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Michigan Regulator Pauses Cannabis Mold Test

By Leo Bear-McGuinness

, Alexander Beadle

Published: Feb 12, 2021    Last Updated: Feb 12, 2021
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Cannabis sold in Michigan may be contaminated with unknown levels of mold and yeast, a group of cannabis testing labs has warned.

The claim follows concerns over the suitability of a specific testing methodology, a quantitative use of the polymerase chain reaction (qPCR), to measure yeast and mold contamination in cannabis samples. According to recent tests performed by the Michigan-based analysts, the qPCR method returns too many false negative results to be reliable.

As a consequence, they say, countless moldy cannabis products could have passed through state labs undetected.

Mold in Michigan

Concerns about Michigan’s moldy cannabis were recently raised by Ben Rosman, CEO of the Ann Arbor-based PSI Labs and founder of the Michigan Coalition of Independent Cannabis Testing Laboratories.

As reported by the Detroit Free Press on January 27, Rosman claimed that his team at PSI had found traces of mold on cannabis products that had gone undetected by the qPCR method.

Speaking to Analytical Cannabis, Rosman elaborated on his reasoning.

“I think the molecular techniques are the gold standard for detection,” he said. “But when it comes to quantification, that’s just where the science isn’t there yet. In our experience, a lot of the issues with the test we found were having to do with false negatives – essentially, non-detection of mold that other techniques were able to pick up in large quantities.”

“If an invalid test has been used to test a lot of product that’s out there, I think it naturally leads to the question, ‘do we know the mold status of any product tested by this technique that apparently has issues quantitating the mold?’”

Within cannabis testing labs, there are currently two general avenues for the quantification of total yeast and mold on a sample: total yeast and mold count (TYMC) methods and a molecular method such as qPCR.

The first test involves culturing any bacteria and fungi from cannabis samples in petri dishes, which can then be examined by a trained microbiologist or an automated system. The qPCR method is a very different approach, though; it amplifies identifying segments of DNA in the sample that are characteristic of known microbiological contaminants and uses this information to quantify any contamination present.

Debate over which method is superior for cannabis testing has been going on for years within the industry. Labs using culture-based TYMCs point to the technique’s long-standing and effective use in the food and drink industry, while those using the qPCR technique argue that it offers a better analysis of the few microbes that do not culture well on all types of growth media, including Aspergillus mold.

Now, following eight months of research, Rosman and his team at PSI Labs have added their support to the former camp, as they found the qPCR method lacking.

“This false negative you’re getting with PCR testing for total yeast and mold, it wasn’t able to quantify yeast and mold at the levels that other techniques can,” Lev Spivak-Birndorf, PhD, co-founder and chief science officer of PSI Labs, told Analytical Cannabis. “That’s been our experience.”

Any cannabis contamination that slips under the radar during testing is a critical issue. In Michigan alone, nearly 250,000 patients qualify for medical cannabis. Many of these patients will live with weakened immune systems, so exposure to microbial contaminants such as Aspergillus mold via their cannabis could result in serious health complications.

The regulator’s response

The PSI team’s findings have certainly made a splash in the Michigan cannabis lab sector. Responding to the Detroit Free Press, the Michigan Cannabis Industry Association (MCIA) said it disagreed with the lab’s findings. As the lab tests were not done with regulatory oversight, the association said, they could be flawed.

However, on January 22, the Michigan Marijuana Regulatory Agency (MRA) issued a temporary veto on the qPCR method for the sole quantification of total yeast and mold, prompted by the preliminary results of an emergency study from the respected testing body AOAC International. The method can still be used, though, if combined with another mode of testing.

So, effective from February 8, labs in Michigan using a qPCR method for TYMCs have two options: 

  • Switch to either a non-molecular automated system method or a plating-based method.
  • Or pair its qPCR method with either duplicate plating or non-molecular automated system analysis. 

All non-molecular automated systems methods and plating-based methods used for TYMCs must also include a 72-hour incubation period, according to the MRA. 

When reached for comment, a representative of the MRA told Analytical Cannabis that “the MRA has not disallowed the use of qPCR,” but rather “has requested a pause in the use of this method until the methodology produces data that aligns with the required validation standards.” This decision may be reviewed as more information is gleaned from the validation study or from future work.

In its initial response, the MCIA said that the suspension of the qPCR method was done “out of an abundance of caution” from the MRA.

PSI Labs, on the other hand, has praised the MRA for its response, but said that more stringent cannabis testing regulations are not necessarily needed.

“This is just a great example of the efforts [the MRA] are making to gather the data, listen to the science, and make an informed decision that most appropriately serves public health and safety,” Lev Spivak-Birndorf told Analytical Cannabis

“[The] MRA didn’t come to this decision lightly. There were several concerns [from] safety compliance facilities, who sent independent data to the MRA. MRA took it upon themselves to conduct audits through the state seed-to-sale tracking system, and they ultimately relied upon the AOAC preliminary results of this study.”

“For us, the goal is to really get this conversation going and get more and more people talking about this stuff so that we can all come to a consensus on what is the best practice.”

Representatives from the MRA have emphasized that there is currently no product recall in place related to products that underwent qPCR testing. Consumers who experience adverse reactions to any cannabis products for sale in the state, they say, should report the product to the relevant retail location or the MRA. 

Where does yeast and mold testing go from here?

The Michigan case isn’t the first time cannabis analysts have lobbied for the wider adoption of appropriate TYMC tests.

In California, where TYMCs are not required by state testing regulations, cannabis scientists have repeatedly warned the state regulator about the potential for yeast and mold to slip through the testing labs and onto dispensary shelves.

“At PacLab Analytics, we have seen cannabis flowers pass BCC’s [the Bureau of Cannabis Control’s] current microbial impurities test while being visibly covered with mold and fungi,” Dr Gary Ward, chief compliance officer at PacLab Analytics , told Analytical Cannabis in 2019. “This flower would not pass microbial testing in other states.” 

Unlike Rosman and the rest of the PSI team in Michigan, however, Ward believed the qPCR method was the more promising test for consumer safety.

“[The BCC decided that] the TYMC test was an expensive outdated method, but that choice was based on the use of antiquated plate methodology and not with knowledge about new qPCR techniques, which are cheap and fast and would protect against hundreds of harmful organisms,” Ward said at the time.

With the AOAC’s investigation into qPCR’s suitability still ongoing, the whole cannabis lab sector will have to wait a bit longer for this verdict on mold testing. The final results are expected to be announced in April 2021.

This article was updated on February 12 to include further testing regulations outlined by the MRA.


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