Vaping aerosols contain thousands of unknown chemicals and substances not disclosed by manufacturers, including industrial chemicals and caffeine, Johns Hopkins University researchers found.

The study is the first to apply to vaping liquids and aerosols an advanced fingerprinting technique used to identify chemicals in food and wastewater. The results, just published in the journal Chemical Research in Toxicology, suggest people who vape are using a product whose risks have yet to be fully determined and could be exposing themselves to chemicals with adverse health effects.