A new Harvard University study has cast doubts about the safety of flavored e-cigarettes, many of which have been found to contain a chemical tied to a respiratory disease commonly known as “popcorn lung.”
Researchers at the Harvard T.H. Chan School of Public Health tested 51 e-cigarette flavors sold by “leading e-cigarette brands.” Of these they found that 39 of the 51 flavors contained diacetyl—a chemical commonly used to add flavorings like butter, caramel, strawberry and butterscotch—that has been linked to bronchiolitis obliterans and other severe respiratory diseases.
The U.S.’s Occupational Safety & Health Administration describes bronchiolitis obliterans as occurring when small airways become inflamed and scarred, resulting in the thickening and narrowing of the airways.
The researchers focused their study, which was published by the National Institute of Environmental Health Sciences, on e-cigarettes sold by the largest cigarette companies and on flavors they thought would be appealing to children, teenagers and young adults.
The largely unregulated e-cigarette industry has been a focal point for controversy in recent years, with some health bodies saying they’re a gateway for new or underage smokers, and that flavored e-cigarettes in particular could attract younger smokers. An August study in the Journal of the American Medical Association found that ninth-graders who used electronic cigarettes were more likely to smoke cigarettes, cigars or hookahs than peers who never tried the battery-powered devices.
U.K. antitobacco group ASH and Public Health England, along with the tobacco industry, have billed e-cigarettes as a way to reduce the incidence of cigarette use.
Popcorn lung, the disease associated with inhaling diacetyl, got its name due to reports in the early 2000s of lung disease in microwave-popcorn workers. The workers were exposed to butter-flavoring chemicals, of which diacetyl was the most prominent.
The Harvard researchers, who released their study on Tuesday, noted that the heating, vaporization and inhalation of flavoring chemicals in e-cigarettes makes smokers’ exposure similar to that of workers in the microwave-popcorn industry.
The study also found two other chemicals—2,3 pentanedione and acetoin—respectively present in 23 and 46 of the 51 flavors it tested. Roughly 92% of the e-cigarettes it tested had one of the three chemicals present.
According to the study, two companies stated their products didn’t contain diacetyl when it was found during testing that they in fact did. Across the websites and packaging for all of the e-cigarette brands studied, the researchers found no health warnings about diacetyl.
The study evaluated flavors from three large cigarette companies, a large independent e-cigarette company and three e-cigarette distributors. It didn’t name the companies.
“We acknowledge that diacetyl shouldn’t be used in e-cigarettes, but equally diacetyl is found in cigarettes at very significant levels, so obviously there is a harm-reduction aspect to switching to e-cigarettes,” said Tom Pruen, chief scientific officer for the U.K.-based Electronic Cigarette Industry Trade Association.
E-cigarettes are currently largely unregulated, although a 2014 Food and Drug Administration proposed rule is seeking to expand the legal definition of tobacco products to include e-cigarettes.
In the U.K. they will fall under the revised EU Tobacco Products Directive starting in May, which will set out safety and quality requirements for e-cigarettes.