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Heavy Metal Contaminants Are “Pervasive” in CBD Products, Study Finds

By Alexander Beadle

Published: Sep 12, 2022   
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Low levels of lead, mercury, arsenic, and cadmium are frequently present in commercially-available CBD products, a new study has found.

Published in the journal Science of the Total Environment, the researchers determined that only 42% of the products tested were within 10% of the CBD content stated on the product’s packaging. This is consistent with other product testing studies which have found that CBD products are often mislabeled.

While CBD may have beneficial therapeutic properties, the pervasive presence of heavy metals and phthalate contaminants in these products is of concern to the researchers. These new findings underscore the need for tight restrictions on CBD product labeling to protect consumers, they say.

Lead, cadmium, arsenic, and mercury found in commercial products

Cannabis is a known hyperaccumulator, meaning that it readily absorbs and accumulates metals present in soil and growing media at much higher concentrations than other plants. Because of this ability, there is a concern that cannabis products made from plants that have accumulated contaminants in their leaves and flowers may present a risk to human health. 

In this study, the researchers used inductively coupled plasma mass spectrometry (ICP-MS) analysis to examine 121 edible CBD products with serving size instructions for the presence of heavy metals.

The researchers found amounts of lead in 42% of the samples tested. Lead is a dangerous neurotoxin. While there are legal limits as to what amount of lead a product may contain before it must carry a warning label (in California, for example, the lead exposure limit is 0.5 micrograms per day) the World Health Organization considers there to be no safe levels of lead exposure.

The amounts of lead found in these products were largely low-level and no products exceeding this 0.5 microgram/day limit in a single serving. However, four products would have exceeded this limit in two servings, which the researchers say is a concern.

Low-level amounts of mercury were found in 37% of products tested and 28% contained arsenic. Cadmium, another dangerous neurotoxin, was found in 8% of products.

In addition to testing products for heavy metals, the researchers also used liquid chromatography tandem mass spectrometry (LC-MS/MS) to examine the presence of phthalates in 84 of the edible CBD products. Phthalates are a type of hormone disrupting chemical, but they are widely used in industrial applications as a plasticizer. When plastics break down in the environment, phthalates can enter the waterways or leach into soil where they may also be absorbed by growing cannabis plants.

The percentage of products containing detectable levels of phthalate concentrations varied between 13% and 80% depending on the phthalate. Di (2-ethylhexyl) phthalate, also known as DEHP, was the most prevalent phthalate detected.

CBD labeling integrity remains a prominent issue

Using liquid chromatography with diode array detection (LC-DAD), the researchers also carried out a cannabinoid labeling accuracy test on 516 edible and topical CBD products, including those used in the heavy metals and phthalate studies. 

As a percentage of the claims made on product labeling, measured CBD content varied between -100% and 339% across all products. In the subset of 121 products also chosen for contaminant analysis, this difference ranged from -91% to 68%.

Overall, just 42% of products contained between 90-110% of the CBD amount listed on the product’s label. In contrast, 40% of products contained less than 90% of what was indicated on the packaging, with the remaining 18% containing an excess of CBD above 110% of the labeled amount.

This substantial variability in CBD content has also been seen in a range of other recent investigations.

In an analysis of 147 products carried out by the US Food and Drug Administration, just 46 fell within the acceptable 10% margin of the CBD content stated on its label. Additionally, 72 products were found to have detectable levels of THC or THCA, which is the main psychoactive component of cannabis.

Analyses looking closely at specific CBD product types have also identified similar problems. A recent investigation from researchers at Johns Hopkins Medicine found that just one-in-four CBD topicals are labeled accurately, with additional concerns being raised over the number of products which did not include any cannabinoid dosing information on the packaging at all.

And it is not just CBD products that are wrestling with labeling discrepancies; a new report from CBD Oracle suggests that more than half of hemp-based delta-9 THC products also vary substantially from their advertised dosage.

The pervasive issues with heavy metal contamination, phthalate concentration, and inaccurate CBD content labeling identified in this latest study are of great concern to the study authors.

“These results highlight the need for tight regulations over CBD product label integrity to protect consumers,” they wrote. “Swift actions and reform by regulatory agencies (e.g., the FDA) have the potential to ensure label accuracy and alleviate concerns of vulnerable consumers who rely on these products for health promotion and lifestyle support.”


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