Blood and Urinary Metal Levels among Exclusive Marijuana Users in NHANES (2005–2018)

Marijuana is the third most used drug in the world. Because the cannabis plant is a known scavenger of metals, we hypothesized that individuals who use marijuana will have higher metal biomarker levels compared with those who do not use. We combined data from the National Health and Nutrition Examination Survey (2005-2018) for n=7,254 participants, classified by use: non-marijuana/non-tobacco, exclusive marijuana, exclusive tobacco, and dual marijuana and tobacco use. Five metals were measured in blood and 16 in urine using inductively coupled plasma mass spectrometry; urinary metals were adjusted for urinary creatinine. Participants reporting exclusive marijuana use compared with non-marijuana/non-tobacco use had statistically significantly higher mean cadmium levels in blood [1.22μg/L (95% CI: 1.11, 1.34); p<0.001] and urine [1.18μg/g (95% CI: 1.0, 1.31); p=0.004] and statistically significantly higher mean lead levels in blood [1.27μg/dL (95% CI: 1.07, 1.50); p=0.006] and urine [1.21μg/g (95% CI: -0.006, 1.50); p=0.058]. Our results suggest marijuana is a source of cadmium and lead exposure. Research regarding cannabis use and cannabis contaminants, particularly metals, should be conducted to address public health concerns related to the growing number of cannabis users. https://doi.org/10.1289/EHP12074.