Elevated levels of cadmium and lead found in exclusive marijuana users

Key takeaways:

• Marijuana users had significantly higher levels of cadmium and lead in blood and urine samples than nonusers.
• Given that marijuana is a relatively unregulated industry, researchers called for more studies.

Individuals who exclusively used marijuana had greater levels of cadmium and lead in their blood and urine than nonusers, a recent study found.

According to Katlyn E. McGraw, PhD, MPH, a postdoctoral fellow at Columbia University Mailman School of Public Health, and colleagues, the cannabis plant “is a known hyperaccumulator of metals present in water, soil, fertilizers and pesticides.”

Because marijuana is unregulated by organizations like the FDA and U.S. Environmental Protection Agency, “there is a need to understand contaminant exposures, including metals, associated with marijuana use,” the researchers wrote in Environmental Health Perspectives.

They aimed to fill this need by analyzing the levels of five metals in blood and 16 metals in urine among 7,254 participants in the National Health and Nutrition Examination Survey 2005-2018 datasets. Participants were divided into four classifications based on drug use:

• exclusive marijuana users (n = 358);
• exclusive tobacco users (n = 1,511);
• dual marijuana and tobacco users (n = 719); and
• non-marijuana and non-tobacco users (n = 4,666).

The researchers found that participants reporting exclusive marijuana use had mean cadmium levels of 1.22 g/L (95% CI, 1.11-1.34) in blood and 1.18 g/g (95% CI, 1-1.31) in urine, significantly higher than those for non-marijuana and non-tobacco users.

Similarly, those reporting exclusive marijuana use had substantially higher mean lead levels of 1.27 g/dL (95% CI, 1.07-1.5) and 1.21 g/g (95% CI, –0.006 to 1.5) in their blood and urine, respectively.

Although urinary and blood lead levels were similar between those who exclusively used marijuana and those who exclusively used tobacco, dual marijuana and tobacco users had higher cadmium and lead levels than those who used neither drug.

McGraw and colleagues additionally noted that lead and cadmium levels were higher in those who reported marijuana use within the past 7 days, whereas metal levels were lower as more time passed since an individual’s last use.

“Taken together, these observations suggest that marijuana use is an important and underrecognized source of cadmium and lead exposure independent of tobacco use and that chronic marijuana use may contribute to adverse health effects associated with chronic, low-level metal exposure,” they wrote.

The researchers concluded future research efforts on marijuana contaminants “must assess other contaminants of concern and potential health effects to inform regulatory, industry and other key stakeholders, to safeguard public health and address safety concerns related to the growing use of cannabis in the United States.”