Full contaminant data, sample history, and sourcing for Union County. For readers who want to go beyond the summary.
Contaminant Data — All Analytes
78 well testing events on record, covering
22 analytes.
Data spans 1934 to 2024.
Contaminant
Samples
Years
Detection Rate
Distribution LowModHigh
vs. Limit
vs. PA Avg
Radon
11
2015–2023
100%
157% of limit
↑ 21% above
Iron
30
1934–2023
80%
150% of limit
↓ 74% below
Manganese
30
1968–2023
90%
16% of limit
↓ 97% below
Nitrate
40
1934–2023
52%
19% of limit
~ typical
Arsenic
32
1971–2023
41%
10% of limit
↓ 66% below
Chloride
33
1934–2023
97%
0% of limit
↓ 98% below
Fluoride
29
1968–2023
69%
1% of limit
↓ 75% below
HFPO-DA (GenX)
municipal
31
2024–2025
0%
—
—
Lead
28
1971–2023
14%
1% of limit
↓ 85% below
Nitrite
33
1981–2023
6%
1% of limit
~ typical
PFHxS
municipal
4
2024
0%
—
—
PFNA
municipal
4
2024
0%
—
—
PFOA
municipal
31
2024–2025
0%
—
—
PFOS
municipal
31
2024–2025
0%
—
—
Sulfate
32
1934–2023
100%
0% of limit
↓ 98% below
Uranium
18
2015–2023
33%
1% of limit
↓ 51% below
PFBS
municipal
31
2024–2025
3%
—
↓ 56% below
pH
43
1968–2023
100%
—
~ typical
Sodium
28
1934–2023
100%
—
↓ 95% below
Total Coliform
6
2005–2023
44%
—
~ typical
E. coli
6
2005–2023
0%
—
—
Hardness
33
1934–2023
100%
—
↓ 94% below
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 Union County
Of the 32 arsenic tests on record for Union County (1971–2023),
59% found none.
Of the 33 chloride tests on record for Union County (1934–2023),
3% found none, and half were below 510 µg/L.
Of the 29 fluoride tests on record for Union County (1968–2023),
31% found none, and half were below 40 µg/L.
Of the 30 iron tests on record for Union County (1934–2023),
20% found none, and half were below 355 µg/L.
Of the 28 lead tests on record for Union County (1971–2023),
86% found none.
Of the 30 manganese tests on record for Union County (1968–2023),
10% found none, and half were below 7.32 µg/L.
Of the 40 nitrate tests on record for Union County (1934–2023),
48% found none, and half were below 15 µg/L.
Of the 27 pfoa tests on record for Union County (2025),
100% found none.
Of the 27 pfos tests on record for Union County (2025),
100% found none.
Of the 32 sulfate tests on record for Union County (1934–2023),
0% found none, and half were below 985 µg/L.
Data Coverage & Gaps
Well-sampled analytes (15+ samples)
Iron 30 samples
Manganese 30 samples
Nitrate 40 samples
Arsenic 32 samples
Chloride 33 samples
Fluoride 29 samples
HFPO-DA (GenX) 31 samples
Lead 28 samples
Nitrite 33 samples
PFOA 31 samples
PFOS 31 samples
Sulfate 32 samples
Uranium 18 samples
PFBS 31 samples
pH 43 samples
Sodium 28 samples
Hardness 33 samples
Limited data (<15 samples) — interpret with caution
Radon 11 samples
Total Coliform 6 samples
E. coli 6 samples
Public vs. Private Water in Union County
38Active public water systems
8,813Residents on public water
69%Households on private wells
Public water systems in Union 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 Union 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 Union 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 Union County. Census data explorer →
USGS Aquifer Atlas — principal aquifer type underlying Union 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 Union County, used in contamination risk scoring. TRI Explorer →
EPA Superfund NPL — National Priorities List sites in or near Union 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.