More must be done to examine the impact of e-cigarettes on health, experts have said.
The call comes as new research showed that almost 30 million people around Europe have tried the battery operated nicotine products.
A new study published in the journal Tobacco Control examined data from 26,500 people across 27 European countries. The authors of the study, from Imperial College London, the US and Greece, found that 20.3% of current smokers, 4.7% of ex-smokers and 1.2% of never smokers had tried an e-cig at least once. When the figures are extrapolated, this means that 29.3 million European adults have tried the products, they said.
But the researchers said that the scientific community is yet to provide information regarding the harm or efficacy of e-cigarettes.
They issued a call for more research into e-cigarettes, saying: “These findings underscore the need to evaluate the potential long-term impact of e-cigarette use on consumer health, cessation and nicotine addiction and formulate a European framework for e-cigarette regulation.”
Meanwhile a separate study, published in a special supplement of Tobacco Control, found that the market of e-cigarettes is growing rapidly.
Researchers from the US sought to identify the number of these products available online. They did two separate internet searches of English language websites, the first between May and August in 2012 and the second between December 2013 and January 2014.
In the period between searches there was a net increase of 10.5 new brands and 242 new flavours every month, they said.
By January 2014, they identified 466 brands with 7,764 unique flavours.
The research was published as a group of health experts from around the globe called on the World Health Organisation (WHO) to put new controls on e-cigarettes.
In a letter to WHO director general Margaret Chan, they raised concerns about what the unregulated products contain.
The group of 129 experts wrote: “By moving to the e-cigarette market, the tobacco industry is only maintaining it’s predatory practices and increasing profits.
“The aggressive marketing and promotion of e-cigarettes to youth is well documented and evidence shows rapid growth in youth e-cigarette use, including disturbing rates among youth who have never smoked a cigarette.
“Manufacturers of electronic nicotine delivery systems are making a range of false and unproven claims, misleading the public into thinking these products are harmless (they are not) and effective cessation aids (unknown).
“Remaining unregulated, risk profiles and potential harms these products may pose to the public are unknown.
“From a population perspective it is important to know what new risks a consumer product may introduce to the market.”
The issue is controversial among the medical profession, with some doctors believing that if the products had tighter regulations it would reduce the number of people who quit smoking.