A sweeping scientific review has concluded that e-cigarettes are likely to cause lung cancer and oral cancer. The finding delivers an evidence-based warning about a product long regarded as a safer alternative to smoking for those trying to quit.
A research team led by cancer researcher Bernard Stewart at the University of New South Wales (UNSW) in Sydney, Australia, published the review in the international journal Carcinogenesis on March 30, Bloomberg reported.
Cell and Animal Studies Stand In for Long-Term Tracking
E-cigarettes have only been in widespread use for about 20 years, so epidemiological studies tracking the decades-long process from use to cancer development are still lacking. Instead, the research team pooled clinical observations, animal studies and cell-level mechanistic research to examine whether e-cigarettes themselves can cause cancer. When nicotine-related compounds, heavy metals and other substances from inhaled aerosol build up in the body, they damage DNA and trigger inflammation, both considered early changes that can lead to cancer. In experiments on mice, animals exposed to e-cigarette aerosol developed lung tumors at far higher rates than control groups, and cancer-related changes also appeared in the bladder.
"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," Stewart said. The research team qualified that this conclusion is a qualitative assessment and does not put a specific number on the level of risk.
Dual Use Raises the Risk Further
So-called "dual use," in which people fail to fully switch to e-cigarettes and instead smoke both cigarettes and e-cigarettes, is also common. According to the research team, more than half of tobacco product users are unable to quit either one. "What we do know from recent epidemiological evidence from the USA is that those who both vape and smoke are at an additional four-fold increased risk of developing lung cancer," said co-author Freddy Sitas, an epidemiologist at UNSW.
The Findings Also Raise Questions for Policy
The review also raises fresh questions about the policies of countries such as New Zealand and the UK, which have embraced e-cigarettes as a smoking-cessation aid. The global e-cigarette market is estimated at $30 billion to $46 billion (about ₩40 trillion to ₩62 trillion), and tobacco companies including Altria Group, British American Tobacco and Imperial Brands have invested heavily in it. "We should not wait another 80 years to decide what to do," Sitas said. Experts stressed, however, that because cigarettes remain far more harmful than e-cigarettes, the findings should not be taken as a reason to return to smoking.
Oral cancer outcomes improve the earlier the disease is caught, which is why screening technology continues to advance alongside this research. As discussed in AI Oral Cancer Screening: A Flagged Spot May Not Be Cancer, a growing number of services now identify suspicious spots from nothing more than a smartphone photo, though they cannot substitute for a definitive diagnosis.
South Korea has overhauled its e-cigarette regulations this year. Synthetic-nicotine liquid e-cigarettes, which use nicotine rather than tobacco leaf as their raw material, had not been classified as tobacco under the Tobacco Business Act, allowing them to bypass health-warning labels, advertising restrictions and smoke-free zone rules. A revised Tobacco Business Act, promulgated on December 23 last year, took effect on April 24 this year after a four-month grace period, bringing synthetic-nicotine liquid e-cigarettes under the same regulations as ordinary cigarettes. Packaging and advertisements must now carry health warnings, and using one in a smoke-free zone can bring a fine of up to 100,000 won. However, warning labels that specifically flag the lung cancer and oral cancer risks raised by this review have not yet been introduced.