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Rot and Recall: What’s Going on in Denver’s Dispensaries?

By Alexander Beadle

Published: Feb 03, 2020   
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Local dispensaries in Denver made headlines at the close of 2019, but not for the best reasons. Reports claimed that 80 percent of yeast and mold tests carried out by city officials on cannabis products had failed.

But was this really an accurate representation of what happened in Colorado’s cannabis sector? And if not, what is actually going on in Denver dispensaries?

The City of Denver’s random inspections

On August 19, the City of Denver issued a notice to all licensed cannabis dispensaries in the city, making them aware that investigators from the Denver Department of Public Health & Environment (DDPHE) would soon begin a random testing drive in order to “evaluate contaminants in products on store shelves.”

“Each sample will be tested for pesticides and total yeast and mold by a state- and ISO-certified marijuana testing facility,” the announcement stated.

Then, in late October, a report appeared in the regional Denver publication Westword. The article stated that, while the official write-up of the test results was still months away from official release, Westword had learned that 20 of the 25 dispensary inspection reports had least one quarantine order, which was reported as an 80 percent failure rate.

“Each of those disciplinary actions was tied to plant matter testing above the maximum allowed for total yeast and mold,” the Westword article read.

Total yeast and mold tests are used in cannabis testing to detect the presence of harmful molds and fungi, which, if left untreated, can begin to produce chemical mycotoxins that are harmful to human health. Particularly dangerous are the aflatoxins, a type of mycotoxin produced by aspergillus fungi species, which are strongly carcinogenic. Acute aflatoxin exposure can be fatal in large doses, as the aflatoxin attacks the liver and causes the organ to fail.

As a result of these potential health risks, it has become commonplace for states with legal cannabis to make total yeast and mold, or other similar tests for microbial contaminants, a mandatory part of the state cannabis testing regimen.

“We want to catch any product that's got contaminants in it via pesticides, molds, or mycotoxins – whatever it is, we want to catch that,” Richard Pruckler, a supervisor for the DDPHE, told Analytical Cannabis. “And that’s really the point of these interventions and recalls.”

“When we identify potential contaminants, we're trying to look to a science-based thought process,” he explained. “Pesticides, whether you consume them via eating or inhalation, we know there are potential public health risks. It's the same thing for total yeast and mold.”

So, did 80 percent of samples really fail?

Since the publishing of the original Westword article, the “80 percent failure rate” has been bandied about frequently in discussions over Denver’s cannabis system.

Over time, this morphed into a report that “80 percent of products tested” failed the city’s total yeast and old tests, when actually 80 percent of dispensaries recorded at least one failure out of the many products tested at each location.

“Based upon what [the DDPHE] have shared publicly, they sampled a total of 150 samples of three different product types,” Heather Krug, state marijuana laboratory sciences program manager at the Colorado Laboratory Services Division, told Analytical Cannabis.

“They did pre-rolls, shake and trim, and flower. They took two samples of each of those matrix types from 25 different dispensaries in the metro area, and then they had those tested for pesticide residues and total yeast and mold.”

“So that 80 percent number is not accurate of the actual overall study,” Krug explained. “The average failure rate for all three of those matrix types was about 30 percent.”

While the DDPHE has yet to release its final report, it has made public the fact that no products at any dispensary failed the pesticide testing, so it can be assumed that the failures seen in the 20 anonymous dispensaries were down to unacceptable levels of microbial contaminants.

Speaking more generally about cannabis testing in Colorado, Krug said that the state has seen an improvement in compliance when it comes to cannabis testing, but believes that microbial testing is possibly the area with the highest failure rate.

“In many ways, that makes a lot of sense because mold is this ubiquitous thing in the environment and is prone to grow in these types of environments where cannabis is grown,” she said.

We are having a lot of ongoing discussions surrounding microbial testing and the limits associated with testing just to ensure that we are still being protected with public health, but also realistic with what is likely to occur within the cannabis plant.”  

Cannabis testing in Denver

To better understand the way cannabis testing works in Denver, Analytical Cannabis also spoke with Richard Pruckler, a supervisor, and Tammy Jeronimus, a public health investigator with the DDPHE.

“Testing regulations are actually set by MED, which is the state Marijuana Enforcement Division. They are the ones that required testing. Our department, the Denver Department of Public Health Environment, doesn't usually get involved unless it's on a complaint basis,” explained Jeronimus.

“[The MED] have a requirement to test for pesticides and total yeast and mold count and potency, but not every harvest batch at every grow is required to test,” Jeronimus continued. “Some grows are what they call process validated, which means that for six weeks they've sent in samples from every harvest batch. And if every single one of those harvest batches passes for total yeast and molds and pesticides, then for the next year they only have to send in one harvest batch per month.”

When asked whether this system might have contributed to recent cannabis products recall actions taken by the city, Pruckler explained that, “the idea behind this process validation is for a cultivation facility to see that they have a good trend of passing test results. And then if so the business, in theory, then shouldn't need to test as frequently throughout the year because they have good practices in place.”

“There is another gap as well,” he continued, “these harvest batches are tested pretty much directly after being harvested. So, there might be some time in between [harvesting and retail sale] for the product to get contaminated with molds, or if it had lower passing levels that maybe those molds could grow before it gets to the retail level.”

So while the testing system is designed to reward good practices, its schedule still leaves some vulnerable periods, such as post-harvest processing, open to contamination. Indeed, only last month, a DDPHE investigation found unsafe levels of yeast and mold in products sold from three more Denver dispensaries.

But despite these incidences, Pruckler says that, as an early adopter of cannabis testing policies, Denver is still leading the field in yeast and mold detection. 

“Denver really likes to lead by example here, and I think that the state health departments do look to Denver a lot for guidance on this,” he told Analytical Cannabis. “We do have the ability, based on the way the city's rules are written, to conduct these kinds of investigations, where the state and federal level would not be able to do this. So we really feel like we're providing some valuable information to get the conversation started.”

Alexander Beadle

Science Writer

Alexander Beadle has been working as a freelance science writer since 2017 and has covered the cannabis industry for Analytical Cannabis since 2018. He has also written for our sister publication, Technology Networks, and the cannabis industry consultant firm Prohibition Partners, among others. Alexander holds a Master's in Materials Chemistry from the University of St. Andrews, where he won a Chemistry Purdie scholarship, and conducted research into zeolite crystal growth mechanisms and the action of single-molecule transistors.


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