The Dangers of Heavy Metals in Your Cannabis Crop

Cannabis cultivators know that their crops must be safe from contaminants to ensure not only quality, but safety, for their consumers. That’s why it’s crucial to know the hidden dangers of unwanted elements—especially heavy metals—and how they can be prevented and eradicated from your operation. Advanced Nutrients’ Michael "BigMike" Straumietis shares his industry expertise on the issue.

Cannabis Business Times: Which heavy metals should growers be concerned about?

“BigMike”: Growers should be concerned about the content of all heavy metals in their final product, because all cannabis is grown for ingestion of some form. However, a few that stand out because they’re so dangerous are arsenic, cadmium, cobalt, copper, lead and mercury.

CBT: How do each of those metals adversely affect the human body?

BM: Heavy metals, depending on their concentrations, can have a wide range of effects on the human body. Everything from headaches, nausea, to organ failure, and cancer in cases of prolonged or extreme exposure. Because cannabis is often combusted, there are increased respiratory risks as well.

If cannabis contains heavy metals and is smoked, the heavy metals mimic other essential elements and replace them in bones and in other cellular processes. In short, these metals bind with sites which were not originally intended for them and, in the process, they remove the original metals from their natural binding sites. This is what causes the malfunctioning of cells and, ultimately, toxicity. Heavy metals also cause oxidative stress, which greatly increases free radicals in the body, causing further damage.

CBT: Why do cultivators need to be especially cognizant of heavy metals for medical marijuana patients?

BM: First, cultivators need to be cognizant of heavy metals for patients simply because medical marijuana patients are using marijuana to improve their health, not make it worse. Medical marijuana patients often have compromised immune systems, which can make them especially susceptible to harm from heavy metals.

Second, cannabis is unique as a crop because it’s frequently combusted when used, which is different than other plants. In other words, because of the way it’s consumed is so unique, there’s still a lot to learn about how this type of use influences things we know, or thought we knew, about heavy metal concentrations—and their effects on the human body—in other crops.

Above: Michael "BigMike" Straumietis

CBT: How can heavy metals be accumulated into plants to begin with?

BM: Cannabis is unique because it’s an accumulator plant—it takes up everything from its environment. Heavy metals typically accumulate in the plant through the root system. This can include fertilizers with large amounts of heavy metals or contaminated soil. Even water from contaminated soils can carry heavy metals and be absorbed by the plant.

CBT: How can cultivators become aware of which heavy metals are present in their plants?

BM: The first thing to do is for cultivators to ensure they’re using fertilizers comprised of high-purity and high-grade minerals. At this time, there aren’t many places where you can directly go to check on the quality of nutrients in regard to heavy metals, but here are some things you should know… 

California, Oregon and Washington all require fertilizers to be registered to be sold in their states. Part of that registration process requires an independent lab test for heavy metals showing that the product is at or below the allowable level. In California, that list is available through CDFA. Washington has the same requirements as California, but doesn't require registration for supplement products (those without plant nutrients), so those products 'escape' regulatory oversight in this state. This is required for Oregon registration too, but only for arsenic, cadmium, mercury and nickel.

In short, anything in the growing environment—growing medium, nutrients, water—can contaminate your plants.

CBT: How do fertilizers contribute to heavy metals within a cannabis plant?

BM: The fact is that the biggest culprit of heavy metal accumulation in plants is low-grade fertilizers. This is because the mined minerals used in cheaper fertilizers can often contain heavy metal by-products if cheaper, lower-grade sources for these minerals are used.

Images courtesy of Advanced Nutrients