Marijuana users have elevated levels of cadmium and lead in their blood and urine

Recent Perspective of environmental hygiene This study compares levels of metal biomarkers in the blood and urine of marijuana users and nonusers.

study: NHANES Blood and Urinary Metal Levels of Exclusive Marijuana Users (2005–2018). Image credit: Inside Creative House / Shutterstock.com

background

Marijuana is one of the most commonly used drugs worldwide. Although many states have legalized recreational and medical marijuana use, the drug remains illegal at the federal level in the United States.

According to 2019 estimates, about 48 million people in the United States have used marijuana at least once in the past year. This reflects the popularity of the product and its widespread use.

Cannabis plants are metal scavengers or accumulators of metals present in soil, fertilizers, water, and pesticides. High levels of metals have been found in unfiltered marijuana smoke and e-cigarettes. Contamination of metals and metalloids (collectively referred to as metals) in marijuana can appear during the production of cannabis plants and can cause significant harm to consumers.

The levels of metallic contaminants such as cadmium (Cd), arsenic (As), lead (Pb) and total mercury (Hg) in marijuana products are regulated by law. However, regulatory limits vary by US state. Exposure to these metals is associated with an increased risk of cancer and cardiopulmonary disease. Therefore, it is important to evaluate metal contaminants in marijuana.

The 2009-2016 National Health and Nutrition Examination Survey (NHANES) reported the presence of Cd in urine and blood samples of long-term marijuana users. Therefore, there remains an urgent need to assess the presence of other metals in addition to Cd from recently collected biological specimens.

About research

NHANES is currently led by the National Center for Health Statistics (NCHS) of the US Centers for Disease Control and Prevention (CDC). The primary purpose of NHANES is to assess the health and nutritional levels of people living in the United States.

In the current study, we acquired NHANES data between 2005 and 2018 to analyze a more geographically diverse sample. Of the 70,190 NHANES participants identified during the study period, 10,921 participants provided data on metals present in blood and urine samples.

This study included individuals aged 18 years and older. A total of 7,254 participants who met all eligibility criteria were considered in this study.

Inductively coupled plasma dynamic reaction cell mass spectrometry (ICP-DRC-MS) and high performance liquid chromatography (HPLC) were used to assess the concentrations of several metals from blood and urine samples.

Four NHANES variables were used to define marijuana and tobacco use by participants. These included serum cotinine levels, current smoking, self-reported marijuana use, and recent marijuana use.

research result

Compared with nonusers, the average exclusive marijuana user tended to be younger, more educated, higher income, non-Hispanic white male, and lower body mass index (BMI). Among participants who were not current marijuana or tobacco users, 47% reported lifetime marijuana use.

Compared with non-marijuana or non-tobacco users, this nationally representative cohort had higher concentrations of cadmium and lead in blood and urine among marijuana-only users. More specifically, higher Cd and Pb levels were observed in exclusive marijuana users who used marijuana within the past 7 days of biopsy collection.

Tobacco-only users had significantly higher Cd levels compared to marijuana-only users. This difference in his Cd levels could be due to differences in frequency of use or differences in his Cd accumulation in tobacco and cannabis plants.

Similar lead concentrations were measured in both biospecimens collected from exclusive tobacco and marijuana users. A person who used both marijuana and tobacco showed higher levels of his Pb and Cd compared to non-users.

These findings are consistent with previous studies reporting higher cadmium levels in marijuana users. Importantly, Cd levels are positively correlated with increased frequency and duration of marijuana use. The current study highlights that blood Cd is a strong but short-term biomarker of Cd exposure, whereas urinary Cd is a long-term indicator of previous smoking.

Female marijuana users had higher urinary Cd levels than males. The extent of metal accumulation did not differ by race or ethnicity. However, a slightly stronger association was observed between marijuana use and blood Cd levels in non-Hispanic white participants.

Higher levels of mercury were observed in those who used only marijuana. However, Hg levels decreased over time since last use. By comparison, using tobacco alone results in higher concentrations of antimony, barium, cadmium, lead, tungsten, and uranium.

Long-term exposure to these metals on human health should be evaluated in the future. Similarly, the presence of other cannabis contaminants should be investigated to understand the health effects of cannabis users.