Propylene glycol is synthetic and a by-product of petroleum. Though it is recognized as safe to inhale, it’s not considered organic, as it is extracted in a way that doesn’t meet the National Organic Program’s criteria. PG is popular with nicotine vapers as the ingredient provides a similar sensation to smoking tobacco products, often referred to as a throat hit. The element is tasteless and odorless, so it doesn’t change the flavor at all. It also flows easily and absorbs quickly into the cotton wick.