PFAS
What it is
PFAS ("per- and polyfluoroalkyl substances") is a family of thousands of manufactured chemicals that share a carbon-fluorine backbone, one of the strongest bonds in organic chemistry. That bond is why they're used for water, oil, and stain resistance — and why they've earned the nickname "forever chemicals": they resist breaking down in the environment and in the body for years to decades. In household and baby products, PFAS most often shows up as a water-repellent or grease-resistant treatment, sometimes intentionally added and sometimes present as a processing-aid contaminant that isn't on the ingredient list at all.
Why it's flagged
Long-chain PFAS compounds (PFOA, PFOS) are classified as carcinogenic to humans by the International Agency for Research on Cancer, and the U.S. EPA has set health advisory levels for several PFAS in drinking water at effectively the lowest levels its instruments can detect, reflecting evidence of harm at very low exposures. Because PFAS bioaccumulates and doesn't break down, even small, repeated exposures — such as from a product worn against skin for hours a day — add to a body burden that is measured in years, not days.
How concerned to be
Avoid entirely where you can identify it. This is not a "the dose makes the poison" ingredient in the way many flagged substances are: PFAS's defining feature is that it persists and accumulates, which is why regulators have moved toward restricting the entire chemical class rather than approving individual uses. The practical difficulty is that PFAS is rarely named directly on a label — it hides behind water-resistance or stain-resistance marketing claims, or isn't disclosed as a processing aid at all, which is why independent lab testing (not the label) is the only reliable way to know if a specific product contains it. A concrete example of what that testing looks like: a 2023 investigation had 65 diapers and diapering accessories from 40 brands tested by a U.S. EPA-certified lab for organic fluorine (a PFAS screening marker) and found detectable levels — 10 to 323 parts per million — in 23% of products overall (17% of disposables, 30% of cloth diapers and accessories), reviewed by four independent scientists including a former director of the National Institute of Environmental Health Sciences. Certifications that sound protective aren't a substitute for this kind of testing: OEKO-TEX Standard 100, for example, does not guarantee a product is PFAS-free, since its extractable-organic-fluorine method can miss fluoropolymers.
What it's called on a label
Look for any of these on an ingredient list: Forever chemicals, PFOA, PFOS, Organic fluorine, Per- and polyfluoroalkyl substances, Fluoropolymer, PTFE, Teflon, Perfluoro-, Polyfluoro-, Water-repellent finish (unspecified).
Sources
- PFAS Explained, U.S. Environmental Protection Agency (2024)
- IARC Monographs Volume 135: Perfluorooctanoic acid (PFOA) and Perfluorooctanesulfonic acid (PFOS), International Agency for Research on Cancer, World Health Organization (2023)
- Assessment of the risks associated with corporal exposure to chemical substances present in disposable diapers for babies, French Agency for Food, Environmental and Occupational Health & Safety (ANSES) (2019)
- Disposable & Cloth Diapers Tested For Indications of PFAS ("Forever Chemicals"), Mamavation, in partnership with Environmental Health News (EHN.org) (2023)