Watch out, e-cigarette smokers – you're inhaling the unknown

Electronic cigarettes sound fantastic. Rather than fill your lungs with tar, they deliver a vapour of nicotine to satisfy your craving, without the nasty side effects. They are popularly perceived as the safe alternative to cigarettes, a harmless way to get a nicotine hit. No wonder 700,000 people were using e-cigarettes in the UK last year, with that figure set to rise to over a million by the end of 2013.
Doctors are desperate to drive down the £5bn a year that smoking-related illness costs the NHS. Anything that could help smokers quit would be welcomed. But e-cigarettes aren't a medicine. There's a reason you buy them from a newsagent rather than get them on prescription. E-cigarettes may look legitimate, but they haven't been through the same stringent safety checks as medicated nicotine replacement therapies.
I want to be certain I'm giving the right advice to patients when they ask about e-cigarettes, not unwittingly jeopardising their health. Hardened smokers trying to quit are using them like prescription drugs, but they don't have any of the same safeguards. E-cigarettes are masquerading as medications – so let's subject them to the same scrutiny.
A quick search of medical journal archives reveals about 200 references to electronic cigarettes over the past five years. These products are relatively new, so there are no long-term studies on the effects of using them regularly. Instead, research is focused on what is being delivered to smokers' lungs in addition to nicotine.
The US Food and Drug Administration analysed the components of e-cigarette cartridges in 2009. They identified trace levels of tobacco-specific nitrosamines (TSNAs) – cancer-causing compounds commonly found in traditional cigarettes, albeit at a much lower concentration.
Although concerning, this isn't a huge surprise – similar levels are found in nicotine patches. But the FDA also found diethylene glycol, a component of antifreeze and brake fluids. Classed as a poison by the World Health Organisation, at high enough quantities it can cause kidney damage, nerve dysfunction and respiratory failure.
In March 2013, researchers from the University of California examined in detail the aerosol contents of e-cigarettes. They found particles of silver, iron, aluminium and silicate, and nanoparticles of tin, chromium and nickel. The researchers noted that concentrations of these elements "were higher than or equal to the corresponding concentrations in conventional cigarette smoke", and that "many of the elements identified in [e-cigarette] aerosol are known to cause respiratory distress and disease".
Other papers concentrate on the social effects of introducing a highly addictive drug to a new audience. The Journal of Adolescent Health identified e-cigarette ad campaigns that disproportionately appeal to a younger market, including "celebrity endorsements, trendy/fashionable imagery, and fruit, candy, and alcohol flavors".
A comparison can be drawn with alcopops, and there are concerns that awareness of e-cigarettes is far greater among adolescents than among the general population. Instead of being an opportunity for current smokers to step down to something less harmful, they could be a gateway into smoking for young people who would not otherwise try cigarettes.
Some commentators have been sceptical about doctors' reticence to embrace e-cigarettes. Although I strongly encourage smokers to quit, I'm not comfortable advocating an unregulated, unlicensed consumer product that is marketing itself as a medicine. It has an unsettling similarity to when some doctors encouraged smoking for health before the damage of cigarettes was fully understood.
With a little research, it is clear that we do not know the risks of using e-cigarettes long-term, and the potential for harm is significant. Until the same regulations as other nicotine replacements are imposed, e-cigarettes should be considered a snake-oil gimmick that could get a new generation hooked on nicotine before their first smoke.