Commercially sold cannabis may still contain toxic fungi and residues, even if it has been irradiated in accordance with standard industry practices, warn researchers at McGill University.
While the finding is unlikely to have serious consequences for most users, the same may not be true for those who use cannabis for medical purposes and whose immune systems may be compromised, said Saji George, food science and agrochemistry professor at McGill University.
“For people who take it for medical reasons, especially those undergoing chemotherapy, for example, or those with a weakened immune response due to treatment or illness, this could be a major problem,” he warned.
Gamma irradiation is the sterilization method commonly used in the production of medical and recreational cannabis. The researchers therefore examined samples of dried cannabis buds that had not been irradiated; irradiated samples sourced directly from a licensed producer; and ready-to-consume samples from a licensed retailer.
Some of their samples were obtained from the Quebec Cannabis Corporation.
George and his colleague Mamta Rani found that gamma irradiation does not completely eliminate toxic fungi or their chemical residues. They then discovered that the advanced analytical methods commonly used in cannabis production cannot detect live spores.
Through additional testing, the team identified spores that could escape mass spectrometry and ELISA tests used to quantify mycotoxins.
“According to industry standards, (the sample) may pass quality control,” said George. “But what we are showing, using advanced instruments, is that it is not completely sterile. These elements are still present in the sample, even though they may be below the detection limit of industry standards.”
This is not a matter of negligence, George emphasized: producers and retailers comply with current regulations and standards, but it appears that these are insufficient to protect the most vulnerable consumers.
Even though producers and retailers “subject their products to a rigorous sterilization process,” he added, “some may still slip through the cracks and reach the market when they are not truly sterile.”
These substances may be tolerated if they pass through the digestive system, George explained, but if smoked, they can “very easily colonize the lungs and become deadly.”
“Smoking is therefore very dangerous for immunocompromised individuals, which is a major concern,” he said. It’s not really good for healthy people either, but we assume that you may not see an immediate effect in them, as you would in an immunocompromised person.”
Consumers who think that smoking cannabis destroys potentially harmful substances are mistaken, the researcher pointed out.
“(These substances) will not be completely destroyed or eliminated,” he said. “They will continue to enter our pulmonary system. There is medical epidemiological evidence of people who have been exposed to these fungal spores and mycotoxins.”
Cannabis industry workers could also be exposed, even if they do not consume it directly, George added.
There are only a few cases in the scientific literature of cannabis users who have become ill from spores, he said, but the subject has never really been studied in detail. It is therefore possible that the phenomenon is simply going unnoticed.
Cannabis buds contain sticky resins that greatly promote contamination, Rani said in a statement. Since fungi are ubiquitous, “we need to be more vigilant at every stage, from cultivation to storage, harvesting, and processing,” she said.
In the immediate term, George said, different quality standards should be applied to recreational and medical cannabis in order to protect vulnerable consumers.
Researchers are also exploring various solutions with industry partners, such as the use of beneficial bacteria to prevent harmful fungi from colonizing crops.
The findings of this study were published in the scientific journal Toxins.
–This report by La Presse Canadienne was translated by CityNews
