One in four teens who use e-cigarettes say they've dripped, letting the nicotine-based liquid drop onto the e-cigarette's heating coils and then inhaling the vapors.
The one in four teens data was found during a 2015 survey from over 7,000 students in eight different CT high schools.
There's a rising trend among e-cigarette users, and a survey finds that teens make up the largest group who practice "dripping".
According to the Centers for Disease Control and Prevention (CDC), electronic vapor products, including e-cigarettes, are now the most commonly used tobacco products among US high school students, surpassing conventional cigarettes in 2014.
But dripping the liquid directly on the coils generates far higher temperatures than traditional vaping, leading to greater emissions of harmful chemicals like formaldehyde, acetaldehyde and acetone.
Additionally, dripping was most prevalent among white males and respondents who had tried more tobacco products or used an e-cigarette more in the past month.
"The teen brain has been shown especially sensitive to nicotine", Krishnan-Sarin said.
Reasons the students gave for dripping included producing thicker clouds of vapor (64 percent), which suggests these users may engage in smoke tricks or vape competitions, the study authors said.
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They come just two months after the US surgeon general called e-cigarettes a public health threat for youths.
The study, conducted in CT, found that among 1,874 students, 1,080 had tried vaping. "Many of them really don't have the background or ability to really put these things together".
So, in one way the fact that 1 in 4 e-cigarette teen users were participating in this alternative use behavior was a surprise.
Funding for it was provided by the National Institutes of Health and the U.S. Food and Drug Administration Center for Tobacco Products.
Story called e-cigarettes an adult product but said he would rather see a teenager use an e-cigarette than a traditional cigarette.
Krishnan-Sarin, however, said more research is needed on the long- and short-term effects of e-cigarettes.