Safer Using Vaping CAHMA PG VG Propylene Glycol USP Grade PG for Ejuice Central Vapors An independent test carried out on popular vape liquid samples readily available in the market suggests that users are at risk of developing cancer and other life threatening health complications. Among the more What's in an e liquid or vape juice? The main ingredients are propylene glycol (PG) and vegetable glycerine (VG). These are solvents that are basically used to dissolve and carry the other ingredients.