The vape of things to come: How safe are e-cigs?
For Matt Ridley, the libertarian commentator, there is a simple analogy for the debate about e-cigarettes.
"Suppose that millions of Britons were driving a dangerous type of car that was killing 80,000 people a year," he says.
"Suppose somebody invented a new car that was much much safer, significantly cheaper, and emitted far fewer fumes. Would you ban the new car, or encourage people to buy it?"
Yet, continuing the analogy, he argues, opponents of e-cigarettes would ban the safe car, on the basis it is better not to drive at all.
It is 16 years since Chinese pharmacist Hon Lik patented his design for the first e-cig, battery-powered device which turned liquid nicotine into a vapour which the 'smoker' could inhale.
Today, there are 2.8 million 'vapers' in the UK. But while e-cigs were initially hailed as a breakthrough in reducing the harm caused by tobacco, there have in recent years been growing questions about whether they are quite as harmless as first thought, and calls for tighter regulation.
Dr Aaron Scott, from Birmingham University, is firmly in the latter camp, and is calling for tighter regulation.
"They’ve advocated for less regulation of e-cigarettes to make it easier for people to take up these devices and I don’t agree with that," he says.
"You can go into a pound store anywhere in the country and buy e-cigarette liquid for £1. You can do that with very little regulation, so it’s very easy for example for kids to get that, it’s very accessible."
In theory, the logic behind e-cigarettes is hard to dispute. It means somebody who is struggling to give up smoking can can satisfy their craving for the addictive drug nicotine, without inhaling the harmful carcinogens that come from tobacco.
However, research into the effects of e-cigs has so far proved inconclusive.
The Birmingham-based British Heart Foundation takes the view that while vaping is far from risk-free, e-cigs can be a useful tool in helping people to quit smoking.
Associate medical director at the charity, Dr Mike Knapton, says: “We would not advise non-smokers to take up e-cigarettes, but they can be a useful tool for harm reduction and to stop smoking.”
The charity says that tobacco smoking causes about 46,000 deaths from cancer and 28,000 from respiratory disease in the UK, plus an estimated 20,000 deaths from cardiovascular disease.
The Royal College of Physicians is firmly supportive of e-cigarettes, and advises GPs to recommend them “as widely as possible as a substitute for smoking”.
The college argues that while vaping is probably more harmful than nicotine replacement therapies, such as patches and chewing gum, the risks are still fairly low.
"The hazard to health arising from long-term vapour inhalation from the e-cigarettes available today is unlikely to exceed five per cent of the harm from smoking tobacco," says the organisation.
The college says that while there are concerns that vaping could encourage young people to move on to tobacco, there is little evidence to support this.
"The available evidence to date indicates that e-cigarettes are being used almost exclusively as safer alternatives to smoked tobacco, by confirmed smokers who are trying to reduce harm to themselves or others from smoking, or to quit smoking completely," the college says.
The college agrees that there is a need for regulation of e-cigs, but said this should not be allowed significantly to inhibit the development and use of a product which has the potential to significantly reduce harm.
However, a 2014 study in the New England Journal of Medicine found that “electronic cigarettes may function as a ‘gateway drug’ that can prime the brain to be more receptive to harder drugs.”
Recent independent studies from Public Health England show that most of the chemicals causing smoking related disease are absent in e-cigarettes, and chemicals that are present pose little danger.
Public Health England's Martin Dockrell says: “For the main carcinogen in tobacco smoke, levels in e-cigarette users were close to that of non-smokers.”
But a small study, published in August 2016, suggested that smoking e-cigarettes for 30 minutes can cause arteries to stiffen, in a similar way to tobacco cigarettes, suggesting more research is needed into their long-term safety
Dr Scott goes further.
"We only have evidence for short-term and in the short-term it’s definitely harmful," he says.
"I think we should be more cautious."
His research paper, funded by the British Lung Foundation, found that, in the short term at least, the vaporised e-liquid fluid had a similar effect on the lungs and body as seen in regular cigarette smokers.
He argues that there is a need for tighter regulation, saying it is just too easy to get hold of e-cigarettes.
Dr Scott says many of the previous studies, which have suggested e-cigs are relatively safe, had only examined the effects of the nicotine liquid before it was vaporised.
“It is well established that the vapourising process changes the chemical composition of the liquid," he says.
“The use of vaped liquid in our study makes this a better reflection of the exposure of the user, allowing us to examine whether e-cigarettes have a negative impact on the viability and function of cells called alveolar macrophages, which are key to the immune response within the airways."
He said the research clearly showed that vapourised e-cigarette fluid was toxic to living cells, increasing the production of inflammatory chemicals and inhibiting cells central to the immune system.
“Importantly, we found that exposure of these cells to e-cigarette vapour induced many of the same cellular and functional changes in function seen in cigarette smokers and patients with COPD.
"While further research is needed to fully understand the effects of e-cigarette exposure in humans, we suggest continued caution against the widely held opinion that e-cigarettes are safe.”