As cannabis related hospitalizations rise, new research out of Arizona State University (ASU) has revealed that black-market cannabis products contain potentially dangerous levels of fungal toxins.

The ASU team, led by Assistant Professor Maxwell Leung, analyzed 118 samples of illicit cannabis products seized by law enforcement in California and Arizona between November 2023 and June 2024. In their work, the ASU team discovered Fusarium mycotoxins in 16% of samples, illustrating the dangers of consuming unregulated products.

Potential Dangers of the Cannabis Black Market

Despite being legal for medicinal use in 39 states and recreational use in 24, the unregulated cannabis black market continues to thrive in the United States. In fact, at an estimated $76 billion, the illicit market may be twice the size of the legal one. The new ASU study emphasizes the potential dangers of such unregulated sales. Without proper oversight, cannabis products are prone to poor handling and unsanitary storage conditions, which can lead to contamination.

Researchers have linked cannabis hyperemesis syndrome to rising emergency room visits. One compound, Fusarenon-X, is known to cause vomiting and may worsen the condition. Cannabis is particularly vulnerable to Fusarium mycotoxins, which are heavily regulated in food but largely ignored, even in many state and federal cannabis programs. For context, the USDA limits total Fusarium mycotoxins to 1,000 ppb in grain products and 2,000 ppb in corn intended for human consumption. Due to their severity, the European Union imposes stricter limits, capping certain Fusarium toxins at 100 ppb.

Testing the Samples

Researchers screened the samples for 23 different types of mycotoxins and fungal metabolites, chosen based on their prevalence in agricultural products. The cannabis was ground into a powder and processed into extracts for testing. Among the contaminated samples, Fusarenon-X and diacetoxyscirpenol were found at concentrations exceeding both EU regulations and some of the looser USDA standards.

Ten samples contained Fusarenon-X at levels ranging from 500 to 1,700 parts per billion. While these results came from illicit cannabis, it’s particularly troubling that legal cannabis is not currently tested for these toxins under most state or federal programs.

“Many Fusarium mycotoxins can contribute to vomiting symptoms in users,” said Leung. “The presence of Fusarium fungi in cannabis can also pose an infection risk in immune-compromised users.”

More Research Required

With much of the U.S. cannabis supply coming from unregulated sources, the ASU study confirms the presence of known toxins in black-market products. The next step, researchers say, is to assess the health risks these toxins may pose across different methods of cannabis consumption. That understanding could help inform whether legal markets should also begin monitoring for Fusarium contamination.

“While these regulatory action levels are meant to provide the reader with a reference, it is important to note that none of these values are developed specifically to address the health risk of Fusarium mycotoxins in inhalable forms,” Leung told The Debrief.

“Cannabis flowers and extracts are heated and vaporized in different ways and temperatures for consumption. Many mycotoxins have high thermal stability, but it is unclear how much of them are converted into vapors and get into the consumer’s airway,” he added. “It is also unclear if the toxicity profile of these mycotoxins is different if inhaled (vs if orally consumed).”

The paper “Evaluation of Fusarium Mycotoxins and Fungal Metabolites in Seized Cannabis in Arizona and California, 2023-2024” appeared on March 19, 2025 in Environmental Health Perspectives. 

Ryan Whalen covers science and technology for The Debrief. He holds an MA in History and a Master of Library and Information Science with a certificate in Data Science. He can be contacted at ryan@thedebrief.org, and follow him on Twitter @mdntwvlf.