It only took three years for some e-cigarette users to develop chronic lung diseases, according to the first long-term study on the effects of vaping.

The study published in the American Journal of Preventive Medicine found that while e-cigarettes might be safer than smoking cigarettes, people who vaped were about 30% percent more likely to have developed a chronic lung disease like asthma or emphysema. The study looked at 32,000 adults who were lung-disease free in 2013 and checked in with them in 2016.

"E-cigarette use predicted the development of lung disease over a very short period of time. It only took three years," Stanton Glantz, the study's author, told NBC News.

As vaping surged in popularity ― and as vaping-related health problems like burned lungs and the accidental ingestion of toxic metals surfaced ― a central fear was how little we knew about the long-term health effects on users. The new study finally gave the public some data on the matter.

Still, cigarette smokers were worse off than people who vaped and people who did both are far worse off. Smokers had a 2.5 times higher risk than nonsmokers of developing a lung disease. People who did both ― vape and smoke cigarettes ― had a 3.3-times higher risk.

“This study actually does support the harm reduction potential of e-cigarettes,” Andy Tan, an assistant professor at Dana-Farber Cancer Institute who has studied e-cigarettes, told Time.

Tan pointed to the stats from the study that showed vaping damages lungs but at a significantly lower rate than cigarettes to back that claim up. But the study also showed that many people who vape also smoke, which means they’re doing more damage than if they did just one.

"Most adults who use e-cigarettes continue to smoke," Glantz told NBC News. "And if they do that, they get the risks of the smoking plus the risk of the e-cigarette."

The lung risks described in the study are different than the vaping-related lung injuries called EVALI that have killed 52 people and hospitalized more than 2,400 since the outbreak began in the summer. The Centers for Disease Control and Prevention ― which has been tracking the cases since August ― has said they haven’t determined a single cause for EVALI cases, but around 80 percent of patients reported vaping THC products.

A separate study in the American Journal of Preventive Medicine, meanwhile, found just how popular vaping is among young people. The study that included 14,560 teens found that 75 percent had vaped nicotine, marijuana, or multiple substances. Twelve percent reported vaping within the last 30 days. For context, a Gallup poll over the summer found just 8 percent of U.S. adults overall had vaped in the week prior.