What PFAS actually are

PFAS stands for per- and polyfluoroalkyl substances. The name describes a class of more than 12,000 synthetic chemicals that share a common structure: chains of carbon atoms bonded to fluorine atoms.

That carbon-fluorine bond matters. It is the strongest single bond in organic chemistry. The strength of that bond is the reason these chemicals don't break down in nature and don't break down in your body.

Scientists at 3M and DuPont first synthesized PFAS in the 1940s and 1950s. They were looking for materials that could resist heat, water, and grease. The carbon-fluorine bond delivered all three properties. By the 1960s, PFAS were in commercial production.

Today, PFAS are used in thousands of consumer products and industrial processes. Most Americans encounter them daily without knowing it.

Where PFAS come from and why they're everywhere

PFAS were designed to repel water and oil. That makes them useful in products where stains, grease, and moisture are problems.

Nonstick cookware is one of the most familiar sources. Teflon, the original brand name for PTFE coating, is a PFAS. So are the coatings on many other nonstick pans.

Stain-resistant treatments for carpet and upholstery rely on PFAS. Scotchgard and Stainmaster both used PFAS formulations for decades. Some still do.

Waterproof and breathable outdoor gear uses PFAS to keep rain out while letting sweat escape. Gore-Tex used PFAS-based membranes for years. Many jackets, tents, and hiking boots still contain them.

Grease-resistant food packaging is another major source. Microwave popcorn bags, fast food wrappers, and pizza boxes are often treated with PFAS to keep oil from soaking through the paper.

Firefighting foam is one of the largest sources of environmental contamination. Aqueous film-forming foam, known as AFFF, was used for decades at military bases, airports, and fire training facilities. The foam contains high concentrations of PFAS. When sprayed on the ground, those chemicals soak into soil and groundwater.

Industrial processes release PFAS into the environment as well. Chrome plating facilities, semiconductor manufacturers, and paper coating plants all use PFAS in production. Wastewater from these facilities can carry PFAS into rivers and treatment plants.

PFAS also show up in cosmetics, dental floss, ski wax, and some pesticides. The list is long because the chemistry is versatile.

Why "forever chemicals"

The term "forever chemicals" was coined by Joe DeWitt, a chemistry professor who studies PFAS. It is not a scientific term, but it is accurate.

Carbon-fluorine bonds resist degradation by sunlight, microbes, heat, and water. In the environment, PFAS do not break down the way most organic chemicals do. Some PFAS have estimated environmental half-lives measured in thousands of years.

Once PFAS enter the human body through drinking water, food, or air, they accumulate in the blood. The body has no good mechanism to break them down or excrete them quickly. PFOA, one of the most studied PFAS, has a human half-life of about three to four years. That means if you stop all exposure today, it will take three to four years for half the PFOA in your blood to leave your body.

The CDC has tested blood samples from Americans as part of the National Health and Nutrition Examination Survey. More than 97 percent of people tested have measurable PFAS in their blood.

The chemicals are in our water, our food, our homes, and our bodies. That is why they are called forever chemicals.

What the science says about health effects

The EPA has determined there is no safe level of exposure to PFOA and PFOS for human health. That conclusion is based on decades of research, including studies of communities with contaminated drinking water.

The most detailed evidence comes from the C8 Science Panel. The panel was created as part of a lawsuit against DuPont over PFOA contamination near the company's Parkersburg, West Virginia plant. The panel studied more than 69,000 people who lived in affected areas and drank contaminated water for years.

The C8 Science Panel established probable links between PFOA exposure and six health outcomes: kidney cancer, testicular cancer, ulcerative colitis, thyroid disease, pregnancy-induced hypertension, and high cholesterol.

More recent research has expanded the list of concerns. Studies have linked PFAS exposure to suppressed immune response, including reduced effectiveness of childhood vaccines. Other studies have found associations with liver damage, lower birth weight, and developmental delays in children.

Research on the broader class of 12,000-plus PFAS is ongoing. Scientists know the most about PFOA and PFOS because those chemicals were used the longest and studied the most. Less is known about the newer PFAS that replaced them, though early evidence suggests some may carry similar risks.

The science is not complete, but the pattern is clear. PFAS accumulate in the body, and exposure is linked to serious health problems.

What the EPA has done so far

In April 2024, the EPA set the first enforceable federal drinking water standards for PFAS. The rule covers six compounds.

The maximum contaminant levels are: PFOA at 4 parts per trillion, PFOS at 4 parts per trillion, PFHxS at 10 parts per trillion, PFNA at 10 parts per trillion, and HFPO-DA, also called GenX, at 10 parts per trillion. The sixth standard is a Hazard Index that limits mixtures of certain PFAS.

Parts per trillion is an extremely small measurement. Four parts per trillion is equivalent to four drops of water in an Olympic-size swimming pool.

Public water systems have until 2027 to begin compliance monitoring. Systems that exceed the limits must install treatment by 2029.

The data underlying CheckYourWater comes from UCMR 5, the fifth cycle of the EPA's Unregulated Contaminant Monitoring Rule. Under UCMR 5, public water systems collected samples between 2023 and 2026 and tested for 29 different PFAS. The program was designed to measure how widespread PFAS contamination is and how high the levels are.

UCMR 5 is the most complete national picture of PFAS in drinking water that currently exists.

What this means for your drinking water

Most public water systems have not yet begun reporting PFAS in their annual Consumer Confidence Reports. Compliance is not required until 2027, so many utilities are still in the testing phase.

UCMR 5 provides the best available data right now. CheckYourWater shows that data for every monitored system in the country.

If your water system detected PFAS above the new federal limits, the utility will be required to notify customers and install treatment. Common treatment methods include granular activated carbon filters and ion exchange systems. Both are effective at removing PFAS from drinking water.

If your system detected PFAS below the limits, the water meets the new federal standard. The EPA has said there is no safe level of exposure, but the standards reflect what is technically and economically feasible for utilities to achieve.

If your system has not been tested yet, or if you get water from a private well, you can request testing. State health departments and some nonprofit organizations offer low-cost or free PFAS testing for well owners.

Enter your zip code at checkyourwater.org to see the PFAS testing results for the system that serves you. You can also search by chemical name to learn more about individual PFAS at checkyourwater.org/chemical.

The data is public. It belongs to you. Use it.