marijuana prescriptions, for example, who might smoke weed every day, seem totally unaffected and breezily pass a field sobriety test – which involves tests for coordination and balance, like walking the line, as well as some for memory and attention – even though they’ve recently ingested lots of the drug.
Beyond that, marijuana moves through the body in a very different way from alcohol.
Marijuana – more specifically, its psychoactive component – leaves the blood very quickly, but it lingers in the fat and brain, meaning its cognitive effects do, too.
According to Dr Richard Clark, director of the division of medical toxicology at the University of California, San Diego, marijuana may even move from these tissues back into the blood days later in ‘chronic’ smokers.
And just to add an extra level of difficulty, the THC in increasingly popular edibles gets converted quickly to anther compound in the stomach, so a THC test might not even detect it, even when a high was in full effect.
Blood and urine tests are available, but sometimes a long time passes between when someone is pulled over and when the test can be administered.
There are two recently developed breathalyzers for THC – one from Hound Labs and another from Cannabix – and several other tests in development, but these face the same challenges of disparity between blood level and actual high.
‘Field sobriety testing introduces subjectivity into something you’d really like to be subjective,’ says Dr Hall.
For now, however, no method is perfect.
‘So what does it all mean,’ Hall said, ‘except it’s better to drive completely sober.’
-Natalie Rahhal, Deputy Health Editor for Dailymail.com