Cannabis Contamination-What You Need to Know

Cannabis Contamination-What You Need to Know 

All usable cannabis needs to be clean in order to protect users from harmful and dangerous exposure to pesticides, pathogens, and adulterants. In order to avoid contaminated cannabis, as a user, you need to insist that the cannabis that you may potential purchase has been thoroughly and properly tested by a professional laboratory, which is qualified to detect microbiological and chemical contamination. 

If you are purchasing cannabis from a company and are told that the lab, they use tests for cannabinoid content doesn’t mean the laboratory has the equipment or capabilities required to detect the necessary range of contaminants, as many laboratories do not. It is important to question cannabis suppliers about the testing protocols to which their cannabis products are subjected too. Testing and quality control measures are crucial to cannabis user’s safety and health. 

Cannabis Powdery Mildew and Mold 

So, what contaminants should you be most concerned about when it comes to your cannabis? Powdery mildew and gray mold are the most common and frequently reported fungal diseases affecting cannabis plants. Powdery mildew is commonly seen on cannabis plants grown indoors because strict preventative measures were not followed and adhered too. Crops grown outdoors in cool to moderate climates with rain during the flowering season are often plagued by gray mold.   

Cannabis Gray Mold 

Big cannabis buds are a prime target for gray mold.  Gray mold can devastate a flowering cannabis crop within a matter of days.  

Gray mold typically appears as a gray fuzz inside of cannabis buds, which often appear to have rotted the cannabis flower from the inside. Neither gray mold or powdery mildew present any health risk to the user, it only negatively affects the cannabis plant itself. Besides an unpleasant taste, a cannabis user smoking cannabis flower contaminated with gray mold would not suffer any ill side effects

Cannabis Powdery Mildew 

Powdery mildew is caused by two varieties of fungus. One type of fungus actually develops from the plant’s respiratory pores. The other type of fungus grows on the cannabis plant’s surfaces. Powdery mildew is often a culprit with indoor cultivation, where the plants tend to be stressed from being overcrowded. Powdery mildew is a sign of poor cultivation techniques. 

Powdery mildew looks like bright white threads on the smaller “water leaves” that surround the bracts (which is the collective term for the sepals, the tiny leaves that envelop the flowers of cannabis). Even if cannabis plants are affected by powdery mildew, infested cannabis should always be rejected. 

Cannabis Pesticides 

The main concerns regarding pesticides is that the actual percentage of cannabis with unacceptable levels of pesticide residues might be higher. As cannabis laws are enacted and refined, then more pesticide screening should be mandated. Cultivator education and certification programs can help encourage and authenticate better practices among cannabis cultivators. As a cannabis user, you should ALWAYS demand clean and screened cannabis.  

Organic pesticides such as pyrethrins can be used on cannabis plants, but it should only be used if the cannabis cultivator truly understands the required amount of time for the active pesticide to completely clear the cannabis plant. Often when a cannabis cultivator who used an Organic pesticide receives positive test results, it usually indicates that they used the Organic pesticide too close to harvest. 

Cannabis Synthetic Plant Growth Regulators 

Synthetic plant growth regulators or PGR’s (such as daminozide and paclobutrazol) are used on cannabis plants to force the plant to flower more quickly, therefore resulting in bigger and tighter buds. They particular types of chemicals are banned from the United States for use on any plants intended for human consumption. Daminozide is considered by the U.S. government as a probably carcinogen in humans. Some corrupt manufacturers of cannabis fertilizers have secretly added these PGR’s into their products without mentioning their inclusion on the products’ labels. 

Always be aware and cautious when you encounter large, indoor cultivated cannabis buds because they are often the result of using the illegal chemicals (often referred to as “plant steroids”). If a bud grown indoors looks too big to be normal, it may actually be toxic. 

Take for example a regular King Kush indoor cultivated bud. It can grow to around 1.5 inches (4 cm), while a King Kush bud grown indoors with PGR’s added-could exceed 4 inches (10 cm). 

Cannabis Pathogenic Molds and Bacteria 

In contrast to gray mold and powdery mildew-there are molds that are dangerous and can infest cannabis. These dangerous types of molds difficult to see with the naked eye. These dangerous molds include Aspergillus, Fusarium, or Penicillium and requires laboratory testing to detect them. These dangerous molds arise from poor curing techniques, not poor cultivation. These hazardous molds love wet, freshly harvested cannabis. These dangerous molds are called opportunistic fungi because they attack rotting plant material. They specifically infest cannabis that remains too wet for too long during the curing process. These pathogenic fungi tend to attack cannabis that is between 15 and 22 percent water weight. The key to preventing these types of molds is drying harvested cannabis as quickly as possible so that the cannabis spends as little time as possible in the moisture “danger zone”. The moisture “danger zone” is the time it takes for the cannabis plant to reach 15 percent water content. Some pathogenic molds can produce poisonous toxins. One of the biggest threats posed is the poisonous toxin aflatoxin which is produced by certain varieties of Aspergillus mold. Aflatoxins are not only toxic, there also very carcinogenic. While very rare, this can easily be prevented by careful drying and storage. 

Dangerous bacteria such as staphylococcus and E. coli are occasionally found on cannabis as well. This type of bacteria develops from human contact (improper handwashing). These bacteria’s can easily be avoided with thorough hand washing techniques. 

Anaerobic bacteria are also a very rare occurrence on cannabis, since the plant is rarely exposed to the low-oxygen environments in which these bacteria thrive upon. However, there’s always exceptions. Take olive oil for instance: when infused with whole, raw cannabis buds, the cannabis buds may provide an anaerobic environment that can result in botulism poisoning. Pretty scary isn’t it? 

Cannabis Pests 

Infestations of pests on dried cannabis flowers indicates poor cultivation techniques and lower-quality cannabis. Pests that attack cannabis plants often weaken and kill them, which lowers the potency of the resulting cannabis product. 

Spider Mites 

One of the most common cannabis found indoors (and often outdoors as well), is spider mites. Eradicating spider mites can be extremely difficult once they are present on the cannabis plant. Spider mites can also infest other cannabis plants in close proximities because they reproduce quickly. Spider mites reproduce so quickly that their population can explode in just a matter of weeks, resulting in thousands of mites feeding on every cannabis plant. Spider mite infestations lower the quality of medicinal effects that the cannabis plant produces because spider mites weaken the plant and interfere with its ability to produce medicinal resin.  

In the 1970’s spider mites were not well understood. cannabis cultivators thought that when spider mites hatched-they were already carrying eggs, which isn’t true. Today however, we know a great deal more about spider mites and infestations can be prevented by using hygienic techniques. 

Broad Mites 

Broad mites are extremely small mites, measuring only ½ mm in size. They have infested over 60 species of plants, including cannabis. Since broad mites are so small, they are often overlooked by cannabis growers. When cannabis cultivators encounter and infestation of broad mites, they are mistaken the damage for a virus. 

Fungus Gnats 

Fungus gnats produce larvae that attack the cannabis plants’ roots, which can weaken the cannabis plant. The adult fungus gnats can get trapped by the trichome resin, and the fungus gnats end up sticking to the finished flower


Thirps are sap sucking insects that jump. Thirps weaken cannabis plants by sucking their sap. There are five different types of thirps that attack cannabis plants. 

Using Pesticides to Ward Off Pests 

cannabis cultivators under attack by insect pests may unfortunately resort to toxins that should never be used on cannabis. Purchasing your cannabis from cultivators who understand that rational pest management and uses preventative measures to eliminate pests before they become an issue is important. 

Cannabis Adulterants 

Believe or not, pet hair is the most common adulterant in cannabis, with human hair coming in close for second place. cannabis cultivators keeping pets around areas where harvested cannabis is trimmed and processed often results in pet hair found in cannabis. As a cannabis user, you need to refuse any cannabis with pet hair. If you end up accepting the cannabis with pet hair, it’s only going to send the wrong message to those who sell cannabis

Anyone working with cannabis (especially trimmers) should be wearing a hair net and long sleeves to avoid contaminating cannabis with his or her own body hair. 

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