Analyzing Pesticide Residues to Meet the Needs of New Cannabis Safety Testing Standards in Canada

In October 2018, the Canadian government legalized the use of cannabis by adults for non-medicinal purposes. In conjuction with legalization, Health Canada has produced new safety standards to ensure the potency of cannabis products is properly characterized in terms of tetrahydrocannabinol (THC) and cannabidiol (CBD) content, and that they are free from potentially dangerous contaminants such as toxic metals, mycotoxins, and pesticide residues.

For fully-licensed laboratories, there is an opportunity to start or scale cannabis testing services to meet the needs of the emerging cannabis sector in Canada. In this article, we look at the support that is available to laboratories to help them adapt to the new cannabis pesticide testing requirements.

Testing for pesticide residues in cannabis products

One of the most important groups of substances that must be tested for under the Health Canada guidelines are pesticides. While pesticides are often not applied to cannabis plants directly, they can end up in the product through several different routes. Cannabis is a particularly thirsty crop, requiring a lot of watering before it can be harvested. Pesticide residues that may be present in trace amounts in water or soil could accumulate in the plant to levels that might be considered unsafe. Furthermore, as the new legislation permits outdoor cultivation, there is also the potential for product contamination through the airborne drift of pesticides that are applied to other crops.

As cannabis is often combusted, there is an enhanced risk of exposure to these potentially harmful compounds as well as thermal degradation products that burning could produce. Health Canada has developed a comprehensive list of 95 pesticides that must be screened for. Most of these pesticides are the same as those that would be screened for in other crops. However, because some pesticides that are considered safe in an edible product may not be considered safe in a burned product, many of the pesticides on the screening list are typically detected at the 10 parts per billion (ppb) level.

Challenges associated with cannabis workflows

For many laboratories, the pesticide screening workflows required by the new Canadian regulations will be novel and unfamiliar. To further add to the challenge of adopting and implementing these tests, cannabis workflows come with a number of specific issues that must be successfully navigated.

With many of the pesticides on the Health Canada list at the ppb level, screening workflows need to be able to confidently quantify analytes at trace levels. Not only must the analytical techniques used to detect pesticide compounds be sufficiently sensitive to reach these ultra-low detection limits, but workflows must also be supported by robust sample preparation steps that ensure complete analyte quantitation. This is a challenge made more difficult by the sticky nature of the resins present in cannabis plant material, which can make methods such as grinding problematic.

To further complicate matters, some cannabinoids can interfere with the detection of specific pesticides, making positive identification more challenging, especially as the concentrations of cannabinoids are significantly higher than those of any pesticides present in samples. Moreover, because some of these cannabinoids are not present in every sample, distinguishing false positives from true matches can be difficult. To overcome this issue, advanced analytical technologies capable of high-resolution mass spectrometry and reliable spectral matching are required.

Another issue adding to the challenge of accurately and reproducibly quantifying pesticides in cannabis samples is the lack of commercially available reference material. To be confident of their results, analytical laboratories require reference samples based on real plant material that has trace levels of pesticides. In the US, difficulties around moving cannabis reference material between states means sourcing material from across the Canadian-US border can have its own set of additional challenges.

Meeting the needs of cannabis testing

These challenges not only highlight the importance of accessing the most capable technologies for cannabis pesticide testing workflows, but also the value of sharing knowledge and best practice between laboratories. Vendors of instruments and consumables are responding to the needs of laboratories, contract research organizations, and licensed dealers, producers, and suppliers across the cannabis sector by offering tools and training to support complete testing workflows. These solutions are enabling fully-licensed laboratories to start or scale operations and produce reliable results that meet the standards set by Health Canada.

Confident pesticide screening demands high-performance instrumentation, and the latest liquid chromatography-mass spectrometry (LC-MS) and gas chromatography-mass spectrometry (GC-MS) systems are ideally suited to deliver against the new Canadian guidelines. Modern triple quadrupole and Orbitrap mass spectrometers have already proven their worth in the food testing sector by offering exceptional accuracy, specificity, and sensitivity, as well as high operational robustness. Together with informatics solutions such as cloud-connected laboratory information management systems (LIMS) to support good data organization and regulatory compliance, these technologies are helping to make cannabis pesticide testing routine for both growing and established analytical laboratories.

As well as making available the right technologies to deliver accurate and reliable cannabis pesticide testing, some companies, such as Thermo Fisher Scientific, are also engaging with fully-licensed testing laboratories to accelerate the development of validated methods and deliver training to support their use. With the new legislation a step-change from what’s gone before, there is significant interest from laboratory managers to see first-hand what’s required to satisfy the new standards. Vendors are meeting this need by providing relevant and insightful educational resources, such as the Thermo Fisher seminar series that the author was invited to speak at, which aim to help laboratories optimize their workflows through sharing best practice and method development advice from industry experts.

The cannabis testing community is also turning to online professional networks to source information on how to develop efficient and effective workflows. LinkedIn networks such as the Cannabis Analytical Laboratory Manager (CALM) group have been specifically set up to enable colleagues and peers to connect, share tips and make best practice more widely available. Forums such as these are proving to be a highly valuable resource for support and networking across this emerging sector.

Conclusion

Cannabis testing workflows come with specific challenges around method development and routine application, which fully-licensed laboratories must successfully navigate to deliver against the new Health Canada cannabis testing requirements. Recognizing the need for reliable and capable analytical solutions, vendors of instruments and consumables are working with laboratories, contract research organizations, and licensed dealers, producers and suppliers across the cannabis testing sector to deliver complete workflow solutions that meet these new testing standards. Some companies are going even further by providing educational resources and training to help laboratories adapt to these new workflows.