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

newly Environmental health perspectives The study compares levels of mineral biomarkers in the blood and urine of marijuana users with those of nonusers.

Study: Urinary blood and mineral levels among exclusive marijuana users at NHANES (2005-2018).  Image credit: Inside the Creative House / Stady: Urinary blood and mineral levels among exclusive marijuana users in NHANES (2005–2018). Image credit: Inside the Creative House /


Marijuana is one of the most used drugs around the world. Although many states have legalized the use of marijuana for both recreational and medical purposes, 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 during the past year. This reflects the popularity and widespread use of the product.

The cannabis plant is a mineral scavenger, or excessive buildup of minerals found in soil, fertilizers, water, and pesticides. High concentrations of the metal have been detected in unfiltered marijuana smoke and vaporizers. Metal and metalloid contamination, collectively referred to as metals, can appear in marijuana during the production of hemp plants, which can greatly harm consumers.

Levels of metal contaminants such as cadmium (Cd), arsenic (As), lead (Pb), and total mercury (Hg) in marijuana products are legally regulated; However, the limits of regulation differ between US states. Exposure to these metals is associated with an increased risk of cancer, heart and lung disease. Therefore, it is important to evaluate the metal contaminants in marijuana.

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

About the study

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

The current study obtained NHANES data between 2005 and 2018 to analyze more geographically diverse samples. Of the 70,190 NHANES participants identified in the study period, 10,921 participants provided data on metals in blood and urine samples.

Individuals 18 years and older were included in this study. A total of 7,254 participants were considered for this study, as they met all eligibility criteria.

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 determine the participants’ use of marijuana and tobacco. These included blood cotinine levels, current cigarette smoking, self-reported marijuana use, and recent marijuana use.


Compared to nonusers, exclusive average marijuana users were more likely to be younger, educated, have higher incomes, be non-Hispanic white males, and have a lower body mass index (BMI). Among the participants who did not currently use marijuana or tobacco, 47% reported having used marijuana in their lifetime.

Compared to non-marijuana or non-tobacco users, this nationally representative group showed higher blood and urine concentrations of cadmium and lead among exclusive marijuana users. More specifically, higher levels of cadmium and lead were seen in exclusive marijuana users who used marijuana within the last seven days of biosample collection.

Compared to exclusive marijuana users, cadmium levels were significantly higher in exclusive tobacco users. This difference in cadmium levels could be due to differences in application frequency or differential accumulation of cadmium in tobacco and cannabis plants.

Similar lead concentrations were measured in both biosamples collected from exclusive tobacco and marijuana users. Individuals who used marijuana and tobacco also showed higher levels of lead and cadmium than non-users.

These results are consistent with previous studies that reported higher concentrations of cd in marijuana users. Importantly, cadmium levels correlated positively with increased frequency and duration of marijuana use. The present study highlights that blood CD is a strong but short-term biomarker of CD exposure, while urinary CD is a long-term predictor of past cigarette smoking.

Female marijuana users showed higher levels of urinary CD than males. The extent of metal accumulation did not differ with respect to race and ethnicity; However, a marginally strong association was observed between marijuana use and blood levels of cadmium in non-Hispanic white participants.

A higher level of mercury was observed in exclusive marijuana users; However, mercury levels have decreased over the time since the last use. Comparatively, exclusive tobacco use has been associated with higher concentrations of antimony, barium, cadmium, lead, tungsten, and uranium.

In the future, the long-term exposure of these metals to human health must be evaluated. Similarly, the presence of other cannabis contaminants should also be investigated to understand their impact on the health of cannabis users.

Magazine reference:

  • Catlin, E., Nigra, AE, Clett, J. et al. (2023) Urinary blood and mineral levels among exclusive marijuana users at NHANES (2005-2018). Environmental health perspectives 131(8). doi:10.1289/EHP12074

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