Journal:An assessment of heavy metal contaminants related to cannabis-based products in the South African market

Full article title	An assessment of heavy metal contaminants related to cannabis-based products in the South African market
Journal	Forensic Science Internationa: Reports
Author(s)	Viviers, Hendrik J.; Petzer, Anél; Gordon, Richard
Author affiliation(s)	National Analytical Forensic Services, North West University, South African Medical Research Council
Primary contact	Email: henrick at nafs dot co dot za
Year published	2021
Volume and issue	4
Article #	100224
DOI	10.1016/j.fsir.2021.100224
ISSN	2665-9107
Distribution license	Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International
Website	https://www.sciencedirect.com/science/article/pii/S2665910721000554
Download	https://www.sciencedirect.com/science/article/pii/S2665910721000554/pdfft (PDF)

Abstract

South African cannabis-based products that were submitted to a private laboratory for the determination of heavy metals residues were analyzed. The presence of each heavy metal residue was determined in order to establish which residues are most prevalent in samples. Two specifications were considered for both oral as well as inhalation limits: United States Pharmacopeia (USP) <232>/<233> and the International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use (ICH) Q3D. To date, no data of this kind exist in South Africa specifically relating to cannabis-based medicinal, recreational, or complementary products. A total of 310 samples were analyzed in duplicate and are reported in an anonymized format. The submitted samples were divided into different category classifications and grouped according to relevance for oral or inhalation specification. The results showed an alarming 15% sample failure rate, compared to the oral specification limit, and a 44% failure rate, compared to the inhalation specification limit. It is of the utmost importance for manufacturers to have the appropriate quality control regimes in place, especially for heavy metal residues, in South Africa. Furthermore, it is imperative to ensure regulation is enforced and the South African public is educated about the risks associated with using these products.

Keywords: cannabis, heavy metals, regulation, residues, South Africa

Introduction

In the cannabis industry, be it medicinal or recreational, there is an abundance of control measures in place to ensure product safety and efficacy. Contamination of Cannabis plants with toxic heavy metals such as arsenic, cadmium, lead etc. can result from numerous origins. Sources of contamination include environmental pollution such as emissions from factories and automobiles, contaminated water, some pesticides, and naturally occurring metals in soil and fertilizers. The contamination of the herbal material ultimately leads to contamination of the products during various stages of the manufacturing process.

During growth, metals accumulate in the biomass of specific plants. Studies conducted on industrial hemp show that the Cannabis plant bioaccumulates heavy metals from the soil, and thus is readily employed for phytoremediation of contaminated soils. There have also been reported cases of post-processing adulteration of cannabis buds, adding heavy metals to increase the weight of the product to purposely increase the street value.

Pesticides that contain arsenic and mercury as part of their structures were commonly utilized until a few years ago, and they are still employed in some capacity to date. These toxic substances are likely to be present in many foods due to their abundance in nature, and it is important to note that associated ingestion or inhalation of these cannabis products would add to the accumulation of heavy metals consumed by people, even if best practice guidelines are followed.

As a result of the new requirements imposed by the United States Pharmacopeia (USP) <232>/<233>, in collaboration with the International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use (ICH) Q3D, the detection limits for certain heavy metals have been lowered. Inductively coupled plasma mass spectrometry (ICP-MS) is a recommended technique for detecting heavy metal contamination. Given that technique, low residue limits can be imposed by USP <232>/<233>.

Heavy metal residues in pharmaceutical end products, active pharmaceutical ingredients, and excipients need to be controlled and should be at a certain limit for safe human consumption. Furthermore, it can be noted in the somewhat unique case of cannabis-based products, that an alternative route of administration of these products does occur, namely inhalation. The pharmacopeial guidelines stipulate three routes of administration, namely parenteral, oral, and inhalation. Cannabis-based products are predominantly administered through oral and inhalation pathways.

Heavy metals are classified into different classes according to their toxic potential, with Class 1 (Table 1) being the most dangerous, Class 2 being less toxic, and Class 3 having the highest limits and being the least toxic. This study will focus on Class 1 and 2 metal residues given they present the greatest health risk to consumers.

Table 1. Heavy metal residue limits imposed by USP <232>/<233> and ICH Q3D R1 Class Heavy metal Limit (µg/g) Oral Inhalation Class 1

Notes

This presentation is faithful to the original, with only a few minor changes to presentation. References aren't listed in the order they appear in the original, but they do for this version, by unavoidable design. In some cases important information was missing from the references, and that information was added. A few words were added, updated, or shifted for improved grammar and readability, but this version is otherwise unchanged in compliance with the "NoDerivatives" portion of the original's license.