There is no known lethal dose of marijuana, which means it can’t kill you. But the stuff that gets sprayed or grows organically on pot buds can.
Studies show that marijuana sampled across the US carries unsafe levels of pesticides, mold, fungi, and bacteria. Earlier this year, Colorado recalled hundreds of batches that tested positive for banned pesticides.
It’s unclear how much cannabis, whether purchased legally in a dispensary or bought from a college roommate’s cousin’s friend, is at risk. But as the industry goes mainstream, experts suggest it’s time legal weed gets quality assurance.
Educating consumers on what they’re smoking might be the first step, according to scientists at Steep Hill Labs, a leading cannabis science and technology firm in Berkeley, California.
In 2016, Reggie Gaudino, vice president of scientific operations at Steep Hill, set out on a scientific experiment. He visited three brick-and-mortar dispensaries in the Bay Area and bought at least five samples of cannabis flower from each.
In order to decide which strains to buy, he asked cashiers, called “budtenders,” for their recommendations. He also chose the strains with the highest percentage of tetrahydrocannabinol, or THC, the main psychoactive ingredient in marijuana. Many patients choose that option from the menu because they believe it will get them the most high, or give them “the most bang for their buck,” Gaudino explains.
It’s unclear if the dispensaries he visited test their products for contaminants at third-party labs — a practice that’s becoming more common as states with newly legalized cannabis roll out regulations.
When Gaudino took the samples back to the lab, he found that 70% of the samples tested positive for pesticide residues. One-third of samples would have failed pesticide regulations in the state of Oregon, which has the most sophisticated system for pesticide-testing of the seven states with fully legalized marijuana.
Fifty percent of the samples that tested positive for pesticides also contained Myclobutanil, a fungicide treatment commonly used on California grapes, almonds, and strawberries. When digested, it’s harmless. But when heated, the chemical turns into hydrogen cyanide, a gas that interferes with the body’s ability to use oxygen normally.
The central nervous system, cardiovascular system, and pulmonary system (lungs) start to fail when exposed to high concentration of the gas.
The news isn’t quite as alarming as it sounds. Donald Land, chief scientific consultant at Steep Hill, tells Business Insider that most people would not be susceptible to falling ill after inhaling a few spores.
However, someone whose immune system is weakened — like a cancer patient undergoing chemotherapy or a person infected with HIV — is much more vulnerable to infection upon inhaling contaminated cannabis. Basically, the people who stand to benefit the most from medical marijuana are also the most vulnerable.
The results of Gaudino’s study have yet to be published in a peer-reviewed journal, though Gaudino tells us a white paper is in the works. The lab plans to test an array of other marijuana products, like concentrates and oil cartridges for vaporizer pens, before publishing.
Land and Gaudino explain that, for the most part, the industry is doing the best it can to provide safe pot.
There is no framework on the federal level that dictates how cannabis should be tested or what threshold constitute a failing grade. Most growers and dispensaries in states with legalized marijuana have to hold themselves accountable for verifying the safety of their product.
Some pay third-party labs like Steep Hill to analyze their product for pesticides and contaminants, but most only want to know the THC content of a given strain, Land says. The more potent the weed, the more they can charge for it.
Fewer than 20 states offer some form of testing, according to estimate provided by Land. The states that offer the most widely available marijuana, including California, Colorado, Oregon, and Washington, have testing facilities — but they don’t all require testing, and regulations can vary on a local level.
More research is needed to understand the health concerns associated with cannabis. Marijuana remains illegal under federal law, making it difficult for scientists to acquire the funding and samples needed for study.
In the meantime, Land suggests marijuana patients and recreational users take responsibility for their health by asking their budtender to see a lab report on the strain they wish to buy. They can compare the results with Oregon’s publicly available threshold levels for safe cannabis.
Even if you can’t make out what the report means, the dispensary’s ability to provide documentation is “absolutely better than nothing,” Land says.