Modern Canna Cannabis, Medical Cannabis

By: Hannah Grzech

Microbes possess a remarkable ability to spread across various environments. These microorganisms have adapted to almost every condition and continue to be a daily pest. Florida provides an especially conducive environment for these bacteria and fungi to thrive. The warm and humid climate that is vital for cannabis cultivation serves as a prime breeding ground for microbes. Although many microbes are harmless and some even deemed beneficial for certain environments, there are plenty that cause detrimental illness. For this reason, it is essential for producers and consumers to be aware of these potentially pathogenic creatures that may be lurking in their favorite cannabis or hemp product. In the same way any product or food is susceptible to contamination, cannabis is no different. The FDA regulation of the food industry has a long history with decades of research to best protect its consumers. The legalization of cannabis-based products in America is constantly evolving and the development of specific FDA regulations are still in its infancy in many cases.

Impact on Consumer Health

It is important to understand what types of microbes found in cannabis put consumers most at risk. We are exposed to baseline levels of various molds and bacteria in our daily lives. These exposures are generally to non-pathogenic species or not in high enough concentrations to cause illness. Those with weakened immune systems or pre-existing diseases are at a higher risk of contracting a life-threatening disease. The most common microbes that are potentially harmful to cannabis consumers include: 


There are over 200 known species of Aspergillus and 20 can cause illness. This fungus is commonly found in soil, plants, and decaying organic matter. The name comes from the Latin word meaning “to scatter” as its main mode of spreading is through air-borne spores that can travel great distances. Aspergillus causes Aspergillosis, a fungal infection that ranges from mild to potentially fatal. There are several types of aspergillosis:

  • Allergic Bronchopulmonary Aspergillosis (ABPA): Which is an allergic reaction causing sinus inflammation and asthma symptoms.
  • Aspergilloma: Which results in the development of a fungal ball in lung cavities. This infection can be chronic and multiple fungal balls can form.
  • Invasive Aspergillosis: potentially fatal lung infection that spreads to other organs through the bloodstream.

Image Credits: Sushmita Baniya

The four most common pathogenic species of aspergillus are A. flavus, A. niger, A. fumigatus, and A. terreus. They produce aflatoxins, which are mycotoxins that can cause major health issues. There are several reports of cannabis users becoming infected by these species. Consumers who enjoy smoking or vaping are at the highest risk for infection since the combustion process does not eliminate Aspergillus spores. This may come as a surprise to most, but spores are extremely persistent by nature, so by aerosolizing them, you are potentially giving them a direct route into your lungs. Common treatments for Aspergillosis are different antifungal agents such as Voriconazole, Itraconazole, or Amphotericin B. Unfortunately, some strains have become resistant to certain medicines as they are constantly evolving. 

Image Credits: Victoria Forster

Salmonella and Shiga-Toxin E. coli 

Food poisoning is not limited to bad shellfish and uncooked chicken. Anything you consume can become contaminated at any point on its journey to your home and make you sick. The main culprits of this are Salmonella and Shiga-toxin producing E. coli (STEC). These nasty bacteria cause gastrointestinal infections resulting in diarrhea, vomiting, fever, and enteritis. Symptoms typically appear within 3 to 4 days of ingestion, but can be delayed up to 10 days, so tracing back the source of your illness can sometimes be difficult. Salmonellosis and STEC infections have no specific treatment besides replacement of fluids and electrolytes, as it leads to dehydration. Antibiotics are reserved for life-threatening cases as they do not appear to be helpful and may increase the risk of developing worse conditions.


The third most frequent cause of food-borne illness is the pathogenic species Listeria monocytogenes, resulting in Listeriosis. This pathogen is responsible for severe infection that can lead to sepsis, meningitis, or encephalitis if it enters the bloodstream or brain. So far, there are no documented cases of cannabis consumers contracting listeria from contaminated products, however, it is found in soil and some food products, so there is a potential risk for cannabis products being contaminated. 

Image Credits: Sagar Aryal

Impact on Cannabis Producers

In recent months, Arizona recalled 4 marijuana products containing Salmonella and Aspergillus contamination. There were no reports of illness, but the recall was issued as a caution, and consumers were advised to immediately dispose or return products from those specific batches. Recalls cost companies millions of dollars and damage their reputation in the industry. It is hard for consumers to trust suppliers that allowed these products to be sold in the first place. Laboratory testing is important because early detection is critical in preventing contaminated products from reaching the market.

Image Credits: TraceX Technologies

Supply Chain Pain Points 

There is not a single point in the supply chain that is not susceptible to microbes. Cannabis can become contaminated during the growing process through untreated manures, irrigation water, or improper ventilation. Products can be compromised during the manufacturing process due to environmental contamination in storage and processing facilities. Since cannabis is often cultivated in indoor grow houses, these can easily become breeding grounds for bacteria and mold. Consumers are not the only ones at risk, plants can also be infected. Plants naturally have a diverse microbiome that aids in their growth and production, so any disruption to its environment or the plant itself can stunt growth and lower potency, ultimately reducing the grower’s yield and profitability.

Mitigation and Prevention

Proper quality assurance practices are crucial. Instead of trying to combat the exponential growth of bacteria, strict preventative measures should be put in place, especially considering microbes often remain invisible to the eye until reaching numbers in the millions. Sterilizing cannabis is not as simple as applying bleach. Producers run into the problem of altering the cannabinoid or terpene profiles of their flowers when trying to eliminate unwanted microbes. 

Image Credits: SQDC

X-ray irradiation is one way some try to decontaminate their plants. This process can inactivate bacterial cells making them non-culturable. The genetic material of the inactivated microbes remain in the products and are still detectable via molecular methods such as qPCR which is used by most labs. There is still not a lot of research into the effects that this process has on the flower’s genetic and chemical makeup, and whether it may become altered and pose safety issues to consumers. Also, the shelf-life of these products is unclear and further research is needed into the possibility of resuscitation of irradiated cells over time. 

Relationships Built on Trust

State regulation of cannabis quality differs per state and is constantly changing. In Florida, the Department of Health’s OMMU is responsible for all aspects of medical marijuana to comply with the state’s current legislation. It is important for both the public and those a part of the industry to understand their state’s laws in order to protect themselves and others. Establishing a close relationship with a reputable certified testing lab is vital for becoming a sustainable operator in the cannabis industry, primed for long-term growth. It not only provides consumers with the peace of mind knowing their products have undergone rigorous quality control by a third party, but also protects companies from any violations that could cost them their license.

Current Microbial Testing Limits

Method development can be tricky when attempting to standardize so many different products. Currently, qPCR is the fastest and most accurate analysis for most required testing like Aspergillus, Salmonella, and STEC since they are not easily culturable. Microbiology proves to be much more unpredictable than chemistry because you are dealing with something that is alive and works at a predetermined pace. Many states require total yeast and mold (TYM) testing, which does not differentiate between pathogenic, benign, or beneficial species. Producers utilizing beneficial microbes to improve growth or experimenting with irradiation may face failing TYM results despite the products being perfectly safe. Also, Listeria testing is not required despite its risks, however, this is expected to change in the near future. Having an open dialogue between producers, testing labs, and state regulators is important for improving the current microbial testing methods and ultimately the safety of the cannabis market. 


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