Study: Marijuana users were found to have higher levels of toxic metals in their blood and urine

Study: Marijuana users were found to have higher levels of toxic metals in their blood and urine

New research found heavy metals in the blood and urine of people who used marijuana. The two metals in question are lead and cadmium, both of which can cause a number of health problems. Experts recommend checking your state's regulations and procedures for testing retail marijuana products to ensure that if you participate in consumption, you are receiving the safest products available.

A new study shows that marijuana smokers may be unknowingly consuming heavy metals.

Heavy metals accumulate in the body and are linked to a variety of health problems, including cancer, cognitive impairment and heart disease.

And people who use marijuana may be at higher risk of these toxins entering their bloodstream.

New research published last month inEnvironmental health perspectivesfound that adults who used marijuana had significantly higher levels of two metals linked to long-term health problems: lead and cadmium.

“Cadmium and lead remain in the body for years, long after exposure has stopped,” said Tiffany Sanchez, PhD, assistant professor of environmental health sciences at the Mailman School of Public Health in Columbia, who co-authored the new studyHealth.

Here's how heavy metals can enter the body through marijuana use, what role the type of marijuana consumption plays in toxin absorption, and why the legalization and regulation of marijuana makes monitoring the substance for heavy metals difficult.

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The level of toxic heavy metals in marijuana consumption

To understand whether or not heavy metals are linked to marijuana use, Sanchez and her team examined blood and urine samples from 7,200 adults who took part in the National Health and Nutrition Examination Survey. Of these, 358 reported using marijuana in the last 30 days.

The team tested blood samples for five metals; They tested urine samples for 16 metals.

Because tobacco use is associated with higher levels of heavy metals in the body, the researchers also tested the samples for an alkaloid called cotinine, which is found in tobacco but not cannabis. They then adjusted the data to ensure they could determine how marijuana use alone contributed to heavy metal use.

The data showed that people who used marijuana, regardless of whether they used tobacco, had 27% higher blood lead levels than those who did not use marijuana or tobacco. They also had 22% higher cadmium content.

“We believe this is due to cannabis use and not tobacco,” Sanchez said.

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The type of marijuana consumption can influence the absorption of heavy metals

The new study did not determine how the way people consumed marijuana — edibles, smoking or vaping — might have differentially affected heavy metal levels. But what experts know about how the body absorbs heavy metals provides clues about which forms of marijuana use are riskier.

“There is no safe limit for lead exposure,” Sanchez said, “and for lead, the absorption rate through inhalation is virtually 100%.”

According to the Centers for Disease Control and Prevention (CDC), the absorption rate through inhalation of cadmium can be as high as 50%.

“Everything you breathe in goes into your bloodstream,” Sanchez said.

Both lead and cadmium cause long-term damage to the body.

In June of this year, the American Heart Association (AHA) released a statement noting that both lead and cadmium increase a person's risk of developing cardiovascular disease, including coronary heart disease and stroke.

Additionally, inhaling cadmium – not consuming it – causes chronic obstructive pulmonary disease.

Research also leads to loss of cognitive function, including memory impairment and dementia.

The toxin is classified as a probable carcinogen and a probable human carcinogen by the Department of Health and Human Services (HHS) and the Environmental Protection Agency (EPA), respectively.

Absorbing lead and cadmium through ingestion or inhalation poses a problem for the body, but the lungs have a harder time getting rid of the toxins than the digestive system.

Irfan Rahman, PhD, director of taste inhalation toxicology research at the University of Rochester Medical Center, sharedHealthWhile the intestines contain enzymes that can help the body eliminate heavy metals (especially lead), the lungs do not have the same system.

This means that inhaling marijuana through smoking or vaping can be more harmful than consuming edibles.

Additionally, the logistics of vaping could represent another aspect of heavy metal exposure for marijuana users.

The reduction process that extracts cannabidiol from the cannabis plant can introduce heavy metals and other pollutants, including solvents used to extract essential oils from the flower, Rahman explained.

If used incorrectly, these lab-made marijuana extracts have a higher chance of releasing metals when they hit the hot coils of a vape pen, he said.

Ultimately, the marijuana plant is uniquely suited to containing higher levels of heavy metals than the average plant – regardless of how it is broken down for consumption.

Cannabis is naturally capable of absorbing heavy metals from the soil in which it is grown, where both cadmium and lead are naturally present, Sanchez says, making the plant a "hyperaccumulator."

These heavy metals are stored in the leaves and flowers of the plant – the part used as medicine.

Regulatory standards surrounding marijuana create opportunities for toxins

Without federal standards for testing, safety inspections for marijuana products occur at the state level, so each state that legalizes marijuana sales must decide for itself which contaminants manufacturers must test for.

The patchwork regulation creates opportunities for people to be exposed to potentially harmful contaminants at a time when marijuana use is on the rise.

The most recent National Survey on Drug Use and Health found that nearly 20% of Americans ages 12 and older had used marijuana at least once in the past year, whether through smoking, vaping or consuming edibles. Among 18- to 25-year-olds, more than a third had used marijuana in the past year.

“I would recommend that consumers know whether it is a legal and regulated asset they are purchasing and whether their state has regulations on metals,” Sanchez said.

A 2022 study found that 36 states and Washington DC tested legally sold marijuana products for at least some pesticides, microbes, solvents and other contaminants. In California alone, nearly 10% of extracts and approximately 2.5% of flowers examined did not meet safety standards.

At the federal level, the Food and Drug Administration (FDA) strictly regulates tobacco products and also tests them for contaminants. However, cannabis doesn't have the same safety net.

“We need consistent standards from the federal government and states should have very strict requirements before companies can enter the market,” Rahman says. “We don’t have the same regulation and oversight for marijuana as we do for tobacco products.”

Many Americans believe marijuana smoke is safer than cigarette smoke - they are wrong