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Marijuana smokers have very high levels of toxic metals in their blood

Marijuana smokers have significantly higher levels of toxic metals in their blood and urine compared to non-marijuana tobacco users, according to a recent study from Columbia University’s Mailman School of Public Health.

The research, led by Professor Tiffany Sanchez, indicates that marijuana may be an under-recognized source of metal exposure, as it remains illegal at the federal level and therefore unregulated by government agencies.

The study authors say the issue has never been more important as marijuana use in the skyrockets in the United States, with an estimated 42 million regular users.

Lead and cadmium levels

The researchers compared participants who exclusively used marijuana with non-marijuana tobacco users and found that those who used marijuana had significantly higher lead levels. 

Specifically, marijuana smokers users had 27 percent higher levels of lead in their blood and 21 percent higher levels in their urine. 

In addition, cannabis users had 22 percent higher cadmium levels in their blood and 18 percent higher levels in their urine compared to non-users.

Total body burden 

Professor Sanchez and her team predicted that because cannabis is known to accumulate metals, marijuana smokers would have higher metal biomarker levels than those who did not use it. 

The study confirmed this prediction, establishing marijuana as a source of cadmium and lead exposure. 

“Both cadmium and lead stay in your body for quite a long time,” said Professor Sanchez. “Cadmium is absorbed in the renal system and is filtered out to through the kidney.  So, when you’re looking at urinary cadmium, that’s a reflection of total body burden, how much you have taken in over a long period of chronic exposure.”

Potential health consequences 

The research aims to help scientists understand the potential health consequences of metal exposure from cannabis use.

Exposure to cadmium is known to cause kidney disease and fragile bones, according to the Centers for Disease Control and Prevention. Additionally, cadmium is considered a cancer-causing agent. 

Lead exposure can also have severe impacts, with children being most at risk for serious side effects. However, adults can also experience symptoms such as high blood pressure, headaches, joint and muscle pain, and fertility issues, as stated by the Mayo Clinic.

The World Health Organization (WHO) reports that there is no safe level of lead in the bloodstream. “Once lead enters the body, it is distributed to organs such as the brain, kidneys, liver and bones. The body stores lead in the teeth and bones, where it accumulates over time,” said the WHO.

Lack of regulation 

Despite the legalization of recreational marijuana use in 23 states, not including Washington D.C., it remains illegal at the federal level. 

This lack of federal regulation means that there is no oversight of contaminants in cannabis-containing products, and researchers note that there has yet to be any regulatory guidance from the FDA or EPA.

Professor Sanchez and her team recommend further investigation into the potential public health concerns of metal exposure from cannabis. 

Implications for marijuana smokers

The study lays the groundwork for future studies that can more specifically look into the adverse health effects of metal exposure caused by cannabis use, said the researchers.

As more states move towards legalizing marijuana, it is crucial to understand the potential risks associated with its use. This research highlights the need for further research and regulation to ensure the safety of cannabis users.

More about marijuana

Marijuana, commonly known as weed, pot, or cannabis, has sparked a plethora of discussions and debates over the years. Native to Central and South Asia, this green plant has traveled far and wide, making its mark in diverse cultures and societies.


People primarily consume marijuana in three forms: as dried flowers, hashish, and as a tincture. The psychoactive compound in marijuana, THC (tetrahydrocannabinol), produces the “high” that users often describe.

Alongside THC, marijuana contains over a hundred other cannabinoids, with CBD (cannabidiol) being one of the most notable. Unlike THC, CBD doesn’t produce a high, but researchers credit it with several therapeutic properties.

Legal status

Historically, societies used marijuana for medicinal and recreational purposes. However, during the 20th century, many countries criminalized its possession and use, linking it to mental health issues, addiction, and criminal behavior. As a result, for many decades, a significant portion of the population viewed marijuana as a dangerous substance.

Medicinal properties

In recent years, perspectives on marijuana have shifted dramatically. Scientists have begun delving deeper into its potential medicinal properties. They have discovered many health benefits, including its efficacy in treating conditions like epilepsy, chronic pain, and multiple sclerosis. Furthermore, advocates emphasize its relative safety compared to substances like alcohol and opioids.

Economics of marijuana

The economic implications of marijuana also hold significant weight. Several countries and U.S. states have legalized its recreational and medicinal use, leading to a booming industry. The cannabis market now generates billions in revenue, creates jobs, and boosts tourism in places like Colorado and Canada.

While many praise marijuana for its benefits, it’s essential to approach its consumption with caution. Like any substance, marijuana has potential side effects, including memory issues, impaired motor coordination, and addiction in some users.

In summary, marijuana stands at the crossroads of history, medicine, and economy. Its journey from ancient civilizations to modern laboratories showcases its intricate relationship with humanity. As research continues and societies grow more accepting, the future of marijuana seems promising.

The study is published in the journal Environmental Health Perspectives.

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