A preliminary comparative analysis of pesticides residues in illicit and regulated cannabis inflorescence in Malta

Abstract

Illicit cannabis consumption presents significant health risks due to the absence of regulatory monitoring in its cultivation, especially with regards to pesticide contamination. In contrast, licensed cannabis produced under regulated frameworks is expected to comply with strict safety standards. This study investigated and compared pesticide residues in illicit cannabis samples seized by law enforcement officers with licensed recreational cannabis inflorescences sourced from Cannabis Associations licensed with the Authority for the Responsible use of Cannabis in Malta. The primary aim was to determine whether illicit cannabis is more likely to contain pesticide contamination. This study thus helped assess public health risks and highlighting the impact of regulatory control. Twenty-four cannabis inflorescence samples were analysed: twelve illicit samples and twelve licensed samples. The methodology employed a QuEChERS (Quick, Easy, Cheap, Effective, Rugged, and Safe) extraction protocol, followed by instrumental analysis using gas chromatography combined with mass spectrometry (GC-MS) and ultra-performance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS/MS). The findings demonstrated that pesticide residues were detected exclusively in illicit cannabis samples, while no pesticide contamination was found in licensed recreational cannabis provided by Cannabis Associations. Two organophosphate pesticides, dichlorvos and chlorpyrifos, were identified across multiple illicit samples. Statistical analysis using Fisher’s exact test confirmed a statistically significant difference in contamination between the two groups (two-sided analysis, p = 0.037). These results highlight the elevated risk associated with illicit cannabis use and emphasise the protective role of regulatory oversight in licensed production. Inhalation of organophosphate pesticide residues may contribute to acute and chronic toxicological effects, presenting a considerable public health concern for consumers of illicit cannabis. These findings support the implementation of strict monitoring frameworks in order to safeguard cannabis quality and strengthen the importance of consumer access to regulated products.