Blood and urine tests from 7,254 people who said they had used marijuana in the past 30 days were examined for heavy metal levels, which makes the new study “unique” — most studies simply measured metal levels in cannabis plants , and not in people who use marijuana, Sanchez said.
“Our study was unable to determine whether or not self-reported cannabis users were using medicinal or recreational cannabis, so we cannot say with certainty whether medical cannabis users specifically had higher levels of the metal,” she said. “This is something that should be evaluated in future studies.”
Heavy metals bind to the body’s cells, limiting their function, according to the Cleveland Clinic, and have been linked to cancer, chronic disease and neurotoxic effects.
“Immunocompromised people, such as those undergoing chemotherapy, may be at greater risk due to exposure to metals or other common cannabis contaminants, such as fungi. However, this is an understudied area,” added Sanchez.
Heavy metals aren’t just in marijuana — tobacco smokers are exposed to even more types of toxins. E-cigarettes, for example, contain high levels of nickel, chromium, lead, and zinc aerosols, while researchers have found that e-liquids and e-cigarette tanks contain arsenic, lead, nickel, tin, manganese, copper, and chromium, according to the studies.
As natural elements, heavy metals are in the soil that crops are grown in and cannot be avoided, one of the main reasons they exist in the air, water and food supply. Some fields and agricultural regions, however, contain more toxic levels than others, in part due to overuse of pesticides containing metals and ongoing industrial pollution.
“There was a time when we used metals as the predominant pesticide for many years, assuming it was safe,” Leonardo Trasande, chief of environmental pediatrics at NYU Langone, told CNN in an interview previous .
Not all plants can absorb high levels of contamination without causing damage. But cannabis has a special property — it’s a “known hyperaccumulator,” meaning it’s extremely good at absorbing heavy metals, pesticides, petroleum solvents, crude oil, and other potentially harmful chemicals, without causing harm to itself.
Due to its wide, deep roots and ability to grow in poor soils, the plant can be grown in many environments. In fact, hemp, which is a cannabis plant, has been successfully used to naturally leach toxic heavy metals from soil around the Chernobyl nuclear power plant disaster and pesticides such as dioxin from highly contaminated farms in Italy, from according to a 2022 revision.
The plant’s use is so promising, according to the review, that the US Department of Agriculture is sponsoring research into how to bioengineer the plant to absorb even greater levels of toxins.
While this is good news for the environment, it is worrisome for marijuana users. A 2021 study found that lead, cadmium, and chromium absorbed by the plant were transported and distributed throughout the stem and the plant’s leaves and flowers. This is a problem, as few states have any oversight of legal recreational or medicinal cannabis.
A 2022 study examined existing regulations on heavy metals in the 31 states and the District of Columbia where recreational cannabis is legal and found that 28 had regulations on arsenic, cadmium, lead and mercury.
However, even in regulated areas, if the herb is purchased from an establishment or an individual, there is no way to know where those plants were grown, Sanchez said.
“This goes back to the fact that cannabis is still illegal at the federal level but legal at some state levels, so there is fragmented regulation around metals, molds and pesticides,” she said.
What can a marijuana user do to protect themselves from contaminants? That’s still a question with no clear answer, Sanchez said.
“One of the biggest things I tell people when we talk about heavy metals in food 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 that we might not be aware of, like cannabis.”
SEE ALSO – Medical marijuana can be used for treatments without causing addiction
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