A new study out of New York University is the first to link nicotine vaping to lung cancer, at least in mice. But researchers say the results are concerning for human e-cigarette users, too.
"What I can say is that e-cigarettes are harmful. Nicotine, once it gets into the cell, it becomes a DNA-damaging agent in humans or in mice," said Moon-Shong Tang, the professor from NYU School of Medicine who led the study.
Published Monday in the National Academy of Sciences' journal Proceedings of National Academy of Sciences, Tang's study exposed three groups of mice to different breathing environments ー nicotine-laced e-cigarette vapor, e-cigarette vapor without nicotine, or to filtered air ー for 20 hours per week for just over a year. Tang said the conditions were meant to mimic what "a heavy e-cigarette smoker smokes for three to six years."
Tang said the results were troubling. Of the 40 mice exposed to nicotine-laced electronic-cigarette smoke (ECS), 22.5 percent developed lung cancer, and 57.5 percent developed precancerous cells on the bladder ー a percentage Tang called "unusually high from our experience." All of the nicotine-exposed mice developed DNA damage in the lungs, heart, and bladder, and demonstrated impaired ability to repair DNA in the lungs. By comparison, of the 16 mice exposed to vapor without nicotine, only one developed precancerous lesions, and none of those exposed to filtered air did.
"Current observations that [e-cig smoke] induces lung adenocarcinomas and bladder urothelial hyperplasia, combined with our previous findings ... implicate ECS as a lung and potential bladder carcinogen in mice. While it is well established that tobacco smoke poses a huge threat to human health, whether ECS poses any threat to humans is not yet known and warrants careful investigation," text from the study's abstract reads.
Tang said he would like to expand the study to look at larger number of mice, and for a longer stretch of time. Whether or not additional research will be possible, however, all depends on funding. The study was ultimately funded by grants from the National Institutes of Health, but Tang said he initially had trouble securing funding because many people think e-cigarettes are a safer alternative to smoking.
"I had great difficulty getting funded because of e-cigarettes. The conventional wisdom is that nicotine is not carcinogenic," Tang said.
It's claims like those that have earned vape maker Juul scrutiny from the Food and Drug Administration. The agency wrote letters to the company last month, warning against unsubstantiated health claims, and citing instances in which the company told children and adults that its products are safer than combustible cigarettes, The Wall Street Journal reported. Juul is also facing the brunt of national outrage over teen vaping, which has surged to levels the FDA called "epidemic" in recent years. Juul CEO Kevin Burns stepped down at the end of September amid the controversy.
Tang's study comes amid a nationwide panic over a vaping-related illness that has sickened more than 1,000 and killed at least 18 nationwide. Recent research from Mayo Clinic and the Centers for Disease Control and Prevention has largely implicated THC vape products, purchased illicitly, to these illnesses, but shares of tobacco companies have still suffered. Altria, Juul's largest investor, has fallen about 10 percent since mid-August, just before the CDC launched its investigation of the vaping illness.