Recent Environmental hygiene perspective This study compares levels of metal biomarkers in the blood and urine of marijuana users and non-users.
study: Blood and urine metal levels in NHANES exclusive marijuana users (2005-2018). Image credit: Inside Creative House / Shutterstock.com
background
Marijuana is one of the most commonly used drugs around the world. Although many states have legalized the use of marijuana for recreational and medical purposes, the drug remains illegal at the federal level in the United States.
According to 2019 estimates, approximately 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 hyperaccumulators of metals present in soil, fertilizers, water, and pesticides. High concentrations of metals have been found in unfiltered marijuana smoke and e-cigarettes. Contamination with metals and metalloids (collectively referred to as metals) in marijuana can appear during the production of cannabis plants and can cause serious harm to consumers.
Levels of metal contaminants such as cadmium (Cd), arsenic (As), lead (Pb), and total mercury (Hg) in marijuana products are legally regulated. However, regulatory limits vary by state in the United States. 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 National Health and Nutrition Examination Survey (NHANES) conducted from 2009 to 2016 reported the presence of Cd in urine and blood samples of long-term marijuana users. Therefore, there is still an urgent need to assess the presence of other metals in addition to Cd from recently collected biological specimens.
About research
The current NHANES is led by the National Center for Health Statistics (NCHS) of the Centers for Disease Control and Prevention (CDC). The primary purpose of NHANES is to assess the health and nutritional levels of people residing in the United States.
In the current study, we acquired NHANES data between 2005 and 2018 in order 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 response cell mass spectrometry (ICP-DRC-MS) and high performance liquid chromatography (HPLC) were used to evaluate the concentrations of several metals from blood and urine samples.
Four NHANES variables were used to define marijuana and tobacco use by participants. These include serum cotinine levels, current smoking, self-reported marijuana use, and recent marijuana use.
research result
Compared to non-users, average exclusive marijuana users tended to be younger, more educated, have higher incomes, non-Hispanic white men, and lower body mass index (BMI). Among participants who did not currently use marijuana or tobacco, 47% reported having used marijuana in their lifetime.
Compared with non-marijuana or non-tobacco users, blood and urine cadmium and lead concentrations were higher among people who only used marijuana in this nationally representative cohort. More specifically, higher Cd and Pb levels were observed in exclusive marijuana users who used marijuana within the past 7 days after biospecimen collection.
Cd levels were significantly higher in tobacco-only users compared to marijuana-only users. This difference in He Cd levels may be due to differences in frequency of use or differences in He Cd accumulation in tobacco and cannabis plants.
Similar lead concentrations were measured in both biological specimens collected from exclusive users of tobacco and marijuana. Those 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 that reported higher cadmium concentrations 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 powerful but short-term biomarker of Cd exposure, whereas urinary Cd is a long-term indicator of past smoking.
Female marijuana users showed higher urinary Cd levels than males. The extent of metal accumulation did not differ by race or ethnicity. However, a slightly stronger association between marijuana use and blood Cd concentrations was observed in non-Hispanic white participants.
Higher levels of mercury were observed in people who only used marijuana. However, mercury levels have decreased over time since last use. By comparison, tobacco alone has higher concentrations of antimony, barium, cadmium, lead, tungsten, and uranium.
In the future, the long-term exposure of these metals to human health will need to be evaluated. Similarly, the presence of other cannabis contaminants should also be investigated to understand their effects on the health of cannabis users.
Reference magazines:
- Catlin, E., Nigra, A.E., Klett, J., other. (2023) Blood and urine metal levels in NHANES exclusive marijuana users (2005–2018). Environmental hygiene perspective 131(8). doi:10.1289/EHP12074