In the most comprehensive look at e-cigarettes to date, from how they are used to how they are marketed and where they are sold, researchers are surprised by how quickly the devices have taken hold worldwide.

In nine studies published in the journal Tobacco Control by the State and Community Tobacco Control Research Initiative (SCTC), scientists looked at where e-cigarettes are sold, the status of state laws regulating e-cig sales and use, and how taxes and pricing may affect the popularity of the devices, among other topics.

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When it comes to e-cig marketing, researchers found that about 10.5 new brands appear online every month, touting 242 novel flavors. “The most surprising thing was how quickly they became available across the country,” says Frank Chaloupka, a professor economics at University of Illinois and a co-author of the study. “A few years ago, they were hardly available anywhere, and by 2012, they were available in about a third of the stores we were going into.”

He and his colleagues found that at least initially, e-cigs were targeted in areas with weaker tobacco regulations, including areas with lower taxes and more lenient smoking policies in public places. E-cig makers, says Chaloupka, likely focused their early marketing strategies in areas with the greatest density of smokers.

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That may be shifting, however, as the latest data suggests that e-cigarettes are now marketed more heavily in higher income communities, and less so in lower income neighborhoods, which traditionally have higher proportions of smokers. That may be because e-cig manufacturers are promoting claims that their products are safer than traditional cigarettes and are also hoping to capture those who may turn to their devices to help them quit smoking. “Groups that are more likely to switch to e-cigarettes in the long run are more interested in the health benefits, and tend to be more highly educated and have higher incomes” says Chaloupka.

That’s supported by evidence from some of the other studies in the series; scientists led by researchers at Harvard University’s School of Public Health conducted the largest study of e-cig use in Europe and found that the bulk of users were young smokers who had tried to kick the habit in the past year. These smokers were twice as likely to try e-cigs as smokers who hadn’t tried to quit.

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On the one hand, the quick penetration of e-cigs into nearly every retail outlet, from pharmacies to convenience stores, grocery stores and gas stations may help more smokers to try the devices and try to quit. On the other hand, the ubiquity of the devices, and the unsubstantiated claims about their safety over regular cigarettes, may lead younger smokers to try them and potentially serve as a gateway to tobacco-based cigarettes. “Just the fact that their availability increased so rapidly means that people, especially kids, may see them a lot more in the stores they go into, and perceive them as normative, and that could by contributing to the big increases in use that we are now seeing,” says Chaloupka. The percentage of teens who have ever tried e-cigarettes doubled from 3.3% in 2011 to nearly 7% in just one year, according to the latest data from the Centers for Disease Control and Prevention.

The Food and Drug Administration recently announced its intention to regulate e-cigarettes as tobacco products; although they don’t contain tobacco, the agency says the devices meet the “statutory definition of a tobacco product.” As such, the FDA wants to ban sales to minors, require health warnings and keep e-cigs out of vending machines. The proposal is up for public comment until July, and may take another year before they become enforceable. In the meantime, 34 states have laws addressing e-cigs, but primarily to prevent minors from buying them and to ensure they don’t violate existing smoke-free air laws.

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The safety of e-cigarettes isn’t clear yet, despite claims by some manufacturers that they are less dangerous than traditional cigarettes. While they don’t envelop smokers in the carcinogenic smoke emitted by burning tobacco, they do contain other compounds such as propylene glycol, which the FDA is still studying for its health effects.

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