Should dispensaries and licensed producers be regulated in a manner similar to the Canadian Food Inspection Agency’s oversight of food safety?

The U.S.–based Cannabis Safety Institute published a paper in 2015 noting that “pesticide use is widespread” and "entirely unregulated" in the marijuana industry. It recommended that laboratories “must be supplied with clear instructions” on which ones to test for.

The institute also pointed out that heavy metals, including arsenic, can be found in soils and in poorly manufactured herbicides—and they can be absorbed by cannabis plants.

But Vancouver marijuana-industry advocate Dana Larsen told the Georgia Straight by phone that dispensaries are often hamstrung if they want to talk about the purity of their products.

That's because Health Canada prohibits licensed labs from testing "illegal" marijuana supplied to them by retail dispensaries.

“So if I send them a bunch of buds from my dispensary and say ‘test this,’ they won’t do it,” Larsen stated. “Because of that, I can’t put on my website that ‘these buds were tested by so-and-so.’ ”

He said that at his Medicinal Cannabis Dispensary, staff examines buds or hash products under a microscope. And this makes it possible to spot mould or mildew.

"If it passes the microscope test, then we do a taste test," Larsen stated. "We smoke a bit of it and see how it burns and how it goes on your tongue. If it passes that, we talk to the grower for a while about their methods and techniques."

There are also licensed labs that will test marijuana for someone who has a prescription from a doctor, even if it's "illegal" marijuana bought at a dispensary.

One cannabis company that takes these issues seriously is Erbachay Health Centers, which has a retail outlet at 8425 Granville Street. It turns away many growers because of quality concerns.

“We test against any pesticide presence, mold (white mildew, bud rot, black mold), any insects such as mites or residue of them, foreign materials or any type of general contamination,” it states on its website.

Erbachay also tests supplies for higher-than-average use of fertilizer.

This begins with a visual inspection using a digital scope that amplifies the view 1,000 times, which offers a glimpse into residuals that might be resting on the plant structure. This can also reveal if there is an excess of nutrients locked into the plant, which is a sign of excessive fertilizer use.

The company states that there are also smoke tests not only for quality but also for taste, which can be another indication of excess nutrients.

Long-term exposure to a group of moulds known as aspergillus in the home or in marijuana has been linked to chronic pulmonary aspergillosis. It results when a fungal ball of spores forms in the lung cavity, according to the website, and this “fungus secretes toxic products” that cause illness.

“Coughing of blood (haemoptysis) can occur in up to 50-80% of affected people,” the website states,

Larsen said that it's not always easy for dispensaries to screen for everything in advance of purchasing cannabis from a grower. That's because only a portion of the supply can be examined under a microscope.

"It's a challenge because it's an organic product," he stated. "You might buy 10 pounds and in one of the bags in the corner, there's a little bit of mould. That's something you have to deal with."

He thinks that if Health Canada won't permit independent testing, the best solution would be to create a secret-shopper or anonymous-buying program.

Under this system, someone would buy buds from different dispensaries and have them tested independently, with the results released in a third-party report.