My BHO/CO2 has way more pesticides than the trim I purchased – how is that possible?

There is unfortunately little data currently available about pesticide residue concentration during cannabis oil extraction. Some of this data was presented at the 2016 Emerald Conference, and the general consensus at the time was that a roughly 10-fold concentration of pesticide residues should be expected compared to the residue concentration in the starting material. Most pesticides in common use are soluble in the same solvents that cannabinoids are – butane, CO2, ethanol, etc.

This 10X should be considered a rule of thumb. Flower and trim may concentrate pesticide residue differently – consider the form of the starting material itself. Trim has a low cannabinoid content, but a larger amount of exposed surface area, so it is reasonable to assume a relatively large ratio of pesticide residue to cannabinoids. Flower, especially if very dense in structure and tightly trimmed, has a much larger cannabinoid concentration than trim, and also has less exposed surface area; thus it makes sense that a flower extract will have a lower ratio of pesticide residue to cannabinoids. Exactly how wide the gap is between the results of using either starting material is unknown – we would love to find out! Regardless, it seems from this thought experiment that a nug run would be favorable to a trim run. Isn’t that always the case?

The safest bet is to not apply any limited or banned pesticides to your own plants, and to test any material for pesticides before you buy it to make oil. A single $250 pesticide test is a lot cheaper than buying a contaminated lot!