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Heavy Metals

Article by Justin Gilbert, Head of Testing & Analytics, Aron Rosenthal and Melissa Bolin

Heavy Metal Testing is a Top Priority

Let’s talk about heavy metals and their relationship to cannabis cultivation. Some of you may be asking, “What in the heck does Black Sabbath and Motörhead have to do with cannabis cultivation?” Good question. Although we’ve heard playing music can stimulate plant growth, this isn’t the “heavy metal” we’re referring to.  We’re mainly talking about Arsenic (As), Cadmium (Cd), Mercury (Hg) and Lead (Pb), known as the “major four” heavy metals and far more dangerous to our youth than the metal bands experts have long warned parents about (remember Tipper Gore?). These heavy metals aren’t just dangerous, they can be deadly, and they pose a real challenge to the cannabis industry as a whole. This article will help you understand heavy metals and what you can do to avoid their concentration in your products.

Let’s start with what a heavy metal is and why they are so dangerous. Generally, a heavy metal is any metallic chemical element that has a relatively high density. But it’s vitally important to add that heavy metals are toxic to humans and other animals even in extremely low concentrations. In humans, heavy metal poisoning has been linked to heart disease, birth defects, respiratory issues, and cancer (just to name a few). At Batch 64, we believe both growers and end users would greatly benefit from standardized testing for heavy metals. Here’s why:

Like many other plants, cannabis can be contaminated by many things in its environment. Toxins can be introduced to a plant from a variety of sources including fertilizer, growing media, irrigation water, pesticides and contaminated soil. But cannabis finds itself in a special category of plants because it is a so-called “hyperaccumulator”, meaning it can accumulate extraordinary amounts of toxins which the plant up-takes through its roots and then stores in its biomass, including the flower. And since cannabis is one of the few plants we consume by ingesting, drinking, and smoking, the health effects of consuming heavy metals stored in cannabis, and all its related products, are not entirely known.

To further complicate the issue, cannabis’s illegal status at the federal level has caused potentially dangerous challenges related to the regulation of analytics and particularly testing for heavy metals. Currently, the regulation of analytics has been left to each state’s discretion and this has resulted in confusion about which heavy metals should require mandatory testing and how we define “safe” levels of concentration. However, most states agree that we should be testing for the “major four” as these are the heavy metals most commonly absorbed by the human body at potentially toxic and even deadly levels.

And now I’d like to describe a challenge to growers in particular. If a heavy metal is present in a fertilizer, grow media, water, etc., that doesn’t automatically mean the plant will be able to uptake it. These chemical elements have to be in a form suitable for the plant to absorb them and require particular soil conditions favorable for their uptake. These conditions include both the soil’s pH and its cation exchange capacity (CEC). For example, as the soil pH decreases, the potential for heavy metal uptake increases. But this is not the case for mercury and arsenic which generally become available for plant uptake as soil pH increases. Furthermore, soil CEC relates to the availability of heavy metals because nearly all heavy metals are themselves cations (positively charged ions). As the CEC of the grow media increases, it will tend to hold on to more heavy metals which can result in making them less available to the plant. Logically, when CEC decreases, heavy metals become more available to the plant. So what does all this mean for growers? Sourcing products from manufacturers that test for heavy metals and controlling your grow media’s pH and CEC are of paramount importance.


So what does this mean to you, as a cultivator and business owner, us at Batch 64 and the end cannabis product consumer?

As the industry matures and cannabis is legalized across the U.S. and in other countries, more stringent regulations related to the plant’s potency, residual solvents, pesticide contamination and heavy metals will emerge. Growers need to be prepared and especially those multi-state operators who are working hard to standardize their operations across many regions. 

But we know heavy metals pose a significant threat to end users now and the cannabis industry can’t wait for state and federal lawmakers to pass legislation to regulate testing and analytics. In fact, industry stakeholders who take proactive steps today to limit the concentration of heavy metals in their products will be in a far better position when regulation gets imposed on the industry.  

This is exactly why at Batch 64 we routinely test for the “major four” heavy metals and also for many others. So when you partner with Batch 64, you are doing much more than merely sourcing products you need to grow and produce. You are sourcing a built-in solution to the problem of heavy metals in soil media because we’ve already tested for them.  So go ahead and turn up the heavy metal music knowing that when you grow with Batch 64, you are growing with confidence.

For more information on our testing & analytics, reach out to us directly here


Nutrients, Sponsored Content: Advanced. “The Dangers of Heavy Metals in Your Cannabis Crop.” Cannabis Business Times, Cannabis Business Times, 5 June 2017,
Tangahu, et al. “A Review on Heavy Metals (As, Pb, and Hg) Uptake by Plants through Phytoremediation.” International Journal of Chemical Engineering, Hindawi, 16 Aug. 2011,
“Water Treatment Solutions.” Lenntech Water Treatment & Purification,

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