Metals in Cannabis Vaporizer Aerosols: Sources, Possible Mechanisms, and Exposure Profiles

Cannabis Vape Product Sales in California Following CDC's Initial Advisory About Lung Injuries

Introduction: The 2019 outbreak of e-cigarette or vaping product use-associated lung injury (EVALI) is believed to have been caused by vitamin E acetate, an additive used in some cannabis vaporizer products. Previous studies have primarily focused on changes in sales of electronic nicotine delivery systems following the initial advisory issued by the Centers for Disease Control (CDC) on August 17, 2019. The present study is intended to examine variation by age groups in sales of regulated cannabis vape products in the state of California before, during, and after the outbreak. Methods: Weekly sales revenue of cannabis vape products (from January 1, 2018, to December 31, 2020) was obtained from a sample of recreational cannabis retailers licensed in California. An interrupted time series analysis, using AutoRegressive, Integrated, Moving Average methods, was employed to estimate changes in the sales and market share of cannabis vape products in the weeks following the CDC advisory. Results: The total volume of regulated cannabis vape product sales increased substantially over the 3-year study period (2018-2020). Sales and market share of cannabis vape products, however, declined in both young and older adults immediately following the advisory, rebounding to pre-EVALI levels only for the young adults. For sales, the potential EVALI effect following the CDC's advisory equates to an 8.0% and 2.2% decline below expected levels in the older and young adults, respectively. Conclusions: The differential age effect on sales may reflect concerns regarding health effects of cannabis vaping products and greater awareness of the outbreak among older adults. Findings highlight the importance of informing consumers about health risks associated with using cannabis vape products acquired from regulated versus illicit sources.

The Dark Side of Cannabidiol: The Unanticipated Social and Clinical Implications of Synthetic Δ8-THC

Introduction: The explosive growth of the cannabis industry in the United States over the past decade has spurred a multitude of products derived from phytocannabinoids produced by Cannabis sativa L. Decades of cannabis prohibition coupled with the more recent 2018 Farm Bill have lead to several unanticipated consequences and the widespread availability of synthetic cannabinoids derived from hemp CBD, including Δ8-THC, Δ10-THC and HHC. Methods: Herein, we review the available literature of the complexity of the chemistry of its current manufacture, namely, the acid-catalyzed ring closure of cannabidiol (ACRCC), the myriad of issues involving the unsolved technical problems with quality control of ACRCC-Δ8-THC and the multitude of isomerized byproducts, and the lack of consistent regulation regarding consumer safety and labeling. Results: We provide what we believe is the first comprehensive listing of all the documented ACRCC-Δ8-THC byproducts. Perhaps, most importantly, we highlight the growing concern that, other than Δ8-THC itself, the compounds in ACRCC-Δ8-THC product mixtures have not been subjected to any human toxicological evaluation. This is especially troubling as ACRCC-Δ8-THC products relate to vaping, and their contribution to a growing and lethal epidemic of electronic cigarette, or vaping, product use-associated lung injury (EVALI). Conclusions: Quality control is totally inadequate in the newly emerging Δ8-THC industry. American consumers are ingesting products that are mislabeled with many compounds that have never received any toxicological testing. EVALI cases continue to be reported with a fatality rate approaching 2% (in California).

External Factors Modulating Vaping-Induced Thermal Degradation of Vitamin E Acetate

Despite previous studies indicating the thermal stability of vitamin E acetate (VEA) at low temperatures, VEA has been shown to readily decompose into various degradation products such as alkenes, long-chain alcohols, and carbonyls such as duroquinone (DQ) at vaping temperatures of <200 °C. While most models simulate the thermal decomposition of e-liquids under pyrolysis conditions, numerous factors, including vaping behavior, device construction, and the surrounding environment, may impact the thermal degradation process. In this study, we investigated the role of the presence of molecular oxygen (O2) and transition metals in promoting thermal oxidation of e-liquids, resulting in greater degradation than predicted by pure pyrolysis. Thermal degradation of VEA was performed in inert (N2) and oxidizing atmospheres (clean air) in the absence and presence of Ni-Cr and Cu-Ni alloy nanopowders, metals commonly found in the heating coil and body of e-cigarettes. VEA degradation was analyzed using thermogravimetric analysis (TGA) and gas chromatography/mass spectrometry (GC/MS). While the presence of O2 was found to significantly enhance the degradation of VEA at both high (356 °C) and low (176 °C) temperatures, the addition of Cu-Ni to oxidizing atmospheres was found to greatly enhance VEA degradation, resulting in the formation of numerous degradation products previously identified in VEA vaping emissions. O2 and Cu-Ni nanopowder together were also found to significantly increase the production of OH radicals, which has implications for e-liquid degradation pathways as well as the potential risk of oxidative damage to biological systems in real-world vaping scenarios. Ultimately, the results presented in this study highlight the importance of oxidation pathways in VEA thermal degradation and may aid in the prediction of thermal degradation products from e-liquids.

Evidence That Metal Particles in Cannabis Vape Liquids Limit Measurement Reproducibility

Cannabis vaping involves the vaporization of a cannabis vaping liquid or solid via a vaping accessory such as a vape pen constructed of various metals or other parts. An increasing number of reports advocate for expansion of the testing and regulation of metal contaminants in cannabis vape liquids beyond the metals typically tested such as arsenic, cadmium, mercury, and lead to reflect the possibility of consumers' exposure to other metal contaminants. Metal contaminants may originate not only from the cannabis itself but also from the vape devices in which the cannabis vape liquid is packaged. However, metal analyses of cannabis vape liquids sampled from cannabis vaping devices are challenged by poor precision and reproducibility. Herein, we present data on the metal content of 12 metals in 20 legal and 21 illegal cannabis vape liquids. The lead mass fraction in several illegal samples reached up to 50 μg g^-1. High levels of nickel (max 677 μg g^-1) and zinc (max 426 μg g^-1) were found in illegal samples, whereas the highest copper content (485 μg g^-1) was measured in legal samples. Significant differences in metal mass fractions were observed in the legal cannabis vape liquid taken from two identical devices, even though the liquid was from the same lot of the same cannabis product. Metal particles in the vape liquids were observed by scanning electron microscopy, and laser ablation inductively coupled plasma mass spectrometry confirmed the presence of copper-, zinc-, lead-, and manganese-bearing particles, metals that are in common alloys that may be used to make vape devices. Colocalized particles containing aluminum, silica, and sodium were also detected. These results suggest that metal particles could be a contributing factor to poor measurement precision and for the first time, to the best of our knowledge, provide evidence of metal particles in cannabis vape liquids contained in unused cannabis vape pens.

Transfer of Metals to the Aerosol Generated by an Electronic Cigarette: Influence of Number of Puffs and Power

Electronic cigarettes (e-cigarettes) are increasing in popularity despite uncertainties about their health hazards. Literature studies have shown that e-cigarettes may be a source of toxic heavy metal exposure to the user, but the mechanism by which metals are transferred from the e-cigarette parts into the aerosol plume that is inhaled by the user is poorly understood. The goal of this study was to quantify the potentially harmful heavy metals chromium, nickel, copper, and lead systematically during the simulated use of a mod-type e-cigarette in order to better understand the mechanism of metal transfer from the e-cigarette parts into the aerosol plume and into the liquid in the storage tank. Aerosol was collected and aliquots of the remaining liquid in the storage tank were collected from 0 to 40 puffs in 10 puff increments and analyzed with atomic absorption spectroscopy. It was found that the concentration of metals increased in both the aerosol and tank liquid the more times the e-cigarette was puffed, but at varying rates for each element and depending on the power applied to the heating coil. For copper, lead, and nickel, the concentrations of metals in the aerosol and tank increased with increasing power but for chromium, the concentration varied with power. Additionally, it was observed that chromium and nickel concentrations were greater in the aerosol than in tank liquid, consistent with the direct transfer of those metals to the aerosol from heating of the nichrome coil element used in this study. For copper and lead, the concentrations were similar or greater in the tank compared to the aerosol, consistent with transfer first into the storage tank liquid, followed by vaporization into the aerosol.