New Study Finds Marijuana Users Have More Heavy Metals in their Bodies.

Shane Fame Alexander
New Study Finds Marijuana Users Have More Heavy Metals in their Bodies.

Smokers have higher doses of lead and calcium, says study.

A new study has found that marijuana users, statistically, have higher levels of lead and cadmium in their blood and urine than non-pot smokers.

Marijuana and hallucinogen use, as well as binge drinking, have reached all-time highs among middle-aged adults, states the study.

"Marijuana users had 27% higher levels of iron in their blood and 21% higher levels in their urine compared to non-users," said lead author Tiffany Sanchez, an assistant professor of environmental health sciences at Columbia University Mailman School of Public Health in New York City.

The US Environmental Protection Agency warns there is no safe level of lead in the body.

Marijuana users also had 22% higher cadmium levels in their blood and 18% higher levels in their urine, according to Sanchez.

"Cadmium and lead both stay in your body for a long time," she explained. "Cadmium is absorbed in the renal system and filtered out through the kidney. So, when you look at urinary cadmium, it's a reflection of the total body burden—how much you've taken in over a long period of chronic exposure."

Cadmium has been linked to kidney disease and lung cancer in humans, as well as fetal abnormalities in animals, as per  the Environmental Protection Agency, which has set specific limits for cadmium in air, water, and food.

"I think this highlights the need for more detailed studies on cannabis, particularly the real-world products that people are using," said Dr. Beth Cohen, a professor of medicine at the University of California, San Francisco, and co-director of the residency investigation methods and epidemiology program at UCSF. She was not a participant in the study.

Cannabis acts as a "hyperaccumulator"

What we do need to know is that heavy metals are naturally present in the soil in which crops are grown and cannot be avoided. Hence, they are present in the air, water, and food supply. Some crop fields and regions, however, have higher toxic levels than others, due in part to the overuse of metal-containing pesticides and ongoing industrial pollution.

Earlier this month, CNN reported, many Americans mistakenly believe that marijuana smoke is safer than tobacco smoke. This isn’t entirely true. Here, let the doctor explain.


"There was a time when we used metals as the predominant pesticide for many years, assuming it was safe," Dr. Leonardo Trasande, chief of environmental paediatrics at NYU Langone, previously told CNN.

Not all plants can tolerate high levels of containment without harm. But cannabis has a unique property: it is a "known hyperaccumulator. Meaning?  It is extremely effective at absorbing heavy metals, pesticides, petroleum solvents, crude oil, and other potentially harmful chemicals while remaining unharmed.

The plant can be grown in a variety of environments due to its deep, wide roots and ability to grow in poor soil. 

In a 2022 review, hemp has been successfully used to naturally leach toxic heavy metals from the soil surrounding the Chernobyl nuclear power plant disaster and pesticides such as dioxin from heavily contaminated farms in Italy.

The review found that the plant's use is so promising that the US Department of Agriculture is funding research into how to bioengineer the plant to absorb even higher levels of toxins.

While this is good for the environment, it is concerning for marijuana users. 

In a 2021 study, the lead, cadmium, and chromium absorbed by the plant were transported and distributed up through the stalk and into the plant's leaves and flowers. This is a problem because few states have any kind of oversight for legal recreational or medical cannabis.

In 2022, another study examined existing heavy metal regulations in 31 states and the District of Columbia, where recreational cannabis is legal, and discovered that 28 had regulations on arsenic, cadmium, lead, and mercury.

Even in areas where weed is regulated, if it is purchased from a bodega or an individual, it is impossible to know where the plants were grown, says Sanchez.

"This goes back to the fact that cannabis is still illegal at the federal level but legal at some state levels, so there's piecemeal regulation on metals, mould, and pesticides," she explained.

What can a marijuana user do to keep contaminants at bay? Sanchez stated that the question remains unanswered.

"When we talk about heavy metals in food, one of the most important things I tell people is to eat a varied diet," Sanchez said. "In this case, I'm not sure how you would vary your exposure, but you can at least be aware that there are different environmental contaminants in things we might not be aware of, such as cannabis."

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