Helping Growers Protect Their Cannabis

Cannabis is subject to contamination by pathogenic fungi, bacteria, plant viruses and other microbial life forms. Growing conditions for cannabis are ideal environments for microbial growth. When human disease is not a threat, allergic responses, physical degradation and off flavors are real concerns. Fungi can produce mycotoxins some of which are extremely dangerous. These produced by Aspergillus and Fusarium infecting cannabis have been shown to cause human illness.

The potential for plant-born infection depends on the temperature, water activity, and transmission-route parameters that characterize the particular product. For instance, smoked plant material is heated to high temperatures that will kill normal cells, but it can still deliver heat-resistant spores to the lungs. Edible food products are usually heated, but if they are not heated they can deliver bacteria to the stomach where certain species can replicate.

Mold is perhaps the single most important quality issue in Cannabis production. Outdoor plants are exposed to a wide variety of fungal species. Indoor plants are exposed to less of these, and can potentially be kept cleaner. In practice, however, many indoor plants are exposed to inappropriate watering, humidity, fertilizer, or ventilation conditions. All of these can contribute to very high levels of mold.  Even under ideal conditions, it is possible that small numbers of cells or spores capable of causing human disease may be present on plant material from contact with air, soil, or water. If any of these species are capable of replicating aggressively either on dried plant material or upon contact with humans, they could theoretically prove to be a threat.

Once plants are harvested they are trimmed, dried, and cured. These processes present significant opportunities for contamination. Harvesting and trimming are the stages at which there is the greatest level of human handling. Human pathogens can easily be transferred to the flower material at this stage.

Certain types of bacteria and fungi, however, are quite resistant to drying; even though they cannot grow at low water activity levels, they remain viable and can grow if conditions change. If the end product of the extraction process is intended for use as a food additive in Cannabis products, it is often subjected to an independent heating process. This makes it as safe as any agricultural product could possibly be. Nevertheless, these conditions don’t rule out all microbial threats.

Microbial threats

* Bacteria resistant to low water-activity. Pathogenic bacteria that are extremely resistant to drying could potentially live on Cannabis, and be transferred to humans or to other items and then to humans. They would not survive the heat of smoking or decarboxylation, but they could nonetheless be carried into homes and come into contact with hosts through their presence on Cannabis. The only organism of concern in this category is Salmonella.

* Fungal spores. These are extraordinarily resistant to heat, and could survive the heat of smoking or
decarboxylation. These are not known to cause disease through the oral route, but the spores of certain species in the genus Aspergillus can enter the lungs, germinate, and cause invasive lung disease in susceptible individuals.

* Bacterial spores. In theory, these could pose a danger just as fungal spores might. Bacterial spores could survive on plant material or in infused edible products, and enter the lung or stomach. However, there are no such spores that pose a threat under the conditions Cannabis is subject to. This will be discussed below in the section dealing with Clostridium Botulinum.

* Toxins. In theory, either bacterial or fungal toxins could be present on Cannabis because of the earlier presence of high levels of toxin producing organisms. These could then be transferred to the lungs by smoking, or transferred into foods and delivered to the stomach. Alternatively, toxin-producing organisms could be present in food products and produce toxins there that remain a threat. We will deal with each of these possibilities below. In short, none of them are possible with Cannabis, because the conditions required for the high level of replication needed for toxin production are never available. In addition, the potential toxins of concern are all rapidly degraded rapidly by heat.