The decision was made after a safety review and a look at the impact of e cigarettes on its smoke free campus policy.

Although e cigarettes emit chemical free steam, they have raised the issue of a lack of regulation for the new product, designed to help people quit smoking.

The battery powered devices resemble cigarettes and deliver nicotine through inhaled vapour.

The sale and use of e cigarette at HSE facilities, including hospitals, will be banned from May 1.

The use of E cigarettes is currently unregulated in Ireland and is not covered by the workplace ban on smoking.

The HSE said it can only recommend “safe and effective products” and methods for quitting smoking.

The organisation raised suggestions that there is no conclusive evidence that e cigarettes are safe for long term use.

It raised fears that the product, which resembles an ordinary cigarette, will promote or re normalise smoking, pollute the environment for non smokers and make it harder for smokers to quit.

A hot debate over e-cigarettes as a path to tobacco, or from it – nytimes.com

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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.