Effect of Propylene Glycol and Vegetable Glycerine Ratio in E-Liquid on Aerosol Formation: Overview of Relevant Properties

BACKGROUND:

Electronic nicotine delivery systems (ENDS) generate an aerosol by vaporising e-liquids that usually consist of propylene glycol (PG), vegetable glycerine (VG), and other ingredients (water, nicotine, and flavours). The chemical and physical properties of these components have a significant effect on aerosol formation and must be identified in order to improve product attractiveness and assess the degree of health risks.

AIM:

The aim of this article is to provide a description of the composition of the e-liquid base and its impact on the physical properties of the liquid used and the behaviour of the aerosol generated and particles separately.

METHODS:

For this purpose, 46 articles were selected using a series of keywords. English language publications were chosen.

RESULTS:

The impact of the PG/VG ratio on the physical properties of the e-liquid (boiling point, viscosity, volatility, hygroscopicity), aerosol emission characteristics (refractive index, light scattering coefficient, particle size distribution, concentration, emission of harmful compounds), vape attractiveness (taste, “throat-hit”, “cloud effect”), nicotine flux, coil temperature, and puff topography is presented.

CONCLUSIONS:

The PG/VG ratio is strongly correlated with the emission of carbonyls, which has adverse health effects and should be optimised. Furthermore, PG and VG also affect the other important characteristics of the aerosol generated by ENDS, which impact on both attractiveness and the consumption of harmful compounds. These findings could be considered for further research with the aim of improving electronic nicotine delivery systems as this can reduce levels of toxicants. This can be achieved by optimising the geometry of the components with respect to heating power and e-liquid.