Cannabis research has expanded along with increased legalization. Scientists have found the drug can have both positive and negative effects. The latest research shows a strong relationship between toxic chemicals and cannabis. A new study finds people who use marijuana have higher levels of cadmium and lead in their blood and urine.

Side view snapshot of crouched researcher wearing a white coverall, gas mask and gloves collecting samples from a scorched anthill on a burnt field, holding a glass flask with blue liquid and tweezers

Toxic Chemicals and Cannabis: The Relationship

The study that examined the relationship between toxic chemicals and cannabis was published in the journal Environmental Health Perspectives on Wednesday. It reviewed data collected between 2005 and 2018 by the National Health Nutritional Examination Survey (NHANES).

7,254 people who reported using marijuana in the last 30 days were asked to submit blood and urine samples. The samples were tested for heavy metal levels.

Previous studies had measured heavy metal levels in the marijuana plant. This study was the first to measure metal levels in users.

Findings of the study on toxic chemicals and cannabis revealed that 27% of marijuana users had higher levels of lead in their blood and 21% higher levels in their urine as compared to nonusers. They also showed that marijuana users had 22% higher levels of cadmium in their blood and 18% more in their urine.

“Our study wasn’t able to tease apart whether or not self-reported cannabis users were using medical or recreational cannabis, so we can’t say definitely if medical cannabis users specifically had higher metal levels,” said Tiffany Sanchez, lead study author and assistant professor of environmental health sciences at New York’s Columbia University Mailman School of Public Health.

What are the Harms of Cadmium and Lead?

Lead and cadmium are both heavy metals. Heavy metals contain molecules that can cause damage to cells that play a critical role in organ function.

Cadmium contributes to lung cancer, kidney disease, and birth defects in animals. If a person or animal is exposed to it for a long time, even small amounts can be dangerous. It accumulates in your body and takes ten to thirty years to digest.

Lead is linked to high blood pressure, renal failure, reproductive organ damage, immunotoxicity, and anemia. Its effects may 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 over a long period of chronic exposure,” Sanchez explained.

Heavy metals can be particularly harmful to immunocompromised people.

“Immunocompromised people, such as those going through chemotherapy, may be at greater risk for metal exposure or from other common cannabis contaminants like molds. However, this is very much an understudied area,” Sanchez said.

Heavy Metals Also Found in Tobacco

Toxic chemicals aren’t only present in marijuana. They are found in tobacco at even higher levels.

E-cigarettes have been shown to contain high levels of zinc, lead, nickel, and chromium. E-liquid and e-cigarette tanks have a presence of nickel, tin, lead, copper, chromium, and manganese.

What is Behind the Toxic Chemicals and Cannabis Relationship?

The toxic chemicals and cannabis relationship forms during the growth stages.

Toxic chemicals can be found in air, water, and food. They are in the soil in which cannabis crops grow. They cannot be eliminated.

However, some areas and regions contain more toxic chemicals than others thanks to the use of pesticides and pollution. Heavy metals are often found in older pesticide products.

Some plants will die when exposed to heavy metals. But cannabis is considered a “hyperaccumulator”. Hence, it can absorb toxic chemicals without becoming damaged.

Cannabis has deep wide roots that help it flourish in low-quality soil. It has even been used to leach toxic chemicals from the soil near the Chernobyl nuclear power plant and dioxide-contaminated farms in Italy. Both areas had previously been labeled unsafe for growing.

The plant’s effects are so beneficial that the U.S. Department of Agriculture is launching a research project that aims to bioengineer cannabis to absorb even higher levels of toxic chemicals.

The toxic chemicals and cannabis relationship is beneficial to the environment. But it’s not great news for cannabis users.

A 2021 study found that the toxic chemicals cannabis plants absorb spread to their stalks, flowers, and leaves. Hence, they are delivered directly to the user’s systems.

Is Smoking Cannabis More Dangerous?

The study on toxic chemicals and cannabis did not consider which type of marijuana consumption is most dangerous in terms of heavy metal damage. But Sanchez said that it’s generally worse to smoke cannabis than consume it orally.

“The absorption rate from inhalation is 100%.” She said.

A Lack of Regulations

Justice. Judge hammer on the table

Regulations could reduce the heavy metals in marijuana plants delivered to consumers. A 2022 study revealed that 28 of 31 states that have legal weed have regulations in place regarding toxic chemicals and cannabis.

However, weed is not federally legal. Therefore, it is difficult to enforce those regulations. As a result, consumers often consume products that contain toxic chemicals and pesticides.

So, what can people do to limit the heavy metals they consume in marijuana products?

“One of the biggest things I tell people when we’re talking about heavy metals in food is to have a varied diet,” said Sanchez. “In this case, I’m not sure how you should vary your exposure- but you can at least be aware there are different environmental contaminants in things that we might not be aware of, such as cannabis.”

Consumers can also stay safe by purchasing cannabis products from reputable, legal dispensaries. Ask for lab tests that prove the items are free of heavy metals.

Beth Cohen, professor of medicine at the University of California, San Francisco, and co-director of UCSF’s program in residency investigation methods and epidemiology who was not involved in the study on toxic chemicals and cannabis, weighed in on its results. “I think this highlights the need for more detailed studies on cannabis, particularly the real-world products people are using,” she concluded.