Propylene glycol, a component of electronic cigarette liquid, damages epithelial cells in human small airways Respiratory Research Springer Nature Link Since their introduction in Europe in 2006 and the U.S. in 2007, the use of e cigarettes a.k.a., vapes has skyrocketed. A recent review from researchers in Australia found the results More cancer patients are vaping UPI.com Vaping and e cigarette use is a troubling trend Fort Plain Central School District Vape Juice Ingredients: What's Inside Your E Liquid? VITAE Glass e Cigarettes Safety Not Yet Proven CANSA The Cancer Association of South Africa CANSA The Cancer Association of South Africa