Medical cannabis needs to be clean to protect patients from needless and occasionally dangerous exposure to pathogens, pesticides, and adulterants. The best way to avoid contaminated cannabis is to insist that it has been tested by a professional laboratory, qualified to detect microbiological and chemical contamination. Just because a lab can test for cannabinoid content does not always mean the laboratory has the equipment or skills needed to detect the necessary range of contaminants, as many laboratories do not. Patients need to quiz their medical cannabis suppliers about the testing regimen to which their cannabis products are subjected. Testing and quality control measures are crucial to patient safety. The vast majority of contaminated cannabis is the product of neglect during cultivation or processing, not malice. Powdery mildew and gray mold are the most frequently reported fungal diseases of cannabis plants. Indoor cultivation sites commonly develop powdery mildew problems unless strict preventive measures are followed and adhered to. Crops cultivated outdoors in cool to moderate climates with rain during flowering season are often plagued by gray mold. Gray mold loves big cannabis buds and can devastate a flowering crop in a matter of days. It typically appears as gray fuzz inside of cannabis buds, which can appear to have rotted the flower from the inside. Neither powdery mildew nor gray mold represent any health risk to the patient—just to the cannabis plant itself. A person could smoke a bowl of gray mold, and besides its unpleasant taste would suffer no ill effects. Powdery mildew is actually caused by two varieties of fungus, one that develops from the plant’s respiratory pores and another that grows upon the plant’s surfaces. Powdery mildew often infests indoor cultivation facilities, where the plants tend to be crowded and stressed. The mildew appears as bright white threads on the smaller “water leaves” that surround the bracts (the collective term for the sepals, the tiny leaves that envelop the flowers of cannabis). While nontoxic, powdery mildew is a sign of poor cultivation technique and infested medicine should always be rejected. Informal polling of several safety screening laboratories indicates that 1 to 2 percent of medical cannabis submitted by California dispensaries tests positive for pesticide residues. For an unregulated industry, as of late 2012, that is both encouraging and slightly ominous. It is heartening that pesticide residues appear to be scarce on California cannabis, but only a very few conscientious dispensaries even test for these residues. There is concern that the actual percentage of medications with unacceptable levels of pesticide residues might be higher. As medical cannabis laws are enacted and refined, then more pesticide screening will be mandated. Cultivator education and certification programs, such as Clean Green in California, can encourage and authenticate better practices among medical cannabis cultivators. And patients should demand clean and screened medicines. The pesticide residues that are detected on contaminated cannabis are rarely toxic to mammals, but they can be devastatingly toxic to honeybees or fish. Organic pesticides such as some pyrethrins can be used on medical cannabis plants, but only if the cultivator truly understands the amount of time required for the active pesticide to clear the plant. Often a positive pesticide test results from a cultivator using an otherwise safe substance too close to harvest. Plant growth regulators (PGRs) such as daminozide and paclobutrazol have been used on cannabis to force the plant to flower more quickly, and to produce bigger and tighter buds. These chemicals are banned in the U.S. for any plants intended for human consumption; daminozide is considered a probable carcinogen in humans by the U.S. government. A few unscrupulous manufacturers of cannabis fertilizers have slipped these PGRs into products without mentioning their inclusion on the products’ labels. Always be somewhat suspicious of huge, indoor cultivated cannabis buds since they are often the result of using these illegal “plant steroids.” If an indoor cultivated bud just looks too big to be normal, the flowers may actually be toxic. Plant growth regulators: A regular King Kush indoor-cultivated bud grows to around 1½in (4cm) while a King Kush bud grown indoors with the addition of PGRs could exceed 4in (10cm). Unlike powdery mildew or gray mold, the dangerous molds that can infest cannabis are difficult to detect with the naked eye. To find Aspergillus, Fusarium, or Penicillium molds requires laboratory tests. All of these dangerous molds are due to poor curing technique, not poor cultivation. These hazardous, pathogenic molds attack wet, freshly harvested cannabis. They are called opportunistic fungi because they attack rotting plant material. Specifically, they infest cannabis that stays too wet for too long during the curing process. These pathogenic fungi typically attack cannabis that is between 15 and 22 percent water weight. By contrast, correctly cured cannabis typically has between 8 and 12 percent water weight. The key to avoiding infestation by these storage molds is to dry harvested cannabis quickly enough so that it spends as little time as possible in the moisture “danger zone”—the time it takes for the plant to reach 15 percent water content. The biggest threat posed by pathogenic molds is aflatoxin, a poison produced by certain varieties of Aspergillus mold. Aflatoxins are not only toxic, but very carcinogenic. They are very rare on cannabis and can easily be prevented by careful drying and storage. Dangerous bacteria such as staphylococcus and E. coli can also occasionally be found on cannabis. These bacteria end up on cannabis from human contact. Simple but thorough hand washing is all that is required to keep these dangerous bacteria in check. Anaerobic bacteria are very rare on cannabis, as the plant is rarely exposed to the low-oxygen environments in which these bacteria can thrive. There are exceptions, however. Olive oil that is infused with whole, raw cannabis buds may provide an anaerobic environment that could result in botulism poisoning.
CANNABIS CONTAMINANTS, PATHOGENS, PESTICIDES, AND ADULTERANTS
Powdery Mildew and Gray Mold
Pesticides
Synthetic Plant Growth Regulators
Pathogenic Molds and Bacteria
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