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

06 May 2022, Version 1
This content is a preprint and has not undergone peer review at the time of posting.


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 by 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 formation of THC was provable. The recovered THC concentrations were ranging between 1% and 48% 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 not to be occurring. The health risk of CBD liquids for electronic cigarettes as well as low-THC cannabis intended for smoking can be assessed by the concentrations in the source material without need to consider significant changes in psychotropic compounds during use by consumers.


Cannabis sativa
Cannabis smoking
Electronic cigarettes
Risk assessment


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