ARUN RATH, HOST:
If you're just joining us, it's ALL THINGS CONSIDERED from NPR West. I'm Arun Rath.
In the state of Colorado, marijuana has moved from underground to behind the counter.
UNIDENTIFIED WOMAN: For cannabis, it's a gram.
UNIDENTIFIED MAN #1: OK.
UNIDENTIFIED WOMAN: And grams are $20, tax included.
UNIDENTIFIED MAN #1: Uh-huh.
UNIDENTIFIED WOMAN: Or we have a joint...
RATH: That's just some of the selection at the Lodo Wellness Center in Denver. They've been selling medical marijuana for several years. But since January 1st, they're also selling legal recreational pot.
UNIDENTIFIED MAN #1: Great.
UNIDENTIFIED WOMAN: You all set?
UNIDENTIFIED MAN #1: Yeah, let's do it.
RATH: It may still sound funny to a lot of you, but you better get used to it. On top of Colorado, legal weed is coming soon to Washington state, and a majority of Americans now say they support full legalization. Critics have been warning of a looming public safety problem: More people driving while stoned. But there's still a lot we don't know. That's our cover story today: Understanding a different kind of DUI.
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RATH: Inside the Lodo Wellness Center in Denver, we decided to ask shoppers just how risky they think it is to get behind the wheel while high on pot.
RYAN: I don't think there is much of a risk. I really don't. I think sometimes when you get stoned on the right stuff that you're more concentrated, actually.
RATH: That was Ryan. He didn't give his last name. Several people at Lodo said it's OK to smoke before driving and definitely safer than drinking and driving.
DANTE COX: Marijuana - you could smoke about an ounce and still have your motor skills. You know, I mean, when it comes to one shot of alcohol, all that goes out of the window.
LAURA COLEMAN: I mean, I've drink wine and driven. And I feel that that has a greater impact on accidents versus marijuana. I think you're just more cautious and more aware of things.
OSCAR COLEMAN: I mean, if you go in and you smoke five hits off a bong, you're not going to be able to go out and drive.
COLEMAN: No. I'd be still sitting in the driveway. But I think if you smoke a joint, you're going to be fine.
DAMIAN CANGEMI: To me, it doesn't seem to affect me in that way. It keeps me in a focused area. I drive a little slower. I might be in the right lane with my blinker on, but that's about it.
RATH: That was Dante Cox, Laura and Oscar Coleman and Damian Cangemi. For advocates of traffic safety, their words are very concerning.
JONATHAN ADKINS: I think this is the next big issue on highway safety.
RATH: Jonathan Adkins is the executive director of the Governors Highway Safety Association.
ADKINS: There's this prevalent feeling in our culture that marijuana is no big deal. Well, it is a big deal if you use it and then get behind the wheel. We need to have the same cultural intolerance for marijuana use behind the wheel as we do with alcohol.
RATH: Alcohol-related crashes still kill around 10,000 Americans a year. And we understand quite clearly the danger it poses as an enormous public health problem. The impact of marijuana is much less clear.
Dr. Marilyn Huestis is with the National Institute on Drug Abuse, and she's done extensive research on marijuana's effect on driving ability. The results, she says, should give smokers pause.
DR. MARILYN HUESTIS: We have so many processes in our brain that help us to do a complex behavior of driving. And under the effects of marijuana, we just don't perform as well.
RATH: After using marijuana, she says people generally have more trouble staying in lanes, they struggle to do multiple tasks at once, and there's a real problem maintaining concentration on long monotonous drives. But how often does marijuana use actually cause accidents?
DR. ANNE MCCARTT: Studies that have looked at the crash risk associated with marijuana have produced mixed results.
RATH: That's Anne McCartt. She's a senior vice president for research at the Insurance Institute for Highway Safety.
MCCARTT: Not only do we not have consensus on the risk associated with the presence of marijuana, we don't have information on the crash risk for different amounts of marijuana. And we don't even have good information on how many drivers involved in fatal crashes test positive for marijuana. So there's a lot we don't know.
RATH: Even with the lack of information we have, is it possible to rank marijuana compared to alcohol or other drugs in terms of the dangers it poses for driving?
MCCARTT: Well, we generally know less about other drugs than marijuana. But I think the evidence thus far suggests that there is a stronger effect of alcohol on crash risk than marijuana. We just have a large body of very strong research on the strong association between blood-alcohol concentrations and crash risk. We've used that science, for example, to enact in all 50 states laws that make it illegal to drive with BACs of .08 percent or higher. We don't have comparable information on marijuana.
RATH: You follow traffic safety issues really for a living. As marijuana becomes more accepted in the U.S., how concerned are you about the impact of that on driver safety?
MCCARTT: I think it is concerning. And as a researcher, I think it's frustrating that we don't have the science that we need at this point to craft effective, enforceable laws for drugs including marijuana. I think policymakers don't have the information that they need on the crash risk associated with marijuana to really know how to proceed.
RATH: And here, the comparison with alcohol is especially telling. At this point, we're used to the public service announcements reminding us of the legal limit.
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UNIDENTIFIED MAN #2: It's a lot easier than you think to blow a .08. Drive sober. Arrive alive.
RATH: Police around the country carry handheld breathalyzers that test for blood alcohol content. But coming up with a similar test for marijuana, that's more difficult, much more. For one, we all know the alcohol content of a Budweiser, but it's a lot harder to know the potency of a wide variety of marijuana products. And here's another complication. Pot's main psychoactive ingredient is THC, and it can linger in the body long after the initial high.
Dr. Timothy Fong is a professor of psychiatry and an addiction specialist at UCLA.
DR. TIMOTHY FONG: THC is a molecule that really loves human fat. And when you ingest it, it sticks in the fat, and then it slowly seeps out over the course of a week or a month if you're a heavy user.
RATH: The most reliable test for THC is the blood test. A few states, like Washington and Colorado, have even established a kind of legal limit for marijuana in the blood: five nanograms of THC per millimeter. But performing that test often requires that police drive a suspect to a hospital, except in Arizona where police are trained to draw blood themselves. And Dr. Fong says it's tough to interpret exactly what those tests mean for driving ability.
FONG: Most of the marijuana testing have been done in human laboratories. And there, you get a wide variety. So if you take 100 people and have the same blood level of marijuana, you'll have 100 different reactions.
RATH: California has been at the leading edge of the legal marijuana movement. In 1996, it became the first state to legalize medical marijuana. The state's office of traffic safety recently conducted a roadside study at night, and they found around 7 percent of drivers had marijuana in their systems.
Now Los Angeles is at the forefront of law enforcement's response. The city has a federal grant to try out a new roadside drug test: oral swabs. Mike Feuer is the city attorney of Los Angeles, and he calls the technology the wave of the future.
MIKE FEUER: This is a technique under which in the field at the time of the traffic stop an officer can test the saliva of the driver and get an immediate result as to whether there are drugs present in his or her system.
RATH: And with this being a new technique, or at least maybe something that a lot of people might be unfamiliar with, is there an issue of admissibility in court in getting that to be recognized?
FEUER: The admissibility in court of the swabbing hasn't been tested in California. It is likely to be tested sometime in the coming months or perhaps next year. It also could be down the road that there is legislation initiated in California. All of us want to assure that we have as effective a means as possible of determining whether a driver is impaired. Not merely because we want to effectively prosecute that driver, but we do want to do everything we can to prevent driving while under the influence in the first place.
And the more commonly known it is that we have a quick and effective technique for determining that, the more I hope people are deterred from getting behind the wheel with drugs or alcohol in their system.
RATH: Advocates who favor marijuana legalization say they agree people should know their limits and should not drive while impaired. But they're concerned that police officers will substitute this new technology and an arbitrary legal limit for their own judgment. Here's Mason Tvert. He's the communications director for the Marijuana Policy Project, a pro-legalization group.
MASON TVERT: I think that people want to have a clear-cut black and white solution. They want a specific number that we can use to just say this person is impaired or not. Unfortunately, it's a little more of a gray area than that. So what we really need to be doing is really judging people's impairment. And that really ends up being a matter of field sobriety tests and using the law enforcement official's judgment.
Simply having a number that we know is not necessarily indicative of impairment doesn't really accomplish much and could actually result in people who are perfectly sober being arrested and charged with being impaired while driving.
RATH: Is there a concern that with maybe a fair number of new marijuana users in these states that these new users could get on the road under the influence and basically set back the gains that your group has made in terms of pot legalization?
TVERT: Quite frankly, I'm really more concerned about excessive and overzealous reporting on the subject as opposed to actual problems. People driving under the influence of marijuana has never proven to be a huge problem. It's something that we need to address and discourage. And when someone does drive while impaired, we need to ensure that they are penalized. But we allow adults to use alcohol responsibly, and we punish adults if they use it irresponsibly. And that includes driving while drunk. We should be doing the same thing with marijuana.
RATH: In fact, that's an area of some common ground. Again, Mike Feuer, the city attorney of Los Angeles.
FEUER: There have been so many tragedies that are completely avoidable that devastate families in ways from which they never recover. So I'm optimistic that as the debate around legalization of marijuana continues in this country, there will be no debate, complete unanimity around the notion that we should be educating the public about the fact that driving while impaired could lead another family to suffer a loss from which they can never recover.
RATH: That legalization debate Mike Feuer mentioned is continuing this year. There's a good chance marijuana initiatives will be on the ballot in Alaska and Oregon. But even as the momentum increases for marijuana legalization, police and lawmakers say they have to respond, even with so much still unknown.