PFAS in Drinking Water: The 2024 EPA Limits and Which Filters Are Certified to Remove Them

What PFAS, PFOA, and PFOS are

You will see PFAS used as a catch-all term, so it helps to know what it covers. PFAS is short for per- and polyfluoroalkyl substances, a large family of synthetic chemicals that have been used since the mid-twentieth century in things like nonstick coatings, stain and water repellents, and firefighting foam. Their carbon-fluorine bonds are unusually stable, which is why you often hear them called 'forever chemicals': they break down slowly and can stick around in water and soil.

Two names come up the most: PFOA (perfluorooctanoic acid) and PFOS (perfluorooctane sulfonate). These are two of the most studied individual PFAS, and they are the two the EPA regulated most strictly in drinking water. That is why, when you go looking at filter standards and certifications, you will see those two singled out by name.

The EPA's 2024 drinking-water limits

Here is the number to anchor on. On April 10, 2024, the EPA finalized a National Primary Drinking Water Regulation for six PFAS, with the rule effective June 25, 2024. It set enforceable limits, called Maximum Contaminant Levels (MCLs), of 4.0 parts per trillion (ppt) each for PFOA and PFOS. A part per trillion is roughly one drop in an Olympic-sized pool, so these are very low limits.

The same rule covered three other PFAS at 10 ppt each (PFHxS, PFNA, and HFPO-DA, the last commonly called GenX chemicals), plus a Hazard Index of 1 for certain mixtures of those and PFBS. You can treat those as the supporting cast. They apply to public water systems, the utilities that supply most homes.

If you are wondering when this all takes effect, the rule phases in. Public water systems got time to finish initial monitoring and reporting, and more years to bring water into compliance where they find exceedances. The EPA has also proposed adjustments to that schedule, so the exact dates a given utility must meet can shift. The one figure to keep in your head is the 4 ppt limit for PFOA and PFOS.

How to find out if your water has PFAS

If you are on a public water system, the easiest place to start is your annual Consumer Confidence Report (CCR), the water quality summary your utility has to publish each year. Utilities serving more than 25 people must put one out, and it lists what was detected. Search your utility's name plus 'consumer confidence report,' or use the EPA's CCR resources to find it. As monitoring data from the 2024 rule rolls in, PFAS results are showing up more often in these reports and in state databases.

Another tool worth a look is the EPA's PFAS Analytic Tools, part of its ECHO system. It pulls national datasets into a searchable map that includes drinking-water testing results and facilities that may use PFAS, so you can see what has actually been measured near you. Coverage varies by location and year, so treat it as a clue, not the last word.

If you are on a private well, no utility tests it for you, so this part is on you. You cannot taste, smell, or see PFAS, which means the only way to know is a lab test. Use a certified laboratory and follow its sampling instructions closely, because PFAS testing is sensitive to contamination from ordinary household materials while you collect the sample.

Which filter certifications actually address PFAS

This is the part that saves you money: most filters do nothing for PFAS, and a vague 'filters contaminants' claim does not count. What you want is certification to a standard that names PFOA and PFOS. NSF originally wrote a dedicated protocol for that, NSF P473. In 2017 the NSF Joint Committee folded those requirements into NSF/ANSI 53 (for activated carbon and anion-exchange systems) and NSF/ANSI 58 (for reverse osmosis systems), so that is where a current PFAS claim lives.

In plain terms, you are looking for one of three things: a filter certified to NSF/ANSI 53 with a specific PFOA/PFOS reduction claim, a filter still referencing the older P473 protocol, or a reverse osmosis system, which pushes water through a fine membrane, certified to NSF/ANSI 58 for PFOA/PFOS. Reverse osmosis tends to handle a broad range of PFAS because it filters at the membrane level instead of relying on the carbon to grab them.

One thing not to over-read: the acceptance level historically built into these PFOA/PFOS certifications was tied to an older EPA health advisory and is higher than the 4 ppt MCL the EPA set in 2024. So a certification confirms the filter reduces PFOA and PFOS to the level the standard specifies; it does not automatically prove it gets you all the way down to 4 ppt. Read the certified claim for what it actually says rather than assuming it matches the newest regulation.

How to verify a PFAS filter claim

Verifying a claim takes about a minute, and it is worth it. Look up the exact model in a certifier's public database: NSF at info.nsf.org/Certified/DWTU, WQA at find.wqa.org/find-products, or IAPMO R&T at pld.iapmo.org. Make sure the listing names PFOA and PFOS specifically, not just 'contaminant reduction' in general.

Be wary of 'tested to' language on PFAS products, because it is doing quiet work. A page that says a filter was 'tested to reduce PFOA and PFOS' but whose model is not in any certifier database is showing you the manufacturer's own result, not a verified certification. For something measured in parts per trillion, the gap between an audited certification and a one-time lab test is a gap you want on your side.

Maintenance is part of performance

One last thing that is easy to forget: a certified PFAS filter only keeps performing if you replace the cartridge or membrane on schedule. The certification is tied to a rated capacity, meaning the volume of water the media is verified to treat. Once you run past that, you are outside what the certification covers.

So follow the manufacturer's replacement interval, and if your water tested high for PFAS, lean toward replacing the media a little early rather than squeezing out the last rated gallon. Think of the filter as something you maintain, not a one-time purchase.