E-cigarettes are back in the news after MPs on the Science and Technology Committee (STC) said rules around the devices should be relaxed to help accelerate already declining smoking rates.

These are some of the key issues in the debate:

– A healthier alternative?

A landmark review by Public Health England (PHE) published in 2015 said vaping is 95% less harmful than smoking tobacco.

The body said much of the public wrongly believed that e-cigarettes carry health risks in the same way cigarettes do. PHE wants to see smokers taking up the electronic devices to reduce the thousands of people dying from tobacco-related diseases every year.

The review by medical research organisation Cochrane found that 18,000 people in England may have given up smoking in 2015 thanks to e-cigarettes.

– That settled it then?

PHE’s findings were criticised at the time by some experts, saying they were based on poor quality evidence. They also pointed to links between some experts, the tobacco industry and firms that manufacture e-cigarettes.

– So they could be more harmful than has been said?

Some studies have linked vaping with lung damage, heart disease and even cancer and infant mortality.

Research by the University of Birmingham published this week said e-cigarette vapour has a similar effect on the lungs and body that is seen in regular cigarette smokers and patients with chronic lung disease.

A study by the New York University School of Medicine found smoke from e-cigarettes damages DNA and can increased the risk of cancer and heart disease in mice.

Campaign to target pregnant smokersAn NHS poster warning of the dangers of smoking while pregnant (NHS Smokefree/PA)

Meanwhile, researchers at the Geisel School of Medicine in the US have warned any kind of nicotine exposure during pregnancy, whether from smoking, skin patches or vaping, heightens the chances of Sudden Infant Death Syndrome. Many experts say much more research needs to be done in the area.

– Can they encourage people to smoke conventional cigarettes?

The STC says concerns that e-cigarettes could be a gateway to conventional smoking, including for young non-smokers, “have not materialised”.

Expert opinion on the issue is divided.

In the UK a person must be 18 to buy e-cigarettes or the e-liquids they vaporise.

Public Health England e-cigarettes reviewMPs have called for e-cigarettes to be made available on prescription (Peter Byrne/PA)

The latest data from the Office for National Statistics suggests young people are smoking in fewer numbers, with the number of 18 to 24-year-olds who smoke falling eight percentage points since 2011.

However a 2017 study of 14 and 15-year-olds from 20 English schools found a “robust association” between vaping and a higher probability of cigarette smoking.