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

Abstract

Nearly two years after vitamin E acetate (VEA) was identified as the potential cause of the 2019–2020 outbreak of e-cigarette, or vaping product-associated lung injuries (EVALI), the toxicity mechanisms of VEA vaping are still yet to be fully understood. Studies since the outbreak have found that e-liquids such as VEA undergo thermal degradation during the vaping process to produce various degradation products, which may pose a greater risk of toxicity than exposure to unvaped VEA. Additionally, a wide range of customizable parameters–including the model of e-cigarette used, puffing topography, or the applied power/temperature used to generate aerosols–have been found to influence the physical properties and chemical compositions of vaping emissions. However, the impact of heating coil temperature on the chemical composition of VEA vaping emissions has not been fully assessed. In this study, we investigated the emission product distribution of VEA vaping emissions produced at temperatures ranging from 176 to 356°C, corresponding to a variable voltage vape pen set at 3.3 to 4.8V. VEA degradation was found to be greatly enhanced with increasing temperature, resulting in a shift towards the production of lower molecular weight compounds, such as the redox active duroquinone (DQ) and short-chain alkenes. Low temperature vaping of VEA resulted in the production of long-chain molecules, such as phytol, exposure to which has been suggested to induce lung damage in previous studies. Furthermore, differential product distribution was observed in VEA degradation products generated from vaping and from pyrolysis using a tube furnace in the absence of the heating coil at equivalent temperatures, suggesting the presence of external factors such as metals or oxidation that may enhance VEA degradation during vaping. Overall, our findings indicate that vaping behavior may significantly impact the risk of exposure to toxic vaping products and potential for vaping-related health concerns.

Vaping Cannabinoid Acetates Leads to Ketene Formation

“…Catalysis, viscosity, airflow, device quality, and user behavior can each exacerbate toxicant formation, apart from the temperature settings . Importantly, the study herein validates the findings of Wu and O’Shea as well as others showing that vaping conditions can lead to ketene formation at apparently lower temperature settings than previously assumed. ,,, …”

“…Therefore, ketene does not survive long enough to be detected intact in vivo . Chemical and physical studies such as reported herein and by others ,− are thus needed to elucidate sources of exposure.…”

“…19 Importantly, the study herein validates the findings of Wu and O'Shea as well as others showing that vaping conditions can lead to ketene formation at apparently lower temperature settings than previously assumed. 8,17,14,16 This work describes a limited set of starting acetates, including three that are highly purified and one commercial formulation. The acetates, under either dabbing or e-cigarette vaping methods, consistently afforded observable ketene emissions.…”

External Factors Modulating Vaping-Induced Thermal Degradation of Vitamin E Acetate

“…Recent research has revealed that the inhalation of aerosols released by e-cigarettes has the potential to negatively impact the lungs of users, despite the prevalent assumption of safety among e-cigarette consumers. , Though many commonly used e-liquid ingredients, including propylene glycol (PG), glycerin (VG), and various flavoring agents, are considered safe for consumption or dermal absorption, emitted aerosols are complex mixtures of compounds formed from the thermal degradation of e-liquids that occurs during the vaping process . This process results in the formation of emission products with different physiochemical properties and a risk of toxicity potentially greater than that posed by the parent e-liquids. − For example, vitamin E acetate (VEA), the proposed cause of the e-cigarette or vaping-associated lung injury (EVALI) outbreak in the United States in 2019, has been found to decompose into thermal degradation products, including vitamin E (VE), various long-chain alcohols, alkenes, carbonyls, and, most notably, the reactive species duroquinone (DQ) and ketene. ,,− While VEA itself is perceived as safe, the inhalation of electrophilic species like DQ produced during vaping poses a serious risk of oxidative damage to lung tissue. ,− As such, to understand the potential health risk to users, the prediction of the thermal degradation behavior of various e-liquids through computational and experimental methods has been of particular interest in recent e-cigarette research.…”

“…In e-cigarette systems, the presence of metal filament wires has been suggested to have strong catalytic effects on the thermal degradation of PG and VG, reducing the temperature needed to observe carbonyl-containing compounds in vaping emissions. , Furthermore, metal catalysis has been found to be an important factor in thermal degradation pathways in analyses of systems such as biochar . The presence of O 2 has also been found to greatly decrease the temperature required to observe the thermal degradation of PG and VG and may play an important role in the low-temperature degradation of e-liquids. ,, …”