Health Effects of E Cigarettes Kansas Health Institute Read "Public Health Consequences of E Cigarettes" at NAP.edu Vaping is unregulated and unsafe get the facts DHW Voice Vaping propylene glycol and vegetable glycerine may lead to lung inflammation 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