Tracking metal presence in cannabis vaping products from source to inhalation

Abstract

Vaping cannabis liquids is a convenient method of cannabis consumption, and is considered to be a less harmful alternative to smoking cannabis. However, vaping cannabis carries its own health risks, with many uncertainties, especially concerning the presence of metal particles in vape liquids. The heterogeneous distribution of these particles within the liquid matrix poses analytical challenges in measurement reproducibility. In this study, total metals analysis was performed on five samples from six different legal Canadian cannabis vape liquid products. The results indicated that metals from the vaping device components, cobalt (Co), nickel (Ni), and zinc (Zn) significantly contributed to within-batch variability. In contrast, all analyzed metals showed significant variability among tested products. Single-particle ICP-MS detected metal particles of aluminum (Al), Co, chromium (Cr), copper (Cu), Ni, tin (Sn), and Zn in the vape liquids. To assess potential consumer exposure, cannabis cartridges were vaped using a vaping machine and the resulting aerosol was analyzed. Although the number of detected emitted particles was below the limit of quantitation, all samples produced aerosols containing metal particles of Co, Cr, Ni, lead (Pb), Sn, and Zn. Further analysis using SEM-EDS on the emptied cartridges showed cracking on the connector pin of an unused device, suggesting a potential source of contamination during use and storage. The elemental composition of the metal components in the cartridges matched the detected particles, providing strong evidence that cannabis vape liquids are contaminated by the metal components of vaping devices.

Keywords: Aerosol characterization; Cannabis vape liquids; Heavy metals; Metal nanoparticles; Public health exposure; Single particle ICP-MS; Trace element analysis; Vape cartridge contamination.

Fig. 1

Comparison of relative variability across replicate samplings the same cartridge (solid line), variability between cartridges of the same production lot (open circle), and differences between distinct products (closed circle).

Fig. 2

Off-line analysis of cannabis aerosol by sp-ICP-MS. (a) Particle size distribution of Zn-containing particles in the aerosol generated from Sample C and (b) the fraction of aerosol samples in which particles containing specific analytes were detected.

Fig. 3

Elemental analysis of Sample D (closed-pod system) and Sample F (510-thread system) by SEM-EDS. (a) Metal components of the closed-pod system mounted on the SEM holder, with Site 1 (contact between the wick and heating wire) and Site 2 (connector pin) indicated for analysis. (b) SEM backscattered electron (BSE) image of Site 1. (c) Close-up of detected metal particles within the wick. (d) SEM image of the connector pin showing a surface crack. (e) Inner channel of the 510-thread cartridge, showing an incision for access to the wicking material. (f) Wicking material with the heating wire mounted on the SEM holder, with Site 1 and Site 2 indicated for analysis. (g) SEM image of Site 1, showing wicking material with incorporated metal particles. (h) SEM image of the heating wire, displaying a metal flake on the surface.