PFAS "Forever Chemicals" in Your Tap Water: A Complete Guide for 2025

PFAS stands for per- and polyfluoroalkyl substances. It's an umbrella term for a family of more than 12,000 synthetic chemical compounds that have been manufactured and used in industrial and consumer products since the 1940s.

What makes PFAS so persistent — and so problematic — is a chemical bond between carbon and fluorine atoms. The carbon-fluorine bond is one of the strongest in all of organic chemistry. It doesn't break down under normal environmental conditions. PFAS compounds don't biodegrade in soil, they don't evaporate from water, and they don't break down inside the human body. They accumulate. In groundwater, in rivers, in sediment, in fish tissue, and in human blood.

That's why they're called forever chemicals. They're essentially permanent once they enter the environment.

PFAS have been used in a staggering range of products: the nonstick coating on your cookware (PTFE, trade-named Teflon), waterproofing treatments on outdoor gear and clothing, stain-resistant carpet and furniture treatments, grease-resistant food packaging, and aqueous film-forming foam (AFFF) — a type of firefighting foam used extensively at military bases and airports. The AFFF connection is why so many contaminated water supplies are located near military installations.

Manufacturers have known about the persistence and toxicity concerns with some PFAS compounds since at least the 1970s, but internal documents that emerged through litigation in the 2000s and 2010s revealed that this knowledge was not always shared with regulators or the public.

The health research on PFAS has expanded dramatically over the past decade, and the picture that's emerged is concerning. Long-term exposure to PFAS at elevated levels is associated with a range of health effects.

Cancer is the risk that gets the most attention, and rightly so. Kidney cancer and testicular cancer have the strongest evidence for a PFAS link. Bladder cancer and breast cancer have also been associated with PFAS exposure in some studies, though the evidence is less consistent.

Beyond cancer, PFAS exposure is linked to thyroid disease (PFAS can disrupt normal thyroid hormone function), immune system effects (particularly in children — some studies show reduced vaccine effectiveness with higher PFAS exposure), hormonal disruption, high cholesterol, pregnancy-induced hypertension, and reduced fetal growth.

It's important to understand that these effects are associated with long-term exposure at elevated levels, not a single glass of water. But because PFAS accumulate in the body over time and have a biological half-life of several years, even lower-level chronic exposure can result in significant body burden over decades.

Children are more vulnerable than adults, because their developing immune and endocrine systems are more sensitive to disruption. And PFAS can be passed from mother to child through both placenta and breast milk, which means prenatal exposure is a concern.

In April 2024, the EPA issued final Maximum Contaminant Levels for six PFAS compounds in drinking water — the first time federal law had set specific enforceable limits for any PFAS.

The two most well-studied PFAS — PFOA and PFOS — each received an MCL of 4 parts per trillion (ppt). That's 4 nanograms per liter. To put that in perspective, 4 ppt is like finding 4 drops of water in an Olympic swimming pool. These are among the lowest MCLs the EPA has ever set for any contaminant.

The rule also sets limits for four other PFAS: PFNA, PFHxS, HFPO-DA (also called GenX chemicals), and an MCL for mixtures of PFNA, PFHxS, PFOA, and PFOS combined. Water systems have until 2027 to complete initial monitoring and until 2029 to comply with the new limits.

The EPA estimates that between 6% and 10% of the approximately 66,000 public water systems in the United States will need to take action to reduce PFAS levels. That translates to water systems serving tens of millions of people.

For context on just how widespread PFAS contamination is: the EPA's fifth Unregulated Contaminant Monitoring Rule (UCMR5), which required large water systems to test for 29 PFAS compounds between 2023 and 2025, found PFAS at detectable levels in roughly 45% of the water systems tested. Not all of those exceeded the new MCLs, but the results confirmed that PFAS in drinking water is not a problem limited to a few hotspot communities — it's genuinely widespread.

There are a few ways to check whether PFAS have been detected in your drinking water.

The first is to look up your water system in the EPA's UCMR5 database. The UCMR5 data — collected between 2023 and 2025 from large public water systems — represents the most comprehensive PFAS screening of U.S. drinking water ever conducted. Not all systems are included (smaller systems serving fewer than 3,300 people were not required to participate), but if your system was tested, the results are publicly available.

The second option is to check WaterSafeCheck, which incorporates UCMR5 PFAS data for ZIP codes where it's available. If your system was part of the UCMR5 monitoring, you'll see PFAS detection information in your report.

The third option — and the most definitive for your specific tap — is to arrange for your water to be independently tested by a certified laboratory. PFAS testing is more expensive than standard tap water tests, typically running between $150 and $400 depending on the number of compounds tested. Look for a laboratory certified by your state environmental agency for PFAS analysis.

It's worth noting that if your water comes from a small community water system or a private well, PFAS testing through federal programs may not have occurred. Small systems and private wells are not covered by the new MCLs — private well owners are entirely responsible for their own testing.

This is where I see the most misinformation in water quality discussions, so let me be very direct: most standard water filters do not reliably remove PFAS.

Standard activated carbon pitcher filters — the type used by Brita and most similar brands — do not remove PFAS at meaningful levels. They're effective for chlorine and some VOCs, but not for PFAS. Some higher-end pitcher filters (particularly those using activated carbon in a granular form with longer contact time) have shown some effectiveness, but the evidence is inconsistent and they're not reliable enough to count on.

The technologies that reliably remove PFAS are: granular activated carbon (GAC) systems — particularly whole-house or under-sink systems with significant contact time, reverse osmosis (RO) systems certified to NSF/ANSI Standard 58, and nanofiltration membranes.

For most households, a reverse osmosis system installed under the kitchen sink is the most practical and cost-effective option for PFAS removal. A good under-sink RO system costs between $200 and $500 installed and removes not just PFAS but also lead, nitrates, arsenic, and most other dissolved contaminants. They require filter changes every 6 to 12 months and membrane replacement every 2 to 3 years.

When shopping for any filter marketed as removing PFAS, look for certification from NSF International or the Water Quality Association for PFAS removal specifically. The NSF has developed standard NSF/ANSI 58 to certify RO systems for PFAS. Verify at nsf.org before purchasing — marketing claims alone aren't reliable.

If you're one of the roughly 43 million Americans who get their water from a private well, the 2024 EPA rule doesn't apply to you. Private wells are not regulated by the Safe Drinking Water Act, and there's no required testing program for PFAS in private wells.

This matters because private wells are often located in rural and semi-rural areas that may be near the same military bases, airports, industrial facilities, and agricultural land that have been sources of PFAS contamination for public water systems. In fact, some of the most severely PFAS-contaminated water sources found so far have been private wells near military bases where AFFF firefighting foam was used for decades.

If you have a private well and live within a few miles of a military base, airport, industrial facility, or landfill, PFAS testing is worth prioritizing. Some states have programs to provide free or subsidized PFAS testing for private well owners in affected areas. Contact your state environmental or health agency to ask what programs are available.