Comparison of particle size distributions between conventional cigarettes and electronic cigarettes based on aerosolization mechanisms, and development of a dosing algorithm for human deposition fraction

Fine particles generated by smoking or vaping from Conventional Cigarettes (CC) and Electronic Cigarettes (EC) (e.g., VAPE, Heat Not Burn (HNB), and Glycerin added Heat Not Burn (GHNB)) pose significant health risks due to their ability to penetrate deeply into the respiratory system and deposit toxic compounds. While previous studies have provided valuable insights, many of them have not fully addressed methodological challenges in replicating human puffing or have focused on limited product types rather than comparing multiple types of cigarette products, including CC, VAPE, HNB, and GHNB, within a single study. In this study, an aerosol sampling system was developed that incorporates an interface that mimics human-respiration and was designed to convert transient puff flow into steady-state flow, integrated with a Scanning Mobility Particle Sizer (SMPS) capable of scanning ultrafine particles down to 10 nm. This setup enabled a consistent comparison across multiple cigarette product types including CC, VAPE, HNB, and GHNB. It was found that the particle peak diameter varied depending on the aerosolization mechanisms and categorized into three aerosolization regions: Combustion, Vaporization, and Thermal Decomposition. A dosing algorithm was derived using a surface area metric to calculate the deposition rates of aerosol particles in the human body. Due to the inherent upper size limit of the SMPS instrument, our quantitative interpretation is reliable for particles a few hundred nanometers in diameter and smaller. The results obtained through the dosing algorithm revealed that aerosol particles generated by CC and HNB exhibited the greatest level of accumulation in the human body, followed by GHNB and VAPE. The presented method provides a consistent experimental framework for comparing different smoking or vaping products and offers a useful indicator for exposure assessment. Moreover, our sampling system and dosing algorithm may also be informative for future studies related to inhalation-based therapeutics and respiratory protection beyond cigarette products, particularly as an experimental and conceptual tool for estimating particle deposition.