How to Choose a Non-Toxic Floss

The safest floss is one made from a natural fiber like silk, not plastic. Here's why.

In recent years, there's been growing concern about dental floss containing PFAS, the so-called "forever chemicals." To help floss glide more easily between teeth, some manufacturers make floss from PTFE (the same fluoropolymer family as Teflon) or apply synthetic coatings. Some of these materials have been linked to PFAS exposure, and PFAS have been associated with a range of health concerns when they build up in the body.

How floss exposes you

No one is actively eating their floss. But every time you floss, it rubs against enamel, squeezes through tight contacts, and sometimes catches on uneven fillings or crowns. That friction causes floss to fray, shed tiny fibers, and occasionally snap.

Even when floss is used correctly, some of that material stays behind in the mouth and along the gumline. If the floss is made with PFAS, those chemicals have a direct route into the body.

The research backs this up. In a 2019 study of California women, those who flossed with a popular PTFE-based floss had about 25% higher median blood levels of PFHxS, a type of PFAS, than those who didn't (Boronow et al., 2019). When the researchers tested 18 floss products, six contained fluorine, a marker of PFAS (Silent Spring Institute).

PFAS have been linked to cancer, thyroid disease, low birth weight, reduced fertility, and other health effects (Silent Spring Institute, 2026).

PFAS-free isn't the whole story

After this research drew media attention, many brands moved away from PFAS. In 2026, the maker of that popular floss confirmed it had removed PFAS from the line entirely (Silent Spring Institute, 2026). Researchers caution that other floss brands may still use PTFE, so it's worth checking the label.

But removing PFAS doesn't change what most floss is made of: plastic.

Why silk?

For more than a century, silk was the gold standard for dental floss. Around 1815, New Orleans dentist Dr. Levi Spear Parmly began recommending waxed silk thread to clean between the teeth, and he promoted daily flossing in his 1819 book, A Practical Guide to the Management of the Teeth (TIME). Synthetic fibers didn't exist yet, so floss was made from nature's best fiber.

Silk remained the standard until World War II, when silk shortages drove manufacturers to switch to cheaper nylon (Spear Education). Plastic has dominated floss ever since.

Silk is strong, gentle on the gums, and natural. Like any floss, silk sheds fibers as you work it through tight contacts. The difference is what those fibers are made of: silk is a natural protein, not plastic.

Plastic floss and the planet

Plastic floss can linger in the environment for decades to centuries. Synthetic fibers like polyester are highly resistant to breaking down in landfills and in nature, and over time they fragment into microplastics rather than disappearing (Microorganisms, 2026).

Silk behaves differently. It's a protein, and research shows soil and marine microbes break silk down, with microbial activity driving its degradation (Lim & Marelli, 2022).

All floss is single-use: it's used once and thrown away. By some estimates, Americans go through millions of miles of floss every year (SWOP). That doesn't count the billions of plastic floss picks and dispensers discarded on top of it.

PFAS-free doesn't mean plastic-free

Many synthetic flosses are now marketed as "PFAS-free" or "non-toxic." But PFAS-free doesn't mean plastic-free. These flosses are still made from plastic, which sheds microplastic fibers with every use.

A growing body of research is raising concerns about microplastics in the human body. In a 2024 study in the New England Journal of Medicine, patients whose arterial plaque contained microplastics and nanoplastics had a higher risk of heart attack, stroke, or death over about three years than those whose plaque did not (Marfella et al., 2024). The study shows an association, not proof that plastic caused the harm, but it's one reason researchers are paying close attention (2024 cardiology review).

The bottom line

Plastic floss comes with a cost to your body and to the planet. A label that says "PFAS-free" or "non-toxic" tells you what's been removed, but not what's still there: plastic fibers that shed with every use and linger in the environment long after you throw them away.

When you shop for floss, look for:

• Natural fiber: silk instead of nylon, polyester, or PTFE

• Natural coating: a plant-based oil or wax (such as coconut or avocado oil) or beeswax, rather than a synthetic coating

• No PTFE on the label: researchers recommend avoiding it entirely (Silent Spring Institute, 2026)

• Plastic-free packaging: biodegradable cardboard packaging or a refillable glass or metal dispenser

To reduce your exposure to microplastics and cut down on single-use plastic waste, make the switch to natural silk floss. Your body and the planet will thank you.

References

1. Boronow KE, Brody JG, Schaider LA, Peaslee GF, Havas L, Cohn BA. Serum concentrations of PFASs and exposure-related behaviors in African American and non-Hispanic white women. Journal of Exposure Science & Environmental Epidemiology. 2019;29:206–217.

2. Silent Spring Institute. Dental flossing and other behaviors linked with higher levels of PFAS in the body. January 8, 2019.

3. Silent Spring Institute. Oral-B stops using Teflon in its popular Glide dental floss. March 31, 2026.

4. Rothman L. How dental floss became a thing in the first place. TIME.

5. Spear Education. A brief history of dental floss.

6. Screening, identification, and degradation mechanism of polyester fiber-degrading bacteria. Microorganisms. 2026.

7. Lim AT, Marelli B. Degradation of regenerated silk fibroin in soil and marine environments. ACS Sustainable Chemistry & Engineering. 2022.

8. Shop Without Plastic. How much dental floss contributes to pollution. December 2023.

9. Marfella R, Prattichizzo F, Sardu C, et al. Microplastics and nanoplastics in atheromas and cardiovascular events. New England Journal of Medicine. 2024;390(10):900–910.

10. Microplastics and nanoplastics: the next frontier of cardiovascular risk? Published December 20, 2024.