But the growing popularity of e-cigarettes has not escaped the notice of the industry's critics, who have stepped up calls for new regulations, including bans on their use in public places, even though the scientific evidence about exposure to their vapors remains inconclusive.
Selling for about $30 to $50 each, e-cigarettes are slim, reusable, metal tubes containing nicotine-laced liquids that come in exotic flavors. When users puff on the device, the nicotine is heated and releases a vapor that, unlike cigarette smoke, contains no tar, which causes cancer and other diseases.The product, introduced in China in 2006, has become a worldwide trend at least in part because it may help smokers of regular cigarettes break the habit.
"It's an addiction - not everyone can quit cold turkey," said Nick Edwards, 34, a Henley employee who says he kicked a 15-year cigarette habit the day he tried his first e-cigarette. "E-cigarettes give you a harm-reduction option."
That's one reason why the market for e-cigarettes is expected to surge, reaching $2 billion by the end of 2013 and $10 billion by 2017, according to Bonnie Herzog, an analyst at Wells Fargo Bank in New York.
Herzog said the U.S. market alone could top $1 billion this year. She predicts that by 2017 e-cigarettes sales will overtake sales of regular cigarettes. That estimate does not take into account the impact of potential government regulations on sales.
E-cigarettes may help smokers save money too. Edwards, for one, says he cut his $60 monthly cigarette bill in half when he switched. On top of the cost of the device, the smoking liquids cost around $10 per refill.
Despite the perceived benefits, critics worry that the addictive nicotine found in e-cigarettes could lure more people into smoking and discourage others from quitting all together.
"Essentially e-cigarette companies are selling nicotine addiction," said Dr. Neil Schluger, chief scientific officer for the World Lung Foundation, which advocates for tobacco control.
"Once you have them addicted to nicotine, you can sell them all sorts of things, including conventional cigarettes," he said. "This is a giant Trojan horse."
In the United States, such concerns have led to calls for increased government regulation.
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The U.S. Food and Drug Administration currently has no regulations on e-cigarettes, but it is expected to release rules this month that would extend its "tobacco product" authority over the devices. New FDA rules could follow.
"Further research is needed to assess the potential public health benefits and risks of electronic cigarettes and other novel tobacco products," said Jenny Haliski, an FDA spokeswoman.
To be sure, no one is expecting the federal government to go as far as Brazil, Norway and Singapore, where the devices are banned outright.
In the United States, Utah, North Dakota, Arkansas and New Jersey have already passed legislation outlawing e-cigarettes wherever smoking is prohibited.
Other jurisdictions are considering new rules of their own. New York City could decide as early as next week whether to prohibit e-cigarette use in public places.
Under Mayor Michael Bloomberg, who leaves office January 1, New York was one of the first cities to ban cigarette smoking in public places, and its decision could influence Chicago and other cities that are considering a similar controls.
The outcome is crucial for tobacco companies, which are banking on the devices to make up for a sharp decline in sales of regular cigarettes in the United States. Smoking among U.S. adults dropped to 18 percent in 2012 from 24.7 percent in 1997, according to the Centers for Disease Control and Prevention.
Reynolds American Inc, which makes Camel cigarettes, began selling its Vuse vapor cigarettes in Colorado retail stores in July and plans on expanding nationwide by mid-2014.
Other companies have also dipped into the e-cigarette business, too. Last year Lorillard Inc, maker of Newport cigarettes, acquired the best-selling blu eCigs brand, while Altria Group Inc, best known for the Marlboro brand, followed suit in August with the launch of MarkTen e-cigarettes.
"As society is transforming, so must the tobacco industry," said Reynolds spokesman Richard Smith. "It's just good business sense."
The arrival of Big Tobacco could mean fierce competition for small e-cigarette companies that do not have the resources or experience to deal with tight government regulation.
But many e-cigarette companies say Big Tobacco is late to the game and has a lot to catch up on. "They are going to need to boost up their game if they want to compete," said Christina Lopez, a saleswoman at Smokeless Image, an e-cigarette shop that sells smaller brands in Hoboken, New Jersey.
HEALTH RISKS UNCERTAIN
To be sure, there is still a dearth of scientific evidence about the safety of e-cigarettes and their effectiveness in helping smokers quit. For regulators, the big question is, are e-cigarettes a treatment for would-be quitters or "gateway" products to nicotine addiction?
Supporters say some e-cigarettes allow users to slowly reduce their nicotine intake and wean themselves off nicotine completely. A study published in the September issue in Lancet, the British medical journal, said the e-cigarettes are as effective as nicotine patches for smokers trying to quit.
Worldwide, conventional cigarette addictions kill 6 million people a year, in part because of the 250 harmful chemicals found in tobacco smoke, which can cause cancer, heart disease and stroke, says the Centers for Disease Control and Prevention.
But e-cigarettes may not be harmless, either. Nicotine addictions, fed by smoking, chewing tobacco or e-cigarettes, can cause high blood pressure, disrupt heart rhythms and lead to obesity and diabetes.
Electronic devices that feature fruit and candy flavors are even more worrying, critics say, because they could introduce children to smoking.
E-cigarette vendors say the sweet flavors make the process of quitting smoking less painful.
"By taking a sort of 'Willy Wonka,' fun approach to a serious matter, it breaks down people's perceptions of e-cigarettes," said Talia Eisenberg, owner of the Henley Vaporium, referring to the fictional candy maker.
The Centers for Disease Control and Prevention said 10 percent of high school students surveyed reported using e-cigarettes in 2012, up from 4.7 percent in 2011.
About 60 percent of current users are over 35 years old, and 43 percent are college-educated, according to Reynolds American.
Twelve states, including New York, have passed laws preventing e-cigarette sales to minors.
At a hearing on the proposed New York City ban on e-cigarette use in public places, Health Commissioner Thomas Farley said allowing it could glamorize all types of smoking and encourage teenagers and children to take up the cigarette habit.
"While more research is needed on electronic cigarettes, waiting to act could jeopardize the progress we have made over the last few years," he said.