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Legal marijuana sales in Colorado have now topped $2 billion. Some of the products that have become popular are highly concentrated forms of THC, the main psychoactive compound in marijuana, and some there are worried about the mental health effects of those products. Colorado Public Radio's Bente Birkeland reports.
BENTE BIRKELAND, BYLINE: Researchers say 80% of legal pot sales go to the 20% of customers who are regular users. And they're not just buying joints or marijuana flower that's become steadily more potent over the years. At the RollUp dispensary in Denver, RollUp's owner, Sherard Rogers, says there are reasons why people want concentrates.
SHERARD ROGERS: They're a cleaner product. They don't have the smell that a typical cannabis product would have, and it's cheaper.
BIRKELAND: Concentrates like hash oils and waxes can be upwards of 80% THC, the main psychoactive component in marijuana. Not a lot is known about the health risks of concentrates, but there are some concerning anecdotes.
CYNTHIA: Our lives were complete hell. And it was all about confiscating dab pens, cartridges, wax canisters, concentrate canisters.
BIRKELAND: Cynthia says her 16-year-old son's personality changed after he started using the highly concentrated products dispensaries sell. NPR is not using her last name to protect the privacy of her minor son. Last year, she called the police after he threw a rock at her head, and he went to the emergency room.
CYNTHIA: All those who saw him come in thought that it was either meth or heroin or high-dosage opioid.
BIRKELAND: But what doctors found was THC. There aren't good numbers for how often people have adverse reactions to cannabis concentrates. Scientists haven't established a causal link between concentrates and psychotic episodes. But Dr. Sam Wang with Children's Hospital Colorado says there is moderate to strong evidence of an association.
SAM WANG: Obviously, we need more research on the impacts of these high-potency products. But also, do we want to wait 10 years down the road to see the overall impacts? Probably not.
BIRKELAND: Colorado's House speaker, Alec Garnett, is proposing higher taxes on marijuana to fund new research. The Denver Democrat also wants to create a statewide system to track whether people buy more per day than the legal limit. He's especially worried about 18- to 21-year-olds, who purchase it through the state's medical marijuana system.
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ALEC GARNETT: It shouldn't be free rein. People shouldn't be able to go and buy 40 grams a day of the highest-potency products on the marketplace because there's no logical reason that you would actually need that.
BIRKELAND: Authorities say restricting young medical users would help prevent them from selling it to teens who aren't able to buy it legally. There is support in Colorado's marijuana industry to require better tracking of purchases and increased taxes for research. But many say they're already heavily regulated and taxed. RollUp Dispensary owner Sherard Rogers.
ROGERS: Aren't parents supposed to have the best interest of their children and be the gatekeepers for their children? It's not as if that we are selling a cannabis product out the back door. I want people coming in who are of age and are using it for the right purposes.
BIRKELAND: It's been nine years since voters here made Colorado the first state to legalize recreational use of marijuana. Last year, sales brought in close to $400 million in state taxes, and the industry has a staunch ally in Democratic Governor Jared Polis. It's not a given that he'd sign new regulations. Any new taxes would have to be approved by voters. Polis and people in the business say they don't want regulations to trample on individual freedom.
Peter Marcus is with Terrapin, a multistate cannabis company based in Boulder.
PETER MARCUS: These products didn't come out of nowhere. And for responsible adults, they should be able to make the decisions for themselves.
BIRKELAND: Colorado lawmakers are taking this issue up now, but don't have much time before the legislative session ends in about six weeks. And Colorado isn't alone in wrestling with how to regulate marijuana concentrates. Currently, Vermont is the only state with a THC cap in place.
For NPR News, I'm Bente Birkeland in Denver.
[POST-BROADCAST CORRECTION: In this report, we say that Colorado was the first U.S. state to legalize recreational marijuana. In fact, both Colorado and Washington legalized it in 2012.] Transcript provided by NPR, Copyright NPR.