When they first came out, a lot of people thought e-cigarettes were a safe alternative to smoking. According to the Masonic Cancer Center at the University of Minnesota, that's not the case. More research is needed to better characerize the long-term safety of e-cigarettes. While there isn't a lot of research, studies are starting to show that the flavoring chemicals in e-cigarettes, as well as in e-liquids without nicotine, aren't as safe to inhale as previously thought. While most people know cigarettes cause cancer many believe that vaping keeps them safe from cancer-causing chemicals. A recent study found during an average vaping session, significant amounts of cancer-causing chemicals (like formaldehyde) were retained in the respiratory tract.