Research in the United States has detected significant levels of metals in the blood and urine of people who use marijuana, indicating that marijuana may be an important and underrecognized source of exposure to lead and cadmium. The study was carried out by researchers at the Mailman School of Public Health at Columbia University.
The research has been published in the journal Environmental Health Perspectives and is one of the first to provide information on biomarker metal levels among marijuana users, and probably the largest study to date linking self-reported marijuana use with internal measures of metal exposure, rather than simply observing metal levels in the cannabis plant.
Marijuana is the third most consumed drug in the world after tobacco and alcohol and its recreational use is legalized in many countries; This is not the case in Spain, where Law 17/1967 on narcotic drugs prohibits the consumption and production of cannabis for recreational purposes, although the medicinal use of this substance is approved.
“Our results indicate that marijuana is a source of exposure to cadmium and lead”
In the United States, however, as of 2022, the recreational use of marijuana has been legalized in a large part of the territory where more than 50% of the population resides, while medical marijuana is legal in 38 states and Washington. DC and in 2019, 48.2 million people (18% percent of Americans) reported using marijuana at least once in the past year.
In Spain, cannabis was the third most consumed psychoactive substance in all time frames in 2021, behind alcohol and tobacco. 28.6% of the students used cannabis at some point in their lives (29.2% in boys and 27.9% in girls), 22.2% used cannabis some day during the last year (22.6% in boys and 21.8% in girls), 14.9% some day during the last month (15.7% in boys and 14.1% in girls) and 1.6% declared themselves a consumer cannabis journal, according to data from the ESTUDES Secondary School Drug Use Survey.
Regulate concentrations of cadmium, lead and mercury in marijuana products
Self-reported measurements for marijuana-only use compared to non-marijuana tobacco use showed significantly higher lead levels in blood (1.27 ug/dL) and urine (1.21 ug/g of creatinine).
“Because the cannabis plant is a known scavenger of metals, we had hypothesized that people who use marijuana will have higher levels of metal biomarkers compared to those who do not use marijuana,” said Katelyn McGraw, a postdoctoral researcher at the Department of Environmental Health Sciences at Columbia Public Health and first author. “Therefore, our results indicate that marijuana is a source of exposure to cadmium and lead.”
Self-reported measurements for marijuana-only use compared to non-marijuana tobacco use showed significantly higher lead levels in blood (1.27 ug/dL) and urine (1.21 ug/g of creatinine).
“Because the cannabis plant is a known scavenger of metals, we had hypothesized that people who use marijuana will have higher levels of metal biomarkers compared to those who do not use marijuana,” said Katelyn McGraw, a postdoctoral researcher at the Department of Environmental Health Sciences at Columbia Public Health and first author. “Therefore, our results indicate that marijuana is a source of exposure to cadmium and lead.”
The researchers combined data from the National Health and Nutrition Examination Survey from the years 2005-2018). Led by CDC’s National Center for Health Statistics (NCHS), NCHS NHANES is a biannual study program designed to assess the health and nutritional status of adults and children in the U.S. The 7,254 survey participants were classified by substance use: no marijuana/no tobacco, exclusive marijuana, exclusive tobacco, and dual use of marijuana and tobacco. Five metals were measured in blood and 16 in urine.
Four NHANES variables were used to define exclusive marijuana and tobacco use: current cigarette smoking, serum cotinine levels, self-reported ever marijuana use, and recent marijuana use. Exclusive tobacco consumption was established in those individuals who answered yes to the question “do you smoke cigarettes now?”, or in the case of individuals with a serum cotinine level >10 ng/ml.
Although 28 states regulate concentrations of inorganic arsenic, cadmium, lead, and total mercury in marijuana products, regulatory limits vary by metal and state. “In the future, research on cannabis use and its contaminants, particularly metals, should be conducted to address public health concerns related to the growing number of cannabis users,” concludes Tiffany R. Sanchez, assistant professor of science. environmental health at Columbia Public Health and lead author.
