Fungal Contaminants
Where Found: Ubiquitous in soil and air; contaminates cannabis through spores during drying or poor storage.
Health Effects: Pulmonary aspergillosis, invasive infections, and sepsis.
At-Risk Populations: Transplant patients, leukemia patients, and others with suppressed immunity.
Where Found: Soil and humid environments post-harvest
Health Effects: Produces ochratoxin A—linked to kidney and liver damage; respiratory infections possible.
At-Risk Populations: Individuals with chronic lung disease or immunocompromise.
Where Found: Grows in cultivation media like peat moss and coco coir.
Health Effects: Produces fumonisins and trichothecenes; may cause hepatotoxicity and neurotoxicity.
At-Risk Populations: Cancer patients; pregnant individuals.
Where Found: Thrives in humid cultivation environments.
Health Effects: Causes allergic sensitization and, occasionally, lung infections.
At-Risk Populations: Individuals with asthma or chronic respiratory conditions.
Where Found: Soil enriched with bird droppings and improperly stored cannabis.
Health Effects: Causes cryptococcal meningitis and pulmonary infections.
At-Risk Populations: HIV/AIDS patients; transplant recipients; potentially immunocompetent (healthy) individuals.
Clinical Case: A woman with no evidence of immunodeficiency developed C. neof
Where Found: Soil enriched with bird droppings and improperly stored cannabis.
Health Effects: Causes cryptococcal meningitis and pulmonary infections.
At-Risk Populations: HIV/AIDS patients; transplant recipients; potentially immunocompetent (healthy) individuals.
Where Found: Found in decaying plant matter and humid post-harvest storage.
Health Effects: Causes mucormycosis, a rapidly fatal invasive infections involving lungs or brain.
At-Risk Populations: Individuals with HIV/AIDS, diabetes, and transplant recipients.
Bacterial Contaminates
Where Found: Soil; thrives in anaerobic post-harvest conditions.
Health Effects: Botulism; neurotoxin-induced paralysis.
At-Risk Populations: Immunosuppressed patients.
Where Found: Contaminated irrigation water, soil, and unclean post-harvest handling.
Health Effects: Gastroenteritis, dehydration, sepsis.
At-Risk Populations: Infants, elderly, immunocompromised individuals.
Where Found: Water and handling equipment.
Health Effects: Respiratory and bloodstream infections.
At-Risk Populations: Hospitalized patients and immunocompromised individuals.
Where Found: Soil and water; often introduced post-harvest.
Health Effects: Severe pneumonia, liver abscesses, sepsis.
At-Risk Populations: Diabetic, elderly, or immunocompromised patients.
Where Found: Irrigation systems, soil, and humid storage areas.
Health Effects: Causes UTIs, sepsis, and pneumonia; resistant strains common.
At-Risk Populations: Burn victims, CF patients, and hospitalized individuals.
Improper Drying, Curing, or Storage Creates Microbial Risks
Even on the healthiest of plants, a diverse community of microorganisms exists. These include:
Epiphytes: Fungi and bacteria living on the surface of the flowers and leaves. Spores of molds like Penicillium and Aspergillus might already be present.
Endophytes: Microbes residing inside the plant tissues. Some can be latent pathogens, waiting for the right conditions.
Freshly harvested buds are full of moisture, a literal playground for microbes. If buds are not dried quickly and efficiently to the proper water content, the environment is ripe for microbial proliferation.
High water activity: microbes, especially molds, thrive when water activity is high, generally above .7 Aw. Slow drying keeps the Aw in the danger zone for too long.
Stagnant Air and Humidity: Poor airflow during drying exacerbates the problems, trapping moisture and creating humid microclimates within piles of drying plant material
Mycotoxin Production: Some of these molds are not just unsightly; they produce mycotoxins, toxic chemical compounds that can be harmful to human health. Even if the mold itself dies or is removed, these toxins can linger. Examples include aflatoxins(from Aspergillus), ochratoxins (from Aspergillus and Penicillium), and fumonisins (from Fusarium).
The consequences of these microbial contaminants can be significant:
- Inhalation Hazards: Smoking or vaporizing cannabis contaminated with mold spores can introduce them directly into the lungs. This poses a particular risk to immunocompromised individuals (cancer patients, transplant recipients, those with HIV/AIDS, etc.) who are susceptible to opportunistic fungal infections like aspergillosis, cryptococcal meningitis, and mucormycosis.
- Mycotoxin Exposure: Inhaling or ingesting mycotoxins can lead to various health issues, including liver damage, kidney damage, immune suppression, and potential carcinogenic effects.
- Allergenic Reactions: Mold spores themselves can be allergens, triggering respiratory issues.
The good news is that these risks are largely preventable with proper post-harvest techniques.
- Prompt and Adequate Drying: Ensuring harvested cannabis dries relatively quickly to a safe moisture level (water activity below 0.70 Aw) is generally recommended. This prevents prolonged periods of high Aw conducive to microbial growth.
- Proper Airflow and Ventilation: Good air circulation during drying helps remove moisture and prevents humid pockets.
- Controlled Curing: A slow, controlled curing process after initial drying helps stabilize moisture levels and further reduces the risk of mold growth while enhancing aroma and flavor. Unfortunately for financial reason, many commercial growers do not take the time to fully cure their products.
- Appropriate Storage: Once dried and cured, storing cannabis in airtight containers in cool, dark, and low-humidity environments is crucial to maintain low water activity and prevent microbial resurgence.
Toxins in Cannabis
Produced By: Aspergillus flavus and Aspergillus parasiticus
Health Risks:
- Aflatoxins are among the most potent naturally occurring liver carcinogens and are strongly associated with hepatocellular carcinoma, DNA damage, and immune suppression.
- Chronic exposure, even in small quantities, can initiate hepatic tumorigenesis.
Why It Matters for C
Produced By: Aspergillus flavus and Aspergillus parasiticus
Health Risks:
- Aflatoxins are among the most potent naturally occurring liver carcinogens and are strongly associated with hepatocellular carcinoma, DNA damage, and immune suppression.
- Chronic exposure, even in small quantities, can initiate hepatic tumorigenesis.
Why It Matters for Cannabis Consumers:
- Aflatoxins are heat-stable and resilient, surviving traditional cannabis drying, curing, and even short-term storage.
- Their inhalation through smoking or vaporizing contaminated cannabis introduces toxins directly into the lungs, bypassing hepatic first-pass metabolism.
- These risks are especially high for immunocompromised individuals, who are both more likely to use cannabis for medical reasons and more vulnerable to toxin-induced immune suppression.
- Studies have directly identified Aspergillus species producing aflatoxins on dispensary-grade cannabis.
Produced By: Aspergillus and Penicillium species
Health Risks:
- Ochratoxin A (OTA) is classified as a possible human carcinogen (Group 2B) by the IARC and is linked to nephrotoxicity, immunosuppression, and possibly urinary tract cancers.
- OTA exposure is also associated with disruptions in cellular protein synthesis and oxidative stress
Produced By: Aspergillus and Penicillium species
Health Risks:
- Ochratoxin A (OTA) is classified as a possible human carcinogen (Group 2B) by the IARC and is linked to nephrotoxicity, immunosuppression, and possibly urinary tract cancers.
- OTA exposure is also associated with disruptions in cellular protein synthesis and oxidative stress.
Why It Matters for Cannabis Consumers:
- OTA forms during improper drying and storage, particularly in high-humidity conditions, which are common in the cannabis supply chain when airflow or climate controls are inadequate.
- OTA is odorless and invisible, and thus undetectable without specialized laboratory screening.
- Despite its known risks, many state cannabis testing protocols do not mandate OTA screening, resulting in possible consumer exposure.
Produced By: Fusarium species
Health Risks:
- Fumonisins are associated with neural tube defects, particularly spina bifida and anencephaly, making them a severe risk during pregnancy.
- They are also linked to esophageal cancer, hepatic and renal toxicity, and neurotoxicity in animal models and human epidemiological studies.
Why It Matters
Produced By: Fusarium species
Health Risks:
- Fumonisins are associated with neural tube defects, particularly spina bifida and anencephaly, making them a severe risk during pregnancy.
- They are also linked to esophageal cancer, hepatic and renal toxicity, and neurotoxicity in animal models and human epidemiological studies.
Why It Matters for Cannabis Consumers:
- Fusarium is commonly found in soil and growing media, particularly peat moss and coco coir, and can contaminate cannabis during cultivation.
- These fungi are capable of translocating fumonisins into the flower tissue, where the toxins can remain post-harvest.
- Unlike aflatoxins, fumonisins are rarely tested for in cannabis quality assurance protocols, unless explicitly mandated by state-level policy.
- Cannabis users, especially those who are pregnant, immunocompromised, or undergoing chemotherapy, are unlikely to be informed of this risk unless purchasing from producers that voluntarily test for fumonisins.