Comparative analysis of metals, pesticides, mycotoxins, microbial contaminants and THC potency in illegal and regulated cannabis inflorescences in Canada.

Abstract

BACKGROUND: Following the legalization of recreational cannabis in Canada under the Cannabis Act (2018), regulatory frameworks were implemented to ensure product safety, quality, and consistency within the legal market. Previous studies revealed significantly greater pesticide contamination in illegal cannabis than in legal products. In light of these findings, the present study expands contaminant surveillance to include the quantification of Δ⁹-tetrahydrocannabinol (THC) and a broader range of potential toxicants, including metals, pesticides, mycotoxins, and microbial agents. METHODS: Fifty legal cannabis products were purchased across Canadian provinces, and 50 illegal samples were obtained via law enforcement seizures. All the samples were tested via validated, accredited/attested methods. THC content was assessed using LC-UV-MS. Pesticides were analyzed via LC-MS/MS and GC-MS/MS; metals via ICP-MS/MS; mycotoxins via LC-MS/MS; and microbial contamination using MALDI-TOF. RESULTS: THC levels in 48% of legal products deviated by more than 20% from their labeled concentrations. Microbiological testing revealed that 20% of legal products exceeded the European Pharmacopoeia microbial limits, prompting appropriate compliance and enforcement measures to address each of these cases. In contrast, 55% of the illegal products exceeded the aerobic plate count thresholds, and 73% surpassed the yeast and mold limits. Mycotoxins were undetected in legal products but were present in 12% of illegal samples. Pesticide residues were found at trace levels (0.01 µg/g) for myclobutanil and dichlobenil in two legal samples, whereas 94% of illegal samples contained pesticides, averaging 3.4 compounds per sample across 24 unique active ingredients. Metal analysis revealed higher levels of arsenic, cadmium, lead, and mercury in illegal products than in their legal counterparts. However, legal samples presented higher chromium concentrations, with peak values approximately threefold greater than those observed in illegal cannabis. The concentrations of arsenic, barium, chromium, copper, molybdenum, nickel, and vanadium exceeded the inhalation concentration limits found in Table 2 of USP <232> of the United States Pharmacopeia (USP) in one or both product categories. CONCLUSION: These findings demonstrate that legal THC levels differ from their label claims as well as that contaminants differ between legal and illegal cannabis products. The results provide evidence to inform regulatory oversight, enhance risk assessment efforts, and support informed decision-making by consumers and policymakers in the context of a legal cannabis framework.