E-cigarette products are damaging to lungs but may be safer than smoking cigarettes, according to a new long-term study released this week.

The same study, however, found that the riskiest behavior was among smokers who used both vaping products and cigarettes, which researchers said was common.

Researchers found e-cigarette users, tracked for three years, had 1.3 times more risk of developing a respiratory disease than people who did not use tobacco, based on a study published in the American Journal of Preventive Medicine on Monday.

People who smoked cigarettes, however, had a 2.5 times higher risk than those who did not smoke, according to the study.

The group most at risk for developing respiratory disease were those who use e-cigarettes and smoke cigarettes. Those users had 3.3 times the risk of developing a respiratory disease than nonsmokers, the study reports. 

Researchers found that the use of both products was common and concluded that the use of e-cigarettes did not actually aid cigarette smokers in quitting. 

“Although switching from combustible tobacco, including cigarettes, to e-cigarettes theoretically could reduce the risk of developing respiratory disease, current evidence indicates a high prevalence of dual use, which is associated with increased risk beyond combustible tobacco use,” researchers wrote in the study.

“In addition, for most smokers, using an e-cigarette is associated with lower odds of successfully quitting smoking.”

Study co-author Dr. Stanton Glantz, a professor of medicine at the University of California, San Francisco, told Time “if you’re going to do one or the other, in terms of the respiratory effects, you’re probably better off with an e-cigarette.” 

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

“Yes, vaping is associated with about 29 percent to 31 percent higher odds of subsequent lung disease within two to three years than not vaping — but compare this with the 156 percent higher odds of using combustible tobacco than not smoking,” Tan told Time. 

The results of what is said to be the first long-term study on the effects of e-cigarette use come as the topic has been thrust into headlines with an influx of reports of illness, and death, due to lung injury associated with e-cigarette use.

The Centers for Disease Control reported 2,409 cases across all 50 states of people hospitalized for e-cigarette product use-associated lung injury as of Dec. 10. The CDC also reports 52 deaths confirmed related to the vaping-associated lung injuries.

No single cause has been identified to explain the cases, but carrier oils, such as vitamin E acetate, heavy metals, flavorings and other toxins have been implicated during investigations.

As the epidemic continues, critics have accused flavored vaping products of targeting youth users. Several states have banned the sale of flavored products.

President TrumpDonald John TrumpDemocrats secure fast-track to the floor for Canada-Mexico trade deal Mexican official says he's 'very satisfied' with USMCA after recent concern More than 700 historians sign letter calling for House to impeach Trump MORE announced in September that his administration would soon give guidance on clearing the market of the flavored products. The administration has yet to give any indication of when it will move forward with a flavor ban after the White House regulatory office finished its review of FDA guidance last month.