Users of marijuana had statistically higher levels of lead and cadmium in their blood and urine than people who do not use weed, a new study found.
“Compared to non-users, marijuana users had 27% higher levels of lead in their blood, and 21% higher levels in their urine,” said lead author Tiffany Sanchez, an assistant professor of environmental health sciences at Columbia University Mailman School of Public Health in New York City.
There is no safe level of lead in the body, according to the US Environmental Protection Agency.
Marijuana users also had 22% higher cadmium levels in their blood than non-users, and 18% higher levels in their urine, Sanchez said.
“Both cadmium and lead stay in your body for quite a long time,” she said. “Cadmium is absorbed in the renal system and is filtered out to 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.”
Cadmium has been linked to kidney disease and lung cancer in people and fetal abnormalities in animals, according to the EPA, which has set specific limits for cadmium in air, water and food.
“I think this highlights the need for more detailed studies on cannabis, particularly the real world products that people are using,” said Dr. 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. She was not involved in the study.
Measured blood and urine
The study, published Wednesday in the journal Environmental Health Perspectives, used data between 2005 and 2018 collected by the annual National Health and Nutrition Examination Survey, or NHANES, which tracks the health of Americans.
Blood and urine tests of 7,254 people who said they had used marijuana in the last 30 days were examined for levels of heavy metals, which makes the new study “unique” — most studies have simply measured metal levels in the cannabis plants, and not the people using marijuana, Sanchez said.
“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 definitively if medical cannabis users specifically had higher metal levels,” she said. “This is something that should be evaluated in future studies.”
Heavy metals bind to cells in the body, limiting their function, according to the Cleveland Clinic, and have been linked to cancer, chronic disease and neurotoxic effects.
“Immunocompromised people, such as those going through chemotherapy, may be at greater risk from metal exposure or from other common cannabis contaminants like molds. However, this is very much an understudied area,” Sanchez added.
Heavy metals aren’t just in marijuana — tobacco smokers are exposed to even more types of toxins. E-cigarettes, for example, contain high aerosol levels of nickel, chromium, lead and zinc, while researchers have found e-liquids and the tanks of e-cigarettes contain arsenic, lead, nickel, tin, manganese, copper and chromium, according to studies.
Cannabis is a ‘hyperaccumulator’
As natural elements, heavy metals are in the soil in which crops are grown and can’t be avoided, a key reason they exist in the air, water and food supply. Some crop fields and regions, however, contain more toxic levels than others, partly due to the overuse of metal-containing pesticides and ongoing industrial pollution.