Study Raises Concerns Over Heavy Metals In Cannabis

A recent study has raised concerns over levels of heavy metals in cannabis plants.

In a recent report, Penn State researchers raised concerns over heavy metal contamination in cannabis causing health problems like cancer and neurological issues in users.

The report examines cannabis’ ability to absorb heavy metals, details health impacts on consumers, and suggests how growers can address the issue.

Because cannabis is a phytoremediator, meaning it extracts environmental pollutants from the soil, toxins absorbed by the plant will remain in it and any products made from it.

Chernobyl and Soil Contamination

A notable example of utilizing cannabis for its phytoremediation properties is the Chernobyl power plant in Pripyat, Ukraine.

On April 26, 1986, an accident happened at the No. 4 reactor at the Chernobyl power plant during a safety test on the steam turbine of a nuclear reactor.

Through a combination of operator negligence and critical design flaws, the core melted down, and at least two explosions ruptured the reactor core and destroyed its building.

The Chernobyl disaster is considered one of the worst nuclear disasters in history.

Later surveys of the 30-kilometer area surrounding the Chernobyl power plant revealed high lead, cesium-137, strontium-90, and plutonium concentrations in the soil, plant, and animal tissues.

In 1998, hemp was planted at Chernobyl to help remove contaminants from soil and reduce toxicity.

But while hemp is beneficial for cleaning toxins from contaminated environments, cannabis plants intended for human consumption must be clean and free of contaminants.

Infinite Chemical Analysis Labs Lab Manager Jayneil Kamdar Ph.D. says cannabis is in a category of plants called hyperaccumulators, which can accumulate heavy metals in the soil more rapidly through their root systems.

“In fact, this hyperaccumulation ability often makes cannabis a promising candidate for phytoremediation of heavy metals in contaminated soil,” says Kamdar. “On the other hand, extra precautions must be taken to ensure that cannabis plants are grown in non-contaminated soil to mitigate the public health risks. It’s imperative that all cannabis and hemp intended for medical or recreational use is tested at a state-certified lab like InfiniteCAL prior to it becoming available on the market.”

According to InfiniteCAL, extensive testing rules and regulations should be implemented to combat contamination.


According to the research team, some cannabis strains are bred to enhance phytoremediation characteristics like long stem length, fast growth, and high root and leaf area.

The Penn State research team learned that lead, cadmium, and chromium travel through the stalk and into the leaves and flowers, exiting through the plant’s trichomes.

Trichomes are a primary focus in the cannabis industry as the hairlike structures are where the plant stores tetrahydrocannabinol (THC) and cannabidiol (CBD) oils.

While cannabis contaminated with heavy metal or other toxins is never safe to consume, it’s particularly concerning regarding medical cannabis patients.

If someone is using cannabis as medicine, it cannot contain contaminants like heavy metals, which can cause various side effects.

Heavy Metal Health Hazards

Penn State Assistant Research Professor Louis Bengyella says heavy metals like lead, cadmium, mercury, and chromium are known carcinogens.

“The heavy-metal content of cannabis is not regulated; therefore, consumers could unknowingly be exposed to these toxic metals,” says Bengyella. “This is bad news for anyone who uses cannabis but is particularly problematic for cancer patients who use medical marijuana to treat the nausea and pain associated with their treatments.”

Bengyella says smoked cannabis represents the greatest danger to human health as it can contain selenium, mercury, cadmium, lead, chromium, nickel, and arsenic.

Bengyella says cannabis consumers, especially cancer patients, may be causing unnecessary bodily harm.

Arsenic can damage blood vessels and other organs and tissues in the body, and lead can affect the gastrointestinal tract and central nervous system.

Cadmium causes bone and lung damage, chromium causes cardiovascular, respiratory, and other internal issues and mercury can damage the kidneys, brain, nervous system, and lungs.

Additionally, heavy metals can cause other severe problems like various cancers, allergies, psychosis, autism, tumors, and chromosomal aberrations.

Finding a Solution

Bengyella says that while the problem is at the consumer level, it needs addressing at the agricultural level.

Study authors say that choosing cannabis varieties that have not been bred for phytoremediation and using heavy metal-free farmland can mitigate contamination.

The authors recommend avoiding abandoned industrial sites and conducting air quality and soil pH tests before choosing a cannabis farming location.

“A blueprint of agronomic strategies to alleviate HMs uptake by cannabis is proposed,” states the study abstract. “We show revamping cannabis global production necessitates a rethinking of agronomic best practices and post-harvest technologies to remove metal contaminants.”