Lead found in blood of cannabis consumers—but the solution may be complicated
According to a new study, some cannabis consumers may have elevated levels of lead and cadmium in their bodies. The toxic compounds have been linked to a variety of health issues, and the findings are re-igniting calls for standardized testing.
The research, published in the journal Environmental Health Perspectives, analyzed urine and blood samples from over 7,200 American adults. The 358 people who reported they’d used cannabis in the last month had 27 percent higher lead levels and 22 percent higher cadmium levels in their blood compared to non-consumers.
The elevated levels of lead and cadmium numbers are concerning. Lead exposure may lead to high blood pressure and cardiovascular issues, while cadmium is considered a carcinogen that may cause cancer or kidney damage.
The results caused study authors to call for better testing of cannabis. But improved testing may not be a silver bullet.
“Accumulator” plant inspires study
Cannabis plants are known as an accumulator, meaning they tend to absorb compounds (including naturally occurring heavy metals) from inputs like soil, water, and fertilizer. The plants are so good at absorption that they’ve been used to reduce soil toxicity near Chernobyl.
While the World Health Organization has set permissible levels of heavy metals in soil, the accumulator ability of cannabis led to the study authors’ hypothesis that consumers would likely have elevated levels of contaminants in their systems
The study was conducted by a team from Columbia University using data from the National Health and Nutrition Examination Survey. The survey examines “fixed sample-size targets for sampling domains defined by age, sex, race and ethnicity, and socioeconomic status.”
Samples were identified as non-marijuana/non-tobacco users, exclusive marijuana users, exclusive tobacco users, or dual users of tobacco and marijuana.
To be considered an exclusive marijuana user, participants had to answer “yes” to the question “Ever used marijuana or hashish?” and report that they had consumed it within the last 30 days.
Of the 358 people who fit in the exclusive marijuana user group, 42 percent were female, 58 percent were male, and 70 percent were white. The study authors surmise that Black and Hispanic populations were less likely to self-report cannabis after being “historically targeted for illicit drug use,” explaining the small sample size in these demographics.
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The survey did not ask about methods of consumption, such as whether the individuals smoked, vaped, or ate edibles. Roger Brown, president of testing facility ACS Laboratory, believes this is a detriment to the research.
“Heavy metals come from many different aspects: soil, rolling papers, leaching metals from poor-quality glass, and ignition mechanisms from vapes,” he explained via email. “We can’t assume it’s just cannabis flower.”
It’s also unknown whether the survey participants were using legal, regulated products or if they obtained their cannabis from the traditional market. Unregulated products are not subject to testing and often contain much higher levels of contaminants, according to recent research out of Canada, a country that requires strict testing for pesticides and heavy metals nationwide.
That’s not to say that all regulated cannabis products in the U.S. are safe. Of the 38 states that have legalized cannabis in some form, only 28 states impose limits on heavy metals like cadmium and lead—and the acceptable levels vary.
“The industry’s standardization would be a significant benefit to all, even though there are individual state barriers to cross because of federal guidelines,” Brown added.
The safety of cannabis products is currently under magnified scrutiny. While more research is needed to confirm the Columbia University team’s findings, the study showcases a need for improvement.
With rumors swirling of cannabis on its way to becoming a Schedule III substance, wider regulation and standardization may be on the way. However, the way people consume cannabis, as well as the plant’s natural penchant for absorbing compounds from its environment, means that testing isn’t a sure path forward.