In using EtOAc and geranyl acetate to compare ketene production under anaerobic and aerobic environments, the results (Figure ) showed that acetates besides phenyl acetatecontaining VEA and cannabinoids, can serve as ketene precursors. This is significant since ester flavorants are the most common class of tobacco e-cigarette flavorants. Exposure to ketene emissions may thus be more prevalent than currently known. This finding suggests the need for further studies on vaping and ketene emissions as well as ketene toxicology.