Chemical Composition of Aerosols from the E-Cigarette Vaping of Natural and Synthetic Cannabinoids

Vaping cannabinoids in electronic (e)-cigarette devices is rapidly increasing in popularity, particularly among adolescents, although the chemistry affecting the composition of the vape aerosol is not well understood. This work investigates the formation of aerosol mass, bioactive hydroxyquinones, and harmful or potentially harmful carbonyls from the e-cigarette vaping of natural and synthetic cannabinoids e-liquids in propylene glycol and vegetable glycerin (PG/VG) solvent at a 50 mg/mL concentration in a commercial fourth-generation vaping device. The following cannabinoids were studied: cannabidiol (CBD), 8,9-dihydrocannabidiol (H2CBD), 1,2,8,9-tetrahydrocannabidiol (H4CBD), cannabigerol (CBG), and cannabidiolic acid (CBDA). Quantification of analytes was performed using liquid chromatography coupled to accurate mass spectrometry. The addition of cannabinoids significantly increased aerosol and carbonyl formation compared with the PG/VG solvent alone. All cannabinoids in the study formed hydroxyquinones during vaping (up to ∼1% mass conversion) except for CBDA, which primarily decarboxylated to CBD. Hydroxyquinone formation increased and carbonyl formation decreased, with a decreasing number of double bonds among CBD and its synthetic analogues (H2CBD and H4CBD). During the vaping process, ∼3–6% of the cannabinoid mass can be observed as carbonyls under the study conditions. Oxidation of the terpene moiety on the cannabinoids is proposed as a major contributor to carbonyl formation. CBD produced significantly higher concentrations of formaldehyde, acetaldehyde, acrolein, diacetyl, and methylglyoxal compared with the other cannabinoid samples. CBG produced significantly higher levels of acetone, methacrolein, and methylglyoxal. Conversion of CBD to tetrahydrocannabinol (THC) was not observed under the study conditions. The chemical mechanism basis for these observations is discussed. Compared with other modalities of use for CBD and other cannabinoids, vaping has the potential to adversely impact human health by producing harmful products during the heated aerosolization process.