July 20, 2012 -- Electronic cigarettes are picking up steam -- and not surprisingly, especially among smokers.

That is the main message that comes from a new study in the American Journal of Public Health.

About 40% of individuals reported they had heard of e-cigarettes, and awareness was highest among smokers. What's more, smokers seem to be among the most likely to use e-cigarettes.

E-cigarettes go by many names including vapors, personal vaporizers, and nicotine vaporizers. There are many brands, flavors, and nicotine strengths available for purchase at convenience stores and on the Internet. They are not regulated by the FDA as a drug delivery device because they are not marketed as quit-smoking aids.

"This is an unproven device and we know very little about its long-term health effects," says researcher Jennifer Pearson, PhD, MPH. She is a research investigator at Legacy, an antismoking group in Washington, D.C. "E-cigarettes are probably less harmful than combustible cigarettes, [but] we don't have data to say that and can't talk about long-term effect."

There are many unknowns and unanswered questions, she says. For example, have they encouraged former smokers to reignite their nicotine addiction? Are current smokers using them to quit or to circumvent smoke-free indoor air laws? And how are they affecting people who have never smoked. "Are they acting as a gateway products?"

Pearson and colleagues call for greater regulation of these products until these questions are answered.