Sen. Richard Blumenthal, D-Conn., is one of the most vehement advocates of restricting the sale of electronic cigarettes. He says the vapor-producing devices, which are booming in popularity, have become "gateway nicotine-delivery devices" for children and he advocates banning flavor options and online sales.

E-cigarettes are hailed by the companies that produce them and former tobacco cigarette smokers who use them as potential life-savers. U.S sales are expected to double this year to $1.7 billion, according to a Wells Fargo Securities estimate published in August. Year-to-date retail sales were estimated at around $700 million and online sales were pegged at $500-625 million.

Blumenthal isn't sold on the health claims and says flavors make e-cigarettes appealing for kids while online sales make them easy to acquire.

"I think flavors ought to be banned," Blumenthal told U.S. News. It's "completely disingenuous" to say adults are the primary users of popular flavor options, he said.

"There may be a handful of adults who like bubble gum-flavored e-cigarettes, but the overwhelming purpose," he said, "is to appeal to kids."

But supporters of e-cigarettes warn banning flavors could do more harm than good. "When people want to quit smoking, a lot of times they don't want to be reminded of what a cigarette tastes like," Gregory Conley, legislative director of the Consumer Advocates for Smoke-free Alternatives Association, told U.S. News. He credits watermelon-flavored e-cigarette liquid with helping him quit conventional cigarettes. "If I was restricted to a tobacco flavor and a menthol flavor and Senator Blumenthal – or the FDA – got flavored electronic cigarettes banned, I would still be smoking."

Conley now blends flavors to mimic the taste of the drink Hi-C.

Just how would flavored e-cigarette liquid be banned? "Perhaps the electronic cigarette industry would do so voluntarily," Blumenthal says, "but if not, I think the [Food and Drug Administration] ought to."

The FDA is currently considering how it will regulate the devices. It's unclear what authority the agency will claim, or if Congress would need to first dole out more regulatory power.

The Wall Street Journal reported in August that some FDA officials were discussing a possible online sales ban, although it's unclear how serious that consideration is. Such a move could knock smaller companies without retail relationships out of the market.

Blumenthal said he supports the idea of an online sales ban "very much." Such a ban would be "very appropriate," he says.

"The online sales are obviously very anonymous and they are prone to children posing as adults," Blumenthal says. "They must know there are all kinds of ways children can buy them."

Celebrity endorsements, such as an August ad for the brand blu eCigs featuring former Playboy model Jenny McCarthy, are also intended to target children, Blumenthal alleged.

The Centers for Disease Control and Prevention announced Sept. 5 that its 2012 National Youth Tobacco Survey found 10 percent of high school students tried an electronic cigarette at least once. More than 92 percent of high school students who reported trying an electronic cigarette had also smoked a tobacco cigarette, but the survey did not ask which they sampled first.

Corresponding 2012 data for conventional tobacco products will be released sometime in the next few weeks, CDC spokesperson Joel London told U.S. News. In 2011, the CDC found, 18.1 percent of high school students smoked a conventional cigarette in the past month – and the CDC estimates between one-third and one-half of high school students have tried a tobacco cigarette at least once.

Congressional skeptics of the e-cigarette industry, which is largely unregulated, pounced on the survey data. Five Democratic senators, including Blumenthal, issued a joint press release at the time promising regulation of e-cigarettes. "This information is a call to action," said Senate Majority Whip Dick Durbin, D-Ill.

Blumenthal says he's concerned for adult users, too. "Many [e-cigarettes] involve carcinogens unknown or unappreciated by the smokers," he said.

But an analysis released in August by Drexel University researcher Igor Burstyn said the chemical composition of various e-cigarette liquids pose a negligible risk to second-hand smokers. Further, Burstyn wrote, "[t]here are no known toxicological synergies among compounds in the aerosol, and mixture of the contaminants does not pose a risk to health."

And a study published in March by the journal Tobacco Control looked at 12 brands of e-cigarettes and found they had far fewer toxins than conventional cigarettes. Large-scale, comprehensive studies on long-term health outcomes, however, haven't been performed yet.

Many e-cigarettes use a liquid that contains nicotine and propylene glycol, which a 2001 study conducted by the Environmental Protection Agency found is not carcinogenic. Companies offer liquid with various nicotine concentrations and liquids are commercially available that have no nicotine at all.

Blumenthal is "talking without any data to support either of his requests for prohibition," Conley says.

"Blumenthal can't show that there are lots of kids stealing their parents' credit cards to buy electronic cigarettes online" and banning flavors might "make electronic cigarettes unpalatable for a lot of people," he added.

An online sales ban would force customers to "go to convenience stores and buy products from the larger companies who are making inferior products," Conley says.

He said less-drastic measures to ensure age compliance could include online third-party age confirmation or age confirmation upon delivery, similar to measures taken for online tobacco and alcohol sales.

Despite his tough talk, Blumenthal clarifies "I'm not trying to ban e-cigarettes." Rather, he insists, he's working to ensure – be it through legislation or mere encouragement of the FDA – that non-adults are not enticed to try them and that "marketing and promotion practices... be completely truthful and accurate in conveying the risk and dangers of their use."

"If there are e-cigarettes that have no carcinogens," he said, "the market will drive people to those products [and] to the extent regulation makes them safer and less addictive, it will strengthen the product's appeal, not diminish it."