A new paper suggesting links between vaping and cancer has triggered strong criticism from leading experts, who warn its conclusions are “misleading” and risk confusing the public.
The study, published in Carcinogenesis, examined potential cancer risks associated with vape use, drawing on laboratory, animal and biomarker evidence.
But in a coordinated response, scientists said the review overreaches, lacks methodological rigour, and fails to reflect the current state of evidence.
“Misleading” and lacking credibility
Professor Peter Hajek, from Queen Mary University of London, said: “The review’s conclusions are misleading.”
He criticised the paper for not comparing vaping with smoking, arguing this allowed it to present “a detection of any level of a suspect chemical, however negligible, as ‘carcinogenic’.”
He added: “The crucial bit of information that the review omits is that vaping exposes users to only a very small fraction of some of the carcinogens in tobacco smoke, and to none at all of the rest.”
Professor Lion Shahab of University College London also raised concerns about how the review was conducted. He said it’s “problematic for several reasons and makes extraordinary claims that are not borne out by the data.”
He said the paper did not follow standard scientific practice, noting:
“No information is provided about how studies were selected, nor were any inclusion or exclusion criteria specified or a protocol preregistered.”
Without clear criteria, he warned, the findings lack credibility, saying:
“this review has little credibility and simply reflects an interpretation of the authors, not an objective assessment of the state of evidence.”
Clive Bates, a tobacco harm reduction expert, said the paper fundamentally misrepresents what the evidence shows. He said: “This is a hazard identification exercise, not a risk assessment. It does not determine whether the possible hazards pose a material risk of causing cancer in vapers.”
No clear evidence vaping causes cancer
Several experts stressed that while vaping is not risk-free, there is currently no solid evidence linking it to cancer in humans.
Professor Shahab said the paper does not provide definitive answers. He said:
“This review does not offer a ‘smoking gun’ that e-cigarettes cause oral or lung cancer.”
Dr Baptiste Leurent, a medical statistician at UCL, warned the paper could easily be misinterpreted. He said: “I believe it might be of interest to public health researchers but could be misleading if presented to the public as providing evidence of an association between vaping and cancer.”
Dr Stephen Burgess, from the University of Cambridge, said the review identifies possible biological mechanisms but stops short of proving real-world harm. He said that “evidence linking these mechanisms to cancer outcomes in humans is more variable, and evidence linking these mechanisms to quantifiable increases in the risk of specific cancers is absent.”
Concerns over selective evidence
Experts also accused the authors of selectively citing studies while ignoring others. Professor Peter Shields, an oncologist at Ohio State University, said:
“This paper really does not add anything we do not already know, but selectively cites studies… that leads the reader down the wrong path.”
He added that key evidence had been overlooked, saying “they missed the boat, and did not cite, are the numerous studies showing substantially reduced carcinogenic exposures when people who smoke switch to vaping.”
Low-quality and limited evidence base
Some critics focused on the overall quality of the evidence used. Dr Gavin Stewart, a specialist in evidence synthesis, said the paper fails to meet basic standards.
He said: “This work does not meet methodological expectations for evidence synthesis and consequently, its conclusions should be treated with circumspection.” He added that it is “impossible to discern if the conclusions are based on robust evidence or no better than opinion.”
This echoes limitations highlighted in the wider evidence base itself. A separate clinical review of vapes and oral cancer risk found that “the current clinical evidence on this topic is limited and insufficient to support using e-cigarettes as a risk factor for OPMD and oral cancer.”
Risk of confusing smokers
Several experts warned that overstating risks could have unintended consequences. Professor Hajek said: “Misinforming smokers risks discouraging them from using e-cigarettes, which are one of the most effective methods that exist to help people stop smoking.”
He added: “Switching from smoking to vaping removes the major source of all smoking related diseases, including cancer.”
Professor John Britton, from the University of Nottingham, also emphasised the relative risks, saying: “The levels of exposure to carcinogens and oxidants sustained by vapers are very low, indicating that the risks of vaping are likely to be very small.”
Bates also highlighted what he said was a critical omission in the paper’s approach. He said: “There is no comparison with smoking, for which there is established strong evidence of multiple cancer risks.”
A ‘stretch of the imagination’
The controversy highlights the ongoing debate around vaping and long-term health risks. While laboratory and biomarker studies suggest potential mechanisms for harm, experts say translating these into real-world cancer risk remains highly uncertain.
Professor Stephen Duffy said: “It would require quite a stretch of the imagination to envisage how vaping compounds could match the cancer-causing effects of combustion smoking.”
