Testing of Oregon cannabis products found high levels of residual pesticides, including nine classified as highly or extremely hazardous by the WHO, with medical cannabis containing 3-12 times more pesticide residue than recreational products.
Cannabis consumers, regulators, cannabis industry workers, and occupational health researchers.
Medical cannabis had 3-12x more pesticide residue than recreational
What the researchers found
Both recreational and medicinal cannabis products contained high pesticide levels, with 50 different pesticides identified. Medical cannabis products had mean pesticide residue levels 3-12 times higher than recreational products. Nine pesticides found were classified as highly or extremely hazardous.
Why it matters
The finding that medical cannabis, used by patients with health conditions, contained significantly more pesticide contamination than recreational products highlights a regulatory gap that could put vulnerable consumers and cannabis workers at risk.
The numbers in context
50 pesticides identified in cannabis products. Medical cannabis had 3-12 times higher mean residual pesticide levels than recreational. 9 of 50 pesticides were classified as WHO Class Ia (extremely hazardous) or Ib (highly hazardous).
How the study worked
Analysis of Oregon state pesticide testing data for both recreational and medicinal cannabis products. The Oregon Department of Agriculture developed testing regulations and a list of approved pesticides following legalization in 2014.
What this study cannot tell us
The study used state testing data, which may not capture all products on the market. Pesticide testing methods and detection limits evolved during the study period. The health effects of pesticide exposure via cannabis consumption are not well characterized.
How to read the evidence
Moderate: systematic analysis of state testing data, though limited by evolving testing standards and unknown health impact of inhalation exposure.
When this study was published
Published in 2020 in Annals of Work Exposures and Health.
The bigger picture
The disparity between medical and recreational cannabis pesticide levels likely reflects differences in testing requirements, suggesting that stricter and more uniform regulation is needed across all cannabis product categories.
Questions still open
- Are cannabis workers being exposed to dangerous pesticide levels? Why were medical products more contaminated than recreational ones? Have pesticide levels changed since stricter regulations were implemented?
Common questions
Why did medical cannabis have more pesticides?
What kinds of pesticides were found?
Read the original research
Evaluation of Pesticides Found in Oregon Cannabis from 2016 to 2017.
Annals of work exposures and health, 64(7), 770-774
Citation
Evoy, Richard; Kincl, Laurel. (2020). Evaluation of Pesticides Found in Oregon Cannabis from 2016 to 2017.. Annals of work exposures and health, 64(7), 770-774. https://doi.org/10.1093/annweh/wxz075
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