1,2 Propylene Glycol: A Biomarker of Exposure Specific to e Cigarette Consumption Some of the most dangerous e cig flavors are cinnamon, vanilla, raspberry, pineapple, and orange. Besides flavors, e cigarette aerosol contains other dangerous chemicals like metals, formaldehyde All E Cigarettes Emit Harmful Chemicals, but Some Emit More Than Others Berkeley Lab Berkeley Lab News Center 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 A Single Session of Vaping Can Hurt Your Lungs