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Teenage stoners are trading poorly rolled joints and spoon pipes for pre-filled wax cartridges and slick battery-operated pens, bringing Generation Z’s love for all things vape into the world of weed.

According to a new national survey of American teenagers published in the journal JAMA Pediatrics, 1 in 11 middle and high schoolers in the U.S. has used a marijuana vaporizer at least once. For the authors presenting the survey data, the peek into teen life raises new concerns about youth cannabis use and heightens existing issues surrounding widespread teen vaping.

"This high rate of cannabis use in e-cigarettes is a public health concern," study author Katrina Trivers, an epidemiologist at the U.S. Centers for Disease Control and Prevention (CDC), told CNN.

Extrapolating the rate of cannabis vape use from more than 20,000 survey respondents to the entire nation, Trivers and her co-authors estimate that some 2 million teens have experimented with marijuana through vaporization.

Because vape technology is a rapidly developing product sector in both legal and illicit cannabis markets, however, and since the latest youth data relies on self-reported responses, there is still much to learn about the newest trend in teen pot use. Likewise, while preliminary research has suggested that cannabis can alter the developing brain, federal prohibition has hindered any significant clinical studies.

The new cannabis-focused study has drawn even more attention to the issue of teenage vaping at large, including both weed pens and nicotine-packed cigarette substitutes like the incredibly popular device Juul. Over the past year or so, vaping has become a significant concern of parents, educators, and regulators, who worry that data about declining teen tobacco use is merely hiding the dirty secret of rising e-cigarette use.

"It is very difficult (if not impossible) to tell whether a vaping device contains nicotine e-liquid or cannabis just from looking at the device or the cartridge," Meghan Morean, an assistant professor of psychology at Oberlin College who was not involved in the latest JAMA Pediatrics study, told CNN. "As vaping in general goes up, then vaping nicotine will go up, and vaping marijuana will go up. I think they're all grouped together."

Responding to calls from school administrators and concerned parents, the U.S. Food and Drug Administration (FDA) sent a letter this month to the nation’s five largest e-cigarette producers, including Juul, demanding that they construct plans to help prevent underrage youth from using their products within 60 days. In an ad campaign released late last week, the FDA tailored anti-vaping public service announcements for middle and high schoolers.

Even with increased attention to teen e-cigarette use in general, the new study’s authors were clear to note that their research about weed vaping should not be interpreted as an increase in total youth cannabis use, but vaporization specifically. In reports from across legal weed states, teens have reported level or decreased overall pot use, with no indication that America’s green rush is causing more high schoolers to try ganja.

"It's not possible to conclusively determine whether the increased popularity of e-cigarettes in recent years has led to more kids trying cannabis," Trivers concluded.