PFAS
California's OEHHA puts the negligible-risk level for PFOA roughly 570 times below the enforceable federal limit.
PFAS are persistent synthetic chemicals that arrive in your water from upstream, before it reaches your pipes. They build up in the body over years, and the health-based goal is effectively zero. The route Stasis can change is your drinking water. A reverse-osmosis filter at the kitchen tap removes more than 94 percent of both legacy and replacement PFAS.
PFAS: what is it, and where does it come from?
PFAS, per- and polyfluoroalkyl substances, are a class of thousands of synthetic chemicals built around the carbon-fluorine bond. That bond does not occur in nature and barely breaks down, which is why they are called forever chemicals. They were engineered for non-stick coatings, stain and water repellents, and firefighting foam. PFAS is a source-water contaminant, not something your home's plumbing adds: it enters supplies upstream from industrial discharge and contaminated groundwater, along with firefighting foam at airports and military sites. What the treatment plant delivers is essentially what reaches your tap, so your water source sets your risk.
PFAS: why does it matter?
PFAS act on several organ systems through identified biological pathways, and the effects show up at the background blood levels already present in the typical US adult. The clearest signal is on the immune system: in one study of children, doubling the level in their blood tracked with roughly half the antibody response to routine vaccines. The chemicals also push cholesterol up by a few percent and disrupt thyroid hormone, the system tied to energy, weight, and mood. Because PFAS clear from the body over years rather than washing out, ongoing low-level intake builds body burden. The US National Academies put the average American already inside the blood range flagged for potential adverse effects.
- IARC, the WHO cancer body, classified PFOA as Group 1, carcinogenic to humans, in 2023, its highest-certainty category, the same as tobacco and asbestos.IARC Monographs Vol. 135: PFOA and PFOS (International Agency for Research on Cancer, WHO, 2023)
- In a study of 587 children, doubling the PFAS level in their blood was associated with about half the antibody response to standard childhood vaccines.Grandjean et al., 2012 (JAMA)
- Across 73 homes, reverse osmosis and under-sink dual-stage filters removed more than 94 percent of both long-chain and short-chain PFAS. Whole-house carbon was widely variable and in some cases raised PFAS in the treated water.Herkert, Merrill, Stapleton et al., 2020 (Environ Sci Technol Lett)
- California's OEHHA sets the negligible-risk goal for PFOA at 0.007 parts per trillion, roughly 570 times below the enforceable federal limit of 4 parts per trillion.CA OEHHA Public Health Goal for PFOA and PFOS, 2024
PFAS: what do we grade it against?
PFAS is held to two different numbers, and they do not agree. The health-based level for PFOA (ppt) is 0.007 (negligible-risk goal, kidney cancer endpoint), from CA OEHHA Public Health Goal, 2024. The enforceable legal limit is 4.0. The table below lists every level on this page next to the source that set it.
| Contaminant | Health-based level | Legal limit | Source (health-based) |
|---|---|---|---|
| PFOA (ppt) | 0.007 negligible-risk goal, kidney cancer endpoint | 4.0 federal MCL; goal of zero | CA OEHHA Public Health Goal, 2024 |
| PFOS (ppt) | 1 health-based goal, liver/pancreatic endpoint | 4.0 federal MCL; goal of zero | CA OEHHA Public Health Goal, 2024 |
| Serum PFAS (ng/mL) | under 2 no expected effects; 2 to 20 carries potential for harm | none set | ATSDR / NASEM benchmark guidance |
Health-based levels come from peer-reviewed research and government risk scientists working without cost constraints, while legal limits are enforceable compromises. Your report grades to the health column.
PFAS across US water systems: what we measured
12,940 US community water systems have a PFOA result on record, most of them sampled between November 2024 and July 2026 under the federal monitoring round that put large systems on the record. 2,685 of them found some.
666 systems average at or above 4.0 parts per trillion (ppt) of PFOA, and they serve 20 million people. None of them is breaking the law: that limit is final, and systems have until April 2029 to meet it. For PFOS the count is 726 of the 12,956 systems with a result.
79% of the systems with a PFOA result recorded no detection at all, which is good news. The bigger number is the untested one: 12,940 results across 38,332 community water systems means roughly 34% of the country's systems have a PFOA number of any kind on record. Not tested is not the same as clean.
The health-based case sits far below the regulation. California's public health goal for PFOA is 0.007 ppt, roughly 571 times lower than the federal limit, set at a one-in-a-million lifetime cancer risk. No laboratory can measure that low, and the federal health goal for both compounds is zero. So these counts use 4.0 ppt, the federal limit, which is the number the law enforces. The toxicology points far lower.
The reporting set is also a picture of large systems. Among systems whose values rest on more than one sampling point, the median serves 10,097 people, against 390 for single-point systems, and the two halves differ sharply on the share above 4.0 ppt (31.5% against 11.5%). That gap reflects the kinds of systems being measured: PFAS is mostly an industrial and urban problem, and the monitoring rule pointed at exactly the systems most likely to find it. Every share here is a share of systems with a result, not of all US water systems.
PFHxS and PFNA, the two limits EPA has moved to rescind
12,802 systems report PFHxS and 457 of them average at or above 3.0 ppt, California's notification level. 12,508 report PFNA and 7 average at or above 10.0 ppt. The April 2024 federal rule set limits for both. In May 2025 EPA said it would keep the PFOA and PFOS limits and move to rescind the other four, including these two. That rollback is a proposed rule out for public comment. The toxicology did not change when the proposal was announced.
We grade these two against their health-based lines, which stay fixed while the federal limit is being reconsidered, so the trend stays comparable year to year.
Which states have the most systems at or above 4.0 ppt?
New Jersey leads the PFOA ranking: 35.8% of its 268 reporting systems average at or above 4.0 ppt, at a state median of 2.32 ppt. South Carolina (24.9%), Massachusetts (15.4%), New Hampshire (14.5%) and Florida (13.4%) follow.
| State | Typical system (ppt) | Above 4.0 ppt | Above the 2029 limit |
|---|---|---|---|
| New Jersey 268 systems reporting, 49% of the state | 2.32 | 36% 96 systems | 96 |
| South Carolina 173 systems reporting, 37% of the state | 0 | 25% 43 systems | 43 |
| Massachusetts 383 systems reporting, 96% of the state | 0.34 | 15% 59 systems | 59 |
| New Hampshire 62 systems reporting, 58% of the state | 0 | 15% 9 systems | 9 |
| Florida 395 systems reporting, 25% of the state | 0 | 13% 53 systems | 53 |
| Pennsylvania 360 systems reporting, 82% of the state | 0 | 13% 47 systems | 47 |
| Delaware 139 systems reporting, 82% of the state | 0 | 12% 16 systems | 16 |
| Alabama 308 systems reporting, 65% of the state | 0 | 11% 33 systems | 33 |
| Maryland 274 systems reporting, 62% of the state | 0 | 9% 25 systems | 25 |
| Ohio 353 systems reporting, 33% of the state | 0 | 8% 27 systems | 27 |
| West Virginia 108 systems reporting, 30% of the state | 0 | 7% 7 systems | 7 |
| Tennessee 281 systems reporting, 64% of the state | 0 | 5% 15 systems | 15 |
| Oregon 460 systems reporting, 62% of the state | 0 | 3% 13 systems | 13 |
| California 694 systems reporting, 26% of the state | 0 | 3% 18 systems | 18 |
| Washington 440 systems reporting, 25% of the state | 2 | 2% 9 systems | 9 |
31 states qualify. A state is ranked only with at least 30 reporting systems and at least 25% of its systems covered, because ranking a state on a small slice of it would publish our own collection coverage as that state's water quality. The 18 states held back average 0.65 times lower above the line than the ranked ones. For PFOA the health-based line and the federal limit are the same number, so those two counts match. The real gap is between that limit and California's 0.007 ppt health goal, which sits below what any monitoring method can measure.
This ranks states, not individual utilities. A single system's value can rest on one sampling point with nothing to check it against, while a state median over dozens of systems holds up, which is why we report the median and not the name.
How this was built, and what it cannot tell you
Every PFAS figure above comes from one dataset of 38,332 community water systems. Below is where the data comes from, and what it cannot tell you.
- Records
- 12,940 community water systems with a PFOA result on record, drawn from 38,332 systems that passed every filter listed here. The full panel set holds 42,081 systems.
- Filters applied
- Community water systems only (316 non-community systems removed). Wholesalers removed (2,164), because their population is already counted under the retail systems that buy from them. Systems whose most recent report predates 2023 removed (929). Systems EPA’s inventory does not classify removed (340).
- Sample dates
- July 2023 to July 2026. Nine in ten records are dated November 2024 or later. The median is October 2025. Some older samples are valid: several analytes are on a three-year monitoring cycle, so a sample taken years ago can still appear in a current report.
- Sources
- Contaminant levels: state drinking-water monitoring records and utility reports, assembled into one panel set dated 2026-06-16. System type, population served and purchased-water status: EPA SDWIS, vintage 2026Q1 (file dated 2026-04-08). Health and legal lines: the Stasis threshold registry, version 2026-08-08, which is the same registry that grades a customer report, so a page and a report can never disagree.
- Provenance
- 2,458 of 12,940 results are reconstructions we computed from raw state monitoring records, rather than figures taken straight from a utility’s published water quality report. Full breakdown: 10,104 the utility tested and reported no detection; 2,457 reconstructed from the state's raw monitoring records, finished (delivered) water only; 378 measured at the supplying wholesaler's treatment plant, inherited with attribution; 1 reconstructed from source-water sampling only; this system has no finished-water record. We compile and interpret these figures; we do not take the samples ourselves.
- Scoring rule
- A system is counted against the health-based level. Both lines are printed on every figure so the gap between them is visible. Non-detects are counted as zero and included in the denominator, so a share above a line is never inflated by dropping clean systems.
- Automation
- Software assembled the dataset. It reads state monitoring records, normalises them and combines them, and every figure on this page comes out of one program rather than being typed by hand. This is how 42,081 systems are held to one standard. A person chooses which comparisons to draw and which limits to name, and reviews what the numbers mean. The health thresholds come from the cited primary literature, not a model.
- Raw data
- The row-level extract is not published. It was assembled out of several hundred separate state and federal sources. The findings, the method, the denominators and the limits are all on this page so the work can be checked, and every threshold cited comes from a public primary source linked in place, but the compilation itself is not a free download. Any figure can still be checked at retail: against a utility’s own published report, or by putting one address into the lookup and comparing what it returns. Researchers and reporters who need specific rows can write to data@stasishome.com and say what they are working on.
- Known limitation: how states qualify to be ranked
- A state is ranked only if at least 30 of its systems have a PFOA result AND at least 25% of its community systems do. 31 states clear both. 18 more clear the first and fail the second, so we hold them back from the ranking. The gate exists because coverage in this dataset runs from under 3% of a state’s systems to over 99%, and ranking a state on a 3% subsample would publish our own collection coverage as that state’s water. The excluded states average 3.9% above the line, against 6% for the ranked ones, 0.65x lower. The direction differs by analyte, and we recompute this figure from the data on every build.
- Known limitation: purchased water
- 7,416 of the 38,332 systems here buy finished water from a wholesaler instead of treating their own. For those systems, plant-level analytes are often sampled under the seller’s permit number, so our record shows “not reported” where the water was in fact tested upstream. A claim that some share of utilities does not test for PFOA would therefore be false, and nothing on this page makes one. Reporting rates are stated against systems that treat their own water: 32.1% of those 30,916 systems have a PFOA result, against 40.5% of the 7,416 that purchase. There is a 8.4-point gap between the two rates, and it is the hole this limitation describes.
- Known limitation: which limit applies when
- The 4.0 ppt figure is the federal MCL 4.0 ppt, compliance from April 2029 (40 CFR 141.61(c)(2) (89 FR 32532); compliance 2029-04-26 (40 CFR 141.900(b)(4))). It is final law; the compliance date is 26 April 2029. A system above it today is not in violation. Some states are stricter and bind now: New York's 10 ppt limits for PFOA and PFOS are in force today. Your own report is graded against the limit in force where you live.
- Known limitation: selection by system size
- Most results here come from a federal monitoring round that sampled systems serving more than 3,300 people plus a representative sample of smaller ones. The reporting set is weighted toward large systems, so it is not a random sample of US water. Every share here is a share of systems with a result, and the denominators appear with each figure.
- Known limitation: 29 PFAS, not all of them
- The federal monitoring round covers 29 named PFAS. The class runs to thousands of compounds. A system showing no detection has no detection of the compounds it was required to test for, which is narrower than clean.
- Corrections
- If a figure here disagrees with your utility’s published report, the published report is more likely to be right and we want to know. Write to data@stasishome.com with the system name and we will check it against the source and correct the record.
These figures describe water systems as a whole. They cannot tell you what is at your own tap, and a system with no result on record is one nobody has tested rather than one known to be clean.
What helps against PFAS?
4 approaches below reduce PFAS in a home, ordered from the most direct fix to the smallest change in habit. The most direct is Reverse osmosis at the kitchen tap (NSF/ANSI 58). Each entry also names what it cannot do, because no single fix covers every exposure route.
Direct fixes
- Reverse osmosis at the kitchen tap (NSF/ANSI 58)
Removes more than 94 percent of both legacy long-chain PFAS and short-chain replacements. It performs consistently on both long-chain and short-chain PFAS, which is why it is the default once PFAS is detected, and worth defaulting to if you have children.
Covers your drinking water, not the PFAS that enters through food packaging, household dust, or consumer products.
- Under-sink carbon block (NSF/ANSI 53)
This is a reasonable mid-tier choice for low or no detection. Removal is chain-length dependent, roughly 60 to 70 percent for long-chain PFAS.
Carbon is widely variable and weaker on short-chain replacement PFAS, around 40 percent, and in some cases removes nothing.
Bigger retrofits
- Whole-house carbon (point-of-entry)
Use this only as a supplement to point-of-use filtration, and only with annual breakthrough testing.
Do not rely on it as your primary PFAS treatment. Once the carbon bed saturates it can desorb captured PFAS back into the water, and in some homes raised PFAS above the incoming level. Breakthrough is invisible: no flow drop, no taste change.
Free and behavioral
- Scheduled filter replacement
A saturated PFAS filter looks and tastes identical to a working one, so you replace it on a schedule rather than waiting for a sign. Carbon cartridges every 12 to 24 months, RO membranes every 2 to 3 years.
See how well each fix works
We do not claim to remove PFAS from your life. Diet, dust, and consumer products carry it too, and we cannot filter those. What we can do is measure your drinking water, the one route we can actually intervene on, treat it at the tap, and tell you what else is worth changing. The federal limit is moving backward right now, while the biology that makes PFAS worth filtering has not changed.
Common questions about PFAS
Is the PFAS in my water coming from my old pipes?
No. PFAS enters your water upstream, before it ever reaches the house, so the contamination is set by your source, not by your pipes. That is why a filter at the kitchen tap is the place to intervene.
Didn't the EPA just set PFAS limits? Why still worry?
The first federal enforceable limits were set in April 2024, and they still stand today. In May 2025 the EPA said it would keep the PFOA and PFOS limits of 4 parts per trillion but move to rescind the other four. That rollback is a proposed rule out for public comment, not yet final law. The underlying science did not change. California is moving the other way and tightened its own levels in late 2025. The biology that makes PFAS worth filtering does not move when the limit does.
Will a regular carbon pitcher or faucet filter handle PFAS?
Partly, and unreliably. Carbon removes roughly 60 to 70 percent of long-chain PFAS but is much weaker and more variable on short-chain replacements, and in some tests removed nothing. It is better than no filtration for an adult-only household with low detection, but reverse osmosis is the consistent option, especially with children in the home.
How do I remove PFAS from my water?
Reverse osmosis at the kitchen tap is the most reliable option. Across 73 homes, reverse osmosis and under-sink dual-stage filters removed more than 94 percent of both long-chain and short-chain PFAS, and a 2022 review put reverse osmosis removal as high as 99 percent. Activated carbon, whether granular or a solid block, also works, but its removal depends on PFAS chain length. You have to replace the cartridge on a schedule before it saturates, because a spent carbon bed can release captured PFAS back into the water. Ion exchange is another established approach and is what many utilities use to treat PFAS at the source. Basic carbon pitchers and faucet filters are the least reliable, partial on long-chain PFAS and weak and variable on the short-chain replacements.
How do I know if PFAS is in my water?
A lab test is the only way. PFAS is invisible and tasteless, and it does not leach from your plumbing, so a single grab sample at the kitchen tap is enough, with no special flush timing required. Because levels depend entirely on your source, neighboring homes on different districts can carry very different risk.
Is there PFAS in bottled and sparkling water?
Sometimes, and carbonated water has tended to carry more. In a 2021 Water Research study of 101 US bottled waters, PFAS were detected above the testing limit in 39 of them. Most levels were low, with a median under 1 part per trillion. Purified brands measured lower than spring brands, because most purified water is treated with reverse osmosis. Consumer Reports' 2020 test of 47 bottled waters found carbonated products worse than non-carbonated, and the two highest single measurements were Topo Chico at 9.76 and Polar at 6.41 parts per trillion; Consumer Reports recommended choosing products below 1 part per trillion of total PFAS. These are point measurements from one-time tests, not ongoing certifications. The FDA does not yet set a PFAS limit for bottled water; a rule is in development and is tied to the EPA's drinking-water limits.
Sources cited for PFAS
Every number on this PFAS page traces to one of the 10 sources below: 4 peer-reviewed, 3 government or regulatory.
Peer-reviewed
Government & regulatory
Institutional & standards
Regional & primary
Related water science
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