A new study has found that marijuana users have statistically higher levels of lead and cadmium in their blood and urine compared to people who don’t use the drug.
In the study, published in the Environmental Health Perspectives journal on Aug. 30, researchers said that they compared cannabis users who exclusively used the drug to people who neither used marijuana nor tobacco. The study concluded that marijuana users had “significantly higher” levels of toxic heavy metals in their bodies.
“Because the cannabis plant is a known scavenger of metals, we had hypothesized that individuals who use marijuana will have higher metal biomarker levels compared to those who do not use,” author Katelyn McGraw, a postdoctoral researcher at Columbia Public Health’s Department of Environmental Health Sciences, said in a statement. “Our results therefore indicate marijuana is a source of cadmium and lead exposure.”
Researchers combined data collected by the National Health and Nutrition Examination Survey (NHANES) between 2005 and 2018. The study, conducted among a group of 7,254 adult participants, measured five metals in participants’ blood and 16 in their urine using an analytical technique that can be used to measure elements at trace levels in biological fluids.
The group was split into four groups—non-marijuana/non-tobacco users, exclusive marijuana users, exclusive tobacco users, and dual marijuana/tobacco users.
Among the participants, researchers found that 358 individuals who exclusively used marijuana in the last 30 days had 1.27 μg/dL (micrograms per deciliter) lead in their blood compared to 0.93 μg/dL in non-marijuana/non-tobacco users, a 27 percent increase. They also found that cannabis users had 1.22 μg/dL mean cadmium levels in their blood, or a 22 percent higher level than non-users.
When researchers collected data from participants’ urinary metal levels, they found that those who exclusively used marijuana had 21 percent higher levels of lead and 18 percent higher levels of cadmium, said Tiffany Sanchez, lead author of the study and assistant professor of environmental health sciences at Columbia’s Mailman School of Public Health.
“Both cadmium and lead stay in your body for quite a long time,” Ms. Sanchez said, Earth.com reported. “Cadmium is absorbed in the renal system and is filtered out to [sic] 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 and Lead
Cadmium is a naturally occurring element used in products such as batteries, pigments, metal coatings, and plastics. It is also found in cigarette smoke and absorbed into plant and animal foods that people eat, according to the U.S. Centers for Disease Control and Prevention (CDC).
When consumed in large amounts cadmium can cause stomach issues, and when inhaled at high levels it can lead to lung damage or death. Cadmium is considered a cancer-causing agent.
“Exposure to low levels of cadmium in air, food, water, and particularly in tobacco smoke over time may build up cadmium in the kidneys and cause kidney disease and fragile bones,” the CDC notes.
Although exposure to lead has declined dramatically in recent decades, it still poses serious health risks to the public, according to the U.S. Environmental Protection Agency (EPA), which noted that there is no safe level of lead in the body.
Lead interferes with a variety of body processes and is toxic to many organs and tissues. Exposure to lead can seriously harm one’s health, children in particular, and has been linked to an increased risk of reproductive problems in both men and women, hearing and vision impairment, high blood pressure, nerve disorders, muscle and joint pain, brain damage, reduced IQ and learning difficulties, according to the CDC.
“Going forward, research on cannabis use and cannabis contaminants, particularly metals, should be conducted to address public health concerns related to the growing number of cannabis users,” Ms. Sanchez said.
In recent years, marijuana consumption has been on the rise across the United States. As of 2019, more than 48 million people—or 18 percent of Americans—reported using the substance at least once in the last year.
Marijuana, which is the third most commonly used drug in the world behind tobacco and alcohol, is legal for recreational use in 21 states, covering more than 50 percent of the U.S. population. People who use marijuana solely as a medication, meanwhile, are permitted to do so in 38 states.
Although nearly 40 states have legalized the substance in some form, it remains completely illegal in some states and at the federal level.
On Aug. 30, the U.S. Department of Health and Human Services (HHS) recommended easing restrictions on marijuana following a review request from the Biden administration last year in October 2022, when President Joe Biden pardoned thousands of Americans convicted of possessing marijuana on a federal level or in the District of Columbia.
The substance is currently classified as a Schedule I drug under the Controlled Substances Act, meaning it has a high potential for abuse and no accepted medical use, along with drugs like heroin and LSD.
HHS is recommending reclassifying marijuana to say it has a moderate to low potential for dependence and a lower abuse potential, which would put it in a class with ketamine and testosterone.
If marijuana classification were to ease at the federal level, that could allow major stock exchanges to list businesses that are in the cannabis trade, and potentially allow foreign companies to begin selling their products in the United States.
Senate Majority Leader Chuck Schumer (D-N.Y.) hailed the step by the HHS in a statement, saying the agency “has done the right thing” by recommending the drug should be moved from a Schedule I to a Schedule III controlled substance.
“DEA should now quickly follow through on this important step to greatly reduce the harm caused by draconian marijuana laws,” Mr. Schumer said.
Reuters contributed to this report.