The DNA changes were similar to those linked to secondhand smoke, study coauthor Moon-shong Tang of New York University tells The Guardian. Specifically, the team found that two mutagenic compounds develop in lung, bladder, and heart cells exposed to e-cigarette smoke. DNA-repair activity and the repair proteins XPC and OGG1/2 were reduced in the lung tissue of mice.
Critics caution that the mice in the study were exposed to higher levels of e-cigarette smoke than those who vape might inhale (although Bloomberg reports that, over 12 weeks, mice were exposed to a dose similar to what a human would intake after smoking e-cigarettes lightly for 10 years). Still, “this study shows nothing at all about the dangers of vaping,” Peter Hajek, director of the Wolfson Institute of Preventive Medicine's Tobacco Dependence Research Unit at Queen Mary University of London, notes in The Guardian. “It doesn’t show that vaping causes cancer.”
In the paper, Tang and his colleagues concede that “it takes decades for carcinogen exposure to induce cancer in humans, [so] for decades to come there will be no meaningful epidemiological study to address the carcinogenicity of [e-cigarette smoke].” Still, the levels of carcinogenic compounds are higher in the blood of vapers than nonsmokers, pointing to the increased risk of developing cancer.
The bottom line, Tang tells Bloomberg, is: “Don’t think a vapor is harmless.”