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Contaminants in cannabis and the cannabis supply chain will be the biggest issue that faces each local jurisdiction as legalization is rolled globally and market share is taken from illegal operations.

In the black (and grey) market, there are no controls for quality assurance. There are no labs to send out both incoming nutrients and outgoing cannabis for testing.

Contamination can result from using banned substances, leeching heavy metals from the soil and growth mediums as well as from fungi, bacteria and insects infestations.

Cannabis is an accumulator plant – meaning is very adept at drawing heavy metals and pollutants out of the soil and water. In fact, it is so versatile it is being used as a phytoremediator at Chernobyl and in Italy to draw dioxin used in steel manufacturing from the soil.

Why does it happen?

There have always been three types of growers, those that maximize short-term profit at the expense of craftsmanship; those who look for the long-term relationship built on transparency, trust and quality with their customers; and those that don’t know any better.

Profits in the cannabis market are directly driven by output in grams and there are many shortcuts. The black market has a long history of using adulterants to add to the final weight (everything from sugar to sand), increase plant yields (products such as sugar flavored water) and in lieu of learning best agricultural practices (powerful fungicides and pesticides such as Eagle 20 and Forbid 4F). Many of these chemicals are systemic pesticides, which means the chemicals linger in the plant’s system for long periods of time and can be passed on to clones.

Even in legal regulated cultivations, the pressure of a successful crop can lead to a culture of rule breaking such as in the case when it was reported that employees hid banned pesticide in ceiling tiles when inspectors were on site.

Because of the illegal nature of the black market, finding reputable suppliers that will accept cash payment for massive amounts of specifically created cannabis nutrients, medium and pesticides is limited. This has resulted in growers using mass-market chemical compounds that were intended for a different application and certainly not suitable for cannabis cultivation.

Insecticide use

You need to have a stringent testing and QA processes in place to test all incoming materials and ensure no contaminants are introduced in your growing area.

Spider mites and aphids can decimate a crop in days. Before you know it you have thousands of pests laying thousands of eggs and very few ways to get rid of them. Mites can enter a grow room through contaminated materials including soil and starting materials or if it is not properly sealed. An infestation can start as simply as a worker who has house plants carrying eggs on their clothing.

A grower in this case has very few options that are as quick as using a powerful pesticide containing Spinosad. Spinosad is allowed for use in food production so why not for cannabis production? A simple Google search will retrieve dozens of products and growers that use the products.

The simple answer is the method of dosing (foliar spraying) combined with the method of combustion is unstudied. What happens when crops containing low levels are concentrated?


When a grow room has been environmentally engineered incorrectly with high humidity levels and not enough airflow powerful fungi and powdery mildew with thrive. One of the more controversial fungicide components found in many popular products is myclobutanil that when heated produces Hydrogen Cyanide.

Why does contamination matter?

For immunocompromised patients, the effects of inhalation of cannabis contaminated with fungi and bacteria can cause opportunistic lung infections and in some cases has been the suspected cause of death for patients.

Where is it happening?

From California to Canada numerous studies have documented high levels of pesticides, insecticides and fungicides in cannabis production both in the regulated and unregulated environments.

In California, state regulators have found contaminants including carbofuran (a neurotoxin) and zinc phosphide in Northern and CentralCalifornia watersheds from massive outdoor grow operations.

Canadians experienced the largest medical cannabis recall when a major producer was forced to issue a voluntary recall on allcannabis produced between Feb – December of 2017 after testing revealed the presence of myclobutanil and/or bifenazate that “exceeded any of the levels permitted in food production for these two pesticides” – Note that neither of these compounds are permitted for cannabis cultivation.

Compounding the issues for producers creating cannabis extracts is that during processing these pesticides become heavily concentrated in the end product – with levels up to 500x the non-concentrated levels.

Who is doing anything about it?

Some governments, as their regulatory frameworks mature and improve are rapidly trying both set the regulations based on best agricultural practices as well as enforcing those same standards (noteworthy examples are Colorado, California and Canada). California is in a unique position as they struggle with supply and are forced to phase in testing regulations over the next 12 months. Other jurisdictions like Arizona have no test regime, as that wasn’t part of their voter referendum.

Prior to the massive cannabis recalls in Canada of myclobutanil used in production, mandatory testing for pesticides was not in place for cannabis producers. Health Canada changed their mind on allowing the sector to police their own practices and changed their protocols to include unscheduled inspections and mandatory testing protocols.

Private consortiums of companies are starting to organize around the issue. Notable examples are The Handpicked Company in California who has teamed up with The Werc Shop, SC Labs and Envirocann to provide education, awareness and best practices.

Associations such as Colorado’s Cannabis Certification Council (made up of The Organic Cannabis Association and Ethical Cannabis Alliance) are beginning certification processes for growers.

At cannaResultant we have made a commitment to transparency in our practices and our supply chain by publishing all our internal and independent testing results to our Blockchain.

Pesticides to avoid for cannabis

Eagle 20 – myclobutanil
Forbid 4F – spiromesifen
Safari 20 – dinotefuran
Hormex Vit B-1 & Growth Hormones
Rally 40WSP – myclobutanil
Nova – myclobutanil
MASALON® Fungicide – myclobutanil
MYCLOSS® Xtra Fungicide – myclobutanil
NOVA® 40W Agricultural Fungicide – myclobutanil
RALLY® 200EW Fungicide – myclobutanil
RALLY 40WSP Fungicide – myclobutanil
SYSTHANE® 125 Fungicide – myclobutanil
SYSTHANE 200EW Fungicide – myclobutanil
SYSTHANE 10WP Fungicide – myclobutanil
SYSTHANE 400WP Fungicide – myclobutanil
EVITO® Fungicide – myclobutanil
Myclobutanil 20EW T & O – myclobutanil
Oberon SC 240 – spiromesifen
Furadan – Carbofuran
Lucid and Avid – Avermectin


Oregon List of approved pesticides