Use of Medical Cannabis Can Expose Patients to Harmful Contaminants What should readers take away from your report?

Response: This study consists of three parts. First, we data mined the compliance testing records of 5,654 cured flower and 3,760 extract samples that accounted for ∼6% of California’s legal cannabis production in 2020–2021. We found contaminants at a higher rate in extracts (9.2%) than in flowers (2.3%). Several contaminants including the insecticide bifenazate and the fungicide paclobutrazol are found in extracts 100 – 1,000 times higher in concentration than in flowers.

Next,  we examined the regulatory documents for medical and recreational cannabis in all 36 legalized states and Washington, D.C. As of May 18, 2022, these jurisdictions regulated a total of 679 contaminants. Such a large number of regulated contaminants indicates a huge discrepancy in contaminant regulations from state to state, given that most states regulate less than 150 contaminants. The regulatory action level of some contaminants may vary up to four orders of magnitude between different states.

Lastly, we reviewed the publicly available medical cannabis use reports to tabulate the susceptible patient populations to contaminants. We identified several patient populations susceptible to contamination toxicity, including cancer patients (44,318; prone to opportunistic infection caused by microbial contaminants) and seizure patients (21,195; prone to neurotoxic effects of pesticides and heavy metals). What recommendations do you have for future research as a result of this study?

Response: The use of medical cannabis can expose susceptible patients to harmful contaminants. This is a public health risk of cannabis use that has been largely ignored. We are currently conducting a follow-up study to investigate cannabis usage, contaminant exposure, and risk awareness in patients with Parkinson’s Disease. More research such as this one is needed to better understand the toxicity of cannabis-contaminant mixture as well as the contaminant exposure level of medical patients. Having this information is crucial in the development of a unified regulatory approach to resolve this public health issue at a national level. Is there anything else you would like to add? Any disclosures?

Response: Lastly, I would like to point out the importance of data accessibility. In this study, we found that most legalized states have their own cannabis testing programs. Yet, little information is available about the findings of these programs. Data accessibility to these programs is key to raising the awareness of the general public and medical community about the health risk of cannabis contaminants. 


Laura E Jameson, Kendra D Conrow, Dorina V Pinkhasova, Haleigh L Boulanger, Hyunji Ha, Negar Jourabchian, Steven A Johnson, Michael P Simeone, Iniobong A Afia, Thomas M Cahill, Cindy S Orser, Maxwell C K Leung. Comparison of State-Level Regulations for Cannabis Contaminants and Implications for Public Health. Environmental Health Perspectives. 130(9):97001.

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Last Updated on September 19, 2022 by