E-cigarettes and their potential health effects have been hotly contested for some time.
Advocates say they are a less harmful alternative to tobacco cigarettes, and could help smokers quit, and, ultimately, save lives.
But many Australian public health experts oppose the use of e-cigarettes, arguing there isn't enough evidence to show they're safe.
They point to Australia's low smoking rates, and say we should continue what we're doing to lower them further. In their view, there's no need for a new, potentially dangerous product.
Last month, Federal Health Minister Greg Hunt said he would never lift the ban on e-cigarettes, despite an ongoing parliamentary inquiry into their use.
"I have a very strong, clear, categorical view that this is not something that should occur in Australia," Mr Hunt told triple j Hack.
But Mr Hunt's position is at odds with health authorities in comparable nations including England, Scotland and more recently, New Zealand, who have backed e-cigarettes in a bid to lower smoking rates and reduce harm.
So why is Australia taking a more pre-cautionary approach?
World leader in tobacco control
Australia has long been considered a world leader in tobacco control — smoking rates have dropped by nearly 10 per cent over the past two decades.
"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," Professor Matthew Peters, Head of Respiratory Medicine at Concord Hospital in Sydney, told The Health Report.
Professor Peters is among the bloc of public health professionals, including Emeritus Professor Simon Chapman and Professor Mike Daube, who don't want to see e-cigarettes introduced in Australia.
"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," Professor Peters said.
The existing legal framework around e-cigarettes 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 — a ban that was upheld by the Therapeutic Goods Administration (TGA) in March.
The TGA decided there was a risk people who had never smoked may take up the habit after using nicotine e-cigarettes.
"There's not much of a step between inhaling nicotine through e-cigarettes and children thinking 'maybe I'll give smoking a try as well'," Emeritus Professor Simon Chapman told PM in February.
The TGA is also concerned vaping may make the practice of smoking more acceptable again, damaging the campaign to decrease tobacco use in Australia.
But some say the TGA looked only at the potential risks of e-cigarettes, not the benefits, and argue Australia is out of step with the UK, US, European Union, Canada and now New Zealand.
Tide is turning overseas
In September, Scotland's national health agency released a statement saying e-cigarettes are "definitely" less harmful than tobacco smoking and that it would be "a good thing" if smokers switched to vaping (though not if they used both at the same time).
And last month, New Zealand's Health Ministry endorsed the use of e-cigarettes as a harm reduction aid and a smoking cessation tool. In England, e-cigarettes have been available for several years and their use, sale, and some advertising of products is legal.
Colin Mendelsohn, Associate Professor in Public Health at the University of New South Wales, says the recent slowdown in Australia's declining daily smoking rates suggests we should look for alternative strategies.
"We have a very large population of smokers who can't quit with what we're currently doing," Dr Mendelsohn said.
"The fact is we have very good evidence from overseas that these products work … and we need additional options to move things forward."
Dr Mendelsohn's calls for Australia to adopt a harm-minimisation approach to smoking are echoed by UK experts, who last month made submissions to the parliamentary inquiry into e-cigarettes.
But the debate regarding the risk posed by e-cigarettes remains unsettled in Australia.
So what does the research say?
Complex and contested evidence
You might have heard that vaping is 95 per cent less harmful than smoking — it's regularly cited by e-cigarette advocates.
That number first cropped up in a 2014 paper published in the European Addiction Research journal, which weighed up nicotine products by their potential to harm users and others around them.
But critics of that research say it was arrived at by the consensus of a group of public health experts, rather than original scientific research.
Professor Peters questions the extent to which the figure has been relied upon in the e-cigarettes debate.
"Let's suppose the 95 per cent figure is not right. What if it's 80 per cent? What if it's 60 per cent? What if it's 40 per cent? And who would know?" he said.
"Nobody on this planet has got 10-year data to say it's safer or not safer."
Public Health England and the Royal College of Physicians subsequently undertook their own reviews of the evidence and came to similar conclusions — that e-cigarettes were unlikely to exceed 5 per cent of the harm of smoking tobacco.
But the Australian Cancer Council, National Health and Medical Research Council and other leading Australian health bodies maintain there is insufficient evidence to support claims they are safe, especially in the long term.
It is a similar story when it comes to research on whether e-cigarettes can successfully help people to quit smoking.
The Royal College of Physicians says e-cigarettes "appear to be effective" as a smoking cessation tool, while the World Health Organisation says the evidence for this is "scant and of low certainty, making it difficult to draw credible inferences".
Most points of evidence are like this: complex and contested.
Arguments abound over whether vaping is safe, whether it can help people quit, whether it's a less harmful alterative, whether it re-normalises the act of smoking itself, whether it's a gateway product for young people, or whether it's just another tool for big tobacco.
While the debate over e-cigarette safety and efficacy continues, others are calling for the legalisation of vaping for an entirely different reason.
"If you look at people with mental illnesses, lower socio-economic Indigenous people, and other marginalised or stigmatised minority groups like LGBTI communities, you will find much higher smoking prevalence rates," said Marewa Glover, associate professor of public health at Massey University in New Zealand.
Dr Glover says vaping could be the key to reducing the high rates of smoking among Maori people, who smoke at a rate more than double that of the general New Zealand population.
"We have had a lot of interest among Maori in vaping and a lot of people are switching over, a lot of Maori are switching over," she said.
"Whether that will work for Aboriginal and Torres Strait Islander people, we don't know."
Professor Peters says the work already done in improving Indigenous health outcomes can't be risked by something that's unproven.
But for Dr Glover, the risk analysis is clear — she likens it to people in a burning building, blocked from the exit by health professionals because they're not sure if the stairs are safe.
"The goal is to reduce harm, it isn't a moral, ideological battle. It's about reducing harm, saving lives, and reducing the cost to people and health systems," she said.