Effect of electronic cigarette atomising power and flavour on aerosol size-segregated metal concentration and inhalation risk

Introduction Although numerous studies have estimated the inhalation dose of metals emitted from electronic cigarettes (e-cigs), the impact of factors including aerosol size and the atomising power of e-cig aerosols on estimating the inhalation dose of metals remains underexplored. A comprehensive understanding of these determinants is essential to assess the health risks associated with inhaling e-cig aerosols, which may contain potentially harmful metals. Objectives The aim of this study is to elucidate the mass and inhalation doses of potentially harmful metals in e-cig aerosols by different particle size and their association with the various atomising powers of e-cig devices and flavours. Methods Size-segregated e-cig aerosols were generated and collected in a exposure chamber, using an 11-stage cascade impactor for the analyses of aerosol mass and metals. The metal deposition dose in the human respiratory tract was calculated using a mathematical respiratory deposition estimation model and metal mass concentration by the size of aerosols. Results In this study, the results showed that neither an increase in atomising power (from 5 to 20 W) nor e-cig flavours resulted in a significant increase in a metal deposition in the respiratory tracts. Although the factors did not significantly affect the calculated respiratory deposition of harmful metals under typical e-cig usage assumption, the estimated hazard index exceeded 1.0. Conclusion The calculated health risks suggest substantial risks of inhalation of metal aerosols from e-cig use.