Aspergillus: The Most Dangerous Cannabis Pathogen

Editor’s Note: This blog was updated in May 2023 with additions to the list of states requiring Aspergillus testing, documented cases of aspergillosis from contmainated cannabis.   

While there have been no documented fatal overdoses from cannabis in the 39 states that have legalized its use, there have been more than two dozen documented cases of cannabis users acquiring aspergillosis from cannabis products contaminated with Aspergillus spores. Some of those cases have even led to death.

News articles and video interviews have argued that Aspergillus testing on cannabis products is not necessary, but we could not disagree more. Aspergillus contamination is responsible for the only documented cannabis-related deaths, and Aspergillus testing is essential to ensuring consumer safety.

What is Aspergillus?

Aspergillus is a saprophytic fungus that helps remove environmental carbon and nitrogen from the Earth’s atmosphere. Aspergillus is most commonly found in the soil around us, where it thrives on naturally occurring organic debris. While Aspergillus predominantly grows underground, its spores propagate rapidly in the air with each fungus capable of producing thousands of conidia. These spores are commonly spread through environmental disturbances and strong air currents, that allow them to be found both indoors and out. Aspergillus spores are tiny, even by biological standards, allowing them to travel great distances in the air.

These spores are everywhere, and there’s a solid chance that you and I breathe in hundreds of them each and every day. While there is usually no risk for healthy individuals, Aspergillus is especially dangerous to immunocompromised individuals, in whom the airborne spores can lead to a debilitating invasive infection, called aspergillosis, which oftentimes proves to be fatal.

Who is at risk?

Those with compromised immune systems, either through disease or medical treatment, are at serious risk of developing an aspergillosis infection. A 1992 study found the incidence of cases of aspergillosis per year to be 1 – 2 patients per 100,000 people; however, this number is likely much higher today due to the increased use of immunosuppressants and stem cell therapy. There are a variety of factors that can increase an individual’s likelihood of developing aspergillosis including, but not limited to:

  • the ingestion of immunosuppressive drugs (after undergoing bone or organ transplants)
  • a low white blood cell count (resulting from chemotherapy)
  • asthma or cystic fibrosis
  • long-term corticosteroid therapy

For these individuals, aspergillosis begins when the spores are inhaled through the mouth where the fungus finds ample breeding opportunity in the lungs that can quickly lead to infection. Once the infection takes hold it can cause serious, and sometimes fatal, bleeding in the lungs. Additionally, due to the invasive nature of the infection, aspergillosis can quickly spread to a patient’s kidneys, heart, and even the brain. Aspergillosis is capable of spreading impressively fast and typically results in death, with little regard for how early the infection is observed by medical professionals. A large study conducted with people who had contracted invasive aspergillosis from organ and stem cell transplants found the one-year rate of survival for these patients to be 59% and 25% respectively.

Due to the increased risk of contracting aspergillosis via organ transplant, some transplant programs have removed patients who use cannabis from their donor waiting list. Cancer patients undergoing chemotherapy and other radiation treatments are also at an increased risk.

Though rare, there have been documented cases of otherwise healthy individuals developing an aspergillosis infection. The most recent case happened in 2016 and occurred in a cannabis user.

Do all cannabis products pose this risk?

The danger posed to medicinal cannabis patients exists solely through the practice of ingesting cannabis by smoking, and inhaling, the product directly into the lungs through combustion. This danger is due to the fact that the heat created through the combustion does not reach the approximately 200 degrees required to effectively eliminate Aspergillus spores. When these spores are present in the plant and smoked they are inhaled directly into the lungs where they pose a serious risk of infection.

Luckily for patients, there are methods of consuming medicinal cannabis that eliminate the risk of developing aspergillosis. Medical cannabis in edible or injestible form typically is not a concern because the stomach is not a suitable environment for Aspergillus to live and thrive.

Who tests for Aspergillus?

The following states require testing cannabis for Aspergillus (updated May 2023):

  • Alabama
  • Alaska
  • Arizona
  • California
  • Colorado
  • Connecticut
  • Deleware
  • Florida
  • Hawaii
  • Iowa
  • Michigan
  • Mississippi
  • Missouri
  • Montana
  • Nevada
  • New Mexico
  • New York
  • Oklahoma
  • Oregon
  • South Dakota
  • Utah
  • Vermont
  • West Virginia

For more information about state microbial testing requirements check out our Cannabis Microbial Testing Regulations by State tool

USP Calls for Aspergillus Testing on Cannabis. Names qPCR Best Method ‘By Far’

Recently, the USP (United States Pharmacopoeia) published an article in the Journal of Natural Products titled, “Cannabis Inflorescence for Medical Purposes: USP Considerations for Quality Attributes”.

This published scientific work was developed by a panel of experts to provide information and guidance to state cannabis regulators and laboratories who are charged with addressing the public health risks associated with medically used cannabis. Their key findings include:

  1. Aspergillus contamination is of “particular concern” especially when consumed by patients who are immunocompromised.
  2. qPCR is “by far the most sensitive” method for detecting pathogenic species of Aspergillus, while conventional plating methods are “very difficult”.
  3. Enrichment is NOT optional when testing for Aspergillus contamination.
  4. The USP’s recommendations and findings have significant regulatory implications.

Test for Aspergillus with PathoSEEK

Medicinal Genomics can help labs test for Aspergillus flavusAspergillus fumigatusAspergillus niger, and Aspergillus terreus using our PathoSEEK® qPCR Detection Assays. The PathoSEEK 5-Color Aspergillus Multiplex assays were specifically designed for use on cannabis matrices and the AOAC PTM has certified its use for:

  • Next-day results. 24-hour enrichment for cannabis flower
  • Multiple matrices. Cannabis flower, infused edibles, and concentrates
  • Multiple instruments. Aglient AriaMX and BioRad CFX96

We can also assist with validation and automation to make testing and scalable. Contact us today to get started!

Documented Cases of Aspergillosis from Contaminated Cannabis

  1. M.J. Chusid, J.A. Gelfand, C. Nutter, and A.S. Fauci, Letter: Pulmonary aspergillosis, inhalation of contaminated marijuana smoke, chronic granulomatous disease. Annals of Internal Medicine 82(5), 682-683 (1975). 
  2. R. Llamas, D.R. Hart, and N.S. Schneider, Allergic bronchopulmonary aspergillosis associated with smoking moldy marihuana. Chest 73 (6), 871-872 (1978). 
  3. S. Sutton, B.L.Lum, and F.M. Torti, Possible risk of invasive aspergillosis with marijuana use during chemotherapy for small cell lung cancer. Drug Intelligence & Clinical Pharmacy 20(4), 289–291 (1986). 
  4. R. Hamadeh, A. Ardehali, R.M. Locksley, and M.K. York, Fatal Aspergillosis associated with smoking contaminated marijuana in a marrow transplant recipient. Chest 94(2), 432–433 (1988). 
  5. D.W. Denning, S.E. Follansbee, M. Scolaro, S. Norris, H. Edelstein, and D.A. Stevens, Pulmonary aspergillosis in the Acquired Immunodeficiency Syndrome. The New England Journal of Medicine 324(10), 652–664 (1991).
  6. W.H. Marks, L. Florence, J. Lieberman, P. Chapman, D. Howard, and P. Roberts, et. al., Successfully treated invasive pulmonary aspergillosis associated with smoking marijuana in a renal transplant recipient. Transplantation 61(12), 1771–1774 (1996). 
  7. M. Szyper-Kravitz, R. Lang, Y. Manor, and M. Lahav, Early invasive pulmonary aspergillosis in a Leukemia patient linked to Aspergillus contaminated marijuana smoking. Leukemia & Lymphoma 42(6), 1433–1437 (2001). 
  8. R. Ruchlemer, M. Amit-Kohn, and D. Raveh, et. al., Inhaled medicinal cannabis and the immunocompromised patient. Support Care Cancer 23(3), 819–822 (2015). 
  9. D.W. Cescon, A.V. Page, S. Richardson, M.J. Moore, S. Boerner, and W.L., Invasive pulmonary aspergillosis with marijuana use in a man with colorectal cancer. Journal of Clinical oncology. 26(13), 2214–2215 (2008). 
  10. A. Bal, A.N. Agarwal, A. Das, S. Vikas, and S.C. Varma, Chronic necrotising pulmonary aspergillosis in a marijuana addict: a new cause of amyloidosis. Pathology 42(2), 197–200 (2010). 
  11. Y. Gargani, P. Bishop, and D.W. Denning, Too many moldy joints – marijuana and chronic pulmonary aspergillosis. Mediterranean Journal of Hematology and Infectious Diseases 3, 2035-3006. Open Journal System (2011). 
  12. S.L. Kagen, M.D. Viswanath, P. Kurup, P.G. Sohnie, and J.N. Fink, Marijuana smoking & fungal sensitization. The Journal of Allergy and Clinical Immunology 71(4), 389–393 (1983). 
  13. S.L. Kagen, Aspergillus: An inhalable contaminant of marihuana. The New England Journal of Medicine 304(8), 483–484 (1981). 
  14. J.L. Pauly and G. Paszkiewicz, Cigarette Smoke, Bacteria, Mold, Microbial Toxins, and Chronic Lung Inflammation. Journal of Oncology 819129, 1-13 (2011). 100 Cummings Center • Suite 406L • Beverly, MA 01915 • 877-395-7608 •
  15. T. L. Remington, J. Fuller, and I. Chiu. Chronic necrotizing pulmonary aspergillosis in a patient with diabetes and marijuana use. Canadian Medical Association Journal 187 (17), 1305-1308 (2015) DOI: 
  16. D. Vethanayagam, E. Saad, and J. Yehya, Aspergillosis spores and medical marijuana. Canadian Medical Association Journal (CMAJ) Letters 188(3), 217 (2016). 
  17. S. M. Levitz, R. D Diamond, Aspergillosis and marijuana. Annals of Internal Medicine 115(7), 578-579 (1991). 
  18. B. R. Waisglass, Aspergillosis spores and medical marijuana. Canadian Medical Association Journal (CMAJ) Letters 187(14), 1077 (2015). 
  19. E. Faccioli, F. Pezzuto, A. D. Amore, F. Lunardi, C. Giraudo, M. Mammana, M. Schiavon, A. Cirnelli, M. Loy, F. Calabrese, and F. Rea, Fatal Early-Onset Aspergillosis in a Recipient Receiving Lungs From a Marijuana-Smoking Donor: A Word of Caution. Transplant International 35 (2022). 
  20. A. P, Salam and A. L. Pozniak, Disseminated aspergillosis in an HIV-positive cannabis user taking steroid treatment. The Lancet Infectious Diseases 17(8), 882 (2017). 
  21. T. E. Johnson, R. R. Casiano, J. W. Kronish, D. T. Tse, M. Meldrum, and W. Chang, Sino-orbital aspergillosis in acquired immunodeficiency syndrome. JAMA Ophthalmology 117(1), 57-64 (1999). 
  22. K. Benedict, G. R. Thompson, and B. R. Jackson, Cannabis Use and Fungal Infections in a Commercially Insured Population, United States, 2016. Emerging Infectious Diseases 26(6), 1308-1310 (2020). 
  23. M. I. Shafi, S. Liaquat, and D. Auckley, Up in smoke: An unusual case of diffuse alveolar hemorrhage from marijuana. Respiratory Medicine Case Reports 25, 22-24 (2018).

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