PFAS are synthetic chemicals that have contaminated drinking water supplies across the United States. Short for per- and polyfluoroalkyl substances, they’re a group of thousands of human-made compounds used since the 1940s in everything from nonstick cookware to firefighting foam. They’ve earned the nickname “forever chemicals” because they don’t break down naturally in the environment or in your body.
Why PFAS Don’t Break Down
The defining feature of PFAS is the bond between carbon and fluorine atoms in their molecular structure. This is the strongest bond in organic chemistry. Fluorine atoms are tiny and hold tightly to electrons, which makes the bond extremely resistant to heat, chemical reactions, and biological processes. That’s why PFAS were so useful in manufacturing: they repel both water and oil, resist high temperatures, and reduce friction.
Those same properties make them a nightmare in the environment. The most commonly studied PFAS compounds barely degrade under natural conditions. Once they reach soil or groundwater, they persist for decades or longer. Research on contamination near military sites suggests PFAS levels in some areas could remain elevated for centuries.
How PFAS Get Into Drinking Water
PFAS enter water supplies through several routes, but one of the largest sources is firefighting foam. The U.S. military is the world’s biggest user of a PFAS-containing foam called AFFF (aqueous film forming foam), which was used for decades at hundreds of military bases for fire training drills and fighting fuel fires. The chemicals in these foams soak into soil, then leach into groundwater at concentrations thousands of times greater than levels the EPA considers safe.
The number of military fire training areas within a watershed is actually a reliable predictor of how contaminated a community’s drinking water will be. But military bases aren’t the only source. Industrial facilities that manufacture or use PFAS, wastewater treatment plants that can’t filter them out, and landfills where PFAS-containing products decompose all contribute to contamination. Even areas without obvious industrial sources can have detectable PFAS levels because the chemicals are so widespread in consumer products and industrial processes.
What PFAS Do to Your Body
Once PFAS enter your body through drinking water, food, or other exposure, they accumulate in your blood and organs. Your body eliminates them extremely slowly. The estimated half-life of PFOA (one of the most studied types) ranges from 2 to 10 years. For PFOS, it’s 3 to 27 years. PFHxS can linger for 5 to 35 years. That means even after you stop being exposed, it takes years or decades for your levels to drop by half.
Epidemiological studies have linked increased PFAS exposure to several health effects:
- Higher cholesterol levels, associated with PFOA, PFOS, and other long-chain PFAS
- Weakened vaccine response, meaning your immune system produces fewer antibodies after vaccination
- Liver enzyme changes, a marker of liver stress
- Pregnancy complications, including pregnancy-induced high blood pressure and preeclampsia
- Lower birth weight in newborns
- Kidney and testicular cancer, linked specifically to PFOA
Animal studies, which typically use higher doses than people encounter from environmental exposure, have confirmed damage to the liver and immune system. The concern with PFAS isn’t usually a single large exposure. It’s the slow, steady accumulation over years of drinking contaminated water, eating food from contaminated sources, and using products that contain these chemicals.
Current Legal Limits for Drinking Water
In 2024, the EPA finalized the first-ever national drinking water standards for PFAS. The rule set maximum contaminant levels of 4 parts per trillion for PFOA and PFOS individually. For three other PFAS compounds (PFNA, PFHxS, and GenX chemicals), the limit was set at 10 parts per trillion. To put that in perspective, one part per trillion is roughly equivalent to a single drop of water in 20 Olympic swimming pools.
The original rule required water systems to test for PFAS by 2027 and meet the new standards by 2029. However, in May 2025, the EPA announced it would delay the compliance deadlines for PFOA and PFOS by two years, pushing them to 2031. The agency also stated it would rescind the standards for four other PFAS compounds entirely. The regulatory landscape is still shifting, which means some communities may wait years before their water systems are required to act.
How Water Systems Remove PFAS
Three main technologies can effectively strip PFAS from drinking water. Granular activated carbon (essentially specialized charcoal filters) can remove 100 percent of PFAS for a period of time, though performance depends on factors like the type of carbon used, how fast water flows through it, and what other contaminants are present. The carbon eventually becomes saturated and needs to be replaced.
Ion exchange resins work similarly, capturing PFAS molecules and holding them. Like activated carbon, these resins remove 100 percent of PFAS initially but lose effectiveness over time and need periodic replacement. High-pressure membrane systems like reverse osmosis take a different approach, physically blocking PFAS molecules from passing through. These membranes are typically more than 90 percent effective across a wide range of PFAS types, including shorter-chain compounds that other methods sometimes miss.
All three technologies are proven and available. The challenge for water utilities is cost and scale. Installing and maintaining these systems for an entire community requires significant investment, which is one reason the compliance timeline matters so much.
How to Check Your Water
If your water comes from a public system, your utility may already have PFAS testing data. The EPA’s fifth Unregulated Contaminant Monitoring Rule required public water systems across the country to test for PFAS between 2023 and 2025. Results from your local system should be available through your water utility or the EPA’s online databases.
If you use a private well, no federal regulation requires testing. You’d need to send a sample to a certified laboratory that uses one of the EPA’s validated methods for PFAS analysis. These tests can detect 29 different PFAS compounds at extremely low concentrations. Costs for private well testing typically range from a few hundred dollars, depending on the lab and number of compounds tested.
Reducing Your Exposure at Home
Point-of-use water filters that use activated carbon or reverse osmosis can reduce PFAS levels in your tap water. Not all home filters are equally effective. Look for units specifically certified to reduce PFAS, and pay attention to filter replacement schedules since performance degrades as the filter ages.
Reverse osmosis systems installed under your kitchen sink are generally the most effective home option, mirroring the technology used at the municipal scale. Pitcher-style carbon filters can help with some PFAS compounds but are less reliable for shorter-chain varieties. If your water has confirmed PFAS contamination above the EPA’s limits, a dedicated under-sink reverse osmosis system is the most practical investment for your household.