By Timothy S. Donahue
Top Takeaways:
- Method vs. reality: Oxford review highlights possible carcinogenic mechanisms but does not prove actual cancer risk in humans.
- Scientific pushback: Critics argue the analysis relies on lab and animal data with unrealistic exposure levels.
- Harm reduction tension: UK health organizations assert that vaping is significantly less harmful than smoking.
It happens every year. This time, however, the pushback arrived quickly. A March 30 paper published in Oxford University Press journal Carcinogenesis concluded that nicotine-based e-cigarettes are “likely to be carcinogenic,” citing biological changes observed in lab and preclinical studies.
The article, titled “The carcinogenicity of e-cigarettes: a qualitative risk assessment,” reviewed studies published between 2017 and 2025 and highlighted evidence of DNA damage, oxidative stress, inflammation, and epigenetic changes in oral and respiratory tissues following exposure to vape aerosols.
Authors highlighted potential exposure to compounds like nicotine-derived nitrosamines, volatile organic compounds, flavoring agents, and trace metals. However, they acknowledged a key limitation: the actual cancer risk in humans remains uncertain. You wouldn’t know that by the media headlines surrounding the story, such as Science Alert‘s misleading “Vaping Likely Causes Cancer, Major Study Finds.”
That caveat quickly became the main focus of criticism. Peter Hajek, director of the Health and Lifestyle Research Unit at Queen Mary University of London, said the review’s framework risks overstating the danger.
“The review’s conclusions are misleading. The authors specify early on that they are not comparing vapers and smokers. This allows them to present a detection of any level of a suspect chemical, however negligible, as ‘carcinogenic.’”
Critics argue that the difference—hazard versus real-world risk—is important. Detecting potentially harmful compounds doesn’t always mean there is a significant cancer risk at common exposure levels.
Marina Murphy, senior director of scientific affairs at Haypp Group, stated that the paper depends too much on early-stage research. “This is largely a qualitative review drawing heavily on low-quality studies, including in vitro and animal experiments using unrealistic exposure scenarios. Such studies may demonstrate biological plausibility, but plausibility alone is a weak basis for public health alarm,” she said.
Murphy noted that common daily exposures can cause similar biological responses. “If I were to pour coffee on cells in a lab, they would die. Should I conclude that coffee will kill me? The answer is obviously no.”
The broader public health community has long distinguished between the risks of smoking and vaping. According to National Health Service guidance, vaping is “substantially less harmful than smoking,” though not risk-free.
The Royal College of Physicians has similarly stated that the health risks of e-cigarettes are unlikely to exceed 5% of those associated with combustible cigarettes, a benchmark frequently cited in harm-reduction debates.
Meanwhile, Cancer Research UK asserts there is “no good evidence” that vaping causes cancer, while highlighting that long-term data is still being collected. John Dunne, CEO of the UK Vaping Industry Association, said the new report risks blurring that distinction.
“The NHS, the Royal College of Physicians, and the Office for Health Improvement and Disparities all agree that vaping—while not risk-free—is significantly less harmful than smoking. This is exactly the kind of confusion that threatens the nation’s smoke-free future.”
The study’s authors did not try to measure cancer risk compared to smoking, a comparison many researchers see as essential for policy relevance. That omission, critics argue, reduces the paper’s usefulness for regulators and consumers alike.
