Mechanistic Rationale for Ketene Formation during Dabbing and Vaping

Area of Science:

• Environmental Chemistry
• Analytical Chemistry
• Toxicology

Background:

• Ketene is a highly toxic vaping emission, but its identification is challenging due to its reactivity.
• Previous theoretical studies suggested low vaping temperatures might not produce ketene, creating discrepancies with experimental findings.

Purpose of the Study:

• To rigorously identify ketene in vaped aerosols using an isotopically labeled precursor.
• To reconcile theoretical and experimental findings regarding ketene formation under different pyrolysis conditions.
• To investigate the prevalence of ketene formation from various vaping compounds, including common flavorants.

Main Methods:

• Utilized an isotopically labeled acetate precursor for enhanced ketene identification in vaped aerosols.
• Accounted for aerobic (experimental) versus anaerobic (simulated/theoretical) pyrolysis conditions to explain discrepancies.
• Analyzed ketene formation pathways beyond phenyl acetate substructures.

Main Results:

• Successfully identified ketene in vaped aerosols with enhanced rigor.
• Explained ketene formation discrepancies by differentiating between aerobic and anaerobic pyrolysis conditions.
• Demonstrated that ketene formation is not limited to phenyl acetate compounds and can occur from other molecules like ethyl acetate.

Conclusions:

• Ketene can be reliably identified in vaped aerosols, even at lower temperatures, by considering aerobic conditions.
• The formation of ketene during vaping may be more widespread than previously assumed, impacting the safety of various e-cigarette flavorants.
• Findings contribute to understanding the generation of aerosol toxicants in electronic cigarettes.