Understanding Sources of Heavy Metals in Cannabis and Hemp: Benefits of a Risk Assessment Strategy

The pharmaceutical industry took over 20 years to change from the qualitative monitoring of a small group of heavy metals to finally arrive at regulations for 24 elemental impurities in drug products, classified by their permitted daily exposure limits and categorized by toxicological impact and method of administration (oral, parenteral, inhalation, transdermal). The entire premise was based on carrying out a comprehensive risk assessment study of their toxicity and the likelihood of finding them somewhere in the drug manufacturing process, which was fully documented in International Council for Harmonization of Technical Requirements for Pharmaceuticals for Human Use Q3C guidelines for elemental impurities. The cannabis industry cannot move beyond the big four heavy metals until this type of risk assessment study is carried out. The objective of this paper is to offer guidance as to which elemental contaminants are worthy of consideration, based on likely sources derived from the cultivation, extraction, processing, packaging, and delivery of cannabis and hemp consumer products and to explore how this well-established pharmaceutical risk assessment process could be adapted by the cannabis industry. It will be broken down into four main sections, which are outlined as follows: the pharmaceutical risk assessment approach; whether risk analysis can be adapted for the cannabis industry; sources of elemental contaminants derived from cultivation practices; and contributions from the cannabis manufacturing process.