Electronic cigarettes are either a potent weapon in the war against tobacco, or they are an insidious menace that threatens to get children hooked on nicotine and make smoking socially acceptable again.

There are health experts who back each point of view. But they do agree that the empirical evidence that will tell them who is right will not be in for several years.

“There are a few studies out there right now, but scientists like to have a gazillion,” said Stanton Glantz, a professor of medicine and director of the Center for Tobacco Control at the University of California, San Francisco.

Among the most pressing questions for researchers: What are the long-term health effects of e-cigarettes on users and people around them? Do e-cigarettes help people kick the smoking habit, or do they actually make it harder? If kids start smoking e-cigarettes, are they likely to graduate to regular cigarettes?

“My big question with e-cigarettes is whether it puts youth on a pathway to smoking,” said acting Surgeon General Boris Lushniak.

Without a renewed focus on the campaign against tobacco, the U.S. will miss its goal of reducing the national smoking rate to 12 percent by the end of the decade.

E-cigarettes are uniquely positioned to undo recent public health gains, Lushniak and others fear.

The battery-operated devices heat nicotine, propylene glycol and glycerin into a vapor, which is inhaled by the user. Unlike conventional tobacco-burning cigarettes, e-cigarettes do not deliver poisonous tars or carbon monoxide.

Currently, the devices are regulated only by a smattering of local governments who have passed laws concerning their sale and use.