its not possible... lol
Although consuming cannabis is legal in Colorado and several other states, driving while under the influence of the drug is not. Nick Pedersen/Getty Images hide caption
toggle caption Nick Pedersen/Getty Images
Although consuming cannabis is legal in Colorado and several other states, driving while under the influence of the drug is not.
Nick Pedersen/Getty Images
This spring, 16 state patrol officers from Colorado and Wyoming took a couple days off their usual work schedule to do something special. They assembled in a hotel conference room in Denver. As instructed, they wore street clothes for their first assignment: going shopping at nearby marijuana dispensaries.
"It's a brave new world," said instructor Chris Halsor, referring to the years since Colorado legalized recreational marijuana.
There are now more marijuana dispensaries in Colorado than there are Starbucks shops, said Halsor, a Denver lawyer and former prosecutor. And though consuming cannabis is legal across the state, driving under its influence is not.
The cops in that conference room, with their buzz cuts and Mountain Dew, are all part of the force charged with keeping the roads safe. But first, they needed a formal pot education — to learn how to identify various marijuana products and paraphernalia when they pull over a driver they suspect is under the influence.
Here's the rub: Despite the increasingly legal use of cannabis in many states, cops still don't have the equivalent of a reliable alcohol breathalyzer or blood test — a chemically based way of estimating what the drug is doing in the brain. Though a blood test exists that can detect some of marijuana's components, there is no widely accepted, standardized amount in the breath or blood that gives police or courts or anyone else a good sense of who is impaired.
Yessenia Hinojos, a budtender at a Denver cannabis dispensary called The Green Solution, describes marijuana strains to A.J. Tarantino (left) and Philip Gurley. Both men are officers with Colorado State Patrol. Rae Ellen Bichell/NPR hide caption
toggle caption Rae Ellen Bichell/NPR
A number of scientists nationally are working hard to create just such a chemical test and standard — something to replace the behavioral indicators that cops have to base their judgments on now.
Article continues after sponsorship
Tara Lovestead, a chemical engineer at the National Institute of Standards and Technology in Boulder, Colo., who is working on setting standards for what a marijuana detection test might require.
It's actually really hard for Lovestead to do this kind of research because she works in a federal lab; federally, cannabis is considered a Schedule 1 substance, "a drug with no currently accepted medical use and a high potential for abuse." So even though Lovestead is in Colorado, getting hold of a sample for research purposes is just as hard as getting hold of heroin.
"We cannot use the stuff down the street," she said.
Aside from being a bureaucratic mess, coming up with a standardized blood or breath test is also a really tricky chemistry problem because of the properties of the main psychoactive chemical in cannabis:delta-9-tetrahydrocannabinol, or THC.
In states like Colorado, there is a THC blood test that law enforcement can use to show "presumed" impairment. If a person has more than 5 nanograms of delta-9-THC per milliliter of blood, it can be "presumed" that they are impaired, according to Colorado law.
![](/proxy.php?image=http%3A%2F%2Fmedia.npr.org%2Fassets%2Fimg%2F2015%2F12%2F21%2Fbreathalyzer-1_sq-5128e1ad32489c6a65f3b2421f1416c9b3d9518c-s600-c85.jpg&hash=e76b52e335fab2bbeecc646b48a14a94)
Shots - Health News
High On The Highway: Scientists Try To Build A Marijuana Breath Test
But Lovestead and others maintain that, scientifically speaking, that cutoff doesn't actually mean anything.
"We just don't know whether or not that means they're still intoxicated, or impaired or not," she said. "There's no quantitative measure that could stand up in a court of law."
Turns out it can be a lot harder to chemically determine from a blood or breath test that someone is high than to determine from such a test that they're drunk.
Ethanol, the chemical in alcoholic drinks that dulls thinking and reflexes is small and dissolves in water. Because humans are mostly water, it gets distributed fairly quickly and easily throughout the body and is usually cleared within a matter of hours. But THC, the main chemical in cannabis that produces some of the same symptoms, dissolves in fat. That means the length of time it lingers in the body can differ from person to person even more than alcohol — influenced by things like gender, amount of body fat, frequency of use, and the method and type of cannabis product consumed.
In one study, researchers had 30 frequent marijuana users stay at a research facility for a month without any access to drugs of any sort and repeatedly tested their blood for evidence of cannabis.
"And it shocked everyone, including ourselves, that we could measure, in some of these individuals, THC in the blood for 30 days," says Marilyn Huestis, a toxicologist with the University of Maryland School of Medicine who recently retired from leading a lab at the National Institute on Drug Abuse.
The participants' bodies had built up stores of THC that were continuing to slowly leech out, even though they had abstained from using marijuana for a full month. In some of those who regularly smoked large amounts of pot, researchers could measure blood THC above the 5-nanogram level for several days after they had stopped smoking.
Conversely, another study showed that people who weren't regular consumers could smoke a joint right in front of researchers and yet show no evidence of cannabis in their blood.
So, in addition to being invasive and cumbersome, the blood test can be misleading and a poor indicator of whatever is happening in the brain.
Recently, some scientists have turned their attention to breath, in hopes of creating something useful.
![](/proxy.php?image=http%3A%2F%2Fmedia.npr.org%2Fassets%2Fimg%2F2017%2F07%2F26%2Fgettyimages-576713119_custom-bb5e00898d43931284f26bc32e6ab96f45f40ac4-s1500-c85.jpg&hash=200436146ee11256e64bef1feb7ca04b)
Although consuming cannabis is legal in Colorado and several other states, driving while under the influence of the drug is not. Nick Pedersen/Getty Images hide caption
toggle caption Nick Pedersen/Getty Images
Although consuming cannabis is legal in Colorado and several other states, driving while under the influence of the drug is not.
Nick Pedersen/Getty Images
This spring, 16 state patrol officers from Colorado and Wyoming took a couple days off their usual work schedule to do something special. They assembled in a hotel conference room in Denver. As instructed, they wore street clothes for their first assignment: going shopping at nearby marijuana dispensaries.
"It's a brave new world," said instructor Chris Halsor, referring to the years since Colorado legalized recreational marijuana.
There are now more marijuana dispensaries in Colorado than there are Starbucks shops, said Halsor, a Denver lawyer and former prosecutor. And though consuming cannabis is legal across the state, driving under its influence is not.
The cops in that conference room, with their buzz cuts and Mountain Dew, are all part of the force charged with keeping the roads safe. But first, they needed a formal pot education — to learn how to identify various marijuana products and paraphernalia when they pull over a driver they suspect is under the influence.
Here's the rub: Despite the increasingly legal use of cannabis in many states, cops still don't have the equivalent of a reliable alcohol breathalyzer or blood test — a chemically based way of estimating what the drug is doing in the brain. Though a blood test exists that can detect some of marijuana's components, there is no widely accepted, standardized amount in the breath or blood that gives police or courts or anyone else a good sense of who is impaired.
![](/proxy.php?image=http%3A%2F%2Fmedia.npr.org%2Fassets%2Fimg%2F2017%2F07%2F26%2Fimg_5005_custom-e56ca38cbd2f0d29d1d491ac80ceaeeda0c1b23a-s1500-c85.jpg&hash=df5bf97f9fb998211616d7357db599da)
Yessenia Hinojos, a budtender at a Denver cannabis dispensary called The Green Solution, describes marijuana strains to A.J. Tarantino (left) and Philip Gurley. Both men are officers with Colorado State Patrol. Rae Ellen Bichell/NPR hide caption
toggle caption Rae Ellen Bichell/NPR
A number of scientists nationally are working hard to create just such a chemical test and standard — something to replace the behavioral indicators that cops have to base their judgments on now.
Article continues after sponsorship
Tara Lovestead, a chemical engineer at the National Institute of Standards and Technology in Boulder, Colo., who is working on setting standards for what a marijuana detection test might require.
It's actually really hard for Lovestead to do this kind of research because she works in a federal lab; federally, cannabis is considered a Schedule 1 substance, "a drug with no currently accepted medical use and a high potential for abuse." So even though Lovestead is in Colorado, getting hold of a sample for research purposes is just as hard as getting hold of heroin.
"We cannot use the stuff down the street," she said.
Aside from being a bureaucratic mess, coming up with a standardized blood or breath test is also a really tricky chemistry problem because of the properties of the main psychoactive chemical in cannabis:delta-9-tetrahydrocannabinol, or THC.
In states like Colorado, there is a THC blood test that law enforcement can use to show "presumed" impairment. If a person has more than 5 nanograms of delta-9-THC per milliliter of blood, it can be "presumed" that they are impaired, according to Colorado law.
![](/proxy.php?image=http%3A%2F%2Fmedia.npr.org%2Fassets%2Fimg%2F2015%2F12%2F21%2Fbreathalyzer-1_sq-5128e1ad32489c6a65f3b2421f1416c9b3d9518c-s600-c85.jpg&hash=e76b52e335fab2bbeecc646b48a14a94)
Shots - Health News
High On The Highway: Scientists Try To Build A Marijuana Breath Test
But Lovestead and others maintain that, scientifically speaking, that cutoff doesn't actually mean anything.
"We just don't know whether or not that means they're still intoxicated, or impaired or not," she said. "There's no quantitative measure that could stand up in a court of law."
Turns out it can be a lot harder to chemically determine from a blood or breath test that someone is high than to determine from such a test that they're drunk.
Ethanol, the chemical in alcoholic drinks that dulls thinking and reflexes is small and dissolves in water. Because humans are mostly water, it gets distributed fairly quickly and easily throughout the body and is usually cleared within a matter of hours. But THC, the main chemical in cannabis that produces some of the same symptoms, dissolves in fat. That means the length of time it lingers in the body can differ from person to person even more than alcohol — influenced by things like gender, amount of body fat, frequency of use, and the method and type of cannabis product consumed.
In one study, researchers had 30 frequent marijuana users stay at a research facility for a month without any access to drugs of any sort and repeatedly tested their blood for evidence of cannabis.
"And it shocked everyone, including ourselves, that we could measure, in some of these individuals, THC in the blood for 30 days," says Marilyn Huestis, a toxicologist with the University of Maryland School of Medicine who recently retired from leading a lab at the National Institute on Drug Abuse.
The participants' bodies had built up stores of THC that were continuing to slowly leech out, even though they had abstained from using marijuana for a full month. In some of those who regularly smoked large amounts of pot, researchers could measure blood THC above the 5-nanogram level for several days after they had stopped smoking.
Conversely, another study showed that people who weren't regular consumers could smoke a joint right in front of researchers and yet show no evidence of cannabis in their blood.
So, in addition to being invasive and cumbersome, the blood test can be misleading and a poor indicator of whatever is happening in the brain.
Recently, some scientists have turned their attention to breath, in hopes of creating something useful.