Does vaping cause cancer? What a major new review actually concludes about lung and oral tumours

Marketed as the "safer alternative" to combustible tobacco, electronic cigarettes — vapes — spread quickly on the promise of eliminating thousands of harmful chemicals released by burning cigarettes. A major new scientific review casts a long shadow over that portrait: an evidence-synthesis published in Tobacco Control in May 2026 concludes that nicotine vapes are "likely" to cause lung and oral cancer.

The study, led by researchers at Imperial College London and the Australian National University, applies the Bradford Hill causal-inference criteria to a screened pool of 380 studies published between 2010 and 2026 — drawing on human biomarker data, animal models and laboratory cell-culture work to assess the case for causation under a single framework.

The human biomarker picture is striking. Long-term vape users carry significantly higher levels of aldehydes, heavy metals — lead, nickel and chromium in particular — and tobacco-specific nitrosamines in urine and saliva than non-smokers. Most of these compounds are classified by the WHO's International Agency for Research on Cancer as Group 1 (human carcinogen) or Group 2A (probable carcinogen).

Flavour compounds are a central concern. Diacetyl — the chemical behind popcorn flavouring — was removed from major brands in 2017 after being linked to bronchiolitis obliterans, the so-called "popcorn lung". But benzaldehyde, menthol and vanillin and many other aromatic compounds convert under heating into genotoxic aldehydes. The review noted that mentholated vape liquids produced the highest measured DNA-damage signals in users' oral mucosa.

Lead author Filippo Calcagni, of Imperial College, said: "It used to be argued that we would have to wait 25 to 30 years to know whether vapes cause lung cancer, because the latency for tobacco-related cancer is that long. The current molecular data tells us that wait is the wrong question — DNA damage, chromatin remodelling and airway hyperplasia are all already under way."

Real-world epidemiology is still early. A 2024 cohort study drawing on the US Behavioral Risk Factor Surveillance System found a 1.5-fold rise in lung-disease incidence among users with more than five years of vaping versus never-smokers, but the sample size and follow-up are too small for cancer endpoints. The new review argues that the combination of strong mechanistic data and limited epidemiology is enough to establish probable causation.

What does this mean in practice for smokers? Calcagni and his team accept that, for established smokers, vape products used as a short-term, targeted, clinician-supervised cessation tool may still carry a net benefit over continued smoking. But for nicotine-naive adults and for adolescents, the risk-benefit balance has shifted: the team called for urgent public-health control of youth vape uptake given a now-credible cancer-risk profile.

Regulators are part way there. The United Kingdom banned disposable vapes in early 2026, principally to dent adolescent initiation. Australia has since 2024 required vapes to be sold only through pharmacies on prescription. The US FDA has pulled most child-friendly flavours from the market, although a menthol exemption remains contested.

The review's limitations are real: human epidemiology is still being built; the dose-response relationship is poorly mapped; and "dual use" — vaping plus smoking — makes it difficult to isolate the pure vaping signal. For these reasons the authors prefer the word "likely" rather than "definite", and have submitted a formal evaluation dossier to the IARC.

The public-health line is clear. A non-smoker should not take up vaping. A smoker using vapes to quit should do so on a time-limited, clinician-supervised basis. Marketing aimed at adolescents demands urgent regulatory action. "Less harmful than cigarettes" does not mean "harmless" — and the new review extends that line to users who reach for vapes after quitting tobacco.