What Is PFAS? Health Risks, Sources & How to Avoid Forever Chemicals

What Does PFAS Stand For?

PFAS stands for per- and polyfluoroalkyl substances, a group of nearly 15,000 synthetic chemicals that all share at least one carbon atom fully bonded to fluorine. Well-known members include PFOA, PFOS, and GenX.

The name sounds intimidating, but it describes a simple idea. “Alkyl” is chemistry shorthand for a chain of carbon atoms. “Fluoro” means fluorine atoms are attached to that chain. The “per” and “poly” prefixes tell you how many.

• The “per” ones, like PFOA and PFOS, are completely coated in fluorine. That makes them the toughest and longest-lasting of the bunch.
• The “poly” ones are only partly coated, so they are a little less stubborn. But over time they can break down into the “per” kind anyway, which is why scientists watch both as one group.

You may also see the older term PFC, short for perfluorinated chemicals. Same family, older label. NIEHS and most agencies switched to PFAS because it covers the poly group too.

How many PFAS are there? The EPA’s CompTox chemicals dashboard tracks a master list of roughly 15,000 structures, while the USGS cites more than 12,000. Exact counts depend on the definition used, but every agency agrees on the important part: current water tests can only detect a few dozen of them.

Why Are PFAS Called Forever Chemicals?

PFAS are called forever chemicals because the carbon-fluorine bond is one of the strongest in organic chemistry, so sunlight, water, and microbes cannot break them apart. Once released, PFAS persist in soil and water for decades and build up in living things.

Think of a carbon-fluorine bond as a knot that nature never learned to untie. The same toughness that makes PFAS so useful in a frying pan or a firefighting foam is exactly what makes them a problem. Normal pollutants eventually rot, rust, or get eaten by bacteria. PFAS just move: from a factory into a river, from a river into a well, from a well into a glass of water, and from that glass into your bloodstream.

Two words come up constantly in PFAS research, and they explain the whole concern.

• Persistence: the chemical does not break down in the environment. Long-chain PFAS like PFOA and PFOS have no known natural half-life in soil or water.
• Bioaccumulation: the chemical builds up in a body faster than the body can clear it. Long-chain PFAS bind to proteins in blood and get reabsorbed by the kidneys instead of passing out in urine, which is why they linger for years.

How Long Do PFAS Persist in the Body?

The best human data comes from Ronneby, Sweden, where a town drank water contaminated by firefighting foam for decades until the source was shut off in 2013. Researchers led by Ying Li and Tony Fletcher then tracked how fast blood levels fell. Their 2018 study in Occupational and Environmental Medicine estimated average half-lives of 2.7 years for PFOA, 3.4 years for PFOS, and 5.3 years for PFHxS. A half-life is the time it takes for the amount in your blood to drop by half, so getting from a high level to a low one takes several half-lives, often a decade or more.

Shorter-chain replacements clear faster. PFBS leaves the body in roughly a month, and the EPA notes that GenX chemicals “do not appear to accumulate as much in humans” as PFOA and PFOS. Faster clearance is better, but it is not the same as safe, since ongoing exposure from water keeps topping the level back up.

Where Are PFAS Found? Common Sources of Exposure

PFAS are found in drinking water, nonstick cookware, grease-resistant food packaging, waterproof and stain-resistant fabrics, some cosmetics and dental floss, and firefighting foam. For most people, drinking water and diet are the two largest sources of PFAS exposure.

Since the 1940s, PFAS have been added to anything that needed to repel water, oil, or stains. That is a long list. The good news is that the sources are not equal. A few account for most of what ends up in your blood, and those are the ones worth changing first.

🚰 Drinking Water

Tap water is the single biggest PFAS source for people who live near a contaminated site, and a meaningful one for everyone else. The USGS study that found PFAS in at least 45% of tap water sampled 716 locations, including private wells, and tested for only 32 of the thousands of PFAS in use. Meanwhile, the EPA’s own nationwide survey (UCMR 5, covering more than 10,000 water systems) found about 8% of systems above the 4 ppt limit for PFOA and about 9% above it for PFOS, with large systems serving more than 10,000 people roughly twice as likely to exceed as small ones. Private wells are not covered by any of this monitoring, so if you are on a well, testing is on you.

🍕 Food Packaging and Cookware

For decades, the grease-proof coating on microwave popcorn bags, pizza boxes, and fast-food wrappers was a PFAS. That changed recently. In February 2024, the FDA announced that manufacturers had stopped selling PFAS grease-proofing agents for paper and paperboard into the US market, and in January 2025 it formally pulled 35 food-contact authorizations for those uses. The FDA calls this “the primary source of exposure to PFAS from authorized food contact uses,” so new packaging is much cleaner than it was five years ago. Imported and old-stock packaging can still carry it.

Nonstick cookware is a different story. The PTFE coating on a Teflon-style pan is still authorized by the FDA, which says negligible amounts migrate into food during normal cooking. Real risks come from overheating (PTFE starts breaking down above about 500°F, releasing fumes that are harmful to birds and can cause flu-like symptoms in people) and scratched, flaking coatings. PFOA has not been used to make Teflon in the US since 2013, but “PFOA-free” does not mean PFAS-free, since the coating itself is a PFAS. Cast iron, carbon steel, stainless steel, and glass are the swaps that skip the question entirely.

🧥 Textiles and Waterproof Gear

The durable water repellent (DWR) finish on rain jackets, hiking pants, and ski wear was traditionally a PFAS, and so was the stain guard on carpets, couches, and “performance” school uniforms. Scotchgard, made by 3M, was PFOS-based until 2000 and then reformulated with shorter-chain PFAS.

The exposure route here is mostly dust: the finish wears off over time, sheds into house dust, and gets breathed in or swallowed, which matters most for crawling babies and toddlers. Many outdoor brands have now switched to PFAS-free DWR, and Minnesota, Maine, and California have banned intentionally added PFAS in apparel and textiles on rolling deadlines through 2032.

💄 Cosmetics and Dental Floss

Long-wear foundation, waterproof mascara, and lipstick sometimes use PFAS for that smooth, water-resistant finish. Look for “fluoro” or “perfluoro” anywhere in the ingredient list, or the abbreviation PTFE. Dental floss is the sneaky one.

Several popular “glide” style flosses are made from PTFE, the same polymer as a nonstick pan, and a 2019 study in the Journal of Exposure Science and Environmental Epidemiology found women who used PTFE floss had higher blood levels of PFHxS. Waxed silk or plant-based floss avoids it. Our dental floss directory scores the plastic-free options so you can swap in one step.

🔥 Firefighting Foam (AFFF)

Aqueous film-forming foam, or AFFF, is the concentrated PFAS product used to smother fuel fires at military bases, airports, refineries, and fire training grounds. Decades of training exercises soaked the ground with PFOS and PFHxS, which then leached into groundwater.

AFFF is why so many contamination hotspots sit next to air bases, and it is the subject of the largest PFAS lawsuit in the country (more on that below). At least 11 states now restrict or ban its use.

PFAS Health Effects: What Does the Science Say?

So what does all this actually do to a body? According to the CDC’s ATSDR, PFAS have been tied to higher cholesterol, a weaker response to vaccines, liver changes, high blood pressure during pregnancy, slightly smaller babies at birth, and a higher risk of kidney and testicular cancer. The strongest evidence is for PFOA and PFOS, since those two have been studied the longest.

Health research on PFAS is unusual because of a single, massive natural experiment. After DuPont’s Parkersburg, West Virginia plant contaminated the Ohio River valley with PFOA (then called C8), a 2005 class-action settlement funded the C8 Health Project, which collected blood and health records from roughly 69,000 residents.

The independent C8 Science Panel spent seven years on the data and, between 2011 and 2012, reported “probable links” between PFOA and six conditions: kidney cancer, testicular cancer, thyroid disease, ulcerative colitis, high cholesterol, and pregnancy-induced hypertension. That list still anchors most of what agencies say about PFOA today.

The EPA’s own summary adds decreased fertility, developmental delays in children, hormone interference, reduced immune response, and increased risk of prostate, kidney, and testicular cancers. Not every study agrees on every effect, and dose matters. The clearest pattern is that immune and cholesterol effects show up at fairly ordinary exposure levels, while cancer signals come mostly from highly exposed communities and workers.

PFAS and Cancer

In November 2023, the International Agency for Research on Cancer (IARC), the cancer arm of the World Health Organization, classified PFOA as Group 1, “carcinogenic to humans,” based on sufficient evidence in animals and strong mechanistic evidence, with limited human evidence for kidney and testicular cancer. PFOS was placed in Group 2B, “possibly carcinogenic to humans.” Group 1 is the same category as tobacco smoke and asbestos. That label speaks to the strength of the evidence, not the size of the risk, so it does not mean PFOA is as dangerous as smoking. It means researchers are confident it can cause cancer under some conditions.

PFAS in Pregnancy and Children

PFAS cross the placenta and pass into breast milk, so a baby’s exposure starts before birth. The effects ATSDR lists with the most support are slightly lower birth weight, pregnancy-induced high blood pressure and preeclampsia in the mother, and a weaker antibody response to childhood vaccines. Breastfeeding is still recommended by every major health body because its benefits outweigh the PFAS concern. The practical move for parents is to filter the water used for formula and drinking, keep dust down in rooms where a baby crawls, and skip stain-treated furniture and PTFE-coated pans.

How Do PFAS Get Into Drinking Water?

PFAS get into drinking water through three main routes: industrial discharge from factories that make or use PFAS, firefighting foam (AFFF) soaking into groundwater at military bases and airports, and leachate from landfills where PFAS-treated products were thrown away. Wastewater treatment plants and biosolids used as fertilizer spread them further.

Water treatment plants were never built to catch PFAS. Standard steps like chlorination, sand filtration, and settling do nothing to them, so whatever is in the source water goes straight to the tap. Contamination follows a predictable geography. The worst hot spots sit downstream of fluorochemical plants (Parkersburg, West Virginia; Fayetteville, North Carolina; Cottage Grove, Minnesota), next to military airfields, and near paper mills, chrome platers, and textile finishers that used PFAS in their processes.

The landfill route is slower but everywhere. Every stain-guarded carpet, waterproof jacket, and greasy wrapper that goes to a dump eventually sheds PFAS into the liquid that drains out the bottom, called leachate. Landfills send that leachate to wastewater plants, which cannot remove PFAS either, so it flows out in the treated water they release or concentrates in the leftover sludge. When that sludge is spread on farm fields as fertilizer, it contaminates soil, crops, and the groundwater underneath. Maine banned sludge spreading in 2022 after PFAS turned up in milk and beef from affected farms.