Carbonyl Composition and Electrophilicity in Vaping Emissions of Flavored and Unflavored E-Liquids

Abstract

It has been demonstrated that propylene glycol (PG), vegetable glycerin (VG), and flavoring chemicals can thermally degrade to form carbonyls during vaping, but less is known about carbonyl emissions produced by transformation of flavoring chemicals and the interactive effects among e-liquid constituents. This study characterized carbonyl composition and levels in vaping emissions of PG-VG (e-liquid base solvents) and four e-liquid formulations flavored with trans-2-hexenol, benzyl alcohol, l-(-)-menthol, or linalool. Utilizing gas chromatography (GC)- and liquid chromatography (LC)-mass spectrometry (MS) methods, 14 carbonyls were identified and quantified. PG-VG emitted highest levels of formaldehyde, acetaldehyde, and acrolein. However, flavored e-liquids contributed to the production of a wider variety of carbonyls, with some carbonyls directly corresponding to the oxidation of alcohol moieties in flavoring compounds (e.g., trans-2-hexenol and benzyl alcohol transformed into trans-2-hexenal and benzaldehyde, respectively). Detections of formaldehyde-GSH and trans-2-hexenal-GSH adducts signify interactions of carbonyls with biological nucleophiles. The global reactivity descriptors (I, A, μ, η, and ω) and condensed Fukui parameters (fk0, fk−, fk+, and dual-descriptor) were computed to elucidate site reactivities of selected simple and α,β-unsaturated carbonyls found in vaping emissions. Overall, this study highlights carbonyl emissions and reactivities and their potential health risk effects associated with vaping.

Formation of Redox-Active Duroquinone from Vaping of Vitamin E Acetate Contributes to Oxidative Lung Injury

“…Ketene, which has an approximate boiling point of −56 °C, was not expected to be observed in our collection. In addition, observation of carbonyl-containing compounds from GC/MS often requires derivatization methods that were not used in this study. , As such, it is highly likely that ketene and other higher volatility compounds are produced during the vaping process but cannot be observed in our results.…”

Temperature dependence of emission product distribution from vaping of vitamin E acetate

“…Furthermore, a study by Jaegers et al [44] found that pyrolysis alone in an anaerobic environment was not able to induce thermal degradation of PG and VG at low temperatures (< 200˚C), despite previous studies observing degradation at temperatures as low as 149˚C during vaping [45]. However, when heated in an aerobic environment, thermal decomposition was observed at 133 and 175˚C, both without and with the addition of metal oxides Cr 2 O 3 and ZrO 2 [44], suggesting that oxidation is a key process during vaping.…”

“…For example, ketene, which is expected to form during VEA pyrolysis, has an estimated boiling point of -56˚C [30] and, as a result, was not expected to be observed in our collection. Furthermore, highly volatile and/or reactive compounds such as ketene and various low molecular weight carbonyl-containing species, etc., often require additional derivatization methods that were not used in this study to be observed using GC/MS [7,45].…”

Effects of Common e-Liquid Flavorants and Added Nicotine on Toxicant Formation during Vaping Analyzed by 1H NMR Spectroscopy

“…Individual flavorants in e-liquids could thermally degrade to contribute to the levels of HPHC formation. Trans -cinnamaldehyde (an α,β-unsaturated aldehyde) could undergo nucleophilic attack at the β–carbon to produce acrolein similar to trans -2-hexenal . However, specific degradation of flavorants will be limited by the amount of flavorant present, which is typically small relative to PG and GL.…”