Columbia University Study Reveals Heavy Metal Risks In Cannabis, Urges Standardized Testing

A 2023 study conducted by researchers at New York’s Columbia University, utilizing data from the National Health and Nutrition Examination Survey by the US Centers for Disease Control, sheds light on the potential health risks linked to heavy metal buildup in cannabis users.

Notably, the study highlighted that legal tobacco products have higher contamination levels than illicit cannabis.

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Cannabis Users' Metal Levels Examined

Cannabis plants, known as hyperaccumulators, absorb metals from soil, water, and fertilizers at exceptionally high levels.

The Columbia researchers analyzed data from 7,254 participants between 2005 and 2018, aiming to determine if cannabis users had elevated levels of 17 different metals in their blood and urine.

Key Findings

• The study revealed that cannabis-only users had 27% higher blood lead levels and 21% more lead in their urine compared to non-users of both cannabis and tobacco.
• Additionally, cannabis users had elevated levels of cadmium, with 22% higher levels in their blood than non-users.
• Both lead and cadmium can cause long-term health damage, including cardiovascular disease, chronic obstructive pulmonary disease, cognitive impairment and cancer risk.
• Exposure to cadmium, a heavy metal, can pose health risks, with cadmium classified as a probable human carcinogen by the US Environmental Protection Agency.
• Vaping poses additional risks as the extraction process for cannabidiol can introduce heavy metals and other contaminants if done incorrectly.
• The type of marijuana consumption method can impact heavy metal absorption, with inhalation presenting higher risks due to nearly 100% lead absorption and up to 50% cadmium absorption.
• The researchers underscored the importance of testing cannabis products for metal contamination, particularly in states where it is legal.

Tobacco Users Have Higher Levels Of Heavy Metals

While the study did not find clear causal associations between cannabis use and other evaluated elements, tobacco users displayed significantly worse outcomes, with three times higher urinary cadmium levels and 26% higher blood lead levels. Legal cannabis products typically undergo more stringent testing than tobacco.

“None of the other 15 elements evaluated in the study—including arsenic, cobalt, manganese, and mercury—showed a clear causal association with cannabis use. And tobacco users proved far worse off. Their urinary cadmium levels were three times higher than those of exclusive cannabis users, for example, while their blood lead levels were 26% higher,” reported Nate Seltenrich for Leafly.

Published in the open-access journal Environmental Health Perspectives in late August 2023, the study is considered a significant contribution to understanding the health implications of heavy metal exposure in cannabis users.

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Photo by JOSHUA COLEMAN on Unsplash.