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Cannabis Consumers Have More Heavy Metals in Their Blood, Study Finds

By Leo Bear-McGuinness

Published: Sep 06, 2023   
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Cannabis consumers have higher levels of cadmium and lead in their blood than people who don’t consume the drug, according to a new study.

After analyzing thousands of blood and urine samples from participants, the researchers found that, compared to those who didn’t consume the drug, marijuana users had 27% higher levels of lead in their blood and 21% higher levels in their urine, on average.

The study was published in Environmental Health Perspectives.

Metal in the blood

To get their findings, the researchers – who were principally from the Columbia University Mailman School of Public Health, New York – accessed records from the National Health and Nutrition Examination Survey, which collects, among other data, blood and urine samples from people across the US.

The researchers divided their samples into four categories: those that had come from people who claimed not to consume marijuana or tobacco (4,666 participants), those from the “exclusive marijuana use” group (358 participants), “exclusive tobacco use” (1,511), and “dual use” (719).

After comparing the heavy metals recorded in all participants’ blood and urine samples – and adjusting the data for covariates such as age, sex, ethnicity, etc. – the researchers found that the “exclusive marijuana” samples had higher levels of cadmium (1.22μg/L higher in the blood) and lead (1.22μg/L higher in the blood) when compared to the sample from participants who didn’t use either cannabis or tobacco.

These heavy metals levels were even higher in the participants who said they’d consumed cannabis in the past seven days.

Cadmium and lead levels were also higher in the “dual use” samples than in the no-tobacco/no-cannabis samples.

Exclusive tobacco use was also associated with higher blood levels of cadmium and lead, higher urinary levels of antimony, barium, cadmium, lead, and uranium, and lower urinary levels of molybdenum when compared with the non-marijuana/non-tobacco use participants.

Heavy implications

Both cadmium and lead are associated with a number of health issues, from bone damage and osteoporosis, to renal dysfunction, arthritis, and brain damage.

How could the metals come to be found in cannabis products? Well, both elements are naturally found in minuscule quantities in many soils around the world. These soils can be considered safe, but if cannabis is then planted, the crops can accumulate the heavy metals and store them in their leaves and stems.

Other materials used in the consumption of cannabis, such as rolling papers and e-cigarette devices, can also be a potential source of heavy metal contamination.

“Cannabis maybe an underrecognized source of environmental contaminants, including metals,” Tiffany R. Sanchez, assistant professor of Environmental Health Sciences at Columbia University Mailman School of Public Health, told Analytical Cannabis.

Dozens of cannabis products are independently recalled every year by state regulators due to heavy metal contamination, but there are no federal regulations governing metal limits.

“Regulation of contaminants in all cannabis products, however, remains piecemeal at the state-level and there has been no guidance from federal regulatory agencies like the FDA or EPA,” Sanchez added.

While Sanchez’s study didn’t distinguish between legal, tested cannabis products and illicit ones (participants were just asked if they consumed cannabis or not), she says future studies could investigate how the legal status of cannabis affects heavy metal exposure.

“To the best of our knowledge, this is the largest known study on biomarkers of metal exposure among cannabis users in a representative population of US adults,” she told Analytical Cannabis.

“The main findings lay the ground work for future studies to investigate differences by cannabis product (e.g., vape, smoke, edible), legal status, and evaluating potential metal-related health consequences among cannabis users.”


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