Scientific study shows alarming concentrations of pesticides in unregulated marijuana

Scientific study shows alarming concentrations of pesticides in unregulated marijuana


A recent study published by the Journal of Cannabis Research shows a “striking contrast” in the safety of cannabis grown for Canada’s legal and illegal markets, highlighting a concerning prevalence of pesticides in unregulated cannabis.

The study involved the analysis of 36 marijuana samples obtained from licensed retailers and 24 illicit samples confiscated by law enforcement. The analysis aimed to identify the presence of any of the 327 different pesticides in these products.

In the legal cannabis sector, the contamination rate was a mere six percent, with only trace amounts of two pesticide residues, myclobutanil and dichlobenil, detected. Significantly, dichlobenil is not one of the 96 pesticides subject to mandatory testing under Canadian statute.

Conversely, pesticides were alarmingly prevalent in illicit market samples, with a staggering 92 percent of the samples containing potentially hazardous chemicals. The study identified “23 unique pesticide active ingredients with an average of 3.7 different pesticides per sample.”

The study’s authors noted that inunregulated samples, pesticides such as chlorpyrifos, imidacloprid, and myclobutanil were measured at concentrations up to three orders of magnitude above the method’s lowest calibrated level of 0.01 μg/g. Astonishingly, one illicit sample alone contained nine different pesticide-active ingredients.


Despite the six percent of legal samples containing low pesticide levels, researchers emphasized that the licensed Canadian cannabis sector has made significant improvements, prior to the introduction of mandatory testing requirements in 2019, contamination rates stood at roughly 30 percent.

The authors assert that the study is the only extensive pesticide multi-residue analysis comparing pesticides in licensed and illicit cannabis markets in a nationwide jurisdiction where cannabis has been legalized.

In essence, these findings support the long-standing argument made by cannabis reform advocates: regulating marijuana sales provides consumers with access to safer products.

A separate study conducted last year examined the varying marijuana testing regulations in U.S. state markets, revealing widespread public confusion. This underscores the “urgent” need for a unified regulatory approach and national-level guidelines for cannabis contaminant regulations. However, establishing such a national framework remains challenging due to federal prohibition. While the Environmental Protection Agency (EPA) has approved certain pesticides for hemp following its federal legalization under the 2018 Farm Bill, it has refrained from doing the same for marijuana while it remains illegal at the federal level. Consequently, the issue of pesticide use in the cannabis industry remains a complex and unresolved challenge.