Dr. Michael Siegel, a hard-charging public health researcher at Boston University, argues that e-cigarettes could be the beginning of the end of smoking in America. He sees them as a disruptive innovation that could make cigarettes obsolete, like the computer did to the typewriter.
But his former teacher and mentor, Stanton A. Glantz, a professor of medicine at the University of California, San Francisco, is convinced that e-cigarettes may erase the hard-won progress achieved over the last half-century in reducing smoking. He predicts that the modern gadgetry will be a glittering gateway to the deadly, old-fashioned habit for children, and that adult smokers will stay hooked longer now that they can get a nicotine fix at their desks.
These experts represent the two camps at war over the public health implications of e-cigarettes. The devices, intended to feed nicotine addiction without the toxic tar of conventional cigarettes, have divided a normally sedate public health community that had long been united in the fight against smoking and Big Tobacco.
The essence of their disagreement comes down to a simple question: Will e-cigarettes cause more or fewer people to smoke? The answer matters. Cigarette smoking is still the single largest cause of preventable death in the United States, killing about 480,000 people a year.
Siegel, whose graduate school manuscripts Glantz used to read, says e-cigarette pessimists are stuck on the idea that anything that looks like smoking is bad. "They are so blinded by this ideology that they are not able to see e-cigarettes objectively," he said. Glantz disagrees. "E-cigarettes seem like a good idea," he said, "but they aren't."
Science that might resolve questions about e-cigarettes is still developing, and many experts agree that the evidence so far is too skimpy to draw definitive conclusions about the long-term effects of the devices on the broader population.
"The popularity is outpacing the knowledge," said Dr. Michael B. Steinberg, associate professor of medicine at the Robert Wood Johnson Medical School at Rutgers University. "We'll have a better idea in another year or two of how safe these products are, but the question is, will the horse be out of the barn by then?"
This high-stakes debate over what e-cigarettes mean for the nation's 42 million smokers comes at a crucial moment. Soon, the Food and Drug Administration is expected to issue regulations that would give the agency control over the devices, which have had explosive growth virtually free of any federal oversight. (Some cities, such as Boston and New York, and some states, like New Jersey and Utah, have weighed in, enacting bans in public places.)
The new federal rules will have broad implications for public health. If they are too tough, experts say, they risk snuffing out small e-cigarette companies in favor of Big Tobacco, which has recently entered the e-cigarette business. If they are too lax, sloppy manufacturing could lead to devices that do not work properly or even harm people.
And many scientists say e-cigarettes will be truly effective in reducing the death toll from smoking only with the right kind of federal regulation - for example, rules that make ordinary cigarettes more expensive than e-cigarettes or that reduce the amount of nicotine in ordinary cigarettes so smokers turn to e-cigarettes for their nicotine.
"E-cigarettes are not a miracle cure," said David B. Abrams, executive director of the Schroeder National Institute for Tobacco Research and Policy Studies at the Legacy Foundation, an anti-smoking research group. "They need a little help to eclipse cigarettes, which are still the most satisfying and deadly product ever made."
Sales of e-cigarettes more than doubled last year from 2012, to $1.7 billion, according to Bonnie Herzog, an analyst at Wells Fargo Securities. Herzog said that in the next decade, consumption of e-cigarettes could outstrip that of conventional cigarettes. The number of stores that sell them has quadrupled in just the past year, according to the Smoke Free Alternatives Trade Association, an e-cigarette industry trade group.
"E-cigarette users sure seem to be speaking with their pocketbooks," said Mitchell Zeller, director of the FDA's Center for Tobacco Products.
Public health experts like to say that people smoke for the nicotine but die from the tar. And the reason e-cigarettes have caused such a stir is that they take the deadly tar out of the equation while offering the nicotine fix and the sensation of smoking. For all that is unknown about the new devices - they have been on the U.S. market for only seven years - most researchers agree that puffing on one is far less harmful than smoking a traditional cigarette.
But then their views diverge.
Pessimists like Glantz say that while e-cigarettes might be good in theory, they are bad in practice. The vast majority of people who smoke them now also smoke conventional cigarettes, he said, and there is little evidence that much switching is happening. E-cigarettes may even prolong the habit, he said, by offering a dose of nicotine at times when getting one from a traditional cigarette is inconvenient or illegal.
A survey from the Centers for Disease Control and Prevention found that in 2012, about 10 percent of high school students said they had tried an e-cigarette, up from 5 percent in 2011. But 7 percent of those who had tried e-cigarettes said they had never smoked a traditional cigarette, prompting concern that e-cigarettes were, in fact, becoming a gateway.
"I think the precautionary principle - better safe than sorry - rules here," said Dr. Thomas Frieden, director of the CDC.
E-cigarette skeptics have also raised concerns about nicotine addiction. But many researchers say that the nicotine by itself is not a serious health hazard. Nicotine-replacement therapies such as lozenges and patches have been used for years. Some even argue that nicotine is a lot like caffeine: an addictive substance that stimulates the mind.
Solid evidence about e-cigarettes is limited. A clinical trial in New Zealand, which many researchers regard as the most reliable study to date, found that after six months, about 7 percent of people given e-cigarettes had quit smoking, a slightly better rate than those with patches.
"The findings were intriguing but nothing to write home about yet," said Thomas J. Glynn, a researcher at the American Cancer Society.
In Britain, where the regulatory process is more developed than in the United States, researchers say smoking trends are heading in the right direction.
"Motivation to quit is up, success of quit attempts are up, and prevalence is coming down faster than it has for the last six or seven years," said Robert West, director of tobacco studies at University College London. It is impossible to know whether e-cigarettes drove the changes, he said, but "we can certainly say they are not undermining quitting."
Carefully devised federal regulations might channel the marketing might of major tobacco companies into e-cigarettes, cannibalizing sales of traditional cigarettes, Abrams of the Schroeder Institute said. "We need a jujitsu move to take their own weight and use it against them," he said.
Benowitz said he could see a situation under which the FDA would gradually reduce the nicotine levels allowable in traditional cigarettes, pushing smokers to e-cigarettes.
"If we make it too hard for this experiment to continue, we've wasted an opportunity that could eventually save millions of lives," Siegel said.
"I frankly think the fault line will be gone in another year," he said. "The evidence will show their true colors."