Tracking the Movement of Electronic Cigarette Flavor Chemicals and Nicotine from Refill Fluids to Aerosol, Lungs and Exhale

Electronic cigarettes (ECs) have been linked to lung diseases, including COVID-19, with little understanding of exposure, retention, and exhalation of EC aerosol chemicals. Here, flavor chemicals and nicotine were quantified in two refill fluids, their transfer efficiency to EC aerosols was determined, exhalation by human participants was measured, and chemical retention was modeled. Nicotine transferred well to aerosols irrespective of topography; however, transfer efficiencies of flavor chemicals depended on the chemical, puff volume, puff duration, pump head, and EC power. Participants could be classified as "mouth inhalers" or "lung inhalers" based on their retention and exhale of flavor chemicals and nicotine. Only mouth inhalers exhaled sufficient concentrations of flavor chemicals and nicotine to contribute to chemical deposition on environmental surfaces. These data help distinguish two types of EC users, add to our knowledge of chemical exposure during vaping, and provide information useful in treating EC-related diseases and regulating EC use.