UC Riverside

The use of e-cigarettes for the inhalation of nicotine and cannabis products has become popular in the United States across many demographics. Their rise in popularity is largely attributed to their ease of access, customization options, and perception as safer alternatives to traditional methods. However, despite their perceived safety, inhalation of vaping emissions has great potential to cause adverse health outcomes in users, as evidenced by events such as the outbreak of e-cigarette- or vaping-associated lung injuries (EVALI) in the U.S. in 2019. While many e-liquid ingredients are considered safe for dermal or oral exposure, the vaping process has been found to result in the thermal degradation of e-liquid ingredients. As a result, the emitted aerosols are complex mixtures of chemicals formed during vaping that may have different chemical and toxicological properties than their parent compounds. However, characterization of these compounds remains challenging due to the wide range of customizable options – such as temperature, use patterns, device construction, and more – that may influence the resulting chemical composition of e-cigarette emissions.This dissertation aims to address the knowledge gaps in the relationship between user- and device-driven parameters on the thermal degradation behavior of e-liquids and the chemical and toxicological properties of e-cigarette aerosol emissions, using VEA as a model e-liquid. First, this work identifies novel VEA vaping products and their potential mixture effects on toxicity upon exposure to human lung cells using a combination of chemical and cellular-based analyses. Second, the change in VEA vaping emission product distribution as a function of variable voltage/temperature settings was characterized using non-target gas chromatography/mass spectrometry (GC/MS) analysis. Finally, a tube furnace reactor system was used to investigate the role of oxygen (O2) and transition metals in the thermal degradation behavior and emission product distribution of VEA. Results from this dissertation contribute to an improved understanding of the thermal degradation behavior and chemistry of e-liquids, and how varying user- and device-driven parameters can alter the chemical and toxicological properties of vaping emissions. Detailed compositional and mechanistic information on e-cigarette emissions will be helpful for future hazard identification and the public health risks associated with e-cigarettes.