Individuals who consume marijuana have high levels of metals in their blood and urine

The results indicate marijuana is a source of cadmium and lead exposure.

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A study at Columbia University Mailman School of Public Health found that people who use marijuana have high levels of metals like lead and cadmium in their blood and urine. This suggests that marijuana could be a hidden source of these harmful metals in the body.

This research is one of the first to show that marijuana users have more of these metals in their bodies, and it’s one of the most significant studies on this topic. They didn’t just look at the metal levels in the marijuana plant; they checked the metal levels in the people who use it. This information was published in the journal Environmental Health Perspectives.

People who only used marijuana had higher lead levels in their blood (1.27 ug/dL) and urine (1.21 ug/g creatinine) than those who didn’t use tobacco or marijuana.

Katelyn McGraw, a postdoctoral researcher in Columbia Public Health’s Department of Environmental Health Sciences and the first author said, “Because the cannabis plant is a known scavenger of metals, we had hypothesized that individuals who use marijuana will have higher metal biomarker levels compared to those who do not use. Our results, therefore, indicate marijuana is a source of cadmium and lead exposure.”

The researchers gathered information from a significant health survey called the National Health and Nutrition Examination Survey, which looked at people’s health and what they ate from 2005 to 2018. This survey is run by the National Center for Health Statistics (NCHS) at the CDC and happens every two years.

The researchers studied 7,254 people from the survey. They put them into four groups based on what they used: people who didn’t use marijuana or tobacco, people who only used marijuana, people who only used tobacco, and people who used both marijuana and tobacco. They checked for five metals in their blood and 16 in their urine.

To decide who was an exclusive marijuana or tobacco user, they looked at whether people smoked cigarettes now, the levels of a substance called cotinine in their blood, whether they had ever used marijuana, and if they had recently used marijuana. Exclusive tobacco users were people who either said they smoked cigarettes now or had high cotinine levels in their blood.

Marijuana is the third most commonly used drug globally, after tobacco and alcohol. In 2022, 21 U.S. states and Washington D.C. (covering over 50% of the population) allowed recreational marijuana use, and medical marijuana was legal in 38 states and Washington D.C.

However, because marijuana is still against federal law in the U.S., there isn’t consistent regulation for contaminants in cannabis products. Federal agencies like the FDA or EPA haven’t provided clear guidance. In 2019, around 48.2 million Americans (about 18% of the population) reported using marijuana at least once in the past year.

In the United States, regulations regarding the levels of inorganic arsenic, cadmium, lead, and total mercury in marijuana products are in place in 28 states. However, these regulations differ from state to state and vary depending on the specific metal being considered.

Tiffany R. Sanchez, Ph.D., assistant professor of environmental health sciences at Columbia Public Health and senior author, said, “Going forward, research on cannabis use and cannabis contaminants, particularly metals, should be conducted to address public health concerns related to the growing number of cannabis users.”

In conclusion, this research underscores the importance of understanding the potential health risks associated with exclusive marijuana use, particularly concerning metal exposure.

Journal Reference:

  1. Katlyn E. McGraw, Anne E. Nigra et al., Blood and Urinary Metal Levels among Exclusive Marijuana Users in NHANES (2005–2018). Environmental Health Perspectives. DOI: 10.1289/EHP12074.