Propylene glycol, a component of electronic cigarette liquid, damages epithelial cells in human small airways Respiratory Research Springer Nature Link E liquide Tabac Menthe Menthol avec ou sans Nicotine Cigaretteelec Researchers at the University of California, Riverside, found that heating propylene glycol, the main ingredient in most e cigarette liquids, can produce two toxic chemicals, methylglyoxal and acetaldehyde, which damage lung cells. Using Vaping safe. Know what's inside. Protect their future. TalkNowAZ.com