How can I avoid failing Pesticide Analysis?

As with everything in agriculture and processing, there are things in your control and things that are out of your control.

Regarding Flower: If you’ve been in your indoor or greenhouse facility for a while and just recently started spot-checking yourself with a few pesticide tests, you may be alarmed to see pesticide levels approaching the action level – even if you’ve never personally applied pesticides anywhere in your facility. Since pesticides of many kinds are in use in many ways, consider the following routes of accidental contamination:

  • If you’ve purchased, leased, or rented used equipment for handling liquids, solids, or plants (foliar sprays, feed mixers, mechanical trimmers) be sure that this equipment has been thoroughly cleaned before use.
  • Some “natural” pesticide products actually contain one or more of the controlled pesticide compounds. The WSLCB periodically sends updates about products containing unapproved pesticides to producers/processors on their mailing list.
  • Temporary hired help may track in pesticide residue on their hands, shoes, or clothing. Be sure any hired help coming from other agricultural operations shower and change clothes and shoes before handling any cannabis for wholesale.
  • Even indoor facilities can be threatened by wind-blown incidental exposure. While unlikely, it is possible that incidental exposure can reach significant levels in the air outside your facility. To minimize this risk, ensure than any air drawn into the building is well-filtered on the way in, and that doors are left open for a short time. An extra door in an entry path can do a lot to minimize unfiltered air exchange with the outside.
  • If you have shared water rights and are irrigating your plants downstream from other agricultural facilities there may be pesticide residue in water from that source that hasn’t been further filtered or treated to remove any pesticide residue.

Regarding Concentrates/Extracts: The general rule-of-thumb for pesticides in concentrates is this: expect about a 10-fold increase in pesticide burden versus the flower used for extraction. Meaning that a flower lot tested at 200 ppb of piperonyl butoxide (PBO) will have an expected concentration of 2,000 ppb (or 2 ppm) of PBO in the extracted form. It is for this reason that we highly recommend that processors and producers submit samples for pesticide R&D prior to the LCB requiring it. Staying ahead of the curve will save you money and time in the long run.

First and foremost is prevention: avoid using pesticide-laden flower or trim (especially trim!) for extraction. If you don’t know or don’t yet trust a certain grower, a single pesticide test is much cheaper than the time and money lost if a seriously contaminated lot contaminates your system. When in doubt, test before you extract! We encourage savvy processors to request to test for pesticides before purchasing a lot from a grower, to further mitigate your risk.

Most pesticides that we test for would be soluble in your extraction solvent (that includes CO2, ethanol, and alkanes), and even with warm-pressing (“rosin technique”) the cannabinoids and terpenes can act as solvents themselves and pull more than their share of pesticide residue out of a lot. Additionally, vacuum distillation isn’t guaranteed to remove all pesticide residue either – most short-path and wiped-film distillation systems currently in use do not have the resolving power (“theoretical plates”) to completely separate THC and CBD, much less pesticide compounds with similar volatility to cannabinoids.

We provide the following hypothetical story to help illustrate the path that pesticides might take from application to presence in the final product. The assumptions and assertions in this passage are plausible, but have not been explicitly proven with data.

Consider the following: A row of plants at a cannabis farm had a natural pesticide blend (including Pyrethrin, Spinosad, or Abamectin) applied directly to them during early vegetative growth. These plants were then treated normally through the rest of the growth cycle with no more pesticides applied until harvest. The plants are harvested. Any residue still stuck to the fan leaves is mostly removed during harvest and curing, unless the residue is released as dispersed dust and lands back on the buds. Ideally, there is relatively little pesticide residue left on the plant.

You purchase that lot after cure for an extract run. The farmer offers to give you the trim for free, and you take her up on it. You want the best material extracted, tested, packaged, and in the store first (the trim is just extra), so your oil processor performs the “nug runs” and resolves a high yield of high-quality finished product. (product A) Your next flower wholesale purchase from an organic grower that you trust is a little behind, so your oil processor runs the trim in the meantime, resolving a low yield of low-quality finished product (product B). Your next wholesale purchase finally goes through, and your oil processor runs the flower and repeats the performance for more high-quality finished product (product C).

You decide to get a pesticide test on all three products, A, B, and C. You are astonished to find that while product A has a significant but small amount of Pyrethrin residue, product C from the organic grower has three times as much residue, and more different compounds detected! Of course, product B turns out very hot and nasty, but you didn’t lose too much money on that lot so you’re OK throwing it away. But product C? How could an organic grower be putting pesticides on her plants?!?

Slow it down! Unlike microbial burden, which can be mitigated by sterilization, pesticide residue does not go away. Furthermore, the ratio of cannabinoids to pesticide residue is much more favorable in the flower than in the trim; think about it, the juicy buds with all the resin in them have only so much surface area to catch pesticides, where the sugar leaves and fan leaves have lots more surface area but very little resin.

Not only that, but pesticide residue stays behind much like leftovers from a previous extraction run. Cleaning your extraction rig will certainly help minimize the amount of cross-contamination, but considering that even one part per million of most unapproved pesticides constitutes a failure, very thorough cleaning would be needed to restore a contaminated rig to cleanliness. In the above passage, the residue found in product C came directly from product B, where product A’s contamination level was relatively small and donated little to the system.