Effects of propylene glycol, vegetable glycerin, and nicotine on emissions and dynamics of electronic cigarette aerosols.

Introduction:
This article examines the effects of propylene glycol (PG), vegetable glycerin (VG), and nicotine on the emissions and dynamics of electronic cigarette (e-cig) aerosols. The study used a tank-based e-cig device with 10 different flavorless e-liquid mixes and measured particle number concentration (PNC), fine particulate matter (PM 2.5), and particle size distributions during puffing and a 2-hour decay period.

Key Points:

* The addition of nicotine in the e-liquid significantly decreased the particle number emission factor by 33%.
* The PM 2.5 emission factor significantly decreased with greater PG content in the e-liquid.
* For nicotine-free e-liquids, increasing the PG/VG ratio resulted in increased particle loss rates measured by PNC and PM 2.5.
* The particle loss rates, however, were significantly different with and without nicotine especially when the PG/VG ratios were greater than 30/70.
* E-cig particle concentration decayed faster inside the chamber compared to DEhS aerosols, presumably due to evaporation.
* The particle size distribution shifted from a tri-modal to a bi-modal or single-mode as the e-cig aerosol aged in the test chamber.
* The study highlights the importance of understanding the effects of e-liquid main compositions on e-cig aerosols for exposure assessment.

Main Message:
The study provides important insights into how the PG/VG ratio and nicotine content in e-liquids affect e-cig aerosol emissions and dynamics. The findings suggest that the addition of nicotine in the e-liquid decreases particle number emission, while greater PG content reduces PM 2.5 emission. Moreover, the presence of nicotine in the e-liquid may contribute to reducing the volatility of e-cig aerosols when the PG/VG ratio is high enough. These results have potential implications for assessing human exposure to e-cig aerosols.

Li L, Lee ES, Nguyen C, Zhu Y. Effects of propylene glycol, vegetable glycerin, and nicotine on emissions and dynamics of electronic cigarette aerosols. aerosol science and technology : the journal of the american association for aerosol Research. 2020;54(11):1270-1281. doi:10.1080/02786826.2020.1771270