Public health experts and scientists generally don't consider e-cigarettes to be safe but early marketing has offered nicotine-based vapes as a less harmful alternative to cigarettes that could supposedly help people quit.
The review, led by the University of NSW and released on Tuesday, has found these kinds of vapes are likely to cause lung or oral cancer.
People who use nicotine-based vapes were found to have changes in their tissue indicative of cancer development, including DNA damage, oxidative stress and inflammation.
Researchers also examined case studies of oral cancer in those who only vaped and looked at animal experiments, including one where mice that breathed in aerosols from e-cigarettes developed lung cancer and changes in the bladder consistent with the eventual occurrence of cancer.
"Objectively and from the totality of available literature ... e-cigarettes are likely to cause lung cancer and oral cancer," lead researcher Bernard Stewart told reporters.
"Not only are we concerned about cancer development, but we cannot definitively say these things are safer than smoking."Â
Vapes can only be sold in Australian pharmacies to help people quit smoking or manage nicotine dependence.
However, the study also showed growing evidence smokers who switch to vapes don't necessarily give up cigarettes, meaning they are stuck in a "dual-use-limbo" that means they are at a four-fold increased risk of developing lung cancer.
As vapes have only been available for sale in Australian since about 2008, it will take decades for scientists to gather enough long-term information from people who have only vaped to definitively prove e-cigarettes cause cancer.
But this study has enough data for its authors to urge regulators to act, comparing the situation to early studies on cigarettes.
It took about a century before smoking was officially recognised as a cause of lung cancer in 1964, even after reports from the 1860s showed links between tobacco and tuberculosis, emphysema and more.
"Vapes have only been going for 20 years here, we don't have to wait 80 years to get a response," co-author Freddy Sitas said.
"We have a very good opportunity to be proactive."
Large, nation and statewide studies must be funded to get early results about the potential for early onset cancer among young Australians, Prof Sitas said.
Rather than examining the impact of e-cigarettes alone, previous studies have focused on comparing vaping to smoking, delaying progress on e-cigarette awareness, according to Prof Stewart.
"Being approached from the perspective of 'is this safer than smoking' is as crazy as saying we'll assess the safety of knives by seeing whether they're more or less dangerous than sub-machine guns," he said.
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