A Columbia University study found significant levels of metals in the blood and urine among cannabis users. The study suggests that chronic cannabis consumption may be a primary source of lead and cadmium exposure. The study is one of the first to report biomarker metal levels among cannabis users. It is also the most extensive study to date that links self-reported cannabis use to internal measures of metal exposure, whereas previous studies mainly assessed metal levels in the cannabis plant. The results are published online in the journal Environmental Health Perspectives.
The researchers combined data from the National Health and Nutrition Examination Survey (NHANES) for 2005-2018. NHANES is a biannual survey conducted by the National Center for Health Statistics (NCHS) to assess health and nutritional trends. The researchers used four NHANES variables to define cannabis and tobacco use: current cigarette smoking, serum cotinine levels, self-reported regular cannabis use, and recent cannabis use. The researchers categorized the 7,254 survey participants by use: non-cannabis/non-tobacco, exclusive cannabis, exclusive tobacco, and dual cannabis and tobacco use.
The study detected five metals in the blood and 16 in urine. Measurements reported by participants for exclusive cannabis use compared to non-cannabis/non-tobacco had significantly higher lead levels in blood (1.27 ug/dL) and urine (1.21 ug/g creatinine).
Federal cannabis prohibition has resulted in a lack of coordinated oversight of cannabis product testing and research. There is no guidance from federal regulatory agencies like the Food and Drug Administration or the Environmental Protection Agency (EPA). Currently, 28 states regulate inorganic arsenic, cadmium, lead, and total mercury concentrations in cannabis products, but regulation limits vary by metal and state policy. This study provides a foundation for future studies of cannabis use and cannabis contaminants that can inform public health policy.