Particle Size Dynamics: Toward a Better Understanding of Electronic Cigarette aerosol Interactions With the Respiratory System

Introduction:
This text is a summary of a scientific review discussing the physical phenomena related to electronic cigarette (EC) aerosol dynamics, which is still not fully understood and can impact the prediction of regional deposition of inhaled mist in the respiratory system. The authors highlight the significance of differences in aerosol particle size distribution for the prediction of regional deposition and the need for accurate determination of the size of droplets in the inhaled EC-mist.

Key Points:

* Emitted EC-aerosol is highly concentrated and contains mainly submicrometer-size particles composed of droplets of e-liquids, which are surrounded by air and a mixture of vapors.
* The major e-liquid components, propylene glycol and glycerol, have a high boiling point and low volatility, but they are hygroscopic and can grow by taking up water vapor from the humid air.
* There are differences in aerosol dynamics and deposition between EC and tobacco cigarettes (TC) aerosols, with slight differences in puffing topography and more prominent effects of droplet coagulation and hygroscopic growth in EC aerosol leading to enhanced regional deposition.
* Nicotine is primarily absorbed from the gaseous/vapor phase in both TC and EC aerosols, not from deposited particles or droplets.
* The inhalation pattern of ECs is similar to TCs, with two periods of drawing a puff and mouth-hold, providing a certain time for changes in initial aerosol properties due to thermodynamic and mass transfer effects.
* The properties and concentration of inhaled aerosol are dynamically altered during a short period of aerosol residence in the upper airways, which has a strong impact on droplet distribution and deposition after aerosol transfer to the lower airways.
* appropriate size determination of droplets released from ECs is essential for the correct prediction of aerosol dynamics and regional particle deposition and absorption of vaporized components.

Main Message:
The main message of this summary is that the understanding of EC aerosol dynamics and interactions with the respiratory system is still incomplete, and the accurate determination of the size of droplets in the inhaled EC-mist is crucial for the prediction of regional deposition and absorption of vaporized components. The differences in aerosol dynamics and deposition between EC and TC aerosols, as well as the impact of inhalation pattern, highlight the need for further research in this area to ensure the safe use of ECs.

Sosnowski, Tomasz R., and Marcin Odziomek. “Particle Size Dynamics: Toward a Better Understanding of Electronic Cigarette aerosol Interactions With the Respiratory System.” Frontiers in Physiology 9 (July 9, 2018): 853. https://doi.org/10.3389/fphys.2018.00853.