Toxicological Assessment of Aged Electronic Nicotine Delivery System Aerosols on Primary Human Small Airway Epithelial Cells

The emerging popularity of electronic nicotine delivery systems (ENDS) has increased safety concerns. ENDS aerosols contain numerous hazardous components including acetaldehyde, formaldehyde, and heavy metals along with various other chemicals. Recent studies showed ENDS use can cause various health risks including gastrointestinal, cardiovascular, neurological, and immune system impairment. Moreover, the long-term respiratory effects of ENDS use have not been fully evaluated. In this study, we hypothesized during normal consumer use ENDS device ageing occurs, which may alter the toxicological properties of emitted aerosols. We propose that the altered toxicological properties of ENDS aerosols may elicit reactive oxygen species (ROS), oxidative stress, cell viability reduction and DNA damage in human primary small airway epithelial cells (SAEC). We utilized a custom built 4-channel puffing machine and a novel condensation trap to automatically generate and monitor aerosols from a mod type ENDS manufactured by VooPoo® using tobacco–flavored e-liquid. ENDS aerosols samples (1-25), (101-126) and (201-226) puffs were collected in the fluorinated ethylene propylene (FEP) tube trap and extracted to be assessed with the in-vitro toxicological assays. Our results revealed that the VooPoo® ENDS device produce different sizes of nanoparticles ranging from 10nm to ~1micron during the device aging process. Increasing particle concentrations were observed throughout the aging process where puffs 1-25 emitted 1 µg/m3, puffs 101-126 emitted 4 µg/m3, and puffs 201-226 emitted 7 µg/m3. Along with the VooPoo® device aging process, the increasing levels of reactive oxygen species, glutathione level, and cellular viability reduction were observed. Moreover, a three-fold increase in DNA damage in SAEC was observed at puffs 201-226 aging stage compared to puffs 101-126 puff fraction. This work suggests ENDS aerosols become more hazardous during normal device usage, which may pose a threat to respiratory health