Major Review Concludes Vaping Likely Causes Lung and Oral Cancer, Drawing Parallels to Tobacco History
Key Insights
A comprehensive qualitative risk assessment published in *Carcinogenesis* finds that nicotine-based e-cigarettes are likely carcinogenic, with consistent evidence across human biomarker studies, animal models, and mechanistic data.
Researchers report that 22.5% of mice exposed to e-cigarette aerosol developed lung adenocarcinomas, while human studies show DNA damage, oxidative stress, and inflammation linked to vaping.
Dual users of both e-cigarettes and conventional cigarettes face a four-fold increased risk of developing lung cancer (search), according to recent epidemiological evidence from the USA.
A landmark qualitative risk assessment has concluded that nicotine-based e-cigarettes are likely carcinogenic to humans, with evidence pointing toward an increased risk of both lung cancer (search) and oral cancer (search). The review, published in the journal Carcinogenesis, represents what the authors describe as "the most definitive determination that those who vape are at increased risk of cancer compared to those who don't."
The international research collaboration brought together experts from The University of Queensland (search), Flinders University, The University of Sydney, Royal North Shore Hospital, The Prince Charles Hospital, and Sunshine Coast University Hospital, spanning disciplines including pharmacy, epidemiology, thoracic surgery, and public health.
"Considering all the findings — from clinical monitoring, animal studies and mechanistic data — e-cigarettes are likely to cause lung cancer (search) and oral cancer (search)," said Professor Stewart, lead author of the review.
A Multi-Layered Body of Evidence
Because e-cigarettes have only been widely available for approximately two decades, long-term epidemiological studies capable of quantifying cancer risk in humans remain years away. In their absence, the research team evaluated converging lines of evidence from multiple scientific domains.
The review identified numerous cancer-causing substances in e-cigarette aerosols, including volatile organic compounds, nicotine-derived nitrosamines, flavor-derived agents, and metals released by heating coils. Human biomarker studies revealed DNA damage, oxidative stress, epigenetic changes, and inflammation in oral and respiratory tissues among vapers — effects often comparable to those observed with cigarette smoking.
Laboratory and animal findings further strengthened the case. In rodent bioassays, mice exposed to e-cigarette aerosol via inhalation developed lung adenocarcinomas at a rate of 22.5%. Mechanistic data were evaluated against key characteristics of carcinogens, implicating a complex aerosol mixture that may act through both genotoxic and non-genotoxic processes.
"The evidence was remarkably consistent across fields," said Associate Professor Freddy Sitas of UNSW, a co-author of the review. "It dictated an unequivocal finding now, though human studies that estimate the risk will take decades to accumulate."
The Dual-Use Dilemma
The researchers also highlighted growing evidence that many smokers who switch to vaping continue using conventional cigarettes — a pattern they describe as "dual-use-limbo."
"What we do know from recent epidemiological evidence from the USA is that those who both vape and smoke are at an additional four-fold increased risk of developing lung cancer (search)," said Associate Professor Sitas, referencing findings discussed in a companion commentary published in Cancer Epidemiology.
This dual-use phenomenon complicates the public health narrative that has often positioned e-cigarettes primarily as smoking cessation tools. While e-cigarettes first entered the market in the early 2000s and became available in Australia around 2008 as potentially safer alternatives to conventional cigarettes, the review challenges the notion that they can be considered risk-free.
Echoes of Tobacco History
The authors draw a pointed historical parallel between today's vaping debate and the early scientific investigation of smoking-related diseases. It took nearly a century between early observations in the mid-1800s and the landmark US Surgeon General's report in 1964 before smoking was officially recognized as a cause of lung cancer (search). During much of that period, warning signs were frequently ignored or dismissed.
"Early reports linked smoking to infectious diseases such as tuberculosis, followed by cardiovascular disease, stroke and lung cancer (search)," Associate Professor Sitas noted. He argued that the same pattern may now be unfolding with vaping — and that researchers should not repeat the delay that occurred with cigarettes.
"E-cigarettes were introduced about 20 years ago. We should not wait another 80 years to decide what to do."
The review also noted that conclusions across published reviews have shifted between 2017 and 2025, moving from calls for more evidence toward explicit concern about e-cigarette carcinogenicity.
Clinical Implications and Limitations
The authors acknowledge that their assessment is qualitative and does not provide a numerical estimate of cancer risk or burden. "We'll only be able to determine the precise risk once longer-term studies are available," Professor Stewart said.
For clinicians, the findings support a precautionary approach. E-cigarettes should not be positioned as a risk-free smoking alternative, particularly given the persistence of dual use and the biologically plausible pathways now linking vaping with oral and lung cancer (search) risk. The current evidence does not yet quantify cancer burden, but it does indicate that the carcinogenic potential of e-cigarettes can no longer be ignored.