Nicotine may have some adverse health effects, but they are relatively minor, said Dr. Neal L. Benowitz, a professor of medicine at the University of California, San Francisco, who has spent his career studying the pharmacology of nicotine.

Another ingredient, propylene glycol, the vapor that e cigarettes emit whose main alternative use is as fake smoke on concert and theater stages is a lung irritant, and the effects of inhaling it over time are a concern, Dr. Benowitz said.

But Dr. Siegel and others contend that some public health experts, after a single minded battle against smoking that has run for decades, are too inflexible about e cigarettes. The strategy should be to reduce harm from conventional cigarettes, and e cigarettes offer a way to do that, he said, much in the way that giving clean needles to intravenous drug users reduces their odds of getting infected with the virus that causes AIDS.

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 that 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.

The scientific uncertainties have intensified the public health fight, with each side seizing on scraps of new data to bolster its position. One recent study in Germany on secondhand vapor from e cigarettes prompted Dr. Glantz to write on his blog, More evidence that e cigs cause substantial air pollution. Dr. Siegel highlighted the same study, concluding that it showed no evidence of a significant public health hazard.

That Big Tobacco is now selling e cigarettes has contributed to skepticism among experts and advocates.

Cigarettes went into broad use in the 1920s and by the 1940s, lung cancer rates had exploded. More Americans have died from smoking than in all the wars the United States has fought. Smoking rates have declined sharply since the 1960s, when about half of all men and a third of women smoked. But progress has slowed, with a smoking rate now of around 18 percent.

Part of the furniture for us is that the tobacco industry is evil and everything they do has to be opposed, said John Britton, a professor of epidemiology at the University of Nottingham in England, and the director for the U.K. Center for Tobacco and Alcohol Studies. But one doesn t want that to get in the way of public health.

Carefully devised federal regulations might channel the marketing might of major tobacco companies into e cigarettes, cannibalizing sales of traditional cigarettes, Dr. Abrams of the Schroeder Institute said. We need a jujitsu move to take their own weight and use it against them, he said.

Dr. Benowitz said he could see a situation under which the F.D.A. 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, Dr. Siegel said.

Dr. Glantz disagreed.

I frankly think the fault line will be gone in another year, he said. The evidence will show their true colors.

Electronic cigarettes may not help people stop smoking: study

NEW YORK A small U.S. study raises new questions about whether using electronic cigarettes will lead people to quit smoking, adding to the debate over how tightly the products should be regulated.

The study, which looked at the habits of 88 smokers who also used e cigarettes, was published as a research letter in the journal JAMA Internal Medicine on Monday. It found that smokers who also used e cigarettes were no more likely to quit smoking after a year, compared to smokers who didn’t use the devices.

Outside experts say the small number of respondents, and a lack of data on whether they intentionally used e cigarettes to help them quit smoking, mean the findings from the Center for Tobacco Control Research and Education at the University of California, San Francisco can’t take the place of much more rigorous study on the subject.

E cigarettes were first introduced in China in 2004 and have since grown into a $2 billion industry. The battery powered devices let users inhale nicotine infused vapors, which don’t contain the harmful tar and carbon monoxide in tobacco.

At issue is how strictly U.S. health regulators should control the products. Advocates say e cigarettes can help smokers quit. Public health experts fear they can serve as a gateway to smoking for the uninitiated, particularly teenagers. Leading U.S. brands include blu by Lorillard Inc and products from privately held NJOY and Logic Technology.

A previous report from the UK found that people who use e cigarettes primarily want to replace traditional cigarettes (see Reuters Health story here ).

“We did not find a relationship between using an e cigarette and reducing cigarette consumption,” Rachel Grana, the lead researcher on the new study, told Reuters Health.

Grana and colleagues at the University of California, San Francisco analyzed 2011 survey data collected from 949 smokers. Of those, 88 reported using e cigarettes.

When the researchers looked at those smokers’ responses a year later, they found that the people who reported using e cigarettes in the 2011 survey were no more likely to quit smoking than the people who didn’t use e cigarettes.

For those who were still smoking in 2012, using e cigarettes also didn’t appear to change how many traditional cigarettes people smoked per day.

The researchers note that the small number of participants who reported using e cigarettes may have limited their ability to detect a link between quitting smoking and using the device.

Dr. Michael Siegel, who was not involved with the new research, told Reuters Health that the new study had several design flaws, including that the researchers did not know why some of the participants tried e cigarettes or how long they had used them. Siegel is an expert on community health at Boston University School of Public Health and has studied e cigarette research.

By comparing people who smoked regular cigarettes and those who smoked e cigarettes, the researchers are assuming “that the groups are exactly equivalent in terms of their motivations and their levels of addiction to cigarettes,” Siegel said. “You can’t make those assumptions. You’re not dealing with comparable groups.”

In an emailed statement, Grana and fellow researchers acknowledged that they did not have information on the participants’ motivations to use e cigarettes, but said their analysis took into account other factors known to be linked to quitting smoking, such as their stated intention to quit and how many cigarettes they already smoked each day.

“These factors may also reflect motivations to use e cigarettes, as e cigarettes are frequently marketed and perceived as cessation aids,” they wrote. “While these factors predicted quitting as expected, we found that e cigarette use did not predict quitting.

Siegel also pointed out that only about eight percent of the people surveyed said they had any intention to quit smoking within the next month. He hopes people will reserve judgment on e cigarettes until randomized controlled studies considered the “gold standard” of medical research are published.

“We need solid data that’s based on solid science before we make decisions,” he said. “I hope no one would take this research letter and make any conclusion based on it.”

SOURCE JAMA Internal Medicine, online March 24, 2014.