Smoking rates in the U.S. have dropped steadily over the last several decades, but e-cigarette use is on the rise. The battery-powered, pen-sized devices, which release nicotine-laced water vapor instead of smoke, are escaping the regulatory scrutiny that traditional light-a-match cigarettes receive, says the American Heart Association.

“E-cigarette use and acceptance of e-cigarettes has the potential to renormalize smoking behavior,” association officials wrote in a new policy statement in the journal Circulation.

They warn that the current holes in regulation could have far-reaching consequences.

“Unregulated e-cigarette use also has the potential to erode gains in smoking cessation and smoke-free laws,” they wrote.

They may have reason to worry. The heart association’s policy statement comes on the heels of a study in the journal Nicotine & Tobacco Research showing that the number of youths (grades 6-12) who had used e-cigarettes more than tripled from 2011 to 2013, skyrocketing from 79,000 to more than 263,000.

The study, conducted by researchers from the Centers for Disease Control and Prevention, also showed that young people who had used e-cigarettes were 1.7 times as likely to intend to smoke cigarettes in the future compared with those who had never used them. A full 43.9 percent of those young e-cigarette users said they would smoke combustible cigarettes in the future, roughly twice the rate of those who had never used e-cigs.

“E-cigarette use was associated with increased intentions to smoke cigarettes,” the CDC researchers wrote.

That trend may continue if current marketing practices keep up; according to the heart association paper, youth exposure to e-cigarette ads shot up more than 250 percent from 2011 to 2013.

“Such marketing practices are likely to recruit a new generation of nicotine addicts,” the policy authors wrote. “The public health community is unified in developing regulation and passing legislation that restricts the marketing and access of e-cigarettes to minors, similar to existing laws restricting marketing and youth access to combustible products.”

More research needs to be done on the effects of e-cigarettes, whether positive or negative, officials said. In the meantime, the heart association tweeted, “We continue to encourage clinicians to use proven smoking cessation strategies first, use e-cigs only as last resort.”