National analysis · EPA UCMR 5

1,504 US water systems measured PFAS above the federal limit

EPA sets an enforceable limit of 4 parts per trillion for PFOA and PFOS. During UCMR 5 monitoring, 1,504 community water systems recorded one or both above that level. Together they serve roughly 69,842,032 people.

By the WaterKnown editorial team · Updated 25 August 2026 · Editorial standards

These are measurements, not violations

This distinction is the whole story and it is routinely got wrong. EPA finalised its PFAS rule with enforceable limits of 4 ppt for PFOA and PFOS, and compliance is required by 2029. UCMR 5 monitoring ran from 2023 to 2025, before that deadline arrived. A system above 4 ppt today is not breaking the law. It is a system that will have to change something within a few years.

That makes this data more useful than a violation list, not less. It is an advance picture of which utilities face treatment upgrades, blending, or new source water, and which households are drinking above the limit in the meantime.

Highest recorded

The 40 highest PFOA and PFOS results in the country

Highest single result at each system during UCMR 5 monitoring, against the 4 ppt limit.

Water system	Location	Population	Compound	ppt	Over limit
Nashville, Town Of	Nashville, NC	5,900	PFOS	490	122×
Running Springs Water District	Running Springs, CA	5,268	PFOS	236	59×
Collegeville Trappe Joint Pwd	Trappe, PA	8,470	PFOA	235	59×
Lubeck Psd	Washington, WV	11,724	PFOA	180	45×
Artondale	Tacoma, WA	5,828	PFOS	154	38×
Emmaus Borough Public Water	Emmaus, PA	14,000	PFOS	153	38×
Gwa Northern Water System	Mangilao, GU	139,207	PFOS	135	34×
New Martinsville	New Martinsville, WV	5,272	PFOS	122	30×
Raynham Center Water District	Raynham, MA	10,964	PFOA	92	23×
City Of Grand Prairie	Grand Prairie, TX	201,843	PFOS	82	20×
Orangewood Water System	Holiday, FL	6,464	PFOS	80.8	20×
City Of Oxford	Oxford, MS	28,500	PFOS	72.2	18×
Irondale Water System	Irondale, AL	10,098	PFOS	59.4	15×
Liberty Utilities - Bellflower-Norwalk	Downey, CA	72,624	PFOS	59	15×
Pa American Audubon	Norristown, PA	8,200	PFOS	57.9	14×
Lafayette	Lafayette, GA	18,177	PFOS	56	14×
Tempe City Of	Tempe, AZ	165,000	PFOS	55.8	14×
Caernarvon Twp Auth	Morgantown, PA	4,245	PFOA	55.8	14×
Montebello Land & Water Co.	Montebello, CA	26,554	PFOS	53	13×
Lake Panasoffkee Water Assn 2Wps	Lake Panasoffkee, FL	4,642	PFOS	53	13×
Collinsville Water Works	Collinsville, AL	3,945	PFOA	52.5	13×
Moses Lake City Of	Moses Lake, WA	32,428	PFOS	52.2	13×
Broken Arrow Municipal Authority	Broken Arrow, OK	116,330	PFOS	51.3	13×
Augusta-Richmond Co Ws	Augusta, GA	204,000	PFOS	51	13×
Dartmouth Water Division	Dartmouth, MA	24,696	PFOS	50.6	13×
Fkaa J. Robert Dean W.T.P.	Key West, FL	86,000	PFOS	50.3	13×
Town Of Thurmont	Thurmont, MD	6,200	PFOS	48	12×
Harrison Co Water Association	Cynthiana, KY	16,736	PFOS	47.9	12×
Aibonito La Plata	Aibonito, PR	16,354	PFOS	46.7	12×
Parkersburg Utility Board	Palestine, WV	34,251	PFOA	46.5	12×
Barrow Utilities & Elec. Coop., Inc. (Bu	Barrow, AK	4,900	PFOS	46.3	12×
Elko City Of	Elko, NV	23,000	PFOS	46	12×
City Of Atwater	Atwater, CA	29,479	PFOS	45	11×
North Miami, City Of	North Miami, FL	89,349	PFOS	45	11×
Bealeton Regional	Warrenton, VA	4,250	PFOA	44.6	11×
Downey - City, Water Dept.	Downey, CA	110,556	PFOS	44	11×
Livingston Twp Div Of Water	Livingston, NJ	27,391	PFOA	44	11×
North Bay Village, City Of	North Bay Village, FL	8,317	PFOS	43.3	11×
Palmerton Municipal Authority	Palmerton, PA	7,000	PFOA	42.5	11×
Verona Water Department	Verona, NJ	13,641	PFOA	42.3	11×

SourceEPA UCMR 5 occurrence data

By state

Where the exceedances cluster

State	Systems above the limit	People served
CA	156	10,379,340
FL	149	10,798,810
NJ	146	6,690,241
MA	105	2,211,284
NC	103	3,998,173
PA	97	4,661,632
TX	73	5,486,810
AL	71	1,835,919
SC	62	2,400,473
OH	48	2,238,686
NY	45	2,442,342
GA	40	1,681,352

How to read a number like 490 ppt

The highest result in the dataset is more than a hundred times the federal limit, at a system serving a few thousand people. Extreme readings almost always come from small systems, and the reason is structural: a large utility draws from multiple sources and blends them, diluting any single contaminated well. A small system with one contaminated source has nothing to blend with.

So the pattern in this data is that the worst individual numbers are at small systems, while the largest number of affected people sit at mid-size systems with moderate exceedances. Both matter, and a list sorted only by concentration hides the second group.

What EPA's limit actually represents

EPA concluded there is no level of PFOA or PFOS in drinking water without risk of health effects. The 4 ppt limit is therefore not a threshold below which harm stops; it reflects what laboratories can reliably measure and treatment can reliably achieve. For what these compounds are understood to do in the body, ATSDR maintains the plain-language summary.

Check your own system

Search any US water system in our national lookup to see its PFAS results, lead levels and violation history. If your system is above the limit and you want to act now rather than wait for 2029, the filter standards that matter are NSF/ANSI 53 certified specifically for PFOA and PFOS, or NSF/ANSI 58 reverse osmosis. We explain the certifications here.

Common questions

How many US water systems exceed the PFAS limit?

EPA's UCMR 5 monitoring recorded PFOA or PFOS above the 4 parts per trillion federal limit at 1,504 community water systems, serving roughly 69,842,032 people. Because monitoring ran from 2023 to 2025 and compliance is not required until 2029, these are measurements rather than violations.

Is 4 ppt of PFOA actually dangerous?

EPA set the enforceable limit at 4 parts per trillion for PFOA and PFOS, having concluded there is no level of either compound in drinking water without risk of health effects. The limit reflects what is reliably measurable and treatable rather than a threshold below which harm stops.

Does my utility have to fix this?

Systems above the limit must come into compliance by 2029 under EPA's PFAS rule, through treatment, blending, or switching source water. Utilities are required to notify customers once compliance monitoring begins.

What can I do in the meantime?

A filter certified under NSF/ANSI 53 specifically for PFOA and PFOS reduction, or an NSF/ANSI 58 reverse osmosis system, is the household option. Certification is granted per model, so check the exact model number in an accredited certifier's database rather than trusting packaging.

Is your system on this list?

Search 17,672 US water systems against EPA's own records.

Check your water PFAS by state