A comprehensive new study led by UNSW Sydney concludes that nicotine-based e-cigarettes are more likely to cause lung and oral cancer.
Published in a magazine carcinogenicThe study assessed a wide range of international studies and brought together experts from multiple institutions including the University of Queensland, Flinders University, the University of Sydney, Royal North Shore Hospital, Prince Charles Hospital and Sunshine Coast University Hospital.
The research team included experts from multiple fields, including pharmacy, epidemiology, thoracic surgery, and public health. They sought to determine whether e-cigarettes themselves could contribute to the development of cancer by examining evidence from various scientific fields.
“To our knowledge, this study is the most definitive determination that people who vape have a higher risk of cancer than people who don’t smoke,” Professor Stewart said.
The review focuses on carcinogenicity, or the causes of cancer, and argues that while e-cigarettes have often been studied as a pathway to smoking, less attention has been paid to the possibility that e-cigarettes themselves directly cause cancer.
Researchers say this study is one of the most extensive evaluations to date of whether e-cigarettes can increase cancer risk, independent of traditional smoking. The analysis combined results from clinical studies, animal studies, and laboratory studies on chemicals produced by e-cigarettes.
“Given all the findings from clinical monitoring, animal studies and mechanistic data, e-cigarettes are likely to cause lung and oral cancers,” Professor Stewart said.
Although the results were very consistent across different research areas, Professor Stewart points out that the exact number of cancer cases caused by e-cigarettes remains unknown.
“Our assessment is qualitative and does not include numerical estimates of cancer risk or burden. The exact risk will only be determined once longer-term studies are available.”
Growing concerns about e-cigarettes and public health
E-cigarettes first entered the market in the early 2000s and became available in Australia around 2008. E-cigarettes were initially promoted as a safer alternative to traditional cigarettes and as a tool to help people quit smoking.
Since then, brightly colored and flavorful e-cigarette products have become increasingly popular, especially among young users. Despite tougher regulations introduced by the Australian government in 2023, e-cigarettes remain common outside schools, bars and train stations across the country. Under current regulations, disposable non-therapeutic e-cigarettes are prohibited and therapeutic e-cigarette products can only be sold through pharmacies for smoking cessation purposes.
“E-cigarettes are known to be a gateway to smoking and, in turn, cancer,” said co-author Associate Professor Freddie Cetas from UNSW.
“However, research has not focused as much on the extent to which they cause cancer on their own,” he says.
“The evidence was surprisingly consistent across all areas,” he says. “It takes decades for human research to estimate risk to accumulate, but for now, a clear finding has been determined.”
the evidence points in the same direction
Scientists have spent more than a century studying the health effects of smoking. Although e-cigarettes are much newer, exposure to nicotine-containing aerosols has already been linked to dependence, poisoning, inhalation injuries, and burns.
Because long-term population studies are still ongoing, researchers must now rely on other forms of evidence to assess the potential cancer risks from e-cigarettes.
The study identified multiple carcinogens in e-cigarette aerosols, including volatile organic compounds and metals emitted by heating coils.
Researchers also looked at some other evidence. These included biomarkers in people showing DNA damage, oxidative stress, and tissue inflammation. A study of mice that developed lung tumors. Laboratory experiments that demonstrate disruption of biological processes associated with cell injury and cancer development.
According to the authors, the collective findings consistently point to the same conclusion.
Combined use may increase risk of lung cancer
The researchers also highlighted growing evidence that many smokers who switch to e-cigarettes also continue to use traditional cigarettes.
“Most people who use e-cigarettes to quit smoking are unable to break either habit and end up in ‘dual use,'” says Professor A. Sitas.
“What we know from recent epidemiological evidence in the United States is that people who both e-cigarette and smoke have an additional four times higher risk of developing lung cancer.”
These findings were discussed in a separate commentary by Professor A/. Cetus and Professor Stewart’s paper has been published. cancer epidemiology.
Researchers see echoes of smoking history
A/Professors Cetus and Stewart say there are striking similarities between today’s debate about e-cigarettes and early scientific research into smoking-related diseases.
It took decades of research before smoking was officially recognized as a cause of lung cancer. Almost a century has passed between early observations in the mid-1800s and the landmark U.S. Surgeon General’s report in 1964.
For most of that period, warning signs were frequently ignored or ignored.
“Early reports linked smoking to infectious diseases such as tuberculosis, followed by cardiovascular disease, stroke and lung cancer,” Professor Sitas says.
He said the same pattern may now be playing out with e-cigarettes, and researchers shouldn’t repeat the delays that occurred with cigarettes.
“E-cigarettes were introduced about 20 years ago. We shouldn’t wait another 80 years to decide what to do.”
