Carbonyls and Aerosol Mass Generation from Vaping Nicotine Salt Solutions Using Fourth- and Third-Generation E-Cigarette Devices: Effects of Coil Resistance, Coil Age, and Coil Metal Material

Abstract

Aerosol formation and production yields from 11 carbonyls (carbonyl concentration per aerosol mass unit) were investigated (1) from a fourth-generation (4th gen) e-cigarette device at different coil resistances and coil age (0–5000 puffs) using unflavored e-liquid with 2% benzoic acid nicotine salt, (2) between a sub-ohm third-generation (3rd gen) tank mod at 0.12 Ω and a 4th gen pod at 1.2 Ω using e-liquid with nicotine salt, together with nicotine yield, and (3) from 3rd gen coils of different metals (stainless steel, kanthal, nichrome) using e-liquid with freebase nicotine. Coil resistance had an inverse relationship with coil temperature, and coil temperature was directly proportional to aerosol mass formation. Trends in carbonyl yields depended on carbonyl formation mechanisms. Carbonyls produced primarily from thermal degradation chemistry (e.g., formaldehyde, acetaldehyde, acrolein, propionaldehyde) increased per aerosol mass with higher coil resistances, despite lower coil temperature. Carbonyls produced primarily from chemistry initiated by reactive oxygen species (ROS) (e.g., hydroxyacetone, dihydroxyacetone, methylglyoxal, glycolaldehyde, lactaldehyde) showed the opposite trend. Coil age did not alter coil temperature nor aerosol mass formation but had a significant effect on carbonyl formation. Thermal carbonyls were formed optimally at 500 puffs in our study and then declined to a baseline, whereas ROS-derived carbonyls showed a slow rise to a maximum trend with coil aging. The 3rd gen versus 4th gen device comparison mirrored the trends in coil resistance. Nicotine yields per aerosol mass were consistent between 3rd and 4th gen devices. Coil material did not significantly alter aerosol formation nor carbonyl yield when adjusted for wattage. This work shows that sub-ohm coils may not necessarily produce higher carbonyl yields even when they produce more aerosol mass. Furthermore, carbonyl formation is dynamic and not generalizable during the coil’s lifetime. Finally, studies that compare data across different e-cigarette devices, coil age, and coil anatomy should account for the aerosol chemistry trends that depend on these parameters.

In vitro toxicological evaluation of aerosols generated by a 4th generation vaping device using nicotine salts in an air-liquid interface system

“…Indeed, approximately 250 chemicals have been identified in aerosols from EC, including both the original ingredients of e-liquids (PG/VG, nicotine, and flavourings) and numerous potentially harmful thermal degradations products, the most abundant being carbonyl compounds and volatile organic compounds (VOC) [ 26 , 27 ]. Although Pod-Mods devices operate at much lower temperatures than 3rd generation devices EC, these devices have been shown to produce trace amounts of thermal degradation products [ 28 , 29 ]. In addition, several toxic metals have been detected in both e-liquids and aerosols from POD-based devices, the concentrations of which may increase over time due to repeated heating of the coil by refilling, a practice not recommended by the manufacturer [ 30 , 31 ].…”

Quantification of Free Radicals from Vaping Electronic Cigarettes Containing Nicotine Salt Solutions with Different Organic Acid Types and Concentrations

“…Interestingly, our results differ from the data from JUUL showing that BA nicotine salts delivered significantly more nicotine compared to freebase e-liquids . It is not clear whether the results are due to differences in e-liquid nicotine concentration, e-cigarette device design, temperatures tested, or other variables …”

“…The generation of vaping aerosol follows a protocol previously reported by our group . Briefly, a refillable fourth-generation Vaporesso XROS 2 pod device (Shenzhen Smoore Technology Limited) with a battery capacity of 1000 mAh and the XROS 1.2 Ω pod was used for aerosol generation.…”

“…Co.). Each set of samples was collected with a new pod to minimize cross-contamination and coil aging effects. ,− …”