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Can Avid Hyperaccumulating Plants like Hemp be Realistically Used as a Source of Medicinal Cannabinoids? Part 2: The Importance of Testing

By Robert Thomas

Published: Mar 04, 2021   
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Part one of this article focused on the phytoremediation properties of hemp and why it has been used to clean up toxic waste sites where other types of remediation have failed. The second part will examine industrial and medical applications of hemp including its use for the production of cannabinoid products and emphasize the importance of regular testing for heavy metals to ensure maximum consumer safety.

Hemp as a source of CBD

It is a very important point to emphasize, that cannabis and hemp have found commercial use as a source of cannabinoids for medicinal and adult recreational use. When used for this purpose, they are strictly regulated by individual states 1, so there is a robust regulatory process with maximum allowable heavy metal limits (Pb, Cd, As, Hg), which is supported by vigorous third party testing procedures to ensure the safety of consumers 2. In addition, hemp is also grown as a source of edible seeds as well as for industrial purposes including biofuels, building materials, plastics, fabrics and much more. Currently, there are very few regulations with regard to heavy metal limits in these products, so they could contain extremely high levels of heavy metals, depending on the source of the hemp and where it’s grown.

Because of the lack of regulatory procedures, clearly hemp used for phytoremediation purposes cannot be used in the production of cannabinoids or for growing seeds. However, it has been mentioned in a number of Internet discussion groups that it could be possibly used to make other products including biofuels, textiles, plastics, or hempcrete (a building material made from hemp). Although this could be a very attractive option, the industry should proceed with caution. Depending on the element, it has been shown that hemp and other hyperaccumulator plants can extract up to 50,000 mg/kg of metallic contaminant out of the soil and still remain healthy. If the contaminant levels are at the low end of this range, I think the risks are relatively low, but if they are at the high end, would the marketplace embrace a product that could potentially have these levels of toxic contaminants, particularly for a consumer product like hemp seeds?

One could argue that hempcrete might not be such a serious problem, particularly if it’s used for outdoor building construction purposes. However, wearing clothes using textiles made from contaminated hemp might not be such a good idea. Moreover, I would strongly suggest that heavily contaminated hemp should not be used in the production of biofuels (eg. bioethanol, biodiesel, etc.) either, especially if the contaminant is a heavy metal. For example, if there are high levels of Pb in the hemp, significant amounts are likely to be extracted into the biofuel. Depending on its use, this could be a potential problem. For example, if the fuel is used in automobiles, engine combustion will generate vaporized Pb particles, which will be emitted out of the vehicle's tailpipe. It’s well-recognized that catalytic converters do not remove lead compounds 3, so all of a sudden this environmentally-friendly biofuel becomes a toxic polluter of lead. The US banned the use of tetraethyl lead as a gasoline additive in the mid-1990s....we should have learned our lesson then!

So clearly, robust hemp regulations are critical to ensuring consumer safety. Let’s take a brief historical look at the regulatory landscape for hemp.

An overview of hemp regulations

The challenges of regulating the hemp industry were compounded when CBD products derived from hemp began to hit the marketplace at high volumes in 2020. Up until then much of the cannabis grown in the US was cultivated in greenhouses where the growing environment is controlled. However, when the growing of hemp for research purposes was legalized in the Agricultural Act of 2014 (also known as the 2014 Farm Bill) 4, outdoor cultivation became more common where there was less control over growing conditions and a higher risk of heavy metal contamination from the soil.

So it’s worth taking the time to summarize the current status of regulations for hemp in the US 5. In the revamped Hemp Farming Act of 2018 (also known as the 2018 Farm Bill), the federal government has made it legal to grow hemp (defined as cannabis containing less than 0.3 % THC) by removing it from the controlled substance list. As a result, growers do not need a permit from the Drug Enforcement Administration (DEA). This adds a new twist to the state-based regulations for cannabis, because the bill directed the U.S. Department of Agriculture (USDA) to issue regulations and guidance to implement a program for the commercial production of hemp which could either be used for a variety of industrial processes (inc. fuels, textiles, concrete, fibers, plastics, etc.), as a health food supplement (eg. hemp seeds) or as a source of CBD products from the hemp flowers (oil, supplements edibles, etc.)

USDA has already begun the process of gathering information for rulemaking. Once complete, this information will be used to formulate regulations that will include specific details for both federally regulated hemp production and a process for how individual states should submit their plans to the USDA. In the short term it is likely that the USDA will look to the states’ departments of agriculture who will be assisted by specialized hemp analytical testing laboratories which were originally required to be registered with the DEA, but in a recent update (Jan 19, 2021), it looks like this could be relaxed as long as the lab has the necessary accreditation according to International Organization of Standards (ISO)17025:2017 6. Currently, potency is the most important requirement because hemp is not allowed to have > 0.3% THC, but it is likely they will be guided by state cannabis commissions for maximum levels of contaminants such as pesticides and heavy metals. And as previously mentioned, it could potentially be more complicated to regulate hemp grown for CBD products, because the vast majority of hemp plants will be grown outdoors where there is less control over the growing environment.

Regulations for states that submit plans will include procedures and information collection regarding: land to be used for planting; testing; effective disposal of plants and products; compliance with law enforcement; annual inspections; submission of information to USDA; and certification that resources and personnel are available to carry out these procedures. States do not need to submit plans for approval until regulations are in place. However, should a state submit a plan, USDA will hold that submission until regulations have been implemented.

The Farm Bill allowed states and institutions of higher education (universities, research organizations), to continue operating under authorities of the hemp research program for the 2019 planting season. The 2018 Farm Bill also extended the 2014 Farm Bill authority for one year, so states were allowed to continue operating pilot programs. The USDA also established a plan to monitor and regulate the production of hemp in those states that do not have an approved plan, as well as issuing regulations to accommodate the 2021 planting season.

Note: the U.S. Domestic Hemp Production Program extended its comment period to allow stakeholders time to provide feedback, and the USDA has indicated it will give itself until Nov. 1, 2021, to issue final regulations. As soon as the regulations have been approved they will be published in the Federal Register, when it will be legal to grow hemp anywhere in the US for the production of CBD-based products. So it will be interesting to see how the Department of Agriculture regulates the industry at the federal level, particularly with regard to heavy metals when cannabis is currently regulated by the individual states.

It’s also worth pointing out that the 2018 Farm Bill also explicitly preserved the authority of the U.S. Food and Drug Administration (FDA) to regulate hemp products under the Federal Food, Drug, and Cosmetic Act, which states that products containing cannabinoid-derived compounds are subject to the same authorities and requirements as FDA-regulated drug products containing any other substance. In fact, this has already come into play, as there have been a number of product recalls for heavy metal limits being exceeded in hemp-derived CBD products 7.

Final thoughts
Hemp is a very powerful and flexible plant with multiple personalities. It has shown itself to be a prolific phytoremediator that can thrive anywhere, including in contaminated soil. In this role it clearly has unique capabilities to clean up toxic pollutants where other approaches have failed. In addition, it can be used to make novel fabrics for clothes, durable plastic materials, paper products, hempcrete for the construction industry, as well as many other applications. However, its role in the manufacture of cannabinoid products is probably creating the most excitement because of its ability to treat multiple ailments including pain management, stress, anxiety, depression, seizures, epilepsy, etc. However, it should be strongly emphasized that because hemp can be used for such a wide range of applications it is critically important that the growing conditions are carefully monitored. When grown outdoors, it will avidly accumulate metals from the soil, irrespective of whether the soil is contaminated or not. So if it is going to be used for cannabinoid production, it’s imperative to make sure the soil chemistry is well-characterized before planting and that the plant and its products are tested for a comprehensive panel of metals 8. Alternatively, if it’s going to be used for phytoremediation purposes, its final end use should be carefully considered, particularly if the application of the final products could pose a safety risk for the consumer.

A word of caution!

The insatiable consumer appetite for cannabis products in the US is being fulfilled from outside the country. Yunnan Province in southern China is now producing CBD-products for the US market 9. This should not be surprising, considering that we cannot produce enough to supply the huge demand. However, what is more disturbing is that metal refining for the electronics industry in China has produced some of the most contaminated waste sites in the world 10. Experience has warned us that consumer products coming from China aren’t always of the highest quality. So it’s imperative that no matter where the products are sourced, especially if it is from outside the US, testing the hemp and CBD products for a comprehensive suite of elemental contaminants is critically important. Our love of the cannabis and hemp plant for their cannabinoids is never going to diminish so we are always going to have to balance that with its heavy metal content. Hopefully, we will not be tempted to sacrifice one for the other and jeopardize consumer safety.

Further reading

1.      Map of Marijuana Legality by State, Governing.com, https://www.governing.com/archive/state-marijuana-laws-map-medical-recreational.html

2.      The Importance of Measuring Heavy Metal Contaminants in Cannabis and Hemp, Analytical Cannabis White Paper, February 10, 2021, Robert Thomas, https://www.analyticalcannabis.com/white-papers/the-importance-of-measuring-heavy-metal-contaminants-in-cannabis-and-hemp-312957

3.      How Does Leaded Fuel Affect Catalytic Converters? Tom Wilkowske, https://itstillruns.com/leaded-fuel-affect-catalytic-converters-7826145.html

4.      2014 Farm Act, US Department of Agriculture, https://www.ers.usda.gov/agricultural-act-of-2014-highlights-and-implications/ 

5.      2018 Farm Bill, US Department of Agriculture, https://www.usda.gov/farmbill

6.      USDA Agricultural Marketing Service, Hemp Production Final Rule: https://www.ams.usda.gov/rules-regulations/hemp

7.      Regulating Heavy Metal Contaminants in Cannabis: What Can be Learned from the Pharmaceutical Industry? Part 4, Robert Thomas, Analytical Cannabis, June 30, 2020, https://www.analyticalcannabis.com/articles/regulating-heavy-metal-contaminants-in-cannabis-what-can-be-learned-from-the-pharmaceutical-312494

8.      Regulating Heavy Metal Contaminants in Cannabis: What Can be Learned from the Pharmaceutical Industry? Part 1, Robert Thomas, Analytical Cannabis, April 9, 2020, https://www.analyticalcannabis.com/articles/regulating-heavy-metals-in-cannabis-part-i-what-can-be-learned-from-the-pharmaceutical-industry-312336

9.      China Cashes in on the Cannabis Boom, New York Times editorial, S. Meyers, May 4, 2019, https://www.nytimes.com/2019/05/04/world/asia/china-cannabis-cbd.html

10.  China: Toxic trails from metal production harms health of poor communities amid soaring global demand for gadgets; G. Shih, Washington Post, January 5, 2020, https://www.business-humanrights.org/en/china-toxic-trails-from-metal-production-harms-health-of-poor-communities-amid-soaring-global-demand-for-gadgets

Robert Thomas

Principal of Scientific Solutions

Rob is a heavy metals expert and has written for Analytical Cannabis on the subject since 2019. Through his consulting company Scientific Solutions, he has helped educate countless professionals in the cannabis testing community on heavy metal analysis. He is also an editor and frequent contributor of the Atomic Perspectives column in Spectroscopy magazine, and has authored five textbooks on the principles and applications of mass spectrometry. Rob has an Advanced Degree in Analytical Chemistry from the University of Wales, UK, and is a fellow of the Royal Society of Chemistry and a chartered chemist.


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