Last year, a national school survey alarmed health professionals, finding nearly 1 in 5 high school seniors used electronic cigarettes in the past month – a rate even higher than students' use of conventional cigarettes, which has been on a multiyear slide.
This year, the annual Monitoring the Future survey made an even more surprising finding: Though e-cigarette use rates appear stable, more than 60 percent of students who use them say they are vaping nicotine- and drug-free liquid, which is available to adult buyers in various flavors.
Only about a fifth of high school e-cigarette users knowingly used nicotine-laced liquids – a level that gradually increases from eighth to 12th grades – and smaller numbers used the devices to consume marijuana or didn't know what was in the liquid.
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The finding that most high school students sampling e-cigarettes aren't using nicotine-laced liquid either is good news or evidence of a nefarious business model, depending on whom you ask.
Dr. Nora Volkow, director of the National Institute on Drug Abuse, which funds the annual University of Michigan-administered survey, tells U.S. News the finding may point to something sinister.
"When the results came back this year, for the first time saying that 60 percent [use e-cigarettes to vape flavored liquids without nicotine], in a way I wasn't surprised," she says, "because that is the way manufacturers are going to be attracting the market for young people."
Volkow, echoing the sentiments of some health advocates and lawmakers, says "the flavors are very appealing and that will make the youth much more receptive to use the same device into the future for other things: delivering nicotine or [marijuana] or you can even use them for alcohol.
"So it's a very good marketing strategy to attract young people, to make them comfortable with these devices, then the next step of using it with a drug is much easier."
That claim is not the universal view. Gregory Conley, president of the American Vaping Association trade group, bashed the suggestion that the booming industry – which largely self-imposed 18-year age restrictions as states passed legislation to catch up – would be trying to hook minors.
"Ms. Volkow should stop and think before making false and demeaning claims about thousands of small business owners who have no connections to the tobacco industry," he says.
"Teen smoking rates are at record lows that were unimaginable just five years ago," Conley says. "But instead of celebrating this public health achievement, activists are rushing to revise their talking points and find new evidence-free accusations to make."
Conley adds that "nicotine-free vapor products began to be produced approximately seven years ago because consumers were telling companies that they wished to not only stop smoking, but also quit nicotine use."
It's unclear if any high school students are vaping nicotine-free e-liquid as part of a strategy to quit smoking.
Conventional cigarette use continued to fall in the 2015 survey results. Only 5.5 percent of high school seniors reported daily cigarette use, down from 6.7 percent last year and 10.7 percent in 2010. The rates also fell among eighth- and 10th-grade respondents.
Though not statistically significant, the rate of past-month e-cigarette use fell from 17.1 to 16.2 percent among high school seniors and 16.2 to 14 percent among sophomores. Among eighth-grade students, past-month use ticked up from 8.7 percent to 9.5 percent, also not statistically significant.