Bernard Stewart, UNSW Sydney

As early as the 1880s, there was evidence that smoking tobacco damaged your lungs. But it took almost 100 years to definitively show that smoking causes lung cancer.

So, what about vapes?

Until now, most research that has looked at the cancer risk for people using vapes, also known as electronic or e-cigarettes, has mainly focused on their role as a gateway to smoking tobacco. This is because we know people who vape are more likely than non-smokers to take up smoking.

But whether they cause cancer by themselves has been unclear. There are still no long-term studies. But now a comprehensive review of the evidence I conducted with colleagues, published today, has found vaping likely causes oral and lung cancers.

What we looked at and what we found

Given there is no long-term research on whether vaping directly causes cancer, we had to look for effects on the body that we know are linked to cancer.

We identified all peer-reviewed research published between 2017 and mid-2025 that looked at health impacts of vapes considered indicative of potential cancer causation.

The aerosol that vapers inhale contains a complex range of chemicals, including nicotine and its byproducts, and vapourised metals. This aerosol demonstrates almost all of the ten “key characteristics of carcinogens” identified by the World Health Organization.

Blood and urine analyses from vapers confirmed they had absorbed chemicals from e-cigarette chemicals that we know are linked to cancer. These studies revealed nicotine and its breakdown products present in their bodies, including carcinogenic (cancer-causing) metals from the heating element and organic compounds from vapourising e-liquids.

There is no doubt vaping alters tissues in the mouth and lungs. We found evidence of mutations in DNA from the mouth and lungs in those who vaped, which is further evidence of carcinogen exposure.

There was also evidence of changes to cancer biomarkers in the lung and mouth tissue of vapers. Cancer biomarkers are changes in cell or molecular structure that precede a tumour developing. Some of these can be observed under a microscope, such as inflammation, while others such as oxidative stress are detected by molecular analysis.

We also examined experiments on mice which found the aerosols in vapes caused lung cancer, as well as cases reported by dentists who thought that oral cancers in certain individual patients (who didn’t smoke) were caused by them vaping.

Our review did also examine studies that had addressed the possibility vaping may cause cancer. However none of these covered the wide range of evidence we had assessed.

What this means

The evidence shows nicotine-based vapes are likely to cause oral and lung cancer. We just don’t yet know how many cases it will cause.

But in the evidence we looked at, there was rising concern, and a significant shift in the conclusions that had been drawn.

Between 2017 and 2019, researchers tended to say there wasn’t enough evidence to conclude that vapes cause cancer. This included papers that typically looked at cancer biomarkers and carcinogenic mechanisms.

By 2024 and 2025, almost without exception, authors were expressing concern. They noted that the idea vaping has a lower cancer risk than smoking could no longer be supported, given the evidence we now have.

Our study, which looks at cancer caused by vapes in their own right, marks a new approach to what we know about the link between cancer and vaping.

What we still don’t know

We still don’t have direct evidence that there are more cancer cases than expected among people who vape.

The fact it took 100 years to demonstrate that smoking causes cancer indicates it will take decades to make a similar case for vaping. And it will be challenging, because definitive proof will depend on a population of people who only vape, not people who smoke and vape.

So we need large and carefully planned studies, which will then allow us to monitor and detect cancer early, and precisely determine if it is caused by – or worsened by – vaping. Lives can be saved by these means, but only if this research is funded and started now.

Bernard Stewart, Professor, Paediatrics and Child Health, UNSW Sydney

This article is republished from The Conversation under a Creative Commons license. Read the original article.