Cannabis absorbs heavy metals that may harm human health

Cannabis plants – the source of medical marijuana, CBD oils and hemp – have a strange propensity to absorb heavy metals from soils. This ability makes them valuable for restoring contaminated soils, it can also lead to health problems in those consuming cannabis products. 

A new meta-analysis led by scientists from Penn State looks at the absorption of heavy metals by cannabis and the ensuing health risks for consumers. 

“Heavy metals, such as lead, mercury, cadmium and chromium, are known to be carcinogenic,” said Professor Louis Bengyella. “The heavy-metal content of cannabis is not regulated; therefore, consumers could unknowingly be exposed to these toxic metals. 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.”

Unfortunately, the problem is made worse by selective breeding of some strains, specifically for phytoremediation, that is the absorption of toxins from soil, air and water. 

“The problem is if we use these strains that were developed for phytoremediation without considering why they were developed in the first place, we may unknowingly expose consumers to heavy metals,” explained Bengyella.

In the study, which is published in the journal Toxin Reviews, Bengyella and colleagues looked at and analyzed previous research on phytoremediation, what happens to absorbed metals and the resulting health problems. 

The researchers found that some commonly grown plants were used for phytoremediation because of their long stem length, fast growth, high root and leaf surface areas, all qualities that improve heavy metal absorption. The team also found that trichomes – hair like structures – are where heavy metals exit the plant.

“Trichomes are important because they store the CBD oil and the tetrahydrocannabinol (THC) that are desired by consumers,” said Bengyella. “This led us to question if these heavy metals are there at the level of the trichome, what can they do to people?”

The scientists turned to the known health effects of heavy metals on people. They found that the metals absorbed by cannabis can cause a variety of health problems. Through reactions inside the human body, the metals can cause damage to enzymes, lipids, proteins and nucleic acids. Heavy metal consumption can lead to cancer and neurological problems. 

“Cannabis consumed in combustive form represents the greatest danger to human health, as analysis of heavy metals in the smoke of cannabis revealed the presence of selenium, mercury, cadmium, lead, chromium, nickel and arsenic,” said Bengyella.

“It is disturbing to realize that the cannabis products being used by consumers, especially cancer patients, may be causing unnecessary harm to their bodies.”

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By Zach Fitzner, Earth.com Staff Writer