The most comprehensive qualitative assessment yet finds vaping likely causes both oral and lung cancer in humans.
E-cigarettes are likely carcinogenic to humans, with evidence linking vaping to lung and oral cancer, a major new review has concluded.
The analysis included all peer-reviewed trials and studies from 2017 to midway through 2025, with additional case studies, animal studies and mechanistic studies, such as laboratory investigations of how e-cigarette aerosols affected cells and tissues.
“We made no publication selection… [and] we approached it qualitatively rather than quantitatively,” said Adjunct Professor Bernard Stewart AM, a cancer epidemiologist from Paediatrics and Child Health at UNSW Sydney, in a news briefing yesterday.
“We started with the physiology; the evidence that someone who vapes is exposed to a range of chemicals, and studies in humans of urinary and blood levels of e-cigarette related chemicals showed unequivocally the presence and absorption of nicotine and nicotine related metabolites.
“These chemicals show up in urine and blood and, more importantly perhaps, they show up in changes to DNA, because many of these chemicals are mutagenic and capable of modifying the structure of DNA.”
The team looked specifically at biomarkers in tissue that were indicative of cancer development, including inflammatory biomarkers and those involved in oxidative stress and epigenetic change, as well as histological and molecular changes.
“[These] unequivocally showed long-term changes consequent upon vaping in oral and lung tissue. There is no doubt that the cells and tissues of the mouth and the lungs are altered by inhalation from e-cigarettes,” Professor Stewart said.
“We determined that objectively and from the totality of available literature, rather than any selection by us of that literature, e-cigarettes are likely to cause lung cancer and oral cancer.”
While the diversity of study designs did not allow for pooled quantitative estimates, there were some notable findings in individual studies, including one which reported a greater than 100-fold increase in nicotine metabolites among vapers vs non-users, as well as animal data showing increased tumour incidence.
Another risk associated with vaping was its use alongside smoking, Associate Professor Freddy Sitas, public health epidemiologist and director at the Centre for Primary Health Care and Equity UNSW told the news briefing.
He highlighted a paper with 5000 cases of lung cancer and 25,000 controls, which showed smoking increased lung cancer risk 16-fold compared with non-smokers.
“That’s the textbook response. But if you smoke and vape, that risk goes up to 38[-fold],” he said.
“So, the device that’s been advertised to stop you from smoking actually increases your risk of lung cancer.
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“We’ve always assumed that vapes are safer than cigarettes. We’re seeing the biological evidence that it is likely to cause lung cancer.”
Despite the strong conclusions, Professor Stewart emphasised the findings should be used to inform policy rather than provoke alarm. The aim of the analysis was not to alert people to yet another “cancer scare”, he said.
“What’s important is regulators have at their disposal a spectrum of evidence and are able to take appropriate action in Australia in relation to what is in Australia and a legal product,” he said.
“The direction we intend is primarily to influence regulators to give them further clarity in the need to control what has been described as a youth epidemic. That is the uptake of vaping by young people who, once addicted, may well take up smoking and then do both, because they can’t avoid the addictive impact of these products.
“It’s not an alternative to smoking, it’s not an alternative to a list of drugs, it’s not an alternative to anything that is in the context of being safer. It is dangerous, and that’s the message.”
Professor Sitas went on to discuss the parallels with early research into smoking, with the first reports of potential associations with disease in the 1860s.
“It took about 100 years – till 1964 – for the evidence to be conclusive enough to show that smoking caused lung cancer. The history of events evolved over time as people became more exposed to tobacco… and we’re seeing a similar evolution of the evidence with e-cigarettes,” he said.
“The fact that it took 100 years to alert the community or to demonstrate to everyone that smoking caused lung cancer is not indicative of the time that’s actually required, but it does indicate that it will take decades, and it will be challenging,” said Professor Stewart.
“If one is going to prove definitively that vaping causes cancer of the oral cavity or the lung, then it will require a population of people who have only vaped and never touched cigarettes.”
Professor Michelle Jongenelis, Director of the Melbourne Centre for Behaviour Change at The University of Melbourne, told media that she was saddened by the deliberate targeting of children and young people.
“The tobacco and nicotine industry need to addict a new generation to nicotine to safeguard their profits, and this evidence shows they are very likely giving our children cancer in the process,” she said.
“Governments in Australia must act immediately to shut down retailers who are selling these cancer-causing products.”
