Full contaminant data, sample history, and sourcing for Warren County. For readers who want to go beyond the summary.
Contaminant Data — All Analytes
77 well testing events on record, covering
22 analytes.
Data spans 1928 to 2024.
Contaminant
Samples
Years
Detection Rate
Distribution LowModHigh
vs. Limit
vs. PA Avg
Iron
34
1928–2023
94%
333% of limit
↓ 43% below
Manganese
30
1984–2023
97%
620% of limit
↑ 23% above
Radon
4
1996–2019
100%
37% of limit
↓ 72% below
Arsenic
26
1985–2023
54%
6% of limit
↓ 79% below
Chloride
33
1928–2023
100%
1% of limit
↓ 94% below
Fluoride
29
1984–2023
79%
4% of limit
~ typical
HFPO-DA (GenX)
municipal
60
2024–2025
0%
—
—
Lead
26
1985–2023
38%
7% of limit
↑ 44% above
Nitrate
26
1928–2023
27%
5% of limit
↓ 71% below
Nitrite
22
1992–2023
5%
1% of limit
↓ 33% below
PFHxS
municipal
2
2024
0%
—
—
PFNA
municipal
2
2024
0%
—
—
PFOA
municipal
62
2024–2025
10%
20% of limit
↓ 79% below
PFOS
municipal
62
2024–2025
11%
20% of limit
↓ 84% below
Sulfate
33
1928–2023
100%
5% of limit
↓ 72% below
Uranium
13
2015–2021
8%
0% of limit
↓ 94% below
E. coli
1
2019
0%
—
—
Hardness
34
1928–2023
100%
—
~ typical
PFBS
municipal
60
2024–2025
10%
—
↓ 85% below
pH
31
1984–2023
100%
—
~ typical
Sodium
34
1928–2023
100%
—
↓ 51% below
Total Coliform
1
2019
0%
—
—
Distribution shows the share of samples in each concentration band relative to the EPA Maximum Contaminant Level (MCL): Low = below half the MCL, Moderate = between half and the MCL, High = above the MCL. Analytes without an MCL (e.g. sodium, pH) show — in the limit columns. State average is based on county median values across PA.
Compare your result with Warren County
Of the 26 arsenic tests on record for Warren County (1985–2023),
46% found none, and half were below 0.365 µg/L.
Of the 33 chloride tests on record for Warren County (1928–2023),
0% found none, and half were below 1.5 mg/L.
Of the 29 fluoride tests on record for Warren County (1984–2023),
21% found none, and half were below 160 µg/L.
Of the 34 iron tests on record for Warren County (1928–2023),
6% found none, and half were below 995 µg/L.
Of the 26 lead tests on record for Warren County (1985–2023),
62% found none.
Of the 30 manganese tests on record for Warren County (1984–2023),
3% found none, and half were below 308 µg/L.
Of the 26 nitrate tests on record for Warren County (1928–2023),
73% found none.
Of the 60 pfoa tests on record for Warren County (2025),
90% found none.
Of the 60 pfos tests on record for Warren County (2025),
88% found none.
Of the 33 sulfate tests on record for Warren County (1928–2023),
0% found none, and half were below 12 mg/L.
Data Coverage & Gaps
Well-sampled analytes (15+ samples)
Iron 34 samples
Manganese 30 samples
Arsenic 26 samples
Chloride 33 samples
Fluoride 29 samples
HFPO-DA (GenX) 60 samples
Lead 26 samples
Nitrate 26 samples
Nitrite 22 samples
PFOA 62 samples
PFOS 62 samples
Sulfate 33 samples
Hardness 34 samples
PFBS 60 samples
pH 31 samples
Sodium 34 samples
Limited data (<15 samples) — interpret with caution
Radon 4 samples
Uranium 13 samples
E. coli 1 sample
Total Coliform 1 sample
Public vs. Private Water in Warren County
64Active public water systems
31,432Residents on public water
52%Households on private wells
Public water systems in Warren County are regulated by the EPA and must test and report contaminant levels. Private well owners are responsible for their own testing — there is no routine monitoring of private wells by any government agency.
CDC Health Outcome Correlations
Where contaminants detected in Warren County have established associations with specific health outcomes, we cross-reference CDC PLACES county-level prevalence data. This is a contextual signal, not a causal claim.
This report aggregates data from the following public databases:
Water Quality Portal (WQP) — groundwater sample results for Warren County from EPA, USGS, and state agencies. Browse WQP data →
EPA Safe Drinking Water Information System (SDWIS) — public water system inventory used to estimate the share of residents on private wells. Browse SDWIS →
Census ACS 5-Year Estimates — well and cistern household counts (variable DP04_0074E) used to calculate the private-well percentage for Warren County. Census data explorer →
USGS Aquifer Atlas — principal aquifer type underlying Warren County, which informs which contaminants are geologically likely. USGS Aquifer Atlas →
EPA UCMR 5 (2023–2025) — PFAS occurrence data from public water systems, used as a proxy indicator for aquifer PFAS exposure. Rows marked "municipal" in the table above come from this source. About UCMR 5 →
EPA Toxics Release Inventory (TRI) — industrial facility chemical releases near Warren County, used in contamination risk scoring. TRI Explorer →
EPA Superfund NPL — National Priorities List sites in or near Warren County, used in contamination risk scoring. Superfund site search →
CDC PLACES — county-level health outcome prevalence (kidney disease, cancer, heart disease) correlated with detected contaminants. About CDC PLACES →
Methodology
Raw records are downloaded from the Water Quality Portal and normalized to µg/L (ppb). Records are deduplicated by sample ID and date, and certified outliers are excluded. Analyte names are mapped to EPA canonical forms. Detection rates, distribution bands, and MCL comparisons are computed from the normalized dataset.
Distribution bands use the EPA Maximum Contaminant Level as the threshold: concentrations below 50% of the MCL are classed as Low, between 50% and 100% as Moderate, and above 100% as High. For analytes without an MCL (sodium, hardness, pH), distribution is not computed.
State comparison uses the median of county median values across all counties in PA with at least one sample for that analyte.