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

ALEXA CANCHOLA, Ruth Meletz, Siri Langmo, Michael Lum, Ying-Hsuan Lin, University of California, Riverside

     Abstract Number: 220
     Working Group: Health-Related Aerosols

Abstract
Exposure to vaping emissions has become a major public health concern in the United States. Studies indicate the vaping process causes breakdown of e-liquids into potentially toxic degradation products. Efforts have been made in predicting the compounds that a particular e-liquid may degrade into, and users may be exposed to. However, while most models simulate thermal decomposition of e-liquids under pyrolysis conditions, numerous factors – including vaping behavior, device construction, and surrounding environment – may impact the thermal degradation process. Vitamin E acetate (VEA) has been found to degrade at low temperatures (< 200 °C) into duroquinone (DQ) and other compounds, despite previous computational models indicating that DQ formation should not occur until 500-600 °C. We hypothesized that the presence of molecular oxygen and transition metals in the e-cigarette body promote thermal oxidation of e-liquids, resulting in greater degradation than predicted by pure pyrolysis. Using a tube furnace reactor, VEA was heated in inert (N₂) and zero air environments in the absence and presence of Ni-Cr and Cu-Ni alloy nanopowders, which are known components of heating coils. Vaping aerosols were analyzed by gas chromatography/mass spectrometry (GC/MS) to assess the impact of the environments on degradation product formation. Thermal characteristics of VEA were also assessed using a combination of thermogravimetric and differential scanning calorimetry analysis. In N₂ environments without the presence of metals, VEA does evaporate until 240 °C, and no substantial formation of degradation products could be observed even at the maximum temperature setpoint. Conversely, substantial degradation of VEA into DQ and various carbonyls in zero air environments was observed, even in the absence of metals, highlighting the importance of oxidation reactions during degradation processes. This study indicates additional mechanisms and external factors that should be considered to help improve predictions of thermal degradation products from e-liquids.