Vaping Likely Causes Lung and Oral Cancer, Australian Review: Strongest Evidence Yet Sparks Urgent Warnings

SYDNEY — Nicotine-based vapes are likely to cause lung and oral cancers, according to a comprehensive new Australian review that analyzed global evidence from 2017 to 2025 and concluded the devices pose a direct carcinogenic risk even without prior smoking history.

The study, led by cancer researcher Adjunct Professor Bernard Stewart of the University of New South Wales and published Tuesday in the journal Carcinogenesis, represents one of the most definitive assessments to date that e-cigarettes are not a harmless alternative to traditional smoking.

"Considering all the findings — from clinical monitoring, animal studies and mechanistic data — e-cigarettes are likely to cause lung cancer and oral cancer," Stewart said. "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."

The review examined more than 100 peer-reviewed studies, including human biomarker data, animal experiments, case reports and chemical analyses of vape aerosols. Researchers focused on nicotine-containing vapes, which dominate the market, and assessed their potential to cause cancer independently rather than solely as a gateway to combustible tobacco.

Key evidence included DNA damage, oxidative stress, inflammation and pre-carcinogenic cellular changes observed in vapers' lung and oral tissues. Animal studies showed lung tumors in mice exposed to e-cigarette aerosol over extended periods, with one experiment reporting adenocarcinoma in about a quarter of exposed subjects after 54 weeks of inhalation.

Human studies revealed changes to the oral microbiome, tissue injury in the respiratory tract and elevated levels of known carcinogens such as formaldehyde, acrolein, benzene and heavy metals like nickel in vape aerosols and users' biosamples. These alterations mirror mechanisms long established in tobacco-related cancers.

Stewart emphasized that while definitive long-term population studies linking vaping directly to cancer diagnoses will take decades — similar to the timeline for proving smoking's harms in the mid-20th century — waiting is not an option.

"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 told reporters. "We're able to determine that in humans, there is unequivocal pre-carcinogenic change as a consequence of vaping."

The findings challenge widespread perceptions, promoted by some manufacturers and even some public health messaging in earlier years, that vaping is substantially safer than smoking. While vapes generally deliver fewer toxins than combustible cigarettes, the review concludes they are not risk-free and carry their own cancer potential, particularly for never-smokers who take up the habit.

Dual users — those who both vape and smoke — face compounded risks, with some data suggesting a roughly fourfold increase in lung cancer likelihood compared to smoking alone.

Young people are a particular concern. Vaping rates among teens and young adults surged globally in recent years before showing some decline in Australia after stricter regulations. Many users start with flavored disposable devices, exposing a generation with no prior smoking history to potential carcinogens during critical developmental periods.

Health authorities have noted rising cases of vaping-related lung injury in the past, though acute EVALI outbreaks were often tied to illicit THC products. The new review shifts focus to chronic cancer risks from standard nicotine vapes.

Chemical analysis in the reviewed studies highlighted toxicants formed during the heating of e-liquids, including carbonyl compounds and volatile organic compounds. Flavorings, while appealing, can contribute to toxicity when aerosolized, with some breaking down into harmful byproducts.

The review also pointed to immune suppression and chronic inflammation as pathways that could promote tumor development over time. Biomarkers in vapers' blood, breath and saliva showed patterns consistent with early carcinogenic processes.

Public health experts called the findings a "wake-up call." The Cancer Institute NSW and other bodies have long warned about vaping harms, including addiction, cardiovascular effects and respiratory damage, but the strengthened cancer link adds urgency to regulatory efforts.

Australia has implemented some of the world's strictest vaping rules, including prescription-only access for nicotine vapes in certain cases and bans on disposable products. Yet enforcement challenges persist, with black-market imports and youth access remaining issues.

Internationally, reactions varied. The World Health Organization has classified e-cigarettes as harmful and recommended against their use for smoking cessation unless under medical supervision. Some countries, including the United Kingdom, have taken a more permissive stance, viewing vapes as a tool to reduce smoking-related deaths.

U.S. regulators have cracked down on flavored products and unauthorized devices while maintaining that vaping is less harmful than smoking but not safe, particularly for youth.

The Australian review urges policymakers to act decisively: restrict marketing, especially to young people; enhance warning labels; limit flavors and nicotine concentrations; and fund further research into long-term outcomes.

It also calls for clinicians to counsel patients honestly about risks, noting that while vaping may help some adult smokers quit combustible cigarettes when used as a complete substitute, it should not be promoted as a safe recreational product.

Stewart drew historical parallels to tobacco. "This has historical parallels with tobacco," he said, warning that society cannot afford to repeat past mistakes of underestimating risks until bodies of evidence became overwhelming.

Critics of strict regulation argue that overemphasizing vaping risks could discourage smokers from switching, potentially costing lives given smoking's proven lethality. The review acknowledges that vaping likely causes less harm than smoking on a per-user basis but stresses the absolute risk for never-smokers is not zero.

Case reports of oral cancers in young vapers, though rare and not proving causation alone, add to the mechanistic and animal data in building the "likely" classification.

The study stopped short of quantifying exact risk levels, noting insufficient long-term epidemiological data. Future research will need large cohorts tracking never-smoking vapers over decades.

In the meantime, experts recommend proven cessation methods — nicotine replacement therapy, counseling and prescription medications — over unmonitored vaping.

For current vapers, particularly youth, the message is clear: quitting now reduces exposure and potential harm. Resources like quitlines and apps can support efforts to stop.

The review's publication comes amid ongoing global debates over vaping's role in tobacco control. With millions of users worldwide, many of them young, the cancer link could influence everything from advertising bans to taxation and product standards.

Parents and educators have expressed alarm, with some surveys showing confusion over vaping safety. The new evidence aims to clarify that nicotine vapes deliver a cocktail of chemicals capable of damaging DNA and promoting cancer pathways.

As Stewart put it: "It's dangerous, and that's the message."

Health officials continue to stress that the best choice is never to start vaping or smoking. For those already addicted, professional help offers the safest path forward.

The UNSW-led team called for more qualitative and quantitative risk assessments while prioritizing prevention. With vaping's popularity among adolescents, the potential future cancer burden could strain health systems if trends are not reversed.

This Australian contribution adds significant weight to the evolving scientific consensus on e-cigarette safety. While more data will emerge, the current evidence tilts strongly toward caution.