Potential Influence of Flavoring Compounds on Aldehyde Production in Electronic Cigarette Aerosol: Case Studies of 3rd and 4th Generation Devices

Introduction Electronic cigarettes (e-cigarettes) may produce harmful aldehyde concentrations in inhaled aerosol. While thermal degradation of propylene glycol (PG) and vegetable glycerin (VG) solvents is an established pathway for aldehyde formation, the contribution of flavoring compound decomposition to aldehyde production is not well described, and prior studies report highly variable results. Materials and Methods A controlled-puffing apparatus, based on the design originated by Khlystov and Samburova, was constructed for aerosol collection on DNPH (2,4-dinitrophenylhydrazine) cartridges and quantification by high-performance liquid chromatography. A third-generation Vaporesso Revenger Mini (Vaporesso) (60 W) was tested with laboratory-produced unflavored, vanillin-flavored, and acetovanillone-flavored e-liquids (5 mg/mL in 30:70 PG:VG; n = 9 puffing sessions per condition, with 20 sampled puffs per session). A fourth-generation JUUL device (JUUL Labs Inc) (6-8 W) was tested with Virginia Tobacco and Menthol pods at 3% and 5% nicotine (n = 4-5 pods per condition, with 40 sampled puffs per pod). Pairwise comparisons used 2-sample, 2-tailed, equal-variance t tests. Results Vaporesso formaldehyde concentrations were 0.56 ± 0.18, 0.73 ± 0.18, and 0.61 ± 0.10 μg/puff for unflavored, vanillin, and acetovanillone e-liquids, respectively, with no statistically significant pairwise differences (P > .05 for all). Vaporesso acetaldehyde concentrations differed significantly between vanillin (0.12 ± 0.05 μg/puff) and acetovanillone (0.07 ± 0.04 μg/puff; P = .02), though neither of the flavored e-liquids differed significantly from the unflavored e-liquid (0.09 ± 0.05 μg/puff). JUUL Virginia Tobacco pods produced 0.06 ± 0.03 μg/puff formaldehyde vs 0.014 ± 0.012 μg/puff for Menthol pods (P < .001). Conclusions The Vaporesso produced approximately 10 times more formaldehyde than the JUUL Virginia Tobacco and approximately 60 times more than the JUUL Menthol. A statistically significant flavor-dependent difference in formaldehyde was observed for JUUL pods. The cross-device magnitude difference is consistent with the higher operating power of the Vaporesso but is confounded by differences in flavor composition, solvent ratio, nicotine content, and puff duration. These results motivate further mechanistic studies of additional flavoring chemicals under controlled puffing conditions to better characterize their contribution to aldehyde emissions in e-cigarettes.