All E Cigarettes Emit Harmful Chemicals, but Some Emit More Than Others Berkeley Lab Berkeley Lab News Center E cigarette, or Vaping Product, Use Associated Lung Injury (EVALI) Fact Sheets Yale Medicine Propylene glycol, a component of electronic cigarette liquid, damages epithelial cells in human small airways Respiratory Research Springer Nature Link 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 Liquid E Cigarettes Liquid nicotine used in e cigarettes still a danger to children despite recent decline in exposures