Tag Archives: mass spec

Heavy Metals Testing: Methods, Strategies & Sampling

By Charles Deibel
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Editor’s Note: The following is based on research and studies performed in their Santa Cruz Lab, with contributions from Mikhail Gadomski, Lab Manager, Ryan Maus Technical Services Analyst, Laurie Post, Director of Food Safety & Compliance, and Charles Deibel, President Deibel Cannabis Labs.

Heavy metals are common environmental contaminants resulting from human industrial activities such as mining operations, industrial waste, automotive emissions, coal fired power plants and farm/house hold water run-off. They affect the water and soil, and become concentrated in plants, animals, pesticides and the sediments used to make fertilizers. They can also be present in low quality glass or plastic packaging materials that can leach into the final cannabis product upon contact. The inputs used by cultivators that can be contaminated with heavy metals include fertilizers, growing media, air, water and even the clone/plant itself.

The four heavy metals tested in the cannabis industry are lead, arsenic, mercury and cadmium. The California Bureau of Cannabis Control (BCC) mandates heavy metals testing for all three categories of cannabis products (inhalable cannabis, inhalable cannabis products and other cannabis and cannabis products) starting December 31, 2018. On an ongoing basis, we recommend cultivators test for the regulated heavy metals in R&D samples any time there are changes in a growing process including changes to growing media, cannabis strains, a water system or source, packaging materials and fertilizers or pesticides. Cultivators should test the soil, nutrient medium, water and any new clones or plants for heavy metals. Pre-qualifying a new packaging material supplier or a water source prior to use is a proactive approach that could bypass issues with finished product.

Testing Strategies

The best approach to heavy metal detection is the use of an instrument called an Inductively Coupled Plasma Mass Spectrometry (ICP-MS). There are many other instruments that can test for heavy metals, but in order to achieve the very low detection limits imposed by most states including California, the detector must be the ICP-MS. Prior to detection using ICP-MS, cannabis and cannabis related products go through a sample preparation stage consisting of some form of digestion to completely break down the complex matrix and extract the heavy metals for analysis. This two-step process is relatively fast and can be done in a single day, however, the instruments used to perform the digestion are usually the limiting step as the digesters run in a batch of 8-16 samples over a 2-hour period.

Only trace amounts of heavy metals are allowed by California’s BCC in cannabis and cannabis products. A highly sensitive detection system finds these trace amounts and also allows troubleshooting when a product is found to be out of specification.

For example, during the course of testing, we have seen lead levels exceed the BCC’s allowable limit of 0.5 ppm in resin from plastic vape cartridges. An investigation determined that the plastic used to make the vape cartridge was the source of the excessive lead levels. Even if a concentrate passes the limits at the time of sampling, the concern is that over time, the lead leached from the plastic into the resin, increasing the concentration of heavy metals to unsafe levels.

Getting a Representative Sample

The ability to detect trace levels of heavy metals is based on the sample size and how well the sample represents the entire batch. The current California recommended amount of sample is 1 gram of product per batch.  Batch sizes can vary but cannot be larger than 50 pounds of flower. There is no upper limit to the batch sizes for other inhalable cannabis products (Category II).

It is entirely likely that two different 1 gram samples of flower can have two different results for heavy metals because of how small a sample is collected compared to an entire batch. In addition, has the entire plant evenly collected and concentrated the heavy metals into every square inch of it’s leaves? No, probably not. In fact, preliminary research in leafy greens shows that heavy metals are not evenly distributed in a plant. Results from soil testing can also be inconsistent due to clumping or granularity. Heavy metals are not equally distributed within a lot of soil and the one small sample that is taken may not represent the entire batch. That is why it is imperative to take a “random” sample by collecting several smaller samples from different areas of the entire batch, combining them, and taking a 1 g sample from this composite for analysis.


California Cannabis CPA. 12/18/2018.  “What to Know About California’s Cannabis Testing Requirements”. https://www.californiacannabiscpa.com/blog/what-to-know-about-californias-cannabis-testing-requirements. Accessed January 10, 2019.

Citterio, S., A. Santagostino, P. Fumagalli, N. Prato, P. Ranalli and S. Sgorbati. 2003.  Heavy metal tolerance and accumulation of Cd, Cr and Ni by Cannabis sativa L.. Plant and Soil 256: 243–252.

Handwerk, B. 2015.  “Modern Marijuana Is Often Laced With Heavy Metals and Fungus.” Smithsonian.com. https://www.smithsonianmag.com/science-nature/modern-marijuana-more-potent-often-laced-heavy-metals-and-fungus-180954696/

Linger, P.  J. Mussig, H. Fischer, J. Kobert. 2002.  Industrial hemp (Cannabis sativa L.) growing on heavy metal contaminated soil: fibre quality and phytoremediation potential. Ind. Crops Prod. 11, 73–84.

McPartland, J. and K. J McKernan. 2017.  “Contaminants of Concern in Cannabis: Microbes, Heavy Metals and Pesticides”.  In: S. Chandra et al. (Eds.) Cannabis sativa L. – Botany and Biotechnology.  Springer International Publishing AG. P. 466-467.  https://www.researchgate.net/publication/318020615_Contaminants_of_Concern_in_Cannabis_Microbes_Heavy_Metals_and_Pesticides.  Accessed January 10, 2019.

Sidhu, G.P.S.  2016.  Heavy metal toxicity in soils: sources, remediation technologies and challenges.   Adv Plants AgricRes. 5(1):445‒446.

Steep Hill, ACCL Find Pesticides in Over 50% of Cannabis Samples

By Aaron G. Biros

On Election Day, voters in California passed Proposition 64, establishing a recreational cannabis market and regulatory environment. While the state won’t issue the first licenses under the new regulatory scheme until 2018, the medical cannabis industry is already well established.

Steep Hill Labs, Inc., based in Berkeley, California, found in October that 84.3% of samples submitted tested positive for pesticide residue, according to a press release. The announcement came before Election Day, but is particularly eye opening given the massive new market created overnight by Prop 64.rsz_steephill_lab_images_25_of_415_copy

Particularly concerning is their detection of Myclobutanil, which was found in more than 65% of samples submitted to the lab. According to the press release, when Myclobutanil is heated (i.e. smoked or vaporized), it is converted to Hydrogen Cyanide, which is extraordinarily toxic to humans and can be fatal in higher doses.

Reggie Gaudino, Ph.D., vice president of scientific operations and director of genetics at Steep Hill Laboratories. (photo credit: Preston Gannaway)
Reggie Gaudino, Ph.D. (photo credit: Preston Gannaway)

According to Reggie Gaudino, Ph.D., vice president of science, genetics and intellectual property at Steep Hill, their more recent study shows they detected pesticides in roughly 70% of the samples they received and 50% of those contained Myclobutanil. Gaudino says that up to a third of those samples would have failed under Oregon’s regulatory standards.

If a lab test were failed, it would contain pesticides at or higher than the required action level. Oregon’s action level, or the measured amount of pesticides in a product that the OHA deems potentially dangerous, for Myclobutanil is 0.2 parts-per-million (PPM). Steep Hill’s instrumentation has a method detection limit down to the parts-per-trillion (PPT) level, which is a more precise and smaller amount than Oregon’s action level.

“Those in the cannabis community who feel that all cannabis is safe are not correct given this data – smoking a joint of pesticide-contaminated cannabis could potentially expose the body to lethal chemicals,” says Jmichaele Keller, president and chief executive officer of Steep Hill. “As a community, we need to address this issue immediately and not wait until 2018.”

Potentially harmful pesticides, and specifically Myclobutanil, have been detected in Colorado and Washington’s recreational markets on a number of occasions, proving this is a widespread issue. Steep Hill’s release suggests that California regulators take a look at Oregon’s pesticide regulations for guidance when developing the regulatory framework.

What’s even more troubling is that not all laboratories have or had the capability of detecting pesticides at sufficiently low levels and because of this, other labs had significantly lower rates of pesticide detection, suggesting possible inconsistencies in testing methods, instrumentation, sample preparation or other variations. During a 30-day period in late September and early October, Steep Hill found, using publicly available data, or data from contracted testing, that other labs were only reporting between 3% and 21% pesticide detection.

Examination of cannabis prior to testing- credit Steep Hill Labs, Inc.
Examination of cannabis prior to testing- credit Steep Hill Labs, Inc.

It is important to note that those samples were not identical and there could be a great degree in variation on the quality of samples sent to different laboratories, so it is not an entirely accurate comparison. Steep Hill does however detect pesticides down to the parts-per-trillion level, whereas many common methods for detecting pesticides look at the parts-per-billion level.

Reggie Gaudino says the Association of Commercial Cannabis Laboratories (ACCL) is using this data to work with Steep Hill and a number of other labs to address these issues. “As a member of the ACCL, and after discussion with ACCL, we have agreed that all future discussion of this issue should not include laboratory names, as this is about educating the industry in general, and making sure all members of the ACCL are developing the best possible methods for detecting pesticides,” says Gaudino. “The ACCL has responded to this data, by inquiring on a larger, industry-wide basis, which represents a better picture of the issue, rather than only in California’s still-technically unregulated market.” The important message is this is a major issue that needs addressing urgently. “As such, the troubling issue remains, across the larger ACCL membership, there is still detection of pesticides in at least 50% of the cannabis being tested.”

ACCL logoAccording to Jeffrey Raber, Ph.D., president of the ACCL, the industry is experiencing a pesticide problem, but it is very difficult to quantify. “It is fair to say that around 50% of the cannabis being tested contains pesticides, but we really don’t know that exact number until a much more comprehensive statistical analysis is performed,” says Raber. “We agree this is a big problem and that it needs to be addressed, but we are not sure just how big of a problem it really is.” With so much variation in labs in a state where not everyone is required to test products, it is very difficult to pin down how consistent lab results are and how contaminated the cannabis really is. “If all of the labs had the same methodology, samples and shared statistical analyses for a real study then we can look at it closely but it seems we are a ways off from that. I can say confidently however that this is a pretty significant problem that needs addressing.”

Still, Steep Hill detecting pesticides in a majority of their samples and some labs finding as little as 3% should raise some eyebrows. “Unfortunately, our recent study discovered that 84.3% of the samples assessed by our triple quadrupole mass spectrometer contained pesticides,” says Keller. “As of today, this tainted product could be sold in most dispensaries throughout the state of California without any way of informing the patients about the risks of pesticide exposure.”

These findings could mean potentially enormous health risks for medical and recreational cannabis consumers alike, unless regulators, labs and growers take quick action to address the problem.