What Are PFAS?
PFAS stands for per- and polyfluoroalkyl substances. That's a mouthful, so people call them "forever chemicals" because once they get into the environment, they don't break down. Ever. They accumulate in water, in soil, and in your body.
PFAS have been used since the 1950s to make things nonstick, waterproof, and stain-resistant. Nonstick cookware. Waterproof jackets. Stain-resistant carpets. Food packaging. Firefighting foam. According to the CDC, PFAS have been detected in the blood of virtually all Americans tested through national health surveys. Separate studies have also found PFAS in umbilical cord blood, meaning exposure begins before birth.
Why "forever"?
Most chemicals break down over time: sunlight, bacteria, or other natural processes destroy them. PFAS have a chemical bond between carbon and fluorine that is one of the strongest in organic chemistry. Nature doesn't have a good way to break it. So PFAS just... stay. In your water. In the ground. In you.
According to EPA, decades of research have linked PFAS exposure to cancer (including kidney and testicular cancer), liver damage, thyroid disease, immune system suppression, reproductive problems, and developmental issues in children. These effects can occur at extremely low concentrations.
The Rule: First-Ever Limits on PFAS in Drinking Water
On April 10, 2024, EPA did something it had never done before: it set legally enforceable limits on PFAS in drinking water. This was the first-ever federal drinking water standard for PFAS, and according to EPA, what EPA called the first new drinking water standard for a contaminant in decades.
The rule set limits for two of the most well-studied PFAS compounds, PFOA and PFOS, at 4 parts per trillion (ppt) each. That's an extraordinarily small amount. Four parts per trillion is roughly equivalent to a single drop of water in five Olympic-size swimming pools. It's also the lowest concentration that laboratory instruments can reliably detect.
What 4 parts per trillion means
The limit is set at the very edge of what science can measure. According to EPA's fact sheet, the health-based goal for PFOA and PFOS is actually zero, meaning no amount is considered safe. The 4 ppt limit is as close to zero as labs can reliably test for.
The original 2024 rule also set limits for four additional PFAS chemicals: PFHxS, PFNA, and HFPO-DA (commonly known as GenX) at 10 ppt each, plus a Hazard Index formula for mixtures of those three chemicals and PFBS. But in May 2025, according to EPA's announcement, the agency said it would keep the PFOA and PFOS limits but rescind the limits for those four and reconsider them through a new rulemaking.
How Many Water Systems Are Affected?
All 66,000 public water systems in the United States are required to monitor for PFAS under the rule. But not all of them have a problem.
According to EPA's UCMR 5 monitoring data, which has tested approximately 95 percent of required water systems so far, about 3,539 sites have detectable levels of PFAS. According to the Environmental Working Group's analysis of the data, 176 million people live in communities where drinking water has tested positive for PFAS.
According to EPA's estimates, between 4,100 and 6,700 water systems serving between 83 million and 105 million people will need to install treatment systems to meet the new limits. About 3,000 of those have PFOA or PFOS levels above 4 ppt. Those are the systems EPA is now specifically targeting through the PFAS OUT initiative.
Small systems hit hardest
According to analysis by the American Water Works Association, roughly 90 percent of the water system entry points that need treatment serve fewer than 10,000 people. Small and rural water systems have less money, fewer staff, and less technical capacity to install and operate complex treatment systems. They're the ones who need the most help, and who will pass the highest per-household costs to their customers.
What Does Treatment Look Like?
PFAS can't be removed by boiling water, running it through a basic filter, or using a water softener. According to EPA's research, the chemicals require specialized treatment. The rule identifies four "best available technologies":
How water systems remove PFAS.
Granular activated carbon (GAC): Water passes through columns of specially treated carbon that PFAS sticks to, like a sponge. According to EPA researcher Thomas Speth, GAC can be 100 percent effective for a time, but the carbon has to be replaced periodically when it's full, and the spent carbon, now loaded with PFAS, has to be safely disposed of.
Anion exchange (IX): Uses a resin that swaps PFAS molecules for harmless ones. More effective on some types of PFAS than GAC, but the spent resin also needs disposal.
Reverse osmosis (RO) and nanofiltration (NF): Forces water through a membrane with pores so small that PFAS molecules can't pass through. According to EPA, these are more than 90 percent effective at removing a wide range of PFAS but are significantly more expensive to install and operate.
All of these technologies create a secondary problem: they remove PFAS from the water, but the PFAS has to go somewhere. Spent carbon gets reactivated or landfilled. Spent resin gets incinerated. Membrane systems produce a concentrated waste stream. None of these are simple or cheap, especially for a small town.
What Does It Cost?
According to EPA's economic analysis, compliance will cost approximately $1.5 billion per year nationwide. But according to an analysis by the American Water Works Association (AWWA), the actual costs could be two to three times higher: between $2.7 billion and $3.5 billion per year, with upfront capital costs of $37 billion to $48 billion.
Those costs will mostly be passed to customers. According to reporting by Undark, the AWWA estimates household water bills could increase by $305 to $3,570 per year, with the smallest communities paying the most because fewer households share the cost.
To help offset costs, Congress dedicated $9 billion through the Bipartisan Infrastructure Law specifically for PFAS and other emerging contaminants in drinking water, plus another $12 billion for general water infrastructure improvements. But according to the National League of Cities, that funding falls short of what's needed.
The Timeline Keeps Shifting
The original rule gave water systems until 2027 to complete monitoring and until 2029 to actually comply, meaning treat their water to get PFAS below the limits. But in May 2025, according to EPA, the agency announced plans to extend the compliance deadline to 2031, giving systems two extra years.
EPA said the extension was needed to give water systems, especially small and rural ones, more time to plan, find funding, and install treatment. According to the law firm BBK, which tracks the rule, EPA said it planned to propose the extension formally in fall 2025 and finalize it by spring 2026. As of April 2026, the rulemaking is still in progress.
Meanwhile, the rule itself is being challenged in court by water utilities and industry groups who argue EPA underestimated costs and used flawed science. EPA is defending the PFOA and PFOS limits while simultaneously trying to drop the other four PFAS limits. According to the Harvard Environmental and Energy Law Program's tracker, the D.C. Circuit denied EPA's request to summarily drop those four limits in January 2026. The case continues.
What Is PFAS OUT?
On April 14, 2026, EPA launched PFAS OUT (short for "PFAS OUTreach"), a new initiative to proactively contact about 3,000 water systems that have known PFOA or PFOS levels above 4 ppt. According to EPA's PFAS OUT page, the initiative will provide webinars, resources, and help connecting water systems to existing funding and technical assistance programs.
PFAS OUT doesn't provide new money. It connects water systems, especially small, rural, and disadvantaged ones, to grants and free engineering support that already exist but that many systems don't know about. According to EPA, outreach to affected systems will begin in summer 2026, with regional webinars later in the year.
If your water system is contacted
According to EPA, no application is required. EPA will reach out directly to water systems with levels above 4 ppt. All resources will also be posted publicly on the PFAS OUT website. Any water system can join the webinars. For questions, contact [email protected].
What Can You Do Right Now?
If you're on a public water system, your utility should be testing for PFAS under the UCMR 5 monitoring program. According to EPA's UCMR 5 Data Finder, you can search by your water system's name or ID to see if PFAS have been detected. Starting in 2027, water systems must include PFAS levels in their annual Consumer Confidence Reports (the water quality reports they send to customers).
If you want to reduce PFAS in your own home in the meantime, according to EPA and the Minnesota Department of Health, the most effective home treatment options are reverse osmosis filters (certified to NSF/ANSI 58) and activated carbon filters (certified to NSF/ANSI 53). Look for the certification on the product packaging. Standard water softeners and iron filters will not remove PFAS. Some pitcher filters can reduce PFAS if they use activated carbon, but only if they are certified to NSF/ANSI 53 for PFAS reduction. Check the packaging.
The bottom line
For the first time, the federal government is requiring water utilities to remove "forever chemicals" from your drinking water. The limits for the two most dangerous PFAS, PFOA and PFOS, are staying. But EPA plans to push the cleanup deadline from 2029 to 2031, EPA plans to rescind limits for four other PFAS, and the costs are enormous, especially for small communities. If you want to know whether PFAS are in your water right now, check the UCMR 5 Data Finder. If your system has a problem, help is on the way, but not as fast as the science says it should be.
Sources: EPA, PFAS National Primary Drinking Water Regulation (April 10, 2024); EPA PFAS NPDWR Fact Sheet; EPA, "EPA Announces It Will Keep Maximum Contaminant Levels for PFOA, PFOS" (May 14, 2025); EPA, "EPA Launches PFAS Out Initiative" (April 14, 2026); EPA, PFAS OUT page; EPA, UCMR 5 Data Finder; EPA, Reducing PFAS in Drinking Water with Treatment Technologies; Harvard Environmental & Energy Law Program, PFAS in Drinking Water Tracker; Environmental Working Group, PFAS Contamination Map; The Driller, "Costs of Complying with PFAS Rules" (August 2024); Undark, "The Cost of Freeing Drinking Water from Forever Chemicals"; National League of Cities, "6 Things for Local Leaders to Know"; BBK Law, EPA PFAS Rule Analysis (May 2025); GAO, Persistent Chemicals: Information on EPA's Analysis of Costs. Have a correction? Contact us.