Diacetyl and Other Ketones in e-Cigarette aerosols: Some Important Sources and Contributing Factors.

Introduction: This article investigates the sources and contributing factors of diacetyl (Da) and other ketones in e-cigarette aerosols. The study focuses on the transfer efficiency of Da, acetyl propionyl (aP), and acetoin (aC) from e-liquids to aerosols, thermal degradation of major e-liquid constituents, and the potential for ketone generation from sugars and flavor additives during vaping.

Key Points:

* The transfer efficiency of Da, aP, and aC from e-liquids to aerosols was found to be 65%, 67.1%, and 92.5%, respectively.
* quantifiable levels of Da were generated from VG and PG at coil temperatures >300 °C, and from sucrose, glucose, and fructose at concentrations tested.
* Thermal degradation of VG, PG, and 1,3-PD resulted in the production of Da, aC, and aP at temperatures >300 °C.
* Sucrose, glucose, and fructose e-liquids gave comparable Da emissions, with emissions increasing with increasing device power and concentration.
* Furanose ring compounds generate Da and aP when heated to 250 °C.
* Pyrolysis of common flavor compounds resulted in the formation of Da and aP at extremely low levels, with 4-ketoisophorone and peppermint oil being exceptions.

Main Message: The study highlights that in addition to direct transfer from e-liquids, Da and aP can be present in e-cigarette aerosols due to thermal decomposition reactions of glycols, sugars, and furanose ring flavors under e-cigarette operating conditions. This information is crucial for understanding the hazards associated with e-cigarette use and for developing appropriate regulatory measures.

Mcadam K, Waters G, Moldoveanu S, et al. Diacetyl and Other Ketones in e-Cigarette aerosols: Some Important Sources and Contributing Factors. Frontiers in chemistry. 2021;9:742538. doi:10.3389/fchem.2021.742538