Prediction of the transport, deposition, and absorption of multicomponent E-cigarette aerosols in a subject-specific mouth-to-G10 human respiratory system.

Introduction:
This text discusses a study that investigates the impact of initial e-liquid composition and inhalation style on the transport, evaporation/condensation, and deposition/absorption of inhaled multi-component EC aerosol in a subject-specific human respiratory system. The study employs a computational fluid-particle dynamics (CFPD) model based on the species transport and discrete phase models to simulate and compare the transport dynamics of multi-component e-cigarette aerosols.

Key Points:

* The CFPD model can predict the gas-liquid phase change dynamics of water, propylene glycol (PG), vegetable glycerin (VG), and nicotine in the aerosols during their transport through the pulmonary route.
* acidity levels in e-liquid can affect nicotine evaporation, with higher levels of acidity reducing evaporation rates and increasing nicotine delivery to small airways.
* Benzoic acid is more effective in reducing nicotine evaporation compared to lactic acid.
* Increasing the PG/VG ratio in the initial e-liquid composition can potentially lead to a reduction in nicotine evaporation rate and an increase in nicotine absorption in small airways beyond generation 10 (G10).
* Droplet size dynamics are influenced more by larger mass components such as PG evaporation and water condensation from the humid air, rather than nicotine.
* The impact of initial e-liquid composition on droplet transport and deposition is relatively insignificant compared to its impact on vapor phase transport and absorption.
* Increasing the follow-up inhalation flow rate after puffing increases liquid phase deposition and nicotine vapor absorption from the mouth to G10, but does not significantly affect evaporation and condensation. a decrease in droplet size results in an increase in the nicotine evaporation rate and subsequent absorption by the airways from the mouth to G10.

Main Message:
The study highlights the importance of considering the impact of initial e-liquid compositions, such as nicotine form, acid type, acid level, PG/VG ratio, and droplet diameter, as well as human factors like breathing intensity, on the transport, phase change, distribution, deposition, and absorption of EC aerosol in a physiologically realistic human pulmonary environment. The CFPD model provides a reliable, non-invasive, and time-efficient alternative to supplement existing in vitro and in vivo studies, aiding in a deeper understanding of nicotine transport and absorption associated with design parameters of EC products, which can improve regulatory oversight and enhance the health and safety of users.

Sperry T, Feng Y, Zhao J, Song C, Shi Z. Prediction of the transport, deposition, and absorption of multicomponent E-cigarette aerosols in a subject-specific mouth-to-G10 human respiratory system. J aerosol Sci. 2023;170:106157. doi:10.1016/j.jaerosci.2023.106157