Columbia University Finds Elevated Metal Levels in Blood of Cannabis Users

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Columbia University Finds Elevated Metal Levels in Blood of Cannabis Users

A recent study by the Mailman School of Public Health at Columbia University has revealed high levels of metals in the blood and urine of cannabis users.

The findings suggest that cannabis might be a significant source of lead and cadmium exposure, but awareness of this remains limited.

This is one of the first studies to link self-reported cannabis use with internal measurements of metal exposure, rather than just studying the metal levels in the cannabis plant itself.

Columbia University Finds Elevated Metal Levels in Blood of Cannabis Users

A recent study has found significant amounts of metals in the blood and urine of cannabis users, indicating that cannabis might be an unrecognized source of lead and cadmium exposure. This study is among the first to connect self-reported cannabis use with internal biomarker levels of metals, raising concerns about public health, especially as cannabis consumption rises while federal regulations remain inconsistent.

The research findings were published in the “Environmental Health Perspectives” journal on August 30th.

Key Findings:

– Cannabis-only users had significantly higher levels of lead in their blood (1.27 µg/dL) and urine (1.21 µg/g creatinine) compared to non-cannabis smokers.

Dr. Katelyn McGraw, a postdoctoral researcher in the Department of Environmental Health Sciences at Columbia University’s Mailman School of Public Health and the lead author, stated, “Given that the cannabis plant is a known metal accumulator, we hypothesized that cannabis users would have higher levels of metal biomarkers compared to non-users. Thus, our study suggests that cannabis is a source of cadmium and lead exposure.”

Research Methodology:

Researchers combined data from the National Health and Nutrition Examination Survey (NHANES) from 2005 to 2018. NHANES, led by the National Center for Health Statistics (NCHS) at the Centers for Disease Control and Prevention (CDC), is a biannual research program aimed at assessing the health and nutritional status of U.S. adults and children.

McGraw and her colleagues categorized 7,254 survey participants based on their usage into non-cannabis/non-tobacco, cannabis-only, tobacco-only, and dual cannabis and tobacco users. Five metals were tested in blood, and 16 metals were tested in urine.

The researchers defined dual cannabis and tobacco use using four NHANES variables: current smoking status, serum cotinine levels, self-reported ever use of cannabis, and recent cannabis use. Those who answered “yes” to “Do you currently smoke?” or had serum cotinine levels greater than 10 ng/mL were classified as exclusive tobacco users.

Popularity and Regulation of Cannabis:

Cannabis ranks as the world’s third most commonly used drug, trailing only tobacco and alcohol. As of 2022, 21 U.S. states and the District of Columbia (representing over 50% of the U.S. population) have legalized recreational cannabis use, while 38 states and D.C. have legalized medical cannabis.

However, because cannabis remains illegal at the federal level, regulation of contaminants in all cannabis products remains inconsistent, with no guidance provided by federal regulatory agencies such as the FDA or EPA. As of 2019, 18% of Americans, or 48.2 million people, reported using cannabis at least once in the past year.

While 28 U.S. states regulate the concentrations of inorganic arsenic, cadmium, lead, and total mercury in cannabis products, the allowable levels vary for different metals and among different states.

Dr. Tiffany R. Sanchez, Assistant Professor of Environmental Health Sciences at Columbia University’s Mailman School of Public Health and senior author, remarked, “Looking ahead, research on cannabis use and cannabis contaminants, particularly metals, should be conducted to address public health concerns associated with the increasing number of cannabis users.”