Agriculture and Food Chemistry

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.

Version notes

Besides some minor editorial changes, the discussion was expanded by inclusion of several relevant new articles


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