The Controlled Cannabis Supply Chain Experiment (Experiment Gesloten Coffeeshopketen, EGC) aims to evaluate the feasibility and public health impact of supplying decriminalized, quality-controlled cannabis to coffeeshops in ten Dutch municipalities. In preparation for the experiment, an exploratory baseline study was conducted to assess the prevalence of contaminants in cannabis currently available in the Netherlands. A total of 105 samples, comprising resin (hashish) and floral (weed) cannabis, were purchased from Dutch coffeeshops and analyzed for aflatoxins, heavy metals, micro-organisms, and pesticides.

Results showed no instances of aflatoxin concentrations exceeding the established limits for the EGC. However, 20% of weed samples displayed microbiological transgressions, with unclear origins and potential health impacts. Notably, one hashish sample contained lead concentrations above the allowable threshold, warranting attention despite the limited health risks associated with the detected level. Pesticides not permitted within the EGC were found in 34% of the analyzed samples, yet calculated consumer exposures were significantly below acceptable daily intake levels. Exposure to these concentrations of pesticide residues probably does not lead to additional health risks.

This baseline assessment highlights the importance of quality control in cannabis production and underscores the potential of regulatory frameworks like the EGC to mitigate public health risks associated with contaminated cannabis. These findings provide valuable insights for policymakers, public health officials, and stakeholders in the cannabis supply chain.