Harmful compound found in charcoal toothpaste 





The toxic compound naphthalene was found in charcoal toothpaste












Their abrasiveness was found to be within the acceptable limits set by ISO








Charcoal-containing toothpastes are gaining popularity, and are often advertised as “natural”. Scientific information on their effect however, is scarce. A new NIOM study found the toxic compound naphthalene in a charcoal toothpaste, raising questions about such products’ safety.

– In this study we investigated properties of charcoal dentifrices, or toothpastes. We looked into how they may affect dentine abrasion, as well as their ability to adsorb fluoride and the presence of harmful substances, Ida S. R. Stenhagen says.

Ida is a senior scientist at NIOM and expert in organic chemistry. Together with her team, she became curious about charcoal dentifrices and their advertised properties. Do they have the capacity to remove stains from teeth? Are they free of toxic substances?

Disturbing find

– One of the more disturbing finds was the presence of naphthalene in one product (NAO Coco teeth whitening), Stenhagen says.

The International Agency for Research on Cancer (IARC) of the World Health Organization (WHO) has concluded that naphthalene is possibly carcinogenic to humans. This has caused the EU to prohibit use of the compound in cosmetics.

– However, considering the production methods, it is not surprising, she adds.

Charcoal is the result of the removing water and other volatile constituents from carbon-based materials, such as bamboo, wood or coconut husk and shell. To increase the porosity, charcoal is activated by exposure to high temperatures often in combination with gases during manufacturing.

Abrasiveness within limits

– Activated charcoal can absorb or remove fluoride from water and soil. This made us question whether it would do the same when present in a toothpaste. Which of course is not good, as fluoride in oral hygiene has proven effect against caries, Stenhagen says.

However, none of the tested dentifrices, showed fluoride-binding properties. The abrasiveness was found to be within the acceptable limits set by ISO, the international organization for standardization.

– The presence of naphthalene however, is a cause for concern, Stenhagen says.

Photo by istock: Young woman brushing her teeth with charcoal dentifrice. The product may come in the form pf a powder or a paste.

In vitro abrasity and chemical properties of charcoal-containing dentifrices
Macla F, Mulic A, Bruzell E, Valen H, Stenhagen ISR
Biomaterial Investigations in Dentistry, Volume 7, 2020- Issue1, pages 164-174

NIOM Newsletter January 2021