Dr. Donald Land: Testing Commercial Cannabis for Pesticides

Dr. Donald Land is the Chief Scientific Consultant for Steep Hill, one of the leading scientific cannabis analysis labs in the world. He is also a Professor of Chemistry at UC Davis. Dr. Land recently joined us to discuss the trending topic of pesticide use in legal cannabis markets, and how Steep Hill aims to protect consumers with thorough pesticide testing.

A lawsuit in Colorado recently became the first example of the risks that come with an unregulated agricultural market. Currently, testing for pesticides is not mandated in several states with legal markets (medical and recreational), although such testing is required for many other products under the FDA and other federal institutions. In this interview, Dr. Land discusses the importance of mandated pesticide tests, as well as the methodologies that Steep HillĀ uses and the inherent risks to consumers in an unregulated market.

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What is the testing process that you use? How does it vary across products, edibles, concentrates, tinctures, etc.?

Testing involves inspection for foreign matter, followed by extraction of toxins. Filtering is used to separate unwanted, inert material that might interfere or clog instrumentation, followed by analysis using chromatography with tandem mass spectrometry for sensitive, selective detection and quantitation. Different types of samples require different details, particularly in the inspection and extraction steps. Edibles are treated differently from flowers, etc.

What pesticides are you testing for and how comprehensive is the test?

Normally, the EPA sets pesticide restrictions for all commodities – what can be used, how it is used, what cannot be used, and the maximum residual levels allowed. Since cannabis is still US-DEA Schedule I, federal agencies, such as EPA, USDA and FDA , are precluded from establishing rules for cannabis and cannabis-related products. Thus, different states are having to develop their own guidelines. Some states have decided to err on the side of caution and require testing for “ALL pesticides at the lowest limits in the EPA schedule.” This test would include thousands of compounds, some of which are no longer manufactured or available even as standards, and would be an incredibly time consuming and expensive test. Meeting these types of requirements is generally not feasible at a cost the market would bear. In other states and localities, short lists of “allowed” pest treatments -typically things like garlic oil, neem oil, and other substances generally regarded as safe for this application -and “disallowed” treatments, which is typically a list of pesticides known or suspected to be in use in that jurisdiction to control mites and mildew, or other prevalent pests threatening cannabis grows. Generally, such lists contain a few dozen specific pesticides that must be monitored for that jurisdiction. Because the EPA has not (and currently can not) approve any pesticides for use on cannabis, any and all pesticide use is federally prohibited and detection of the presence of any known pesticide controlled by the EPA would warrant destruction of the contaminated portions of the crop.

How common is pesticide contamination in the samples that have been tested? What sort of contamination has been seen?

At present, required pesticide testing is in the earliest stages of implementation in several states, but not much data is available yet from those efforts. In CA, where pesticide testing has been practiced only voluntarily for a few years by a small minority of producers and sellers, only a very small subset (<1%) of samples actually get tested. Of those tested, about 1-2% test positive for an EPA regulated pesticide, typically miticides or fungicides. However, since the test is voluntary, it is unlikely that producers who use pesticides would choose to test, so this is likely lower than it would be in a mandatory testing situation. Also, absence of residues does not necessarily mean pesticides were not used. Pesticide manufacturers must, to receive EPA approval for sale and use, demonstrate that the active compounds break down relatively rapidly after application and does not persist. Thus, most pesticides, applied early enough prior to harvest, may no longer be detectable in the harvested product. Greater regulatory control in this regard should unify policies across many jurisdictions in the future.

Are there plans to expand pesticide testing into the other states in which Steep Hill operates?

Steep Hill tests for pesticides, mycotoxins and other toxicants to help ensure the safety of cannabis being consumed. When California was the first state to move down the path of legalization of cannabis markets, testing was not part of the thought process until Steep Hill was founded in 2007. Since that time, the value of safety and quality testing has been verified and every cannabis market legalized since that time has required safety and quality testing. California appears to be on the verge of establishing new laws regarding its legal cannabis market and testing plays a prominent role in regulations currently before California lawmakers. Additionally, some CA cities and counties have established their own guidelines for testing requirements. Thus, Steep Hill, with offices open or opening soon in WA, CO, NV, NM, and OR, in addition to CA and others, has invested heavily in state-of-the-art equipment capable of meeting the most stringent testing requirements. Steep Hill’s standard operating procedures are adjusted to ensure full compliance with the laws of each jurisdiction. For producers interested n getting ahead of the curve, Steep Hill can test at the most sensitive levels required in any jurisdiction as the nation nears legalization of interstate commerce and the creation of national brands.

Realistically, how worried should the average consumer be about pesticide contamination?

Cannabis crops are often extremely valuable. With wholesale prices often greatly in excess of $1,000 per pound, a mature outdoor plant could produce in excess of five pounds after harvest, meaning individual plants are worth many thousands of dollars each. When infestations of insects, molds or other pests take hold, they can spread like wild fire and devastate hundreds of thousands of dollars worth of potential product. Faced with this prospect, it is not hard to understand why some resort to imprudent, often dangerous application of toxic chemicals to prevent the loss. The extreme high potential value of cannabis and the lack of regulation and oversight of production make this industry much more susceptible to bad actors applying toxic pesticides in unsafe practices that could reach the consumer. The fact that many consumers choose to inhale smoke or heated vapors directly into the lungs and, from there into the bloodstream, exacerbates the dangers of the presence of toxins. For a consumer who regularly purchased cannabis once per week, the currently observed rates of contamination would imply that about once per year or so, that consumer’s purchase would be contaminated with pesticides.

Are there any easy ways for consumers to identify products that have been sprayed with pesticides?

Unfortunately, pesticides are generally used and are toxic in such small amounts that their presence can only be reliably detected using expensive analytical instrumentation with rigorous testing technique. Growers know whether they have used pesticides or not, how much and when. For other foods, FDA and EPA inspections and random testing with the threat of loss of license is the incentive for compliance. Also, EPA approval of some effective pest control methods means farmers have alternatives for treatment. Unfortunately, none of that infrastructure so far exists for cannabis. Consumers should make sure they purchase their cannabis from within the established, regulated system in their jurisdiction and make sure that their lawmakers know the importance of testing and regulation of pesticides and other toxins or microbiological contamination.


Thank you for taking the time to answer our questions, Dr. Land! To learn more about Steep Hill, visit their website. Questions or comments? Post them below!


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