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 E liquide 10ml Blend Mint JWELL E liquide tabac menthe 6mg Cdiscount What's hiding in that vape puff? Vapes might look clean or harmless on the outside, but inside the aerosol is a mix of chemicals and metals created when the liquid is heated.