Navigating the Frontier of Pesticide Analysis

By Caroline Gordon and Joshua Esquivel | November 24, 2017

The upcoming California cannabis regulations are creating a call to action for accredited laboratories to finalize development of highly accurate and reliable methods for detecting trace amounts of pesticides. Commercial cannabis testing laboratories have traditionally utilized Gas Chromatography (GC) and/or High Performance Liquid Chromatography (HPLC) to detect residues in cannabis flowers, extracts, and edibles. However, these instruments and their related methods are insufficient for multi-residue analysis of cannabis products at the detection limits outlined by the state, and even with more sensitive instrumentation (LC/MS/MS and GC/MS/MS), there are still many analytical challenges that must be overcome.

Pesticide usage on cannabis is problematic for a number of reasons. For one, it is unclear what constitutes a safe level of usage or consumption. Generally the EPA under FIFRA determines which pesticides are permitted for a crop and sets MRLs (maximum residue limits) for each. However, since cannabis is a DEA Schedule I substance, the EPA has not approved any pesticides for use on cannabis. Second, cannabis is an extremely high value crop susceptible to pest infestation and fungal infection. In an unregulated environment, this leads to overuse of pesticides as a preventative measure to protect crop yields. Third, cannabis is both inhaled as a vapor and consumed as an edible. The risk profile of pesticides can vary significantly depending on the method of consumption. Last, cannabis is often sold in concentrated forms, such as hash, wax, or shatter. However, the process of concentrating cannabinoids has the unintended consequence of concentrating pesticides and other contaminants as well.

A variety of pesticides are utilized in cannabis cultivation, some of which can pose serious health risks to consumers. The most common pests that affect cannabis are spider mites,aphids, and fungus gnats. Some of the most common pesticides used to eradicate these pests are “Avid” (Abamectin 2.0%), “Forbid 4F” (45.2% Spiromesifen), and “Pylon Miticide”(Insecticide with chlorfenapyr). The most commonly used fungicide is Eagle 20 which utilizes myclobutanil as the active ingredient. These products can provide effective hindrance of pests, but have been shown to have adverse health effects for humans. For example, it has been discovered that Abamectin can cause reproductive problems such as stillbirths, decreased viability, decreased lactation, and decreased weight in newborns. For another example, myclobutanil can result in the creation of dangerous byproducts such as hydrogen cyanide and hydrogen chloride upon decomposition at high temperatures (i.e. when smoked).

While California state regulators have properly identified the public health need to test for these pesticides, it is still unclear how regulations will be enforced. There are no standards for pesticide residue testing of cannabis, so each laboratory has its own proprietary methodology, often developed for instrumentation inadequate to the purpose of achieving the limits of detection mandated. While spot checking or auditing of results would ordinarily be a good way to weed out bad or incapable laboratories, the state itself has limited experience performing this kind of auditing, and may not be initially prepared for its oversight role. And as we have seen in food testing and other cannabis markets, when the playing field is not level, testing volume tends to accumulate at the labs with the lowest standards, at least in the short run.

While the frontier of cannabis research on analytical methodology is developing at a rapid rate and best practices from other industries are being adopted, there is going to be high variability in the quality of lab results in the short term. Until official testing standards have been adopted and/or quality standards are enforced, perhaps the best advice for growers and manufacturers is to to look for quality indicators when choosing a testing partner. Laboratories that have ISO 17025 accreditation, state-of-the-art instrumentation (i.e. LC/MS/MS and GC/MS/MS), adequate facilities, and experienced analysts may be more expensive than those that do not, but the potential for a brand-damaging recall is far more costly.


Caroline Gordon and Joshua Esquivel are analysts at Anresco Laboratories, which has performed multi-residue analysis of foods for over thirty years and is now applying its expertise to cannabis.