BERLIN (Deutsche Presse-Agentur) -- Concern is rising over the use of electronic cigarettes -- or e-cigarettes -- that produce an aerosol mist for inhaling rather than tobacco smoke and are used by many smokers to help kick the habit.

The small devices generally contain a rechargeable battery and an atomizer for vaporizing a liquid intended to simulate some of the pleasures of smoking without the harmful effects. The potential risks involved and the precise contents of the liquids, along with their side-effects have been little researched. However, warnings are becoming increasingly loud, leading some countries to ban the devices.

"Consumers should be able to rely on a product that is safe from a health viewpoint and that is by no means certain in the case of the e-cigarette," Martina Poetschke-Langer of the DKFZ German cancer research centre says. She cautions that lessons should be drawn from the mistakes of the past when promoting a new product.

"The standard cigarette caused millions of deaths over the course of the last century and would never have been allowed if we had known a hundred years ago what we know now," she says.

The precise legal status of e-cigarettes is far from clear. Many US doctors back the device as an aid to stopping smoking, but across the border in Canada, the federal health authorities have come out against them. The British body Cancer Research UK sees them as safer than real cigarettes and possibly useful in breaking smoking dependence.

Germany's 16 states have taken differing approaches. "Things could be starting to move here. The states are talking about how to proceed in unison," Poetschke-Langer says. But the trade is booming, with consumers in states where e-cigarettes are banned simply ordering them over the internet.

Barbara Steffens, health minister in Germany's most populous state of North Rhine-Westphalia, where they are banned, notes that, "Not everything on the market has been licensed and tested." In her view, the liquids contain levels of nicotine that are so high that they need to be classified as medications and thus fall under the stringent provisions of the medications act.

Many questions remain. The e-cigarettes contain widely varying amounts of nicotine, which is a stimulant and relaxant, and is also highly addictive, along with aromas like chocolate-caramel and liquorice.

Consumer Alexandra Funck says she is aware of the controversy. "E-cigarettes don't contain all that muck. Sure, they're not healthy, but they're less harmful," says the 42-year-old from Dusseldorf who is using the devices to quit smoking.

"You also don't have the butts and the ash. Your clothes don't stink and you don't irritate others," said Funck, who is angry at the ban in her state of North Rhine-Westphalia. "Then you should ban normal cigarettes or sell them only through the pharmacies."

While the producers insist their product is much less harmful than ordinary cigarettes, German doctors are not so sure, pointing to a study that reveals harmful effects on the bronchial passages. They blame the propylene glycol, an anti-freeze agent contained in the liquid, which makes up 90 per cent of the inhaled vapour.

Poetschke-Langer says the e-cigarette is likely to be just as addictive as the ordinary kind and notes that there is no good evidence that they assist in stopping smoking.

The US Food and Drug Administration (FDA) has found carcinogenic substances like nitrosamines in the liquid, and there is little clarity on whether there might be effects on "passive smokers" in the immediate environment of the e-smoker.

The product is banned in Norway, Turkey, Switzerland and even in China, where it was invented some 10 years ago. There are strict controls in Denmark, Canada and Austria, and the European Commission is probing the health effects.

Copyright 2012 dpa Deutsche Presse-Agentur GmbH