Pesticide Testing in Cannabis

Your customers want to be sure that the cannabis you sell has been tested by an accredited laboratory and is safe to consume.

When cannabis is produced on a large scale, routine testing on each batch and lot is needed prior to sale. Here’s some insight into the testing for pesticides.

What is a Pesticide?

One aspect of product safety, whether for food or cannabis, is the presence of pesticides. The word “pesticide” has long been associated with damaging and negative connotations. However, by definition, pesticides are not inherently negative. Technically they are defined as chemical or biological compounds that will deter, disable, or otherwise discourage pests such as insects and weeds. Our Canadian food industry has a wide application of many pesticides, which are closely regulated by the Canadian Food Inspection Agency. Many foods may contain small amounts of pesticide residues but are considered safe for consumption. However, there is little research on the safety of certain pesticides when incinerated and inhaled, as with cannabis smoking.

It is paramount that cannabis be routinely analyzed for pesticide content.

It is likely due to these concerns that Canada’s regulators have taken the precautionary approach to pesticide use on cannabis. Under the Access to Cannabis for Medical Purposes Regulations (ACMPR), medical cannabis cannot be treated before, during, or after the drying process with a pest control product that has not been registered under the Pest Control Products Act for use on cannabis. Currently there is a list of 22 compounds that are allowed, most of which are potassium salts and food products like garlic salts and mineral oil. None of these products have limits set by Health Canada, and therefore would not be subject to analytical lab testing.

There are, however, hundreds of chemically synthesized pesticides that could be used in cannabis production. One such example is myclobutanil, a fungicide used to treat powdery mildew, which was found in product from a few Canadian licensed producers back in 2017, resulting in major recalls. The number and diversity of available pesticides creates a challenge for testing facilities and regulators who monitor the product. Laboratories need to know what pesticides they should be looking for in the product, especially if they are very toxic. The regulators (Health Canada, EPA, etc) will come up with a list that will apply specifically to cannabis, but unfortunately this list will change constantly, as more new pesticides are developed and brought into use. Currently, there is a drafted list of 95 pesticides with their maximum residue limits for dried, fresh flower, and cannabis oil, which may be tested for under the Cannabis Act after October 17th, 2018.

What’s the Maximum Limit for a Pesticide?

Maximum residue limits are determined from research into the health effects of pesticide exposure. A low-level exposure to a very toxic pesticide may be more dangerous than a high exposure to a relatively low toxicity pesticide. Every pesticide that comes onto the market for use is assessed for toxicity by governing bodies (EPA, Health Canada), and will be registered for use only if the estimated exposure raises no concerns. However, as cannabis is typically consumed in a unique manner, relative to food or other products, this exposure pathway, as well as possible interactions with immunocompromised patients, has not been comprehensively researched.

Many people wonder why there is a limit for each pesticide. Why wouldn’t it just be zero? Unfortunately, in analytical chemistry there is no such thing as zero. Every instrument and technique will have a limit below which it will not be able to determine if something is there or if it is just noise or background. The other issue is that pesticides are unfortunately extremely ubiquitous. The food industry has been utilizing a wide range of pesticides for decades, and many of these are still in our water, soil, and buildings around us. The more sensitive our instruments become at detecting compounds, the more of these background long-life pesticides will be found.

Chromatography and Spectrometry

The instruments and techniques used to analyze for pesticides is another topic with wide debate. In legal cannabis jurisdictions, such as California and Oregon, detailed lists of pesticides have been available for some time, and this has allowed instrument manufacturers and researchers to develop methods to support these regulations. (At the time of writing this article, no such methods were available for the Canadian list.)

By and large, if you want to analyze for pesticides, you are going to need mass spectrometry. Depending on the type of pesticides, this will either be liquid chromatography mass spectrometry or gas chromatography mass spectrometry. The chromatography part of the instrumentation is what enables the chemical extract to be separated down to the individual pesticides (should they be present). The “mass spec” (as the spectrometer is colloquially called) essentially breaks the compound apart into mass fragments that can be traced back to identify the compound or pesticides in the chemical extract.

There are hundreds of chemically synthesized pesticides that could be used in cannabis production.

Most mass spectrometrists curse the day the cannabis extract first came into their lab with a pesticide analysis request. It is the most complicated extract out there. The reason is all those wonderful cannabinoids and terpenes that make this cannabis plant so valuable. These compounds create matrix effects that wreak havoc on testing instruments. Pesticide analysis is essential, so to do it right you not only need one mass spec, but two in each instrument! One mass spec is required to filter out the background matrix, with an additional one to analyze and generate quantifiable results for each pesticide of interest.

As Canada enters into a new era of legalization, there still exists a struggle for legitimacy. It is hard to say what the future will hold, as it is possible the prohibition of pesticide use on cannabis in Canada may not last forever. Either way, it is paramount that cannabis be routinely analyzed for pesticide content at an accredited laboratory before any batch or lot is sold.

Emily Kirkham is CARO Analytical Services’ Technical Manager and leader of CARO’s Cannabis Testing Division. She is passionate about the analytical testing business, public health and safety, and channelling that passion into building a world-class cannabis testing division in support of the legal cannabis market.