1,2 Propylene Glycol: A Biomarker of Exposure Specific to e Cigarette Consumption Vaping Equals Vaping: An Attack on Your Immune System NC DNA Day Blog PG Propylene Glycol vs VG Vegetable Glycerin All you need to know 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