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This finding is even more concerning, the research team points out, as 70% of cannabis is smoked or vaped, meaning toxins can be delivered directly to the lungs and worsen the lung tissue damage caused by smoking. Therefore, they advocate for tighter controls and protective measures.
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Spores pose significant health risks
Gamma irradiation damages the DNA and RNA of microbes and degrades mycotoxins, harmful compounds produced by certain fungi. Although this process significantly reduces the microbial load, viable spores of mycotoxigenic fungi, DNA fragments, and traces of toxins remain after irradiation, the research team found.
These residues pose significant health risks, particularly for certain populations, including people with cancer, those who have received a transplant, or those living with HIV. Moreover, the study reports many cases of pulmonary fungal infections and other opportunistic infections in healthy individuals exposed to contaminated cannabis products.
Combined methods for stricter control
The research team analyzed dried cannabis buds: non-irradiated samples, irradiated samples obtained directly from a licensed producer, and ready-to-consume samples from a licensed retailer. They used three complementary approaches:
- counting and identification of live bacteria and fungi using culture-based methods;
- molecular tests (PCR and quantitative PCR) for detecting fungal DNA and toxin-producing genes;
- ELISA tests, which allow quantification of mycotoxins, such as aflatoxins and ochratoxins, through antibody detection.
Common advanced analysis methods used in cannabis production, such as mass spectrometry and the ELISA test, do not allow detection of live spores, the research team emphasizes. However, she explains, they must absolutely be detected to ensure the safety of cannabis products, especially those used by immunocompromised individuals.
By performing complementary tests, the team was able to identify spores that could escape detection by mass spectrometry and the ELISA test.
"Just one viable spore can cause illness; so we had to push the analysis beyond the limits of the ELISA test. The consequences may be minimal for the general population, but the risk is very real for immunocompromised individuals," argues Saji George, co-author of the study and professor in the Department of Food Science and Agricultural Chemistry.
Collaboration with industry
Since it is extremely difficult to eliminate a fungus, the importance of prevention cannot be overemphasized, the research team stresses. They are exploring various solutions with industry partners, for example, using good bacteria that prevent harmful fungi from colonizing crops.
"Cannabis buds contain sticky resins that greatly promote contamination. Since fungi are ubiquitous, we must increase vigilance at all stages, from cultivation to storage, including harvest and processing," says Mamta Rani, co-author of the study and research associate in the Sustainable Food and Agricultural Nanotechnology (SAFE-Nano) Laboratory at McGill University.
"Producing clean cannabis is possible. Some companies we work with have achieved this through strict hygiene practices and controlled environments," says the researcher.
And Saji George adds: "We are not trying to tarnish the industry's image, but rather to ensure its viability and provide guidelines for the production of safe products. We need to tighten safety standards, especially for therapeutic cannabis."