The first results from Health Canada’s Cannabis Data Gathering Program found that nearly half of the 50 samples of legal cannabis tested had THC levels under 80% of their label claim.

Although none of the illegal samples of dried flower tested included labelled THC levels, the results showed THC levels ranging from less than 10% to more than 25%. 

Health Canada first announced it would launch a new data-gathering program for cannabis markets in Canada in 2023, looking at both legal and illegal products currently on the market. 

The project collected 100 samples of dried cannabis flower, 50 from the legal market and 50 from the illegal market. 

In addition to testing for THC, samples were also analyzed for heavy metals, mycotoxins, pesticides, and microbial contaminants. While there were some examples of pesticides, mycotoxins and other forms of microbial contamination in some legal samples, they paled in comparison to what was found in the samples of illegal cannabis. 

Heavy metals, however, were present in both sample streams and, at times, more common in legal products. 

Heavy metals

Metals like copper, molybdenum, and nickel were found in a large proportion of both legal and illegal samples, some in concentrations that exceeded Health Canada’s allowable limits. Heavy metals like arsenic, cadmium, lead and mercury were more common in samples of illegal cannabis, but only one illegal sample had arsenic levels above the United States Pharmacopeia (USP) tolerance limit set for inhalation. 

Arsenic was present in 44% of illegal products and 18% of legal products. Copper was detected in all 100 samples, with 100% of legal products and 98% of illegal products exceeding the USP limit (3.0 µg/g). 

Molybdenum, a trace mineral, was found in almost all samples, with 74% of legal products exceeding the USP limit (1.0 µg/g) compared to just 16% of illegal samples. 

Nickel was present in 78% of illegal samples and 72% of legal samples. In total, two samples exceeded the USP limit (0.6 µg/g), namely one legal product (2%) and one illegal product (2%). The highest level observed in the legal products (4.69 µg/g) was more than five times higher than in the illegal products (0.91 µg/g).

Mycotoxins

While six samples of illegal cannabis tested positive for mycotoxins like ochratoxin A—produced by certain moulds, such as Aspergillus and Penicillium—or deoxynivalenol—associated with vomiting, diarrhea, and gastrointestinal inflammation in humans and animals—none of the six mycotoxins tested were found in legal samples.  

Pesticides

Almost all illegal samples (94%) had multiple pesticides in their testing results, averaging 3.4 pesticides per sample. A total of 24 different pesticides were identified, some at very high levels. The most commonly found pesticides in illegal samples were myclobutanil and paclobutrazol.

Out of the over 300 pesticide residues tested, only two samples of legal products showed trace levels (0.01 parts per million [ppm]) of pesticides.

Microbials

While a few legal samples were found to test positive for microbial contaminants, illegal cannabis products were found to have significantly higher levels of microbial contamination, often exceeding European Pharmacopeia (Ph. Eur.) limits. 

These included pathogens such as Enterobacter cloacae and bacteria associated with respiratory infections such as Klebsiella spp. and Pseudomonas aeruginosa.

Ten legal samples were found to contain microbial contaminants above the European Pharmacopeia (Ph. Eur.) limits, leading to one product recall. Over half (55%) of the 49 illegal samples tested for microbials were found to be above the total aerobic microbial count (TAMC) limit, with levels reaching up to 9 million colony-forming units (CFU)/g, compared to only 6% of legal products. 

Microbial contaminants like  E. coli and Salmonella spp. were only found in illegal products, and Aspergillus spp. appeared twice as often in illegal samples than in legal products (14 legal and 37 illegal samples).

Sourcing samples

The fifty samples of legal cannabis products were purchased from five retailers across Canada, both online and brick-and-mortar stores. The samples, which had labelled THC levels up to around 25%, came from 50 different licensed producers. Sampling was done between September and December 2023. Product age is not considered a likely reason for these amounts of deviation from labelled THC due to the low presence of CBN, a marker of THC degradation.

The 50 illegal samples came from law enforcement seizures, mainly in BC and Ontario. 

Almost half of the illegal samples showed THC levels above 17.5%, with a few reaching around 25-27.5%. Another 21 had THC levels between 12.5% and 17.4%, while six were below 12.5% THC. 

Health Canada plans to continue the testing program in the future. 

Several provinces have also released testing results of illicit products shared through law enforcement actions. In 2022, Ontario shared a study showing that illicit edibles have significantly less THC than advertised and high levels of pesticides. New Brunswick and British Columbia have also released similar testing results from illicit products.

Concerns around inflated THC numbers in the legal market have prompted many in the industry, from labs to producers, consumers, and retailers, to call on the federal and even provincial governments to do more to ensure that THC levels reported on labels are accurate. 

The Ontario Cannabis Store says they have seen a decline in the number of high-THC products in its catalogue after launching an internal testing program in 2024.

In 2023, Rob O’Brien, the CEO and CSO of Supra Research and Development in Kelowna, BC, shared his independent testing results online from 46 different cannabis products he purchased from BC Cannabis Stores.

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