Absence of Relevant Thermal Conversion of Cannabidiol (CBD) to Tetrahydrocannabinol (THC) in E-Cigarette Vapor and Low-THC Cannabis Smoke

Introduction: Recent research claimed that cannabidiol (CBD) in commercial electronic cigarette (e-cigarette) liquids can be converted into psychotropic amounts of ∆9-tetrahydrocannabinol (THC). This study aims to validate this claim using a realistic e-cigarette setup. Additionally, this study also investigates if such a conversion may occur during smoking of CBD-rich cannabis joints. Methods: Two different CBD liquids were vaporized using two different e-cigarette models, one of which was operated at extreme energy settings (0.2 Ω and 200 W). The smoke of six CBD joints was collected using a rotary smoking machine according to ISO 4387:2019. Analyses were conducted using nuclear magnetic resonance (NMR) spectrometry as well as liquid chromatography tandem mass spectrometry (LC-MS/MS). Results: For the condensed e-cigarette liquids, no increase in THC concentration could be observed. For the CBD joints, no THC formation was provable. The recovered THC concentrations were ranging between 1% and 48% (0.034 mg and 0.73 mg) of the THC amount initially contained in the joints before smoking. Conclusions: Using realistic conditions of consumer exposure, relevant conversion of CBD to THC appears to not be occurring. The health risk of CBD liquids for electronic cigarettes, as well as low-THC cannabis intended for smoking, can be assessed by concentrations in the source material without the need to consider significant changes in psychotropic compounds during use by consumers.