Identification, Quantification, and Evaluation of the Cytotoxicity of Electronic Cigarette Exhaled Aerosol Residue (ECEAR)
Electronic cigarettes (ECs) produce EC exhaled aerosol residue (ECEAR), which is the residue left on surfaces when EC users have exhaled or stopped vaping. It contains nicotine, nicotine alkaloids, tobacco specific nitrosamines (TSNAs), as well as flavor chemicals. The purpose of this dissertation was to identify and quantify chemicals in ECEAR and to detect cytotoxicity of ECEAR using in vitro models. Firstly, refill fluids and their aerosols were analyzed to quantify flavor chemicals and nicotine and to determine their transfer efficiency to aerosols. Human participants then vaped the same refill fluids to create exhale which was used to identify and quantify what is retained and what contributes to ECEAR. Not only did nicotine and cinnamaldehyde transfer better than other flavor chemicals, they were better retained by users, especially cinnamaldehyde. Participants were divided into two topographies: mouth and lung inhalers. The mouth inhalers exhaled more chemicals, while lung inhalers retained almost all inhaled flavor chemicals and nicotine. Keratinocytes and EpiDerm tissues were exposed to refill fluids at various concentrations and times. Cytotoxicity was induced at a 1% concentration of Churrios refill fluid and reactive oxygen species (ROS) were increased in keratinocytes. EpiDerm(TM) skin tissues had increases in the secretion of IL-1alpha, IL-6, and MMP-9 upon exposure to Dewberry Cream and Churrios refill fluids, indicating an inflammatory response. Churrios ECEAR extract also increased IL-1alpha secretion. These data show that refill fluids and ECEAR can induce an inflammatory response and the production of ROS in skin cells. The concentrations of nicotine and tobacco alkaloids were then measured in ECEAR collected from three field sites. A vape shop sample exposed for 1 month contained as much as 108 mg of nicotine/m2, and the concentration increased with exposure time. The living room of an individual EC user had ECEAR, although concentrations were lower than in the vape shop. Lastly, ECEAR was detected and quantified in a business located near a vape shop in a multiunit tenant building, indicating that EC aerosols can move through ventilation systems and contaminate indoor surfaces away from their origin. In conclusion, ECEAR builds up on indoor surfaces and can affect the skin of those actively or passively exposed.