Recent research suggests that using marijuana may lead to higher exposure to toxic metals like cadmium and lead.
- Exclusive marijuana users had 22% higher blood cadmium and 27% higher blood lead levels compared to non-users.
- Individuals who smoked marijuana within the past week (7 days) had the highest levels of cadmium and lead in their bodies.
- Cadmium and lead can have harmful health effects, even at low levels of exposure.
Source: Environmental Health Perspectives 2023
Marijuana & Toxic Metals
A new study published in Environmental Health Perspectives noted that people who use marijuana may be exposing themselves to high levels of toxic metals like cadmium and lead.
Researchers analyzed data from over 7,000 participants in the National Health and Nutrition Examination Survey (NHANES) from 2005 to 2018.
They compared metal levels in blood and urine samples from people who reported using only marijuana, only tobacco, both, or neither.
The results showed that those who exclusively used marijuana had significantly higher levels of cadmium and lead compared to non-users.
People who recently used marijuana also had higher mercury levels.
The study provides evidence that marijuana use could be an important source of exposure to these toxic metals.
Examining Metal Levels in Marijuana Users
Researchers used data from NHANES, an ongoing nationally representative survey conducted by the CDC, to analyze cadmium, lead, and other metal levels in different groups:
- Non-marijuana/non-tobacco users: No marijuana use in the past 30 days, no tobacco use.
- Exclusive marijuana users: Used marijuana in the past 30 days, no tobacco use.
- Exclusive tobacco users: Tobacco use, no marijuana in past 30 days.
- Dual users: Both marijuana and tobacco use.
Blood and urine samples were tested for levels of 17 metals using a highly sensitive mass spectrometry technique.
Marijuana & Heavy Metals in Blood & Urine
Compared to non-users, exclusive marijuana users had:
- 22% higher blood cadmium levels
- 27% higher blood lead levels
- 18% higher urinary cadmium
- 21% higher urinary lead
And among those who only used marijuana:
- Those who used marijuana within the past 7 days (week) had the highest cadmium and lead levels.
- Levels decreased with more elapsed time since prior use.
These findings were independent of tobacco use and persisted in sensitivity analyses accounting for potential confounding factors.
Results suggest marijuana use itself is linked to meaningfully higher cadmium and lead exposure – independent of tobacco and other factors.
Possible Sources & Mechanisms
The researchers hypothesize the higher metal levels come from several sources related to marijuana:
- Metals in soils where cannabis plants are grown
- Contaminated fertilizers and irrigation water
- Metal-containing pesticides
- Contaminated drying or processing equipment
- Lead leaching from vape device cartridges
The cannabis plant easily absorbs and accumulates metals from its surrounding environment.
Smoking and vaping marijuana then directly exposes the lungs to these contaminants.
More research is needed to clarify the sources of exposure and how metals get into marijuana products.
But these findings make it clear that in the real world, marijuana use can result in substantially more cadmium and lead exposure.
Health Risks of Cadmium & Lead Exposure from Marijuana
Cadmium and lead are heavy metals that can accumulate in the body over time.
Even low-level chronic exposure can potentially harm health.
Cadmium is a carcinogen that has been linked to lung, kidney, and prostate cancer.
Common sources are tobacco smoke and contaminated food and water.
Lead is a neurotoxin that is especially harmful to children’s developing brains and nervous systems.
In adults, lead exposure can increase risk of high blood pressure, kidney damage, and reproductive issues.
Lead persists in the environment from old paint, contaminated soil, and other sources.
There is no known safe level of exposure for either cadmium or lead.
The higher levels seen in marijuana users versus non-users in this study raise concerns about the potential health risks, especially with long-term use.
Marijuana Users Should Beware of Toxic Metals
This study has important implications in the context of marijuana’s expanding legalization.
It suggests that marijuana use could contribute to health issues caused by chronic exposure to these toxic metals.
However, more research is required to directly examine potential health impacts.
The study was cross-sectional, meaning metal levels were only measured at one point in time.
To confirm the findings, large cohort studies should track marijuana users over many years to relate metal exposures to health outcomes.
Nonetheless, the results already provide enough evidence that marijuana contaminants need more regulatory oversight and industry accountability.
Currently, marijuana is largely unregulated at the federal level.
Better monitoring of marijuana products, growing practices and contaminated equipment is critical to protect public health.
Consumers also need more awareness of the potential harms.
More research on marijuana exposures will inform policies and regulations to make marijuana use safer as it becomes more common across the country.
In the meantime, these findings indicate there are real potential risks associated with metals in marijuana, which need to be taken seriously by regulators, the marijuana industry and users.
- Paper: Blood and Urinary Metal Levels among Exclusive Marijuana Users in NHANES (2005-2018)
- Authors: Katlyn E. McGraw et al.