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It was a cornerstone of the pitch for legalizing marijuana in Massachusetts: Mandated laboratory testing would ensure that cannabis products sold in regulated stores are free of pesticides, mold, and other contaminants.
Behind the scenes, however, a bitter scientific and business feud has split into two camps the state’s four marijuana testing labs, which currently serve medical dispensaries and will soon join the lucrative recreational market.
Each camp says that the other’s methods can’t be trusted. And both complain that cannabis companies, which under the state’s medical marijuana regulations are required to contract with private labs for testing, routinely “shop” for favorable results by sending samples to different labs.
The state Department of Public Health, which oversees medical marijuana, has declined to referee the dispute or update its testing regime, despite warnings from the labs that a lack of standards and holes in protocols are undermining confidence in the system. And now, the state Cannabis Control Commission is poised to adopt, nearly wholesale, the same rules for testing recreational cannabis, too.
“It’s hard to walk into a dispensary right now and really trust that the products are safe,” said Kamani Jefferson, president of the Massachusetts Recreational Consumer Council, which represents marijuana consumers. “They can point to the label and say it’s been tested, but until the state steps in and sets some standards, they can’t really say it with a straight face.”
Setting rules on the quality of marijuana is inherently challenging. While the plant has been the subject of some medical research, decades of prohibition mean there are no established standards for how much and what kinds of contamination might be considered dangerous. Some states have looked to standards for produce, but those are of limited value, since marijuana is more frequently smoked or vaporized than eaten.
In Massachusetts, the Department of Public Health set relatively tight limits for medical marijuana on microbial contamination from mold, yeast, and bacteria, amid concerns that patients with compromised immune systems could be susceptible to infection from tainted cannabis products.
The debate between the labs in the state stems from differences in how they test marijuana for microbes.
Two of the labs — Proverde Laboratories in Milford and MCR Labs in Framingham — use a traditional “plating” technique, in which samples of cannabis are placed in a petri dish containing a gel-like medium that encourages the growth of microbes. After an incubation period, technicians count how many visible spots, or “colonies,” of mold or other contaminants have grown in the gel, and use a standard formula to calculate whether that means the marijuana is unacceptably contaminated according to health department limits.
Two newer labs — CDX Analytics in Salem and EVIO Labs in Southbridge — employ a faster, DNA-based technique called qPCR. Using expensive mass spectrometers and chromatography machines, the companies say, they can precisely measure microbial contamination by detecting how many times microbes’ genetic codes divide.
Proponents say the DNA technique detects exactly what’s in the marijuana at the moment of testing, while the various gel media used in plating could stifle growth of certain microbes and boost others, distorting the relative presence of different contaminants in the sample being tested.
“With a DNA-based method, you get a real-time survey of what’s in the cannabis — it’s representative of what’s actually being sold on the shelves,” said Brianna Cassidy, CDX’s chief scientist. “With the culture-based method, you’re only counting whatever happens to grow in that environment you’ve created on the plate.”
Worse, Cassidy added, the false positives produced by plating are encouraging marijuana growers to use fungicides and other chemicals to remedy nonexistent contamination.
But Chris Hudalla, Proverde’s chief scientist, said plating is a proven technique long used to test food for safety. He argued that the DNA labs could miss contamination by some microbes by testing only for certain species and also complained that the formula used by those labs to translate their results into the state’s standard unit of measurement — colony forming units, or CFUs — is highly flawed guesswork.
“Plating has been tested and accepted by every food manufacturer and scientific organization,” Hudalla said. “The method they’re using is accepted by nobody.”
Hudalla noted that marijuana regulators in Nevada have banned labs there from using qPCR, after concluding the method failed to consistently detect samples with known contamination.
Proverde says it flags more than 30 percent of samples from medical marijuana companies for microbial contamination in excess of state limits. CDX says it fails roughly 15 percent.
Despite that discrepancy, the health department has allowed the two techniques to continue side by side.
“While different testing methods may produce variation in test results, this issue is not unique to medical marijuana and aligns with safety testing in other food and drug industries across the country,” a health department spokeswoman said in a statement.
Hudalla, however, complained that marijuana growers — who are allowed to contract with more than one lab — are exploiting the variation in results, costing his plating lab business.
“The industry knows they have a higher passing rate with qPCR, and they don’t care whether it’s right or wrong,” he said. “They continue to release contaminated products to consumers, and we’ve lost significant revenues to them because DPH and the CCC permit them to use this technology.”
Added Proverde owner Dorian Des Lauriers: “One dispensary owner told us that if we didn’t give him a clean certification, he’d never test with us again, and he implied he’d ruin our reputation. . . . We’ve been blackballed.”
CDX, for its part, says some of its competitors are fudging marijuana potency tests by first drying out samples in an oven. Removing moisture would reduce the weight of the cannabis being tested, making it seem like the concentration of THC — the primary psychoactive compound in marijuana — was higher.
“If we did potency tests like that, I’d have 24 [dispensaries] as customers instead of six,” said Eamon Travers, CDX’s vice president of business development.
Both groups of labs, however, agree on two things: The state needs to revamp its system for collecting marijuana samples for testing and also step up its tests for pesticides.
Under its current rules, the health department allows marijuana companies to pick their own samples. Other states, including Maryland and California, require independent third parties to conduct sampling, so cultivators cannot submit buds only from selected “clean” plants.
But Massachusetts health officials, citing varying production schedules, crop sizes, product types, and lab methods, maintain it makes sense to let licensed marijuana growers pick their own samples and batch sizes within health department guidelines.
A health department spokeswoman said every medical dispensary must develop “an individualized sampling plan that adheres to national and international standards.” She also said growers are subject to routine inspections, including of their sampling protocols.
The labs also agree that the current system for testing pesticides is inadequate, as it only requires tests for nine common chemicals.
“There are hundreds of commercially available pesticides,” Proverde and MCR complained in a co-signed letter to marijuana regulators earlier this year. “The current protocol is a short list of pesticides to avoid, leaving everything else as fair game.”
While health department regulations encourage labs to test for as many pesticides as possible, dispensaries have little incentive to pay for tests beyond those required, the labs wrote.
Hudalla said the Massachusetts Department of Agricultural Resources, which regulates pesticide use, recently asked Proverde for results showing pesticides in medical marijuana.
A spokeswoman for the department said the agency does not comment on pesticides investigations.
The cannabis commission, which will absorb the medical marijuana program later this year, declined to comment.
The agency has created a category of license for “standards” labs that would study the best ways to test cannabis. So far, no companies have applied.Dan Adams can be reached at firstname.lastname@example.org. Follow him on Twitter @Dan_Adams86.