The deposition of aerosols inhaled into the human respiratory tract is key to evaluate exposure and risk during product use.

A method based on a differential mobility spectrometer (DMS) was established for determining the physical properties of smoke aerosols generated from a combustible cigarette, an electronic cigarette and a heat-not-burn product. The concentration, the count median diameter (CMD) and the geometric standard deviation (GSD) of aerosols generated from all three types of product were determined. On the basis of aerosol physical properties, a Multiple Path Particle Dosimetry (MPPD) model was used to predict the deposition of aerosols in different parts (buccal cavity, tracheal bronchi, alveoli) of human respiratory tract and lungs.

The results showed that: (1) There was no significant difference in the concentration of smoke aerosols between the three different products. The CMD of aerosols from the electronic cigarette (CMD, 17.8-22.4 nm) was lower than for the heat-not-burn product (CMD, 51.8-53.9 nm) and the cigarette (CMD, 174-191 nm); (2) For the aerosols from all three products, the deposition rate was the lowest in the buccal cavity, moderate in the tracheal bronchi, and the highest in the alveoli. The total deposition rate of aerosol was found to be the highest for electronic cigarettes (45.9 %) > heat-not-burn cigarettes (37.2 %) > cigarettes (28.3 %). The highest aerosol deposition rate for all three products was in alveoli, which accounted for more than 60 % of the total deposition; (3) Inside the lungs, the highest deposition rate of aerosol was found in the right lower lung.