Summary: A new study published in Environmental Health Perspectives found that people who exclusively use marijuana have higher levels of toxic metals like cadmium and lead in their blood and urine compared to people who do not use marijuana or tobacco.
Key Facts:
- Exclusive marijuana users had 22% higher blood cadmium levels and 27% higher blood lead levels compared to non-users.
- Marijuana users also had 18% higher urinary cadmium and 21% higher urinary lead.
- The metals were highest among those who had used marijuana in the past week, and lower in those with more time since last use.
- Cadmium and lead can have harmful health effects, including cardiovascular disease, kidney damage, and neurodevelopmental impairment.
Source: Environmental Health Perspectives (Vol. 131, Issue 8)
This large study analyzed national health data from over 7,000 adults who had participate in the National Health and Nutrition Examination Survey (NHANES) from 2005-2018.
The researchers categorized people into 4 groups based on self-reported marijuana and tobacco use:
- Non-marijuana/non-tobacco users – No marijuana use in past 30 days, no tobacco use
- Exclusive marijuana users – Used marijuana in past 30 days, no tobacco use
- Exclusive tobacco users – Tobacco use, no marijuana use in past 30 days
- Dual users – Both marijuana and tobacco use
They measured the levels of 5 metals in blood (cadmium, lead, mercury, manganese, selenium) and 16 metals in urine (arsenic, cadmium, lead and more) in these groups using sensitive laboratory techniques.
Key Differences in Metal Levels
Compared to non-marijuana/non-tobacco users, exclusive marijuana users had:
- 22% higher blood cadmium
- 27% higher blood lead
- 18% higher urinary cadmium
- 21% higher urinary lead
Exclusive tobacco users and dual users also had elevated cadmium and lead compared to non-users.
But exclusive tobacco users had much higher urinary cadmium levels (3 times higher) likely due to more frequent smoking.
Cadmium and Lead Exposure from Marijuana Use
Cadmium and lead are toxic heavy metals that can accumulate in the body over time.
Prior research shows that even low-level chronic exposure can cause health problems:
Cadmium is linked to kidney disease, osteoporosis, cardiovascular disease, and cancer.
Main sources are tobacco smoke and contaminated food.
Lead is linked to cardiovascular disease, kidney dysfunction, and neurodevelopmental impairment in children.
Main sources are lead paint, pipes, dust, and contaminated soil.
This study provides evidence that marijuana use may be an under-recognized source of exposure to these harmful metals in the U.S.
The cannabis plant easily absorbs cadmium and lead from contaminated soil and water.
Smoking or vaping marijuana releases metals into the lungs and bloodstream where they can accumulate over time with repeated use.
Higher Metals with Recent Marijuana Use
The researchers found that blood and urinary cadmium and lead levels were highest among those who had used marijuana in the past week compared to non-recent users:
- Blood cadmium was 23% higher with use in past 7 days
- Blood lead was 39% higher with use in past 7 days
- Urinary cadmium was 20% higher with use in past 7 days
- Urinary lead was 31% higher with use in past 7 days
As time since last use increased, the levels of these metals decreased.
This suggests that frequent ongoing marijuana use may lead to greater accumulation of toxic metals in the body compared to occasional use.
Potential Health Impact for Frequent Marijuana Users
With expanding legalization, marijuana use is increasing in the U.S. Nearly 20% of adults reported using marijuana in the past year based on 2018 national data.
The long-term health impact of metals exposure from frequent marijuana use is unknown.
Chronic inhalation of cadmium and lead during smoking may increase risks for:
- Cardiovascular disease – cadmium and lead are linked to hypertension, atherosclerosis, and peripheral artery disease.
- Kidney dysfunction – cadmium specifically damages kidney tubule cells.
- Osteoporosis and fractures – cadmium leaches calcium from bones.
- Neurodevelopmental impairment in youth – lead is toxic to the developing brain.
More research is urgently needed to understand the health risks, especially for those who use marijuana daily or multiple times per week over many years.
However, this study indicates that frequent marijuana use may contribute to increased body burden of cadmium and lead over time.
Limitations and Need for Further Study
This study has some limitations. As a cross-sectional study, it can only show associations at one point in time – not prove that marijuana use caused the higher metals.
Other unmeasured factors may influence the results. Self-reported marijuana use may also be inaccurate or under-reported due to legal concerns.
Additionally, this study could not differentiate between types of marijuana use – smoking, vaping, edibles, etc. Contaminants likely vary between products and delivery methods.
Further large longitudinal studies are needed to clarify the impact of long-term frequent marijuana use on metals exposure and related health outcomes.
Research is also needed on metals in different marijuana products and delivery systems like vape pens.
In summary, this important study indicates that exclusive marijuana use, especially frequent ongoing use, may contribute to increased cadmium and lead exposure in US adults.
The potential health impact of chronic metals exposure from marijuana use requires more research. But it suggests that marijuana, like tobacco, may expose users to toxic heavy metals through consumption.
References
- Study: Blood & Urinary Levels among Exclusive Marijuana Users
- Authors: McGraw et al. (2023)
