Aerosol deposition doses in the human respiratory tree of electronic cigarette smokers

Aerosols from eight e-cigarette solutions with different nicotine levels and flavoring were characterized in terms of particle number size distributions. Results were used to provide dosimetry estimates applying the Multiple-Path Particle Dosimetry model. Particle number concentrations were found to range between 3.26×10^9 and 4.09×10^9 part×cm-3 for e- liquids without nicotine and between 5.08×10^9 and 5.29×10^9 part×cm-3 for e-liquids with nicotine, whereas no flavor effects were detected on particle concentration data. Particle size distributions were unimodal with modes ranging between 107-165 nm and between 165-255 nm, for number and volume metrics respectively. Averagely, 6.25×10^10 particles were deposited in respiratory tree after a single puff. Highest deposition densities and mean layer thickness of e-cigarette liquid on the lung epithelium were estimated at lobar bronchi. Our study shows that e-cigarette smoke is a source of high particle dose in human respiratory system, from 23% to 35% of typical daily dose of not smoking individual.