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Thirdhand smoke (THS) describes the persistent contamination on indoor surfaces following smoking. Cannabis THS is a chemically distinct form of THS which remains poorly characterized, relative to tobacco. Understanding its fate is necessary to mitigate exposure to cannabis smoke components and potentially harmful transformation products. In this work, the heterogeneous reaction of surface-bound Δ9-tetrahydrocannabinol (THC), a component of cannabis smoke, with ozone was examined. Cannabis smoke deposits were collected inside a Teflon chamber on glass, cotton, and tile surfaces. Samples were exposed to high (100 ppb) and realistic indoor ozone concentrations (20 ppb) inside a flow tube and to low ozone levels (2 to 29 ppb) present in a genuine indoor environment. Chemical transformations were monitored by liquid chromatography-tandem mass spectrometry (LC-MS/MS), with epoxide and dicarbonyl products detected. Rapid initial loss of THC was observed on all surfaces, but a small fraction (5%–10%) persisted for extended time scales. A short loss lifetime (a few hours) was observed for THC deposited on glass and tile under typical indoor ozone exposures, leading to almost complete loss at longer times. THC decay on cotton was approximately five times longer than on glass, with up to 10% of THC remaining after 1 week of exposure.

Mass spectrometry (MS) is an essential analytical technique used in many fields of science, including chemistry, biology, medicine, and more (Gross, 2011). Its uses are varied, from biotechnology studies of biomolecular sequencing (Maux et al., 2001), genetic analysis of human DNA (Null et al., 2001), exploration of the structure of single cells (Jones et al., 2003) and even examination of extraterrestrial objects (Fenselau & Caprioli, 2003). This incredible breadth of applications using MS results in highly complex data, which often requires significant processing in order to obtain actionable insights.