WASHINGTON - The federal government's move to regulate e-cigarettes is a leap into the unknown.

Most everyone agrees that a ban on selling them to children would be a step forward. But health and public policy experts cannot say for certain whether the electronic devices are a good thing or a bad thing overall - whether they help smokers kick the habit, or are a gateway to paper-and-tobacco cigarettes.

The proposed rules, issued Thursday by the Food and Drug Administration, tread fairly lightly. They would ban sales to anyone under 18, add warning labels, and require FDA approval for new products - less restrictive than some companies had feared, with their full effectiveness likely years in the future.

Bonnie Herzog, an analyst at Wells Fargo, said the proposal was "positive for the industry."

But some public health advocates lamented the fact that the proposal did not take aim at e-cigarette advertising or sweetly flavored products, which they said risk introducing a new generation of young people to conventional cigarettes when little is known about the long-term health impact of the devices.

"It's very disappointing because they don't do anything to rein in the Wild West marketing that is targeting kids," said Stanton Glantz, director of the Center for Tobacco Control Research and Education at the University of California, San Francisco.

FDA Commissioner Margaret Hamburg said at a briefing that the proposal represented the "foundational" step toward broader restrictions if scientific evidence shows they are needed to protect public health.

That declaration worries some companies.

"The window is still open for a more draconian approach," said Jason Healy, president of Lorillard Inc.'s blu eCigs unit, with 48 percent of the market. "I think the proposal shows a good science-based reaction here from the FDA, but there is a lot we have to go through during the public-comment period."

Some in the sharply divided public health community welcomed the FDA's light touch.

Michael Siegel, a professor of community health sciences at Boston University, said a ban on flavorings would have "devastated the industry, as the flavors are a key aspect of what makes these products competitive with tobacco cigarettes."

Similarly, a ban on e-cigarette advertising, he said, "would have given tobacco cigarettes an unfair advantage in the marketplace."

E-cigarettes use batteries to heat a liquid, producing an inhalable vapor laced with nicotine - providing the kick and addiction of regular cigarettes, but without the cancer-causing tar and ash that come from burning tobacco.

The long-awaited proposal would subject the $2 billion industry to federal regulation for the first time. A law passed in 2009 gave the FDA authority to regulate cigarettes, smokeless tobacco, and roll-your-own tobacco, and stipulated the agency could extend its jurisdiction to other nicotine products after issuing a rule to that effect.

One year later, New Jersey implemented the first comprehensive e-cigarette restrictions in the nation, treating them the same as regular cigarettes for sales (prohibited to anyone under 19) and usage (banned in most public places).

Only in the last several months, with rules still not proposed by the FDA, did several major cities follow suit. Mayor Nutter signed bills into law April 9 that banned sales to minors under 18 immediately and added the electronic devices to the city's comprehensive smoke-free law effective July 1.

At Popie's Vapor Lounge in Marlton, owner Robert Eichenberger said before the FDA's announcement that he was not opposed to reasonable federal regulations, particularly concerning quality and purity.

"What I vape, I want to know has been produced in a laboratory setting that is sterile and uses safe products," he said.

Kyra Donaldson, 20, of Mount Laurel, visits the shop almost daily to relax with an e-cigarette. She also enjoys riding her bicycle at the beach: Since she quit smoking and started "vaping," she said, she has had fewer problems with asthma and can more easily exercise.

"I could barely make it to the lighthouse," she said. "Now I can bike to the lighthouse and back."

Testimonials like these abound, but have not been backed by a body of evidence, partly because e-cigarettes are so new. Scientists say that many e-cigarette aficionados continue to smoke tobacco. And some worry that, given the past track record of big tobacco, the industry will find ways to attract new customers who might then move the other way - from e-cigarettes to regular.

For now, the FDA's proposed regulations would prohibit companies from distributing free e-cigarette samples, forbid vending machine sales except in adults-only venues, and prohibit sales to minors.

Companies would also have to warn consumers that nicotine is addictive, but no other health warnings would be required. The addiction warning would have to be added no later than two years after the rule is set. And e-cigarette companies would not be allowed to make health claims in advertising.

The proposal is subject to a public-comment period of 75 days.

Vince Willmore, a spokesman for the Campaign for Tobacco Free Kids, said the proposal "by no means does everything we think needs to be done, but it starts the process. What is critical now is that they finalize this rule and then move quickly to fill the gaps."

He said the FDA should aim to establish the rule within a year, but many are skeptical that it will.

"The reality," said UCSF's Glantz, is that "by not addressing the youth-directed marketing, it means it won't be addressed for a very long time."

Some e-cigarette companies that sell primarily through convenience stores were surprised at the lack of restrictions on online sales, since it can be difficult to verify a customer's age over the Internet.

The FDA's proposal leaves many questions unanswered about how new products would be approved and regulated over the long run - a key issue, since some industry analysts expect their sales to outpace the $85 billion conventional-cigarette industry within a decade.

Inquirer staff writers Barbara Boyer and Don Sapatkin contributed to this article, which also contains information from
the Associated Press.