Portland State University. Department of Chemistry
Robert M. Strongin
Term of Graduation
Date of Publication
Doctor of Philosophy (Ph.D.) in Chemistry
Cannabinoids -- Research, Tetrahydrocannabinol, Terpenes, Decomposition (Chemistry), Vaping, Cannabis, Electronic cigarettes
1 online resource (xvii, 198 pages)
Consumption of cannabis concentrates using the relatively novel non-combustion methods dabbing and vaping has steadily grown in popularity as cannabis legalization in North America has allowed increased access to sophisticated cannabis products and technology. In order to assess the safety of these products, it is necessary to gain a chemical understanding of the decomposition reactions that occur when the active ingredients are heated in the conditions seen when dabbing or vaping. This dissertation contains a manuscript that details efforts to structurally characterize a toxic cannabis concentrate adulterant, and three manuscripts that studied the chemical decomposition of the two primary cannabis concentrate ingredients, the psychoactive [delta]9-tetrahydrocannabinol (THC) and aromatic terpenoids. The known airway toxicant pine rosin or colophony was identified as a major component of a cannabis extract adulterant using liquid chromatography-mass spectrometry and nuclear magnetic resonance spectroscopy (NMR). Though this agent has previously been identified as a hashish adulterant in Europe, this was the first report of its use in North America. THC and cannabis terpenoids were shown to decompose to generate potentially harmful levels of known toxicants such as methyl vinyl ketone, 1,3-butadiene, methacrolein, benzene, toluene, and a slew of other volatile organic compounds (VOCs) with unknown health impacts. Characterization and quantification methods for such VOCs using NMR and automated thermal desorption-gas chromatography-mass spectrometry are presented. Given the lack of previous understanding related to THC and cannabis terpenoid (e.g. ß-myrcene) decomposition when heated to the temperatures seen during dabbing and vaping (250-400 °C), special attention is paid to the chemical mechanisms that occur. ß-myrcene decomposition was studied by characterizing the VOCs released when dabbing a site-specifically deuterated isotopologue of this molecule. THC decomposition was studied by characterizing its dabbing and vaping-released VOCs, and comparing these to a structurally similar cannabinoid, cannabinol. Chemical mechanisms that account for large shares of the VOCs released by these molecules are described. Curiously, THC and ß-myrcene share a common reactive intermediate that is the source of isoprene, 2-methyl-2-butene, 3- methylcrotonaldehyde, and 3-methyl-1-butene, and it was shown that the relative proportions of these four VOCs is temperature dependent. It was shown that the ratio of the two primary cannabis concentrate ingredients, THC and terpenoids, impacts the release of VOCs and transfer of active ingredients. Specifically, increasing the mass percent of ß-myrcene in THC for a synthetic cannabis oil from 7% to 14% led to significant decreases in the the release of degradants and carcinogens such as benzene, 1,3-butadiene, and isoprene, and more efficient transfer of THC when vaping. However, the opposite effect was observed for dabbing: increased mass percent of this terpene led to an increased release of degradation products. In addition to these insights, a novel quantitative risk assessment model for cannabis inhalation was described that allowed for preliminary determination of the relative cancer and non- cancer chronic health risks associated with dabbing, vaping, and smoking cannabis. Further chemical and toxicological characterization of other aerosol components will allow the expansion of this model to provide an accurate description of the chronic health impacts associated with these cannabis consumption modalities.
© 2021 Jiries Meehan-Atrash
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Meehan-Atrash, Jiries, "Chemical Characterization of Toxicologically Relevant Molecules in Cannabis Concentrates and Vaporizer Aerosols" (2021). Dissertations and Theses. Paper 5687.