Things to Know: Heavy Metals in CBD

Posted: January 5th, 2021

- Richard, the Farm Doc

Hemp as a hyperaccumulator of heavy metals

The hemp plant is very efficient at extracting heavy metals from the soil and concentrating them in the roots, leaves, and to a lesser degree the flowers.  Even soil containing minimal amounts of heavy metals can produce hemp CBD oil with significant levels of heavy metals, especially if processed from the leaves and stems, in addition to the flowers.3,4,5 

Hemp used for phytoremediation and phytomining

Phytoremediation is the use of plants to remove, degrade, and concentrate toxins from soil.  Phytomining is the use of plants to commercially extract and concentrate valuable metals from the soil.  Hemp is an ideal plant for both of these indications, with the added benefit that there are multiple safe uses of the fiber after remediation, depending on the compound being extracted.1 

How heavy metals affect health

Heavy metals are defined as those with a density > 5 g/cubic cm.  All plants and animals require trace amounts of many heavy metals for normal cell functions.6 However, too much is toxic, resulting in disease.  The heavy metals most likely to cause disease in humans, which have been shown to accumulate in hemp roots, leaves, and to a lesser extent flowers. are lead, cadmium, mercury, and arsenic.3  Diseases associated with these heavy metals are low blood count, kidney and brain damage (lead); peripheral artery disease (cadmium); brain damage and muscle weakness (mercury); heart disease, elevated blood pressure, cancer and stroke (arsenic).  

Testing CBD products for heavy metals: importance of using a DEA registered lab.

There are multiple methodologies for testing plant matter for heavy metal content.7  The quality and reliability of test results can vary significantly from lab to lab depending on the methodology used, and the quality controls applied.  Given the importance of knowing the level of heavy metals in the CBD products you are taking, it is optimal to see results from a DEA registered lab.  The USDA keeps a list of these labs.2

What to look for in test results: RavenRidge Family Farm results.

RavenRidge Family Farm uses estate grown hemp to make our CBD products.  We test the CBD oil generated each growing season for heavy metals.  Below are the results for our 2020 season, from Sativa Testing, a DEA registered lab.2






Peer Reviewed Scientific Articles:

  1. Heavy metal tolerance and uptake of Cd, Pb, and Tl by hemp; M. Di Candito et al; Advance in Horticulture Science; Vol. 18, No.3 (2004), pp 138-144

  2. Cannabis contaminants: sources, distribution, human toxicity and pharmacologic effects; Laura M Dryburgh et al; Br J Clin Pharmacol. 2018 Nov; 84(11): 2468-2476.

  3. Effects of Soil Contamination on Some Heavy Metals Content of Cannabis sativa; Murad Ali Khane el al; J.Chem.Soc.Pak, Vol. 30, No. 6, 2008


  1. Diet and Health: Implications for Reducing Chronic Disease Risk; National Research Council (US) Committee on Diet and Health. Washington (DC): National Academies (US); 1989

  2. Measuring Heavy Metal Contaminants in Cannabis and Hemp; Robert J. Thomas; CRC Press; First Edition, 2020.


  1. RavenRidge 2020 Heavy Metals test results.

Learn more about Richard

Richard "The Farm Doc" is a Family Physician, committed to providing science based information to help people make informed decisions about their health, and to understand the connection between their health and the health of our soil, plants, and planet.

Full bio here.

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