Every Pennsylvania public water system that reported a PFAS detection during EPA UCMR 5 monitoring, how many sit above the 2024 federal limits, and the standard Pennsylvania applies. Concentrations are in nanograms per litre, the same unit as parts per trillion.
This is the United States view of the North American PFAS dataset. The complete dataset, including all 3,452 US systems and 97 Canadian sites, lives on the main PFAS contamination map.
State enforceable standard
Warminster/Warrington/Horsham (former NAS JRB Willow Grove) most affected communities.
Compound
Limit (ng/L)
Note
PFOA
14
PFOS
18
US EPA PFAS National Primary Drinking Water Regulation (2024)
Last reviewed 2026-08-13. Verify against the agency source before making a compliance or remediation decision.
Full Pennsylvania regulatory brief
Ranked by how far the worst single compound sits above its 2024 federal limit. Values are the maximum each system reported during its UCMR 5 monitoring period.
Water system
PWSID
Worst compound
Max ng/L
Times the limit
Collegeville Trappe Joint Pwd
PA1460022
PFOA
235
58.8x
Emmaus Borough Public Water
PA3390032
PFOS
153
38.3x
Audubon Water Company
PA1460055
PFOS
57.9
14.5x
Caernarvon Twp Auth
PA3060052
PFOA
55.8
13.9x
Palmerton Municipal Authority
PA3130012
PFOA
42.5
10.6x
Horsham Water&Sewer Authority
PA1460033
PFOS
33.8
8.4x
City Of Lancaster, Pa
PA7360058
PFOA
23.8
6.0x
Northampton Bucks Co Mun Auth
PA1090089
PFOS
23
5.8x
Suez Water Pa Bethel
PA1230012
PFOA
22.3
5.6x
Buckingham Twp Cold Spring
PA1090137
PFOA
22
5.5x
Aqua Pa Hatboro
PA1460028
PFOS
21.5
5.4x
Aqua Pa Chalfont
PA1090005
PFOS
19
4.8x
Coraopolis Water & Sewer Auth
PA5020010
PFOS
18.8
4.7x
Kennett Square Mun Water Works
PA1150108
PFOA
17.7
4.4x
Perkasie Regional Authority
PA1090046
PFOS
17.6
4.4x
Ashland Area Water Authority
PA3540030
PFOS
17
4.3x
N Middleton Water Auth
PA7210049
PFOS
16.9
4.2x
Jamie Hollanders
PA1090329
PFOA
16.8
4.2x
Upper Southampton Mun Auth
PA1090063
PFOS
16.4
4.1x
Paw Penn District
PA3060069
PFOS
16.4
4.1x
Open the full map and filter Pennsylvania pins
Every count above is read straight from a published government file. Nothing is modelled, averaged, or estimated. The rules below are the exact rules used to produce the figures for Pennsylvania.
Who is in UCMR 5. All public water systems serving more than 3,300 people, plus a national sample of 800 smaller systems. Private wells and most small systems are not monitored, so they cannot appear here.
Which systems are listed. Only systems whose state field is PA and that reported at least one measured PFAS detection. Systems that monitored and found nothing are not shown, and their absence is not evidence of contamination. That gives 169 systems in Pennsylvania.
Systems that cannot be placed. 87 systems nationally reported a detection but have no serviced ZIP code published by EPA, so they carry no location and are excluded from these counts. National totals on the map page include them.
Which value is used. The highest result a system reported for each compound across its sampling events. Results flagged by EPA as non-detects are excluded, as are the lithium results carried in the same file.
The above a limit count. A system is counted when its maximum result for a compound exceeds the 2024 federal Maximum Contaminant Level: 4 ng/L for PFOA and PFOS, 10 ng/L for PFHxS, PFNA, and HFPO-DA. That is 116 systems in Pennsylvania.
The Hazard Index count. Calculated with EPA's own mixture method for PFHxS, PFNA, HFPO-DA, and PFBS. A system is counted when the index is above 1. That is 18 systems in Pennsylvania.
What monitoring data is not. Exceeding a 2024 limit in this dataset is not a compliance violation. The federal limits carry a 2029 compliance date, which EPA proposed on 18 May 2026 to move to 2031 for PFOA and PFOS in a rule that is not final, and treatment may have been installed since the sample was taken.
If any figure on this page does not match its source file, tell Nelson and it will be corrected or removed.
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