PFAS are a group of thousands of synthetic chemicals built around chains of carbon and fluorine atoms, one of the strongest chemical bonds known. That bond is so durable that PFAS resist heat, water, oil, and virtually every natural process that breaks down other substances, earning them the nickname “forever chemicals.” They’ve been manufactured since the mid-20th century for use in everything from nonstick cookware to firefighting foam, and they’ve since spread into drinking water, soil, and the bloodstreams of nearly every person on the planet.
Why They Don’t Break Down
The defining feature of PFAS is the carbon-fluorine bond at their core. It is one of the strongest covalent bonds in chemistry, and it makes these compounds resistant to thermal, oxidative, and photochemical degradation. In practical terms, that means sunlight won’t break them apart, bacteria in soil can’t digest them, and normal water treatment processes don’t destroy them. Once PFAS enter the environment, they stay there for decades or longer.
Adding more fluorine atoms to the chain makes the problem worse. Each additional fluorine strengthens the molecule’s resistance to biological attack. This is why PFAS accumulate in groundwater, rivers, and oceans rather than cycling out the way most organic pollutants eventually do.
Where You Encounter Them
PFAS show up in a surprisingly wide range of everyday products. Their ability to repel water and grease made them attractive to manufacturers across many industries. Common sources include:
- Nonstick cookware coated with materials like Teflon
- Food packaging such as fast-food wrappers, paper plates, and pizza box liners
- Water-resistant clothing and textiles, including carpets treated with stain repellents
- Personal care products like lotions, cosmetics, and dental floss
- Household products including paint, varnishes, sealants, and some laundry detergents
- Waterproofing sprays and ski wax
Beyond consumer goods, one of the largest contamination sources is aqueous film-forming foam (AFFF), a firefighting foam used extensively at military bases and airports. Drinking water contamination has been documented near more than 300 U.S. military sites that used these foams for fire training. The chemicals seep into soil, get trapped in the layer above the water table, and slowly transform into more mobile compounds that leach into groundwater. Researchers have estimated that some of these precursor chemicals have a half-life exceeding 66 years, meaning contamination from a single training exercise can sustain elevated groundwater levels for well over a century.
The Most Common Types
The PFAS family contains thousands of individual compounds, but two have drawn the most scrutiny: PFOA (perfluorooctanoic acid) and PFOS (perfluorooctane sulfonate). These are “long-chain” PFAS that were used heavily for decades and are the most studied in terms of health effects. PFOA alone has been detected in roughly 90% of tested samples in some environmental surveys.
As concern grew, manufacturers began phasing out PFOA and PFOS in favor of newer alternatives. These replacements include GenX (technically called HFPO-DA), PFHxS (perfluorohexane sulfonic acid), and PFHxA (perfluorohexanoic acid). The shift doesn’t necessarily solve the problem. Many of these newer compounds share the same fundamental carbon-fluorine structure, and only a small fraction of all PFAS are currently monitored or regulated.
Health Risks Linked to PFAS
PFAS are absorbed into the body through contaminated water, food, and sometimes air, and they accumulate in the blood over time. The health effects depend on the level and duration of exposure, but the body of evidence has grown significantly in recent years.
Thyroid problems are one of the more established concerns. PFOA and PFOS have been linked to thyroid hormone disruption, including hypothyroidism. A study published in The Lancet’s eBioMedicine found a 56% increased rate of thyroid cancer diagnosis for each doubling of one form of PFOS in the blood. When researchers looked specifically at cases diagnosed at least a year after the blood sample was taken (to rule out reverse causation), the association was even stronger, with a roughly 2.7-fold increase in risk.
Beyond the thyroid, PFAS exposure has been associated with immune system suppression (including reduced vaccine response in children), elevated cholesterol, liver damage, reproductive problems, and certain cancers including kidney cancer. These chemicals act as endocrine disruptors, interfering with the body’s hormone signaling in ways that can affect multiple organ systems.
How Much Is in Your Blood
Nearly everyone in the United States has measurable levels of PFAS in their blood. The good news is that levels of the two most common types have dropped substantially since monitoring began. Between 1999 and 2019, blood levels of PFOS declined by more than 85%, and PFOA levels fell by more than 70%, according to data from the CDC’s national health surveys. These declines reflect the phaseout of long-chain PFAS from many manufacturing processes.
The bad news is that newer replacement chemicals are now showing up in blood samples, and their long-term health effects are less understood. People living near contaminated military sites, industrial facilities, or wastewater treatment plants tend to have significantly higher levels than the general population.
Drinking Water Limits
In 2024, the EPA finalized the first-ever national drinking water standard for PFAS. The limits are measured in parts per trillion, reflecting just how small the concentrations of concern are. The enforceable limits are:
- PFOA: 4.0 parts per trillion
- PFOS: 4.0 parts per trillion
- PFHxS: 10 parts per trillion
- PFNA: 10 parts per trillion
- GenX: 10 parts per trillion
For mixtures containing two or more of the regulated compounds, the EPA uses a hazard index that accounts for the combined effect. To put these numbers in perspective, one part per trillion is roughly equivalent to a single drop of water in 20 Olympic-sized swimming pools. These are extremely low thresholds, and many public water systems will need to install new treatment technology to comply.
At the state level, some governments are going further. As of early 2026, Maine and Vermont have banned the sale of products made with PFAS across categories including cosmetics, cookware, food packaging, menstrual products, cleaning products, and children’s items.
Reducing Your Exposure at Home
If your drinking water is a concern, home filtration can help, but effectiveness varies dramatically by filter type. Research from Duke University tested multiple systems and found that under-sink reverse osmosis filters achieved near-complete removal, reducing PFAS levels by 94% or more. Two-stage filters performed similarly well, though fewer have been tested.
Activated carbon filters (the most common type in pitcher-style filters) removed an average of 73% of PFAS, but individual results ranged from total removal to no reduction at all. The inconsistency makes them a less reliable choice. Whole-house systems using activated carbon were even more unpredictable. In four out of six systems tested, PFAS levels actually increased after passing through the filter, likely because previously captured chemicals were released back into the water.
Beyond water filtration, you can reduce exposure by choosing PFAS-free cookware (look for ceramic or cast iron), avoiding stain-resistant fabric treatments, and checking cosmetics and personal care products for ingredients containing “fluoro” in the name. Microwave-safe paper containers and grease-resistant food wrappers are common sources that are easy to replace with glass or stainless steel alternatives.