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In news that may give pause to potheads, researchers led by Columbia University have found that people who consume cannabis products have surprisingly high levels of the heavy metals cadmium and lead in their bodies.

"For both cadmium and lead, these metals are likely to stay in the body for years, long after exposure ends," study author and an assistant professor of environmental health sciences at Columbia's Mailman School of Public Health Tiffany Sanchez told NBC News of the findings.

That's according to a new study published in the journal Environmental Health Perspectives, in which the scientists examined data from the blood and urine samples of more than 7,000 participants. Breaking them up into the categories of those who exclusively used weed, exclusively used tobacco, used both, and used neither, they found something alarming: the people who used marijuana had significantly higher levels of cadmium and lead in both urine and blood samples compared to those who don't use tobacco or marijuana at all.

If that sounds surprising, you're not alone. The conventional wisdom — backed by a preponderance of evidence — is that while pot might not be great for you, its potential for harm is pretty low compared to most other drugs.

But the researchers had a hunch going into the experiment that the herb might be linked to heavy metal exposure, which can lead to a vast array of medical issues ranging from cancer to brain damage.

"Because the cannabis plant is a known scavenger of metals, we hypothesized that individuals who use marijuana will have higher metal biomarker levels compared with those who do not use," the researchers wrote in the paper.

The term "scavenger" refers to how marijuana plants suck up metals via soil, fertilizers, water and pesticides. If that's where the heavy metals in users' blood is coming from, there may be a silver lining for stoners: weed carefully grown to be isolated from sources of heavy metals could still be safe.

The study also found that dual users and exclusive tobacco users both had high levels of cadmium and lead in participants' blood and urine samples, which aligns with common knowledge about the dangers of smoking cigarettes.

The study didn't differentiate between methods of consumption, such as the difference between smoking and eating edibles.

This research is intriguing and ominous because marijuana ranks as the third most used drug across the globe — and in an era of rapidly spreading legalization and decriminalization, there's often an attitude among users that it has no potential for harm.

"Because marijuana is relatively unregulated in an industry experiencing exponential growth, there is a need to understand contaminant exposures, including metals, associated with marijuana use," the paper reads.

More on marijuana: Marijuana Addicts Say Nobody Takes Them Seriously

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