Study examines medicinal, recreational cannabis markets

The researchers looked at state regulations, potential public health risks

September 16, 2022

A new study urges that state and federal regulators need to take a closer look at the health and safety risks of the growing medicinal and recreational cannabis market.  

“Cannabis regulation is unlike any agricultural commodities, food or drugs in the U.S. Currently, there are no national-level guidelines based on conventional risk assessment methodologies or knowledge of patients’ susceptibility in medical use of cannabis,” said lead author Max Leung, an Arizona State University assistant professor in the School of Mathematical and Natural Sciences.  Gloved hands handle a cannabis plant. A new study urges that state and federal regulators need to take a closer look at the health and safety risks of the growing medicinal and recreational cannabis market. Image courtesy: National Institute on Drug Abuse Download Full Image

“Therefore, our research team conducted the first comprehensive study to examine three main concerns: 1) the current landscape of state-level contaminant regulations, 2) identifying cannabis contaminants of concern in samples, and 3) explore any patient populations who may be susceptible to contaminants.” 

The cannabis market has grown significantly in the past decade from a $10 billion industry in 2017 to what is projected to be a $50 billion industry by 2026, and within the past year, an estimated 55 million users. Currently, 15 states have made medicinal cannabis legal, but little attention has been paid to its implications in chemical exposure and consumer safety. 

At the federal level, cannabis is still listed as an illegal substance. This limits the efforts of several federal agencies in assessing and mitigating the public health risk of cannabis contamination. Currently, cannabis is neither federally regulated as an agricultural (food) or a pharmaceutical commodity, so the USDA does not monitor its growth and the FDA does not consider it a drug. 

So how is a cannabis user to know what they are putting into their bodies is safe? “There is surprisingly limited information on the contaminant level of cannabis products sold in this country,” Leung said. 

Without any federal guidelines, it’s been left entirely up to the states to craft a patchwork of cannabis regulations and policy.

“Individual legalized states and D.C. set their own rules with huge discrepancies,” Leung said.  

From their study, Leung and colleagues found that as of May, 36 states and the District of Columbia have listed a total of 679 cannabis contaminants as regulated in medical or recreational cannabis. Most of these contaminants were pesticides (551, which included 174 insecticide, 160 herbicide and 123 fungicide subcategories), followed by solvents (74), microbes (21), inorganic compounds (12), mycotoxins (5) and 16 classified as “other.” 

“What was interesting is that many pesticides in this document were highly unlikely to be utilized in cannabis cultivation and processing,” Leung said.

These pesticides included chlorpropham (a plant hormone that prevents potatoes from sprouting), oxytetracycline (an antibiotic) and norflurazon (an aquatic herbicide for Hydrilla control). 

“What was also alarming to us is that the U.S. EPA tolerance document and individual jurisdictions also listed a total of 42 legacy pesticides that were no longer registered for any agricultural use in the U.S., such as dichlorodiphenyltrichloroethane (DDT), chlordane, lindane and parathion.” 

As to the amount of contaminants levels, there were large inconsistencies from state to state. Different state jurisdictions showed significant variations in regulated contaminants and action levels ranging up to four orders of magnitude. 

How often was this a problem? The research team also mined data testing records of cannabis flower and extract samples produced in California, the largest state cannabis market in the U.S. Their sample data represented about 6% of California’s legal production in 2020 to 2021. 

“As mandated by California’s Medicinal and Adult-Use Cannabis Regulation and Safety Act, all cannabis and cannabis products in the legal market of California are required to be tested for 68 pesticides, four inorganics, 20 solvents, six microbes and five mycotoxins,” Leung said. 

“The cannabis manufacturers must submit their products – including cannabis flowers and cannabis products such as edibles, concentrates and other consumables — to a state-licensed cannabis testing laboratory. All products must be certified for compliance testing before they can be sold legally. The products that failed the state’s regulatory levels in the compliance testing are subject to recalls.”

The tallied an overall failure rate of 5.1% for the California cannabis samples, which included an average of the failure rate of 2.3% identified for flowers and 9.2% for extracts in California samples. Insecticides and fungicides were the most prevalent categories of detected contaminants, with boscalid and chlorpyrifos being the most common. The contaminant concentrations fell below the regulatory action levels in many legalized jurisdictions, indicating a higher risk of contaminant exposure. 

Lastly, Leung’s team reviewed the medical cannabis use reports released by state-level public health agencies from 2016 to 2021. Currently, there are 37 U.S. medical cannabis programs and close to 100 qualifying medical conditions listed by these programs. 

“Cannabis and cannabis products are often marketed as alternative options to standard medical treatments,” Leung said. “As such, medical cannabis can potentially expose susceptible patients to harmful contaminants.” 

“Immunocompromised patients with cancer and HIV, women of reproductive age and patients with seizures and epilepsy are among those who are more susceptible to the health hazards of pesticide and microbial contaminants that may be found in cannabis."

The majority of patients were prescribed medical cannabis for use in alleviating pain (799,808 patients), followed by post-traumatic stress disorder (164,383 patients), spasticity associated with multiple sclerosis or spinal cord injury (78,145 patients), cancer (44,318 patients) and epilepsy (21,195 patients). 

“Our findings have two important public health implications,” Leung said. “First, the scattershot approach of regulations at the state level can confuse cannabis manufacturers and discourage compliance while subjecting cannabis users to a higher level of contaminant exposure in some jurisdictions. Second, given the current status of cannabis contaminant regulation in the U.S., it is unclear whether the health benefit of cannabis usage outweighs the health risk of exposure to cannabis-borne contaminants.” 

To help better inform the public and policymakers, Leung recommends further investigations to examine the safety considerations in susceptible patient populations across all medical conditions. 

“The progression and prognosis of many qualifying conditions may be worsened by exposure to detected contaminants in cannabis,” Leung said. “This study demonstrates an urgent need for a unified regulatory approach to mitigate the public health risk of cannabis contamination at a national level.” 

The study “Comparison of State-Level Regulations for Cannabis Contaminants and Implications for Public Health” was published online Sept. 14 in the peer-reviewed journal Environmental Health Perspectives. To access the publication, go to DOI:10.1289/EHP11206.

Joe Caspermeyer

Manager (natural sciences), Media Relations & Strategic Communications


Research of wild primate shows maternal effects key to gut microbial development

September 16, 2022

The bacteria that reside in the human gut, otherwise known as “the gut microbiome,” are known to play both beneficial and harmful roles in human health.

Because these bacteria are transmitted through milk, mothers can directly impact the composition of bacteria that their offspring harbor, potentially giving moms another pathway to influence their infant’s future development and health. A baby gelada foraging in Simien Mountains National Park in Ethiopia. Their early-life gut microbiome, from infancy through first years of life, are shown to be maternally influenced as they get older. Photo credit: Sharmi Sen/University of Michigan Download Full Image

Now, a study of wild geladas — a non-human primate that lives in Ethiopia — provides the first evidence of clear and significant maternal effects on the gut microbiome both before and after weaning in a wild mammal.

This finding, published in Current Biology, suggests the impact of mothers on the offspring gut microbiome community extends far beyond when the infant has stopped nursing.

A research team co-led by Stony Brook University anthropologist Amy Lu and biologists Alice Baniel and Noah Snyder-Mackler at Arizona State University came to this conclusion by analyzing one of the largest data sets on gut microbiome  development in a wild mammal.

They used high throughput DNA sequencing to identify and characterize the bacteria residing in the guts of young geladas and identified 3,784 different genetic strains of bacteria belonging to 19 phyla and 76 families. However, this diversity was not equally distributed across the developmental spectrum: similar to what is seen in humans, younger infants had the least diverse microbial communities that gradually became more diverse as they got older.

These changes reflected what the infant was eating, specifically when they switched from consuming milk to consuming more solid foods. These diet-focused bacteria actually help infants process foods — for instance, milk glycans, which cannot be digested without the help of bacteria. 

However, it was the team’s findings of strong maternal effects on the infant gut microbiome both before and after weaning that was the most groundbreaking.

“Infants of first-time moms showed slower development of their gut microbiota, meaning that their guts were specialized toward milk digestion for longer compared to kids from other moms. This may put offspring of newer moms at a slight developmental disadvantage,” Baniel said. “In addition, even after infants were weaned, their microbiome community was more similar to mom’s than to other adult females in the population, suggesting that moms may be sharing microbes with their offspring.”

According to Lu, “Early life gut microbial development is known to have a large impact on later life health in humans and other model organisms. Now we have solid evidence that mothers can influence this process, both before and after weaning. Although we’re not 100% certain how mothers do this, one possible explanation is that they transfer specific bacteria to their offspring.”

According to Snyder-Mackler, “These early life changes might have far-reaching consequences – impacting the health and survival of these offspring once they become adults.”

Future work from this research team is therefore going to examine how differences in the gut microbiome during infancy influence other aspects of development, such as growth, the maturation of the immune system or the pace of reproductive maturation. Luckily, because they are continuing to study the same infants as they age, they’ll eventually be able to link the infant gut microbiome and the early-life maternal effects to health, reproduction and survival in adulthood. 

The research was funded by several grants from the National Science Foundation, the National Geographic Society, the Leakey Foundation and from the University of Michigan, Stony Brook University and Arizona State University.

Joe Caspermeyer

Manager (natural sciences), Media Relations & Strategic Communications