New Review Finds Strongest Evidence Yet That Vaping Causes Cancer

The most comprehensive scientific assessment of e-cigarette carcinogenicity to date concluded that nicotine-based vapes are likely to cause oral and lung cancers, drawing on eight years of laboratory, biomarker and animal research to reach a verdict that could reshape public health policy and clinical guidance around the world.

The review, titled "The carcinogenicity of e-cigarettes: a qualitative risk assessment" and published in the journal *Carcinogenesis*, was led by Adjunct Professor Bernard Stewart AM, a cancer researcher at UNSW Sydney. His team included investigators from the University of Queensland, Flinders University, the University of Sydney, and clinicians at Royal North Shore, The Prince Charles and Sunshine Coast University hospitals, assembling pharmacists, epidemiologists, thoracic surgeons and public health researchers to evaluate the evidence from multiple scientific perspectives.

"To our knowledge, this review is the most definitive determination that those who vape are at increased risk of cancer compared to those who don't," Stewart said.

Because no long-term population studies directly linking vaping to human cancers yet exist, the team assessed whether e-cigarette aerosols produce the "key characteristics of carcinogens" established by the World Health Organization. They found that aerosols contain nicotine and its metabolites, volatile organic compounds, and vaporized metals shed by heating elements. Human tissue studies showed DNA mutations and changes in cancer biomarkers in mouth and lung samples taken from people who vape; blood and urine tests confirmed absorption of carcinogenic metals; and mice exposed to e-cigarette aerosols in laboratory experiments developed lung tumors. Dentists also submitted case reports of oral cancers appearing in patients who had only ever vaped and had never smoked.

Stewart was unambiguous about what that biological evidence means. "There is no doubt that the cells and tissues of the oral cavity, the mouth and the lungs are altered by inhalation from e-cigarettes," he said. "We're able to determine that in humans, there is unequivocal pre-carcinogenic change as a consequence of vaping."

Co-author and UNSW epidemiologist Associate Professor Freddy Sitas drew an explicit parallel to the history of tobacco, warning against waiting for the same kind of decades-long confirmation cycle. "Early reports linked smoking to infectious diseases such as tuberculosis, followed by cardiovascular disease, stroke and lung cancer," Sitas said. "E-cigarettes were introduced about 20 years ago. We should not wait another 80 years to decide what to do."

The stakes are compounded by the demographic profile of early adopters. Many adolescents who began vaping in the 2010s are now entering their twenties and thirties, ages at which cancer risk from long-term carcinogen exposure could manifest far sooner than historical tobacco timelines would suggest. Epidemiological data from the United States already shows that people who both vape and smoke face a four-fold increased risk of developing lung cancer compared to those who do neither.

The authors called for accelerated longitudinal studies tracking vapers over time, standardized biomarker protocols, and tighter chemical characterization of e-liquids and device emissions. In the meantime, they urged clinicians to tell patients directly, especially adolescents and never-smokers, that the available evidence points toward a real cancer risk rather than mere scientific uncertainty. The review acknowledged that definitively proving causation in humans will require studies focused exclusively on people who vape and have never smoked, a population that is still relatively young, but argued that waiting for that proof before acting would repeat a public health failure the field has witnessed before.