Your dentist reminds you that flossing is a healthy habit that is crucial to keeping your teeth healthy and clean. The brand of dental floss you’re using, however, may be exposing you to harmful chemicals.

A recent peer-reviewed study published in the Journal of Exposure Science and Environmental Epidemiology found women who used a particular brand of dental floss had a high level of the chemical perfluoroalkyl (per-fluoro-AHL-kill), or PFAS, in their bodies.

PFAS chemicals are common and found in a lot of household products, including nonstick cookware, flame-retardant fabrics and water- and stain-resistant clothing. This is the first time the chemicals have been found in dental floss. Researchers say this is concerning because the chemicals have been linked to various health issues, including cancer, fertility problems and weight gain.

To conduct the study, researchers measured blood samples from 178 middle-aged women – half white, half African-American. They also interviewed the women about various habits that could lead them to PFAS exposure, including fast food consumption. They found women who reported using one brand of dental floss had higher levels of PFAS exposure than women who did not use the floss. Overall, the researchers tested 18 different dental flosses and found PFAS chemicals in three products that are marketed as having Teflon-like strength.

What do you do if you’re nervous about chemical exposure? First, don’t forgo flossing altogether. Flossing is important to limiting bacteria in the mouth and preventing periodontal disease. Instead, read the labels and choose a non-PFAS or an all-natural dental floss.