Study Shows Vaping Likely Causes Lung Cancer

For years the public health message on vaping has been hedged — less harmful than cigarettes, probably, we think, based on what we know so far. A comprehensive review published in the journal Carcinogenesis is pushing that framing aside.

The study, led by cancer researchers at the University of New South Wales and drawing on more than 100 scientific studies worldwide, concluded that nicotine-based e-cigarettes are likely to cause lung cancer and oral cancer — not just as a gateway to smoking, but on their own.

“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,” said UNSW Adjunct Professor Bernard Stewart, who led the research.

Three Types of Evidence, Same Direction

What makes this review different from prior studies is its scope. Rather than relying on a single type of data, researchers examined three independent streams of evidence and found they all pointed the same way.

First, biomarker studies in humans. People who vape show measurable DNA damage, oxidative stress, and tissue inflammation — the same pre-carcinogenic changes seen in smokers, just from e-cigarettes alone. “We’re able to determine that in humans, there is unequivocal pre-carcinogenic change as a consequence of vaping,” the researchers stated.

Second, animal research. Mice exposed to e-cigarette aerosols developed lung tumors at significantly higher rates than unexposed control groups. One study in the review reported a 22.5% cancer rate in exposed mice.

Third, laboratory evidence showing that e-cigarette aerosols contain a mixture of known carcinogens — formaldehyde, acrolein, heavy metals — that disrupt biological pathways directly linked to cancer development at the cellular level.

None of these data streams alone would be conclusive. Together, the researchers say, they form a pattern that can no longer be ignored.

The Dual-Use Problem

One of the most alarming findings concerns people who both vape and smoke — a group that turns out to be larger than widely acknowledged. Many people who turn to vaping as a smoking cessation tool end up doing both rather than fully switching. A 2024 study cited in the review found a four-fold higher risk of lung cancer among people who vape and smoke compared to those who only smoke.

Young people who never smoked but start vaping are also three times more likely to become regular cigarette smokers, compounding the problem further. The “safer alternative” premise has always depended on vaping actually replacing cigarettes, not layering on top of them.

Why Researchers Say ‘Likely’ and Not ‘Confirmed’

The researchers are careful with their language, and the distinction matters. Saying vaping “likely” causes cancer rather than definitively does is not a hedge born of uncertainty about the direction of the evidence — it’s an acknowledgment that long-term population data takes decades to accumulate.

Cancers can take 20, 30, or 40 years to develop after initial carcinogen exposure. Widespread nicotine vaping has only existed for roughly 15 years. There simply hasn’t been enough time for the full epidemiological picture to emerge from human population studies — the gold standard for establishing causation.

That lag is exactly what happened with cigarettes. It took from the mid-1800s until 1964 for scientists to establish the causal link between smoking and lung cancer. The researchers cite that history explicitly as a warning.

“Early reports linked smoking to infectious diseases such as tuberculosis, followed by cardiovascular disease, stroke, and lung cancer,” said co-author Associate Professor Freddy Sitas. “The same pattern may now be unfolding with vaping — and researchers should not repeat the delay that occurred with cigarettes. We should not wait another 80 years to decide what to do.”

What This Means Right Now

The research doesn’t establish how much lung cancer risk vaping carries relative to smoking — that quantification will come from the long-term population studies still underway. But the directional conclusion is clear enough that researchers believe waiting for that precision before acting on the findings is a mistake.

For the millions of people who vape under the assumption that it’s a safe activity rather than a harm-reduction tool relative to cigarettes, this review is a direct challenge to that assumption. E-cigarettes appear to cause the same kinds of pre-cancerous biological changes as cigarettes. They contain many of the same carcinogens. And combining vaping with smoking appears to multiply the risk rather than offset it.

The science isn’t finished. But it’s further along than the public conversation has reflected.

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