Propylene glycol & vegetable glycerin E Cigarettes, Vapes, and other Electronic Nicotine Delivery Systems (ENDS) FDA Propylene glycol hi res stock photography and images Alamy Flavor induced inflammation and cytotoxicity in human aortic smooth muscle cells: Potential implications for E cigarette safety ScienceDirect Vaping and ecigarettes TIL propylene glycol, the chemical in e cig vapor, is used in asthma inhalers and has had decades of research done on its safety. (sourced study in link) : r todayilearned