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Heavy Metals in Cannabis and Testing Requirements

Updated: Sep 21, 2022

Do you know what’s in your soil? Chances are that your cannabis plant, whether unbeknownst to you or not, is going through a process called bioaccumulation. This process takes place when a contaminant accumulates in a living organism. Types of contaminants can include heavy metals (e.g., arsenic, cadmium, lead, and mercury), which can be dangerous to the human body if ingested. Cannabis plants are no exception and can absorb these harmful contaminants through their roots, leaves, and seeds. Recreational cannabis consumers and medical cannabis patients in particular want to know that what they are putting into their bodies is natural and healthy. Many products are now being tested (mandatorily) for cannabinoid levels, pesticides, and heavy metals (Altmier, 2021). These metals naturally occur in the soil because they are part of Earth’s crust, but rarely at toxic levels. However, it becomes an issue when human activities like mining, agriculture, and industrial waste create pollution leading to a higher amount of metals in some areas (United States Department of Agriculture [USDA], n.d.).

Both hemp and cannabis are known as being hyperaccumulators which means that they can tolerate high levels of metals. After Chornobyl occurred in 1986 in Ukraine, industrial hemp was planted to clean up the toxic waste site, specifically radioactive isotopes that leaked into soil and ground waters (Thomas, 2021). In other uses, hemp is beneficial in the same use for assisting in cleaning up pesticides, solvents, crude oil, polyaromatic hydrocarbons, and toxins. The plant never goes to waste after its cleaning job is done because it can be distilled into ethanol to be used as biofuel (Placido and Lee, 2022).

However, on the opposite side of the spectrum, the fact that this plant can uptake and tolerate high levels of heavy metals is a problem for consumable hemp and cannabis products. Hemp, in this case, can tolerate high levels of cadmium, nickel, and lead. Most metal concentration is found in the leaves (Placido and Lee, 2022). According to the agency for Toxic Substances and Disease Registry (ATSDR), Cadmium is ranked as the seventh most harmful substance (DeJesus, 2021). The consumer boom has been great for hemp growers, but without federal regulation on the amount of heavy metals allowed, it presents a potential health risk to consumers in places where heavy metals testing is not required on hemp or cannabis products. Further to this, products coming from the illicit market that do not adhere to mandatory testing requirements pose an even larger threat.

The Hemp Industries Association is attempting to enact change by advocating for federal regulation regarding “National standardization for hemp testing and labeling requirements” (Erickson, 2019). According to the United States Domestic Hemp Production Program’s Laboratory Testing Guide, which was issued on January 15, 2021, the only testing required is still only regarding the levels of THC. The Hemp Industries Association was investigating this issue back in 2019, which means no progress has been made in regulating the testing of metals in hemp products.

Legislation passed in 2020 made it legal to cultivate hemp anywhere in the U.S. as long as it meets the requirement of being below the 0.3% THC threshold (Farm Bureau, n.d.). Those cultivating hemp will need to monitor the soil where they plant and the fertilizer they use. Due to the amount of legal hemp cultivation, it will become that much more challenging to monitor the levels of metals in CBD products.

If the metals, including Arsenic, lead, cadmium, chromium, and mercury, are unknowingly ingested, they can create a host of medical issues. These chemicals will wreak havoc on the body from the blood vessels, gastrointestinal tract, central nervous system, lung damage to the kidney, and brain, causing severe health issues like cancer or neurological issues (Solis-Moreira, 2022). The biggest issue concerning heavy metals present in cannabis and hemp is that there is a lack of federal legislation. This means it is up to individual states to regulate and require testing for heavy metals to ensure that the products are safe for consumption.

When it is up to the individual states, (there ends up being) a lack of consistency and cohesiveness as far as which metals are tested for, what the limits are based on, if the consumer’s body weight is taken into consideration, or what the delivery method is (e.g., edible, smoke, etc.) (Open Access Government, n.d.). At the forefront of this issue is the current scheduling of Cannabis, a Schedule I, which means it is not currently accepted for medical use and has a high potential for abuse (Drug Enforcement Administration [DEA], n.d.).

Since cannabis cultivators cannot currently rely on federal regulation or, for that matter, the consistency of state regulation, growers will have to be more stringent than ever to ensure that the products they make are consumer safe. As for consumers, Tami Wahl, a Washington D.C.- based attorney and lobbyist for the CBD market, advises consumers to really know their brand due to possible compromises or cut corners within the industry (Erickson, 2019).

Researchers at the Florida Department of Agriculture found something interesting happened with lead-based ink in dropper bottles used with CBD extract products. The sample tested 36 times higher than the state’s maximum limit, which was 0.5 parts per million. Other products like rolling paper have been found to contain high levels of lead as well (Thomas and DeStefano, 2022). An excellent way to ensure safe packaging is to check with local state regulations, browse sustainable and durable options, and ask for Certificates of Analysis from your supplier.


Here are some things to look out for in attempts to limit the amount of heavy metals in your cannabis and hemp plants.

  1. Pick your land carefully: Conduct a full background check to know the history.

  2. Know your Neighbors: To prevent cross-contamination, establish how far away the nearest farm is to you.

  3. Test, Test, Test!: Test the land’s soil for heavy metals, PH levels, nutrient levels, pesticides, and microbial. Also, test the fertilizer you plan to use.

  4. Get to Know your Supplier: Find out what pesticides they use, how they harvest, and if they grow domestically.

  5. True Transparency: Provide QR codes on packaging for your consumers and tell them about the third-party testing labs you use.

  6. Avoid Certain Areas: Specifically, industrial areas that may have a high level of metals in the soil.

  7. Fresh Air: When scoping out the land you plan to use, conduct an air quality test.

  8. Use Durable and Sustainable Packaging

At Steep Hill, we provide heavy metals testing to ensure your products are safe for consumption. Check out our website to find a Steep Hill location closest to you and get in touch to find out how we can help your testing needs.


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Cannabis May Contain Heavy Metals and Affect Consumer Health. Science Daily. (December 16, 2021). Retrieved May 25, 2022, from

DeJesus, C. 10 Tips to Avoid Heavy Metal Contamination in Soils. Cannabis Business Times. (June 28, 2021). Retrieved May 25, 2022, from

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LaJeunesse, S. Cannabis May Contain Heavy Metals and Affect Consumer Health, Study Finds. Penn State. (December 24, 2021). Retrieved May 25, 2022, from

Measuring Heavy Metals in Cannabis and Hemp. Open Access Government. (May 4, 2020). Retrieved May 25, 2022, from

Placido, D. and Lee, C. (2022). Potential of Industrial Hemp for Phytoremediation of Heavy Metals. Plants Basel, 11(5), 595. doi: 10.3390/plants11050595

Rabab, H et al. (2019). Enhanced Tolerance of Industrial Hemp (Cannabis Sativa L.) Plants on Abandoned Mine Land Soil Leads to Overexpression of Cannabinoids. Plos One, 14(8), doi: 10.1371/journal.pone.0221570

Schaneman, B. Cannabis Packaging Companies Seek Sustainable Solutions to Woo Customers. MJ Biz Daily. (November 12, 2021). Retrieved May 25, 2022, from

Solis-Moreira, J. Cannabis Farms with Heavy Metals in Soil Could Be Creating Toxic Marijuana Products. Study Finds. (February 4, 2022). Retrieved May 25, 2022, from

Thomas, R. Can Avid Hyperaccumulating Plants Like Hemp Realistically Be Used as a Source of Medicinal Cannabinoids? Part 1: The Conflicting Personality of Hemp. Analytical Cannabis. (February 17, 2021). Retrieved May 25, 2022, from,of%20contaminants%20in%20the%20soil.

Thomas, R. and DeStefano, A. Understanding Sources of Heavy Metals in Cannabis and Hemp: Benefits of a Risk-Assessment Strategy-Part 4. Analytical Cannabis. (May 25, 2022). Retrieved May 27, 2022, from

USDA Releases Long-Awaited Industrial Hemp Regulations. Farm Bureau. (n.d.). Retrieved May 25, 2022, from

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