Certain Dental Flosses Raise Body Levels of Toxic Chemicals

Liam Davenport

January 16, 2019

Flossing teeth could increase the body's levels of per- and polyfluoroalkyl substances (PFASs) — widely used chemicals linked to a number of diseases and certain cancers — warn US researchers.

Changing daily behaviors could reduce exposure, they say.

PFASs have the unique ability to resist both water and lipids and are used in a wide range of consumer products, such as food packaging, nonstick cookware, carpets, furniture, and waterproof clothing.

The research, published online January 8 in the Journal of Exposure Science & Environmental Epidemiology, looked at 11 PFASs in blood samples from almost 180 women.

It showed that using Oral-B Glide to floss one's teeth was associated with higher levels of the PFAS perfluorohexanesulfonic acid (PFHxS) in the body.

The team found that five other flosses tested positive for fluorine compounds.

Lead author Katherine E. Boronow, MS, Silent Spring Institute, Newton, Massachusetts, said: "This is the first study to show that using dental floss containing PFAS is associated with a higher body burden of these toxic chemicals."

And the results overall strengthen "the evidence that consumer products are an important source of PFAS exposure," she noted in a press release from her institution. "Restricting these chemicals from products should be a priority to reduce levels in people's bodies."

"The good news is, based on our findings, consumers can choose flosses that don't contain PFAS," she added.

Six of 18 Dental Floss Products Had Detectable PFAS Levels

PFASs have been detected in drinking water and, in one study, were found in 95% of serum samples from a nationally representative cohort.

The researchers point out that exposure to two forms of PFAS, perfluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS), are linked to kidney and testicular cancer. In addition, they are associated with reduced semen quality, ulcerative colitis in adults, and in children, thyroid disease, immune responses, and reductions in sex and growth hormone levels.

To examine exposure to six common PFAS chemicals, the researchers studied data from the Child Health and Development Studies, as a part of which 300 women were tested for environmental chemicals between 2010 and 2013.

They were also asked about behaviors related to PFAS exposure, including food consumption, dental flossing, and stain-resistant treatments on furniture and carpets.

Complete data were available for 178 women, including 87 African Americans and 91 non-Hispanic whites. Participants were aged 48 to 56 years, and 94% lived in California.

Among the PFASs tested, PFOS was detected at the highest concentrations, at a median of 4.74 ng/mL, followed by PFOA, at a median of 1.80 ng/mL.

Overall results showed that African American women had lower levels of PFOA and PFHxS compared with non-Hispanic white women.

In African Americans, but not other ethnicities, frequent consumption of prepared food in coated cardboard containers was associated with higher levels of four PFASs.

Having stain-resistant carpet or furniture and living in a city served by a PFAS-contaminated water supply were also associated with higher levels of some PFASs.

With regard to dental floss in particular, the team tested 18 products using particle-induced γ-ray emission spectroscopy.  

Oral-B Glide and five competitor flosses contained detectable fluorine (including three branded as Glide and two with labels inviting customers to compare the products with Oral-B Glide).

Specifically, flossing with Oral-B Glide was associated with 24.9% higher median levels of PFHxS.

Further Follow-Up Required

Procter & Gamble, which manufactures Oral-B Glide, told Medscape Medical News: "We have confirmed none of the substances in the report are used in our dental floss."

"The safety of the people who use our products is our top priority. Our dental floss undergoes thorough safety testing and we stand behind the safety of all our products," the company said in a statement by email.

Boronow and colleagues do concede, "Consumer product sources of PFASs are difficult to untangle."

"While this study did not capture all the potentially important sources of PFASs, our results strengthen the evidence for exposure to PFASs from food packaging and implicate exposure from polytetrafluoroethylene-based dental floss for the first time — a finding that warrants prompt follow-up in a future study."

"Additional data are required to verify this finding, for example, demonstrating the potential for PFASs in floss to migrate into saliva or onto hands."

They also stress: "Environmental contamination by PFASs, for example in drinking water, remains a major public health threat."

The study was funded by the Eunice Kennedy Shriver National Institute of Child Health and Human Development and California Breast Cancer Research Program.

The authors have reported no relevant financial relationships.

J Expo Sci Environ Epidemiol. Published online January 8, 2019. Full text

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