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What Are PFAS? 5 Facts About Forever Chemicals

By Verdolea Research Last updated

PFAS are a family of synthetic chemicals found in everything from nonstick pans to rain jackets. Here is what they are, why they last so long, and what the evidence says about health.

At a Glance

  • PFAS are a family of thousands of synthetic chemicals defined by carbon–fluorine bonds.
  • Many are extremely persistent, which is why they are called "forever chemicals."
  • They are used widely, from nonstick coatings and food packaging to water-repellent textiles and electronics manufacturing.
  • Nearly everyone in the US has measurable PFAS in their blood.
  • Exposure to certain PFAS is linked to effects on cholesterol, immunity, development, and some cancers.

1. PFAS Are a Large Chemical Family

Ball-and-stick model of PFOA, a chain of eight carbon atoms surrounded by fluorine atoms, ending in a carboxylic acid group.

PFAS stands for per- and polyfluoroalkyl substances. In perfluoroalkyl substances, every hydrogen on part of the carbon chain is replaced by fluorine; in polyfluoroalkyl substances, only some are. The family includes small molecules such as PFOA and PFOS, and large polymers such as PTFE.

How many exist depends on the definition used. EPA's chemical database lists more than 20,000 PFAS structures, although only a small fraction are in commercial use.

2. Why They're Called "Forever Chemicals"

The carbon–fluorine bond is one of the strongest single bonds in organic chemistry. Fluorine atoms are small and strongly electronegative, so they form a tight shield around the carbon chain. That structure resists heat, sunlight, microbes, and most chemical reactions.

The result is persistence, both in the environment and in the body. In one study of retired production workers, the average time for blood levels to fall by half was about 3.8 years for PFOA and 5.4 years for PFOS.

3. They Are Used Almost Everywhere

  • Cookware: PTFE nonstick coatings.
  • Food packaging: grease-resistant wrappers and paperboard.
  • Textiles: stain- and water-repellent finishes on clothing, carpets, and furniture.
  • Firefighting foam: a major source of drinking water contamination near airports and military bases.
  • Industry: semiconductor manufacturing, medical devices, and many other processes.

Their properties (heat resistance, low friction, chemical inertness) are hard to replace, which is why restrictions tend to target one use at a time rather than the whole class.

4. Exposure Is Nearly Universal

According to the CDC's Agency for Toxic Substances and Disease Registry, nearly all people in the US have PFAS in their blood. The main exposure routes are drinking water, food, food packaging, and household dust. Blood levels of PFOA and PFOS have declined since manufacturers phased them out, but newer PFAS have replaced some of them.

5. What the Health Evidence Shows

EPA reports that exposure to certain PFAS may lead to:

  • Higher cholesterol levels and risk of obesity.
  • Reduced immune response, including lower vaccine response.
  • Developmental effects in children, such as low birth weight.
  • Reproductive effects, including high blood pressure in pregnancy.
  • Interference with hormones.
  • Increased risk of some cancers, including kidney and testicular cancer.

In 2023, the International Agency for Research on Cancer classified PFOA as carcinogenic to humans (Group 1) and PFOS as possibly carcinogenic (Group 2B). The evidence is strongest for these well-studied compounds; most other PFAS have little health data.

In 2024, EPA set enforceable drinking water limits of 4 parts per trillion for PFOA and PFOS. In 2026, it proposed keeping those two limits while withdrawing limits for four other PFAS.

How to Reduce Exposure at Home

  • Drinking water: check your utility's water quality report. If PFAS are a concern, use a filter certified to NSF/ANSI 53 or 58 for PFOA and PFOS reduction, such as activated carbon or reverse osmosis.
  • Cookware: choose uncoated or PTFE-free pans, and avoid overheating nonstick. See our guide to PFAS-free cookware.
  • Food packaging: limit grease-resistant takeout wrappers and containers, and see what has changed in food packaging.
  • Textiles: skip optional stain- and water-repellent treatments.
  • Dust: vacuum with a HEPA filter and damp-mop regularly.

The Bottom Line

PFAS are useful because they are so stable, and that same stability makes them persist in water, soil and our bodies. You can't avoid them completely, but filtering drinking water and choosing products without PFAS coatings are practical steps with measurable effect.

Sources

  1. U.S. EPA. Our Current Understanding of the Human Health and Environmental Risks of PFAS.
  2. U.S. EPA. CompTox Chemicals Dashboard: PFAS structure list.
  3. ATSDR. PFAS: What to Know.
  4. Olsen, G. W., et al. (2007). Half-life of serum elimination of perfluorooctanesulfonate, perfluorohexanesulfonate, and perfluorooctanoate in retired fluorochemical production workers. Environmental Health Perspectives, 115(9), 1298–1305.
  5. IARC. IARC Monographs evaluate the carcinogenicity of PFOA and PFOS (2023).
  6. Waste Dive. EPA to formally rescind certain PFAS drinking water regulations (2026).
  7. U.S. EPA. Identifying Drinking Water Filters Certified to Reduce PFAS.
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