A new study has found similar levels of DNA damage among vapers and cigarette smokers, adding to evidence that e-cigarettes, initially marketed as a safer alternative to traditional cigarettes, pose similar health risks. 

In the study, published in the journal Nicotine & Tobacco Research, researchers from the Keck School of Medicine of the University of Southern California analyzed epithelial cells taken from the mouths of 72 healthy adults who were split into three groups, matched for age, race, and gender: current vapers (who had never smoked), current smokers (who had never vaped), and people with no history of smoking or vaping.

They found that vapers and smokers had similar levels of DNA damage: 2.6 times and 2.2 times that of non-users, respectively. DNA damage was higher among those who vaped or smoked more frequently. 

Regarding devices, vapers who used pods had the highest levels of DNA damage, followed by those who used mods. In terms of flavors, sweet-flavored vapes were linked to the highest levels of DNA damage, followed by mint/menthol- and fruit-flavored vapes.

“For the first time, we showed that the more vapers used e-cigarettes, and the longer they used them, the more DNA damage occurred in their oral cells,” says Ahmad Besaratinia, PhD, MPH, professor of research population and public health sciences at the Keck School of Medicine and the study’s senior author, in a press release. “The same pattern held up in smokers.”

DNA damage to oral epithelial cells, which line the mouth, is an early change associated with an increased risk for many types of chronic disease, including cancer and inflammatory diseases.

The findings are “highly relevant” for public health agencies and regulators who aim to keep dangerous products away from vulnerable groups, including children and adolescents, says Besaratinia in a press release. The most popular products, including flavored vapes—which are used by about 85% of teens who vape—also appear to be the most harmful in terms of producing DNA damage.

The team’s next task is to replicate the findings in a larger group of participants. They also plan to study other biological effects resulting from DNA damage that are even more closely related to the onset of chronic disease.