Blood and urinary metal levels among exclusive marijuana users in the National Health and Nutrition Examination Survey (2005-2018)

Abstract

BACKGROUND AND AIM Marijuana is the third most used drug in the world behind tobacco and alcohol; as more states legalize marijuana, recreational use continues to grow. Because cannabis, the marijuana plant, is a known scavenger of heavy metals, we hypothesized that individuals who use marijuana have higher metal biomarker levels compared to those who do not. METHODS To examine the relationship between marijuana use and metal exposures, we acquired and combined seven cycles of data from the National Health and Nutrition Examination Survey (2005-2018) for n=7,254 participants. Five metals were measured in blood and 16 in urine using inductively coupled plasma-mass spectrometry; urinary metals were adjusted for urinary creatinine. Individuals were grouped by: non-marijuana/non-tobacco use, current exclusive marijuana use, current exclusive tobacco use, and dual use; and by recent marijuana use: in the last 7 days, 30 days, or year. We built generalized linear models with non-marijuana/non-tobacco use as the reference. RESULTS We found 0.22µg/L (0.11, 0.34) and 0.18µg/g (0.06, 0.31) higher cadmium levels and 0.27µg/dL (0.07, 0.5) and 0.21 µg/g (-0.006, 0.50) higher lead levels in blood and urine, respectively, in participants reporting current marijuana use compared to non-marijuana/non-tobacco use when adjusting for sociodemographic factors, eGFR, and NHANES cycle year. We found 0.23µg/L (0.12, 0.35) and 0.20µg/g (0.03, 0.39) higher cadmium levels and 0.39µg/dL (0.11, 0.75) and 0.31µg/g (0.01, 0.70) higher lead levels in blood and urine, respectively, in those who had used in the last week compared to participants reporting no marijuana use. CONCLUSIONS Our results suggest that marijuana is a significant source of cadmium and lead exposure. Regulations regarding cannabis contaminants, particularly for metals, need to be addressed at the national level in order to address safety and public health concerns related to the growing number of cannabis users in the US. KEYWORDS metals, marijuana, cannabis