Cannabis Products May Have Heavy Metal Contamination

Janet Tiberian Author
By Janet Tiberian, MA, MPH, CHES
May 15, 2022
Cannabis Products May Have Heavy Metal Contamination

Cannabis is a group of plants with psychoactive properties that are used to produce industrial hemp, CBD oil, and medical and recreational marijuana. Unfortunately, many people don't realize that cannabis plants can absorb a lot of dangerous heavy metals.

Heavy Metals in Cannabis

Horticulturists have spent years studying cannabis plants. As they gained a deeper understanding of it, they’ve realized that these plants absorb a lot of heavy metals from the soil such as selenium, mercury, cadmium, lead, chromium, nickel and arsenic. Unfortunately, heavy metal content in cannabis is not regulated by the federal government, which means cannabis product users can be exposed to and contaminated with heavy metals, potentially causing: 

  • Headaches
  • Gastrointestinal distress 
  • Anemia
  • Neurological issues 
  • Lung irritation 
  • Lung damage 
  • Memory loss 
  • Miscarriages 
  • Premature labor 
  • Weak bones 
  • Achy joints  
  • Sore muscles 
  • Fatigue

To add insult to injury, certain strains of cannabis plants are bred to help remove pollutants like heavy metals from soil. The process is called phytoremediation, and it helps keep the soil safer but raises the heavy metal level even higher in cannabis plants. 

“Phytoremediation plants help control heavy metals and other forms of organic pollution in the soil,” says Bernard Kaminetsky, MD, medical director, MDVIP. “The means people using CBD products such as oils, creams and gummies may unknowingly be exposed to high levels of heavy metals.”  

Penn State University researchers conducted a metanalysis of studies on heavy metal contamination in cannabis to help determine the: 

  • Path heavy metals take in cannabis plants 
  • Possible effects on consumer health  
  • Agricultural strategies to help cannabis plants absorb lower amounts of heavy metals

Their findings were published in Toxin Review. Here’s a summary.

  • Strains selected for phytoremediation have specific characteristics such as long stems, high root and surface areas, quick growth, high photosynthetic activity and an ability to survive on just a few nutrients.
  • Metals are transported and distributed through the stalk and into the leaves and flowers of the plant and exit via hairlike structures on the flowers called trichomes, which store CBD oil and tetrahydrocannabinol (THC) used in cannabis products.
  • Heavy metals consumed via cannabis usually aren’t metabolized; instead, they accumulate in the body. When they reach a toxic level, reactive oxygen species and free radicals are produced as byproducts. Both reactive oxygen species and free radicals are linked with accelerating the aging process and triggering cardiovascular disease, cancers, cataracts and neurological disorders. 
  • Smoking cannabis – whether for recreational or medicinal purposes -- provides the greatest harm from heavy metals. People living in states where medical marijuana is legal and are using it to stave off chemotherapy side effects may want to talk to their doctor about marijuana edibles, tinctures, oils and butter. Another alternative is vaporizing marijuana. 
  • Cannabis growers should consider plant strains that were not bred to absorb heavy metals and choose farmland free from heavy metals.

People who are worried about the substances they are consuming should consider discussing their concerns with their primary care physician.


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About the Author
Janet Tiberian Author
Janet Tiberian, MA, MPH, CHES

Janet Tiberian is MDVIP's health educator. She has more than 25 years experience in chronic disease prevention and therapeutic exercise.

View All Posts By Janet Tiberian, MA, MPH, CHES
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