Cannabis is a plant, and plants are natural playgrounds for all kinds of unwanted insects, fungi, and moulds. It's no surprise, then, that some commercial cannabis growers use pesticides to keep their crops healthy, just like farmers use pesticides to protect their tomatoes or lettuce.
Unlike tomatoes or lettuce, though, cannabis isn't usually eaten raw — it's mostly inhaled via smoking or vaporizing.
"Nobody has any idea of what happens when you combust and then inhale pesticides," explained John Coleman, an organic chemist and chief operating officer of cannabis testing firm Anandia Labs in Vancouver.
"There's just no data. So in the absence of data, the safety play is, if you're using a pesticide, you shouldn't be smoking the product."
A handful of pesticides, though, have been approved for use on cannabis crops by Health Canada. The federal department, which regulates both legal cannabis production and pesticide use in Canada, maintains a short list that currently includes just 21 approved pesticides for commercial cannabis production.
What do the approved pesticides have in common?
All 21 pesticidal products approved by Health Canada for use on cannabis don't require testing for leftover residues because they are "naturally occurring, with a low toxicity, and are not anticipated to create health risks with proper use," a spokesman said.Advertisement
Each one was approved for use on cannabis following a departmental review of information, including "manufacturer-supplied scientific studies and information from published literature."
The pesticides on Health Canada's approved list can be described as "biological pesticides," "biologically based" or naturally occurring inorganic chemicals, according to Keith Solomon, a professor emeritus of environmental toxicology at the University of Guelph.
"Basically, they're seen to be safe because they occur in nature, and people would probably be exposed to them and in a general sense, they're not dangerous to humans," he said.
"Most of these things, by the time you consume the crop, whether it's an apple or cannabis, the amount present on the apple or the cannabis is going to be so small it's really not a concern" - environmental toxicologist Keith Solomon
"When you say the word 'pesticide,' people always think of this dangerous chemical," said Emily Kirkham, an analytical chemist and the founder of consulting firm National Laboratory Services.
"These things are mineral oils and soaps, and biological agents, bugs to kill other bugs. The harm that they can cause is extremely low."
The Health Canada-approved product Actinovate, for example, uses the bacteria Streptomyces lydicus to attack fungus. The insecticide Bio-Ceres uses the naturally insecticidal fungus Beauveria bassiana to kill cannabis-munching bugs like aphids and thrips. The active ingredient in Vegol Crop Oil, used to control insects, mites and fungus, is canola oil. And the active ingredients in Lacto-San are lactic acid and citric acid, both produced naturally by fermentation.
Other products approved for use on cannabis include foliar soaps, used to kill a variety of pests.
"It would be equivalent to, you take your dish out of the soapy water and put it on the drying rack, and you then eat something off that dish," said environmental toxicologist Keith Solomon. "It's really very similar to that in terms of exposure."
"Most of these things, by the time you consume the crop, whether it's an apple or cannabis, the amount present on the apple or the cannabis is going to be so small it's really not a concern."
Even if those biological pesticides are harmless to humans, said Solomon, their chemical names or trade names can sound scary to some people — a phenomenon known as chemophobia.
"Calling a pesticide 'Doktor Doom Formula 420' — I certainly wouldn't spray that in my mouth," joked Solomon. (For reference, the active ingredient in that particular product — used to kill aphids and mites, and to suppress powdery mildew — is canola oil.)
"The names are designed to be attractive to the people who use these things, which is basically to kill pests. So sometimes they have names that are a little bit in left field."
Use of banned synthetic pesticides on cannabis
All kinds of synthetic pesticides have been approved for use on the food we eat every day, following what Solomon calls "a very rigorous registration process."
Generally speaking, food producers have to show that any pesticide residues on their finished product are well below regulatory threshold levels.
"That's what's missing from cannabis," Solomon said.
"There are no tests or registration procedures that have been gone through to allow approval of what I would call synthetic pesticides on cannabis, and all of those would require testing and all sorts of things like that before they would be allowed," he said. "And I'd also want to look and see how much residue is present on the cannabis at the time of consumption."
Some legal cannabis producers in Canada have had to recall their products after residues from synthetic pesticides were found on their crops.
In late 2016, the prohibited-for-cannabis pesticide myclobutanil was found in marijuana being sold by licensed producer Mettrum, which is now owned by Canopy Growth Corp. That discovery, which was revealed by the Globe and Mail before Health Canada informed the public, was followed by voluntary pesticide-related recalls at licensed cannabis producers Organigram and Aurora (which had resold Organigram's product to its clients).
Consumers of the Organigram cannabis told the Globe they suffered adverse symptoms including rashes, aches, nausea, burning lungs, abdominal pain and dramatic weight loss.
In March 2017, Health Canada inspectors started making surprise inspections of legal cannabis farms and testing random samples for any sign of banned pesticides. Those inspections and tests have resulted in three product recalls for "low levels of pesticides not authorized for use on cannabis," a Health Canada spokeswoman said.
On top of that, the cannabis producers who got caught using banned pesticides must now test all their cannabis for residue from those pesticides and share those test results with the regulator before the cannabis can be sold.
"A number of licensed producers have opted to test their products for the presence of unauthorized pesticides and some are disclosing those results publicly," said the spokeswoman.
The future of pesticide regulation in Canadian cannabis
Health Canada is developing a new plan for regulating pesticides in cannabis in the future. In a December 2017 consultation document, the department proposed mandatory, third-party laboratory testing for all commercially produced marijuana.
Those labs will test the cannabis against a new list of 95 banned pesticides, a list that will be "reviewed by Health Canada and amended at least once per year." The list sets exact limits for the amount of banned pesticide active ingredients contained in cannabis, measured in parts per million.
"The products must be stored and cannot, under any circumstances, be sold or provided to another party before receipt of the results," says the document.
Health Canada chose the 95 pesticides on its banned list "from a broader list of currently or historically existing pest-control products based on an assessment of their probability of usage during production of cannabis." The list includes banned pesticides that have been found in Canadian cannabis and legal cannabis produced in the U.S.
If a licensed producer of cannabis fails a pesticide residue test, they'll have to quarantine the product in question, "begin a root cause analysis to identify the source of contamination," and fix it. Ultimately, the document says, any cannabis with pesticide levels beyond Health Canada's thresholds can't be sold to consumers.
Government-mandated, third-party testing of cannabis is a huge business opportunity for Canada's cannabis-testing laboratories. But preparing for the new pesticide testing regime will take lots of work, said Emily Kirkham of National Laboratory Services.
"In analytical chemistry, it's not like what you see on CSI," she said. "You can't just say, 'OK, I'm going to give you this cannabis, tell me all the pesticides that are in it.' It doesn't work that way."
"It takes time to develop a comprehensive pesticide (testing) method, and to ensure that you can reach the requirements, meet the detection limits. The labs didn't even know if this was possible without actually trying it."
Preparing to test for the banned compounds on Health Canada's list is "a bit of a herculean effort," said Anandia's Coleman. Right now, Anandia can test for a proprietary list of 51 undesirable pesticides. With new, cutting edge equipment like a gas chromatograph with a triple-quadrupole mass spectrometer, the company is refining its methodology and expanding the list to encompass all the compounds on Health Canada's list.
Coleman expects other major cannabis testing laboratories in Canada to have that testing capability "in fairly short order, if they haven't got it already."
That kind of third-party testing for pesticides will be critical for Canada's cannabis industry, he said.
Although major pharmaceutical companies often do quality-assurance testing in their own in-house laboratories, Coleman said that process is subject to "an incredible amount of oversight" by government regulators.
"With a nascent industry like the cannabis industry, that infrastructure really isn't in play yet," he said.
"So having third-party, independent labs who have no vested interest in the product do the testing, I think is incredibly important."