'More research' needed into safety of electronic cigarettes
Andreas Flouris and Dimitris Oikonomou, from the Institute of Human Performance and Rehabilitation in Greece, are concerned that not enough research has been carried out into the safety - or otherwise - of so-called 'e-cigarettes'.
Their position has been endorsed by Cancer Research UK, which is also concerned by the current lack of information.
E-cigarettes are battery-powered devices that simulate cigarettes by allowing the user to inhale a nicotine vapour.
Sales of the devices are thought to be increasing and a number of celebrities - including Kate Moss and Leonardo DiCaprio - have been spotted using them.
However, few studies have been conducted into the health effects of smoking e-cigarettes and those that have been published have reached differing conclusions.
One, carried out by the US Food and Drug Administration (FDA), found that the amount of nicotine provided with each puff often varies from the amount stated on the label, prompting the agency to express concern about e-cigarettes.
In contrast, a private enterprise called Health New Zealand (HNZ) found that the labelling on e-cigarettes reflected their actual nicotine content.
The FDA's research also detected the presence of diethylene glycol - a highly toxic liquid - in one of the cartridges it investigated, while both the FDA and HNZ found cancer-causing chemicals called tobacco specific N-nitrosamines.
In its report, the FDA suggested that e-cigarettes may therefore be harmful, but HNZ recommended their use as they are likely to be less dangerous than tobacco products.
Meanwhile, a Greek organisation called Demokritos has maintained a neutral stance on the subject after conducting its own research.
Drs Flouris and Oikonomou note that this "represents all the knowledge we currently have about e-cigarettes" and that the European Centre for Disease Prevention and Control is yet to publish any research on the subject.
"Alternative smoking strategies aimed at reducing the threat to public health caused by the tobacco epidemic are always welcome," the researchers conceded.
However, they observed: "To date, our knowledge about the acute and long-term effects of e-cigarette use is, at best, very limited.
"The scarce evidence indicates the existence of various toxic and carcinogenic compounds, albeit in possibly much smaller concentrations than in traditional cigarettes."
Jean King, Cancer Research UK's director of tobacco control, said: "There has been little research into how safe e-cigarettes are. And there's also very little regulation to control these products or their marketing. The only way to be sure of any risks or benefits is through rigorous testing.
"Anyone trying to quit smoking should use medicinal nicotine products such as patches, gum or inhalators, because these have been tested and found to be safe and effective. We believe that e-cigarettes should undergo the same rigorous tests and meet the same standards as all other medicinal products containing nicotine."