Risk assessment of metals measured in regulated Canadian dried cannabis and cannabis vaping products: case study and perspectives

In 2018, the Cannabis Act and its regulations established a strict legal framework for controlling production, distribution, sale and possession of cannabis across Canada. At that time, smoking dried cannabis was the most prevalent mode of consumption, and remains so to date, but cannabis vaping products have become increasingly popular since they were made commercially available in late 2019. Heavy metals are a recognized class of impurities in cannabis products that can pose consumer health concerns. The Cannabis Regulations ensure a quality-controlled supply of cannabis by requiring good production practices (GPPs) and refer to pharmacopoeias for impurity tolerance limits. For elemental impurities, pharmacopoeias specify tolerance limits based on route of exposure and as a permitted daily exposure (PDE). This paper presents a risk assessment case study based on levels of metals measured in legal products that have been published by Health Canada on dried cannabis and cannabis vaping liquids to illustrate the challenges in assessing risks from a regulatory and quality control perspective, using daily or almost daily typical (50th percentile) and heavy (95th percentile) use as a worst case scenario. Applying PDEs from established pharmaceutical quality control standards for the newly legalized cannabis industry has its own challenges, characterized by existing uncertainties which must be addressed, in particular as they relate to exposure characterization. This risk assessment identifies that there is a low risk to health from heavy metals in Canadian legal and regulated inhaled cannabis products, especially as most cannabis consumers in Canada are not daily or almost daily users. These findings suggest that the goal of the Cannabis Act to mitigate risks to health by providing access to a quality-controlled supply of cannabis has been achieved in this regard.