E cigarettes can emit formaldehyde at high levels under conditions that have been reported to be non averse to users Scientific Reports E liquide cigarette elecronique sans propylene glycol Vegetol Pure Test Kit: Propylene Glycol in Indoor Air as an Indicator of Vaping LCS Laboratory Inc. The combination of propylene glycol and vegetable glycerin e cigarette aerosols induces airway inflammation and mucus hyperconcentration Scientific Reports