In an alarming new study, researchers discovered that people who smoke marijuana have higher levels of toxic heavy metals in their blood and urine.
Compared with non-users, marijuana users had:
- 27% higher levels of lead in their blood
- 21% higher levels of lead in their urine
- 22% higher levels of cadmium in their blood
- 18% higher levels of cadmium in their urine
The study, conducted by researchers with Columbia University’s Mailman School of Public Health and involved over 7,200 subjects between 2005 and 2018, focused on people who admitted to smoking marijuana within the previous 30 days.
“We believe this is coming from cannabis use and not tobacco,” said Dr. Tiffany Sanchez, PhD’s lead author.
Heavy Metals Health Hazards
~ Dr. Tiffany Sanchez, Assistant Professor of Environmental Health
Heavy metal poisoning is when microscopic metal particles accumulate in the body after exposure, in this case, from inhaled marijuana. According to the Cleveland Clinic, heavy metals bind to the body’s cells and inhibit their proper function.
The symptoms of heavy metal poisoning can be life-threatening without treatment.
“There is no safe level for lead exposure, and with lead, the absorption rate is virtually 100%.”
~ Dr. Sanchez
Lead poisoning can cause dozens of health issues, including:
Central Nervous System
- Loss of appetite
- Cognitive impairment
- Memory loss
- Personality changes
- Blindness in parts of the visual field
- Hearing loss
- Unusual taste
- A blue line along the gums
- Scratchy throat
- Abdominal pain
- Decreased urine output
- Kidney failure
- Loss of coordination
- Tingling in the hands and feet
- Wrist and foot drop
- Delayed reaction time
- Low sex drive
- Sperm dysfunction
- Pregnancy complications
With heavy or chronic exposure, the damage can be permanent.
“Both cadmium and lead stay in your body for quite a long time. Cadmium is absorbed in the renal system and is filtered out through the kidney. So, when you’re looking at urinary cadmium, that’s a reflection of total body burden, how much you have taken in over a long period of chronic exposure.”
~ Dr. Sanchez
Like lead and other heavy metals, toxic cadmium exposure can cause severe health problems, including:
- Permanent loss of smell
- Decreased bone density, also known as osteoporosis
- Softer, weaker bones
- Permanent bone deformation
- Increased risk of fractures
- Pain in the spine, joints, back, and legs
- Abnormal waddling gait
- Irreversible kidney damage – the kidneys shrink by up to 30%
- Kidney stones
The rate of cadmium absorption through inhalation can be as high as 50%, which may lead to Chronic Obstructive Pulmonary Disease (COPD).
Additional Health Concerns
Both lead and cadmium have been identified as probable human carcinogens by the Department of Health and Human Services, the Environmental Protection Agency, and the International Agency for Research on Cancer.
In June 2023, the American Heart Association reported that lead and cadmium exposure increased a person’s risk of cardiovascular disease and stroke.
Lead and cadmium also damage the immune system and cell structure. This effect can also be transmitted through breast milk.
By far, children are the most vulnerable to the harmful effects of exposure to toxic heavy metals. For example, young children absorb up to 5 times more lead than adults from a given source. Heavy metals also affect their still-developing brains to a much greater degree.
As a result, it is estimated that lead poisoning causes 10% of all intellectual disability cases without an otherwise known cause.
Cancer and AIDS patients are often prescribed medical marijuana, which may do more harm than good. “Immunocompromised people, such as those going through chemotherapy, may be at greater risk from metal exposure or from other common cannabis contaminants like molds,” Dr. Sanchez explains.
The Method Matters
“Cannabis consumed in combustive form represents the greatest danger to human health, as analysis of heavy metals in the smoke of cannabis revealed the presence of selenium, mercury, cadmium, lead, chromium, nickel, and arsenic. It is disturbing to realize that the cannabis products being used by consumers, especially cancer patients, may be causing unnecessary harm to their bodies.”
~ Dr. Louis Bengyella, Assistant Research Professor, Plant Science, Penn State
No matter how the heavy metal exposure occurs, it can cause severe health problems. However, the worst damage seems to come from inhalation rather than ingestion because it is harder for the lungs to remove the toxins than the digestive system.
While the gut has enzymes that help the body remove heavy metal toxins, no such system exists in the lungs.
Vaping marijuana may be the worst of all.
The process that extracts cannabidiol from the plant can also introduce heavy metals and other contaminants. Therefore, products with lab-made extracts can release concentrated toxic metals when they hit the hot coils of the vaporizer. These toxins are taken directly into the lungs.
Why Does Marijuana Have So Much Heavy Metal?
“Heavy metals, such as lead, mercury, cadmium, and chromium, are known to be carcinogenic. The heavy-metal content of cannabis is not regulated; therefore, consumers could unknowingly be exposed to these toxic metals. This is bad news for anyone who uses cannabis but is particularly problematic for cancer patients who use medical marijuana to treat the nausea and pain associated with their treatments.”
~ Dr. Bengyella
The cannabis plant is uniquely suited to contain higher levels of heavy metals than most plants. This is because it is a “hyper-accumulator,” meaning it is naturally adept at absorbing metals, pesticides, crude oil, and other harmful chemicals directly from the soil it grows in without harming itself.
In fact, cannabis plants were used to leach toxic heavy metals from the ground surrounding the site of the Chernobyl nuclear power plant disaster site and to absorb dioxin and other dangerous pesticides from contaminated areas in Italy.
While this sounds promising for the environment, it is terrible news for marijuana users.
In 2021, a Penn State study found that those absorbed toxins travel up the stalk and into the flower and leaves of the plant – the same parts of the plant that are smoked.
The Bottom Line About Unsafe Marijuana
There are no safety standards for marijuana at the federal level. Furthermore, most states have inadequate regulations regarding cannabis and heavy metals, and some have no regulations. Consumers in those states have no protection.
The specific issue of toxic heavy metal contamination is an accurate snapshot of the cannabis industry as a whole – products that are marketed as safe and harmless and even as medicine are in actuality unregulated, impure, contaminated, and harmful to the user’s health.
Every Brain Matters is a trusted educational resource for individuals and families wanting to stay safe from the harms associated with marijuana and the drug culture.
We reject the false narrative that industrialized marijuana is a harmless expression of personal freedom. Based on the latest scientific evidence and personal stories, our position is that the THC in marijuana is a dangerous and addictive drug. Like all drugs of abuse, it can destroy lives.
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–The Every Brain Matters Editorial Staff