Norman Swan: In England, Scotland and New Zealand, vaping is being endorsed as a way of helping smokers to quit. The idea is you substitute tobacco for an electronic cigarette that mainly delivers nicotine. Those governments reckon on saving thousands of lives and millions of pounds and dollars to their healthcare systems through nicotine vaping, yet here public health experts mostly oppose the legalisation of e-cigarettes, saying there isn't enough evidence to show vaping's safe.

So is Australia missing out? James Bullen takes a look.

Matthew Peters: The whole idea that you can have an unknown liquid, super-heated, with any possible alteration of the chemicals that are put into it, and then for it to be wise to inhale deeply into your lungs is just nonsense.

Greg Hunt: I have a very strong, clear, categorical view that this is not something that should occur in Australia.

Marewa Glover: We have all these people in this burning building, and some of these public health people are standing in the way of the exit door and saying: 'No, no, you can't go down the stairs, we don't know if it's safe.'

Colin Mendelsohn: Smoking rates have plateaued for the first time ever. And I think that's telling us we need to look at alternative strategies to add to what we're doing.

James Bullen: Colin Mendelsohn, Associate Professor in the School of Public Health and Community Medicine at the University of New South Wales, and a tobacco treatment specialist. In fact, smoking rates haven't quite plateaued, but the drop-off in the number of people smoking has slowed in recent years. And that still begs the question of whether we need to try a different strategy.

Colin Mendelsohn: The fact is that we have very good evidence from overseas that these products work, and they're much less harmful, and we need additional options to move things forward. We have a very large population of smokers who can't quit with what we're currently doing.

James Bullen: He's not alone. Last month, experts flew in from the UK to make submissions to a parliamentary inquiry that's currently looking into the use and marketing of electronic cigarettes in Australia.

The existing legal framework around e-cigarettes, or vaping, is complex. In some states, you can buy just the vaping device, while in other states their sale is illegal. But buying, possessing or using liquid nicotine in an e-cigarette is illegal across Australia.

The UK experts argue e-cigarette use is less harmful than regular smoking, and could help smokers quit. The argument revolves around the smoke. Cigarette smoke is notorious for producing carcinogens. But advocates say the vapour produced by an e-cigarette has fewer chemicals and is less harmful.

Colin Mendelsohn: In the UK, for example, there are currently 1.5 million former smokers who now vape. There's another million and a half who are doing both, and many of them are transitioning to vaping. There are at least 600,000 or 700,000 ex-smokers and ex-vapers. So there's a clear movement, it's clearly helping many people.

James Bullen: Those are figures from an Action on Health and Smoking, or ASH survey in May this year. ASH does support the adoption of e-cigarettes. And England isn't the only country making moves in this area. In September, NHS Scotland released a statement saying e-cigarettes are 'definitely' less harmful than tobacco smoking and that it'd be a good thing if smokers switched to vaping, though not if they used both at the same time. And just last month, New Zealand's Health Ministry also endorsed the use of e-cigarettes as a harm reduction tool.

But at the same time as the tide appears to be turning overseas, things are moving nowhere fast here in Australia.

Greg Hunt: I have a very strong, clear, categorical view that this is not something that should occur in Australia.

Sarah McVeigh: Does that mean it won't happen under your government?

Greg Hunt: It's not going to be happening on my watch as far as I'm concerned.

James Bullen: Federal Health Minister Greg Hunt speaking to Sarah McVeigh on triple j's Hack about e-cigarettes a few weeks ago.

Matthew Peters: The idea that another jurisdiction can look at a public health problem and form a different view and we have to slavishly follow them is nonsense. This is a very experienced country when it comes to tobacco control, we have very low rates of smoking that are going lower and we don't need to experiment with something like e-cigarettes at the moment.

James Bullen: Professor Matthew Peters, head of Respiratory Medicine at Concord Hospital in Sydney. He's among public health professionals including Simon Chapman from Sydney University and Mike Daube of Curtin University in Western Australia, who don't want to see e-cigarettes introduced here.

Matthew Peters: We just can't have a product available to the public on a hunch that it might be safer than smoking over the long run. Because it's no more than a hunch.

James Bullen: The 'hunch' Professor Peters is referring to when it comes to e-cigarettes is an oft-cited figure about the difference in harm between regular cigarettes and vaping. Some claim that vaping is 95% less harmful than smoking.

That number first cropped up in a European Addiction Research paper, 'Estimating the Harms of Nicotine-Containing Products Using the MCDA Approach'. That MCDA, or multi-criteria decision analysis, weighed up nicotine products by their potential to harm users and others around them. Regular cigarettes received a weighted overall score of 100, while e-cigarettes got a score of about five. Professor Peters says that figure was arrived at by consensus. He questions the extent to which it's been relied upon in the e-cigarettes debate.

Matthew Peters: It's true that both the Public Health England and the Royal College of Physicians believe they came to that number independently, but it's striking that that is the number they've agreed on. It was always a guess, and the Royal College of Physicians made the statement with considerable qualifications. Let's suppose the 95% is not right. What if it's 80%? What if it's 60%? What if it's 40%? Who would know? Nobody on this planet has got 10-year data to say that it's safer or not safer.

James Bullen: But Dr Colin Mendelsohn says the 95% figure makes sense.

Colin Mendelsohn: Almost all the chemicals in cigarette smoke are not present in vapour. Those that are present are in most cases less than 1% of what they are in smoke. When you work out the numbers, look at the chemistry, the toxicology, the physical aspects of vapour, I think 95% is a conservative estimate and I wouldn't be surprised if they're even less harmful than that.

James Bullen: All the points of evidence are like this, complex and contested.

Beyond the health of the general population, another area Dr Matthew Peters is concerned about is the potential risk of e-cigarettes to young people, that it's a gateway to cigarettes.

A recent study by the Canadian Medical Association Journal, with a sample of about 40,000 people, showed that the use of e-cigarettes by high school students was associated with later cigarette smoking. It's a finding that's also been made in similar research.

Matthew Peters: There's now overwhelming evidence that the use of electronic cigarettes in various forms in adolescence trebles the likelihood that they'll progress to smoking. In addition, there's also good evidence in young people that respiratory disease in users is emerging; chronic bronchitis, marked increases in asthma, dramatic increases in absences from school for those with asthma.

Colin Mendelsohn: All that study has shown us is that kids experiment with stuff, and kids who experiment with one thing are more likely to try another. The reality is that e-cigarette use in young people is almost always short-lived and experimental, and regular use is almost exclusively in kids who already smoke.

James Bullen: While the debate continues, others are calling for the legalisation of vaping for an entirely different reason. Smoking is especially prevalent in disadvantaged groups, and some advocates reckon you could improve the health of those groups with e-cigarettes.

Marewa Glover: It's really what's happening for your sub-groups.

James Bullen: Dr Marewa Glover is an Associate Professor of Public Health at Massey University in New Zealand.

Marewa Glover: If you look at people with mental health illnesses, lower socio-economic indigenous people, and other marginalised or stigmatised minority groups like LGBTI communities, you will find much higher smoking prevalence rates. And it's just not okay to keep focusing on the national average and leave these groups totally out of the picture.

James Bullen: Her research addresses the smoking rate in Maori communities, which is more than double that of the general population. Dr Glover thinks vaping could be the key to reducing the high rates of smoking among Maori people. With a similarly high smoking rate among Aboriginal and Torres Strait Islander peoples here, could the same sort of intervention work?

Marewa Glover: In New Zealand, yes, we have had a lot of interest among Maori in vaping and a lot of Maori are switching over. Whether that will work for Aboriginal and Torres Strait Islander people, we don't know. Aboriginal and Torres Strait Islander people need to be given information and they need to be given a chance to decide for themselves what pathways or methods they are interested in.

James Bullen: Professor Matthew Peters says the work already done in improving health outcomes in these groups can't be risked by something that's unproven.

Matthew Peters: Indigenous health and the health of those people who are suffering from psychological illness or socio-economic disadvantage more broadly need good health outcomes. You really can't compromise their treatment, their longer-term future with some grand experiment which on the available evidence is not that useful, and at least in kids, in the short term, quite harmful.

Norman Swan: That story by James Bullen.