Summary
Introduction:
This text provides an analysis of the impact of e-liquid composition, coil temperature, and puff topography on the aerosol chemistry of electronic cigarettes. The study was conducted using a 3rd generation device and various coil temperatures, puff durations, and PG:VG ratios in the e-liquid solution. The loss of mass from the e-liquid conversion to aerosols was compared with independent measurements in the particle and gas phases for carbon mass closure analyses.
Key Points:
* The particle mass was strongly correlated to the measured coil temperature and independent of coil identity.
* The production of carbonyls from vaping had a strong dependence on coil temperature and, in general, a vertical offset around zero.
* The different response curves for carbonyls were due to the different chemical pathway forming specific carbonyls.
* The two major pathways for the thermal degradation of PG and VG in e-cigarette devices are heat-induced dehydration and h-abstraction by radicals.
* Most of the simple carbonyls, including formaldehyde, acetaldehyde, acetone, and acrolein, exist primarily in the gas phase.
* The partitioning of carbonyl compounds between the gas and particle phase is influenced by many factors and has been subject to numerous studies in cigarette smoke.
* The relative production trends clearly show that PG decomposition was responsible for all of the propionaldehyde and most of the acetaldehyde, while VG decomposition was responsible for all of the dihydroxyacetone and nearly all of the acrolein.
* The nicotine percentage in the particle phase (0.15% - 0.4%) at the same vaping temperature (375 ± 5 °F, corresponds to 191 ± 3 °C) fluctuated with different PG:VG ratios.
Main Message:
The study highlights the importance of coil temperature, puff duration, and PG:VG ratio in affecting both the aerosol production and the composition of e-cigarette aerosols. The majority of the mass lost from the e-liquid could be accounted for as PG and VG, and volatile/semivolatile compounds dominated the total aerosol. The chemical mechanisms for forming carbonyls appeared to be well understood, but some exceptions, such as acetone and acetaldehyde, require further investigation. The user's exposure to toxic carbonyls such as acrolein may change during the vaping process, and users may be exposed to high relative concentrations of VG and its degradation products as the e-liquid is depleted. Therefore, further research is needed into aerosol composition and toxicology as a function of the e-cigarette puffing lifecycle, in addition to e-liquid composition, puffing regimen, and vaping device operational conditions.
Citation
Li Y, Burns aE, Tran LN, et al. Impact of e-Liquid Composition, Coil Temperature, and Puff Topography on the aerosol Chemistry of Electronic Cigarettes. Chemical research in toxicology. 2021;34(6):1640-1654. doi:10.1021/acs.chemrestox.1c00070
