Dental floss dangers: New study addresses potential harms of flossing

The American Dental Association recommends daily between-teeth cleaning using floss or another interdental cleaner may help prevent cavities and gum disease. But a new study suggests certain types of floss and other behaviors may actually increase the amount of toxic chemicals in the body.

The research, published this week in the Journal of Exposure Science and Environmental Epidemiology, comes from the Silent Spring Institute in collaboration with the University of California, Berkeley's Public Health Institute. For the study, scientists examined the blood samples of 178 California-based middle-aged women and measured 11 different per- and polyfluoroalkyl substances (or PFAS) chemicals previously linked to a various health implications, from testicular cancer and thyroid disease to decreased fertility and high cholesterol.

The participants, half of whom were white or African-American, are part of the university’s child health and development studies, a multigenerational analysis of environmental chemicals on disease.

To understand behavioral changes, the researchers compared blood measurements with interviews with the women in which they were asked about nine behaviors that may lead to higher PFAS exposures, according to a news release. They also tested the presence of chemical markers of PFAS in six different dental flosses.

“In addition to specialized industrial applications and use in fire-fighting foams, PFASs are frequently used in consumer products,” according to the research. “Most commonly, they are used in nonstick and water-, stain-, or grease-resistant coatings, which are applied to a diverse range of products, including food packaging, cookware, carpet, furniture, textiles, and outdoor performance gear.” PFAS tend to be detected in water, soil and in American bodies thanks to their “extensive use and persistent nature.”

The findings 

According to the study, women who flossed with a particular dental floss — Oral-B Glide — had higher levels of the PFAS perfluorohexanesulfonic acid (PFHxS) compared to women who did not. The National Institutes of Health notes PFHxS has been previously linked to high cholesterol and altered thyroid function.

To further analyze the finding, researchers tested for fluorine (a PFAS chemical marker) in 18 different flosses using a technique called particle-induced gamma-ray emission spectroscopy.

When they did so, the three Glide products examined tested positive. Two similar store-brand products marketed as comparable to Oral-B Glide, plus another marketed with “single strand Teflon fiber” also tested positive for fluorine.

Previous reports have highlighted Glide's use of Teflon-like compounds. Teflon is the brand name of PFAS polytetrafluoroethylene, which the Environmental Working Group has warned against using via dental floss due to risks of cancers, hormone disruption, brain and liver problems, as well as low birth weights.

This is the first study to find “evidence that flossing with PTFE-based dental floss could contribute to an individual’s body burden of PFASs, but additional data are required to verify this finding,” researchers wrote.

The lesson: Avoid dental floss with PFAS, lead author Katie Boronow said in a statement.

In addition to the floss findings, researchers noticed higher PFAS levels when participants:

  • Had stain-resistant carpet or furniture.
  • Lived in a city with a PFAS-contaminated drinking water supply.
  • Ate food prepared in coated cardboard containers (African-American women in particular).

Authors also noted that in this particular study, African-Americans ate french fries more often than non-Hispanic whites, “so we infer that they may also consume more fast food such as hamburgers, which are sold in paper wrappers.” Fluorinated chemicals are frequently detected in fast food packaging.

A potential limitation, according to the study, is that there are other behaviors that may contribute to PFAS exposure the researchers didn’t measure. This is why any racial differences regarding PFAS chemicals were left unexplained. Another limitation: the number and location of participants. But authors report figures were comparable with a nationally representative sample.

Future work should dive into Hispanic and Asian-Americans as race differences may help identify “major exposure pathways,” according to the study.

Though PFSA environmental contamination via drinking water, for example, is considered a major public health threat most consumers can’t do much about, “this study strengthens the evidence that consumer products are [also] an important source of PFAS exposure,” Boronow saida. “Restricting these chemicals from products should be a priority to reduce levels in people's bodies.”

Read the full study at