About 20% of cigarette smokers and young adult non-smokers believe e-cigarettes contain fewer harmful chemicals than regular tobacco-based cigarettes, while about 30% say that they did not know how the levels compare, according to a Rutgers University study.

The study, published in Addiction, measured perceived levels of harmful chemicals in e-cigarettes compared with cigarettes using national samples of more than 1,000 adults ages 18 and older who smoke cigarettes and 1,000-plus adults ages 18 to 29 who are nonsmokers. The study also measured associations with e-cigarette/cigarette relative harm perceptions, e-cigarette use, and interest.

About half of the participants believe that nicotine-based electronic cigarettes have the same amount or even more harmful chemicals than regular tobacco-based cigarettes.

“Our results were interesting to see given that previous review reports suggest e-cigarettes expose users to fewer types and lower levels of harmful and potentially harmful chemicals than cigarettes,” says Olivia Wackowski, PhD, of Rutgers Center for Tobacco Studies, an associate professor at the Rutgers School of Public Health and lead researcher of the study, in a release. “It was also interesting to find that only about half of adult smokers who thought e-cigarettes have fewer harmful chemicals also thought e-cigarettes are less harmful to health.”

The study also found an interest in e-cigarette use was significantly higher among those who perceive them to have fewer harmful chemicals than traditional cigarettes and to be less harmful.

E-cigarette harm perception relative to typical cigarettes is a common question included on major national health and tobacco surveys in the United States. However, surveys of e-cigarettes typically haven’t included a question about the perceived exposure to or level of harmful chemicals in e-cigarettes relative to cigarettes.

According to the study researchers, measuring perceptions of e-cigarette and cigarette chemical exposure is important because e-cigarette communications often directly refer to chemicals in some way, which may impact perceptions about chemicals and harms from using e-cigarettes compared to cigarettes.