New Study Finds Significant Levels of Metals in Marijuana Users
A recent study conducted at Columbia University Mailman School of Public Health has discovered high levels of metals in the blood and urine of marijuana users. This research highlights that marijuana may serve as an important yet underestimated source of lead and cadmium exposure. The study, published in the journal Environmental Health Perspectives, is one of the first to examine biomarker metal levels among marijuana users and the largest of its kind to link self-reported marijuana use to internal measures of metal exposure.
The study’s findings reveal that individuals who exclusively use marijuana, compared to those who do not use it at all, exhibited significantly higher lead levels in their blood (1.27 ug/dL) and urine (1.21 ug/g creatinine). This indicates that marijuana consumption is associated with increased cadmium and lead exposure.
Lead author Katelyn McGraw, a postdoctoral researcher in Columbia Public Health’s Department of Environmental Health Sciences, explains, “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 that marijuana is a source of cadmium and lead exposure.”
The research team gathered data from the National Health and Nutrition Examination Survey (NHANES) spanning from 2005 to 2018. They analyzed information from a total of 7,254 survey participants and categorized them based on marijuana and tobacco use. Five metals were measured in the blood, while 16 were analyzed in urine samples.
To define exclusive marijuana and tobacco use, the researchers relied on four NHANES variables: current cigarette smoking, serum cotinine levels, self-reported past marijuana use, and recent marijuana use. Exclusive tobacco use was determined by individuals who identified themselves as current cigarette smokers or had a serum cotinine level exceeding 10ng/mL.
Marijuana is the third most commonly used drug globally, after tobacco and alcohol. In the United States, 21 states and Washington D.C. have legalized recreational marijuana use, covering over 50 percent of the population. Additionally, medical marijuana is legal in 38 states and Washington D.C. However, due to marijuana’s federal illegality, there is a lack of regulation regarding contaminants in cannabis-containing products. The Food and Drug Administration (FDA) and the Environmental Protection Agency (EPA) have not provided any guidance in this regard. As of 2019, approximately 18 percent of Americans, or 48.2 million people, reported using marijuana within the past year.
Despite regulations in 28 states concerning inorganic arsenic, cadmium, lead, and total mercury concentrations in marijuana products, the limits vary between metals and states. Therefore, further research is required to address public health concerns related to the increasing number of cannabis users, particularly regarding cannabis contaminants like metals.
The study was supported by grants from the National Institutes of Health (NIH) National Institute of Environmental Health. The co-authors of the study include researchers from Columbia University Mailman School of Public Health, Columbia University Irving Medical Center, and Emory University School of Medicine.
This study sheds light on the potential health risks associated with marijuana use and emphasizes the need for comprehensive regulation and further research regarding contaminants in cannabis products.