Full contaminant data, sample history, and sourcing for Blair County. For readers who want to go beyond the summary.
Contaminant Data — All Analytes
185 well testing events on record, covering
20 analytes.
Data spans 1933 to 2024.
Contaminant
Samples
Years
Detection Rate
Distribution LowModHigh
vs. Limit
vs. PA Avg
Radon
14
1994–2017
100%
86% of limit
↓ 33% below
Nitrate
108
1933–2017
99%
74% of limit
↑ 315% above
Manganese
56
1967–2011
55%
80% of limit
↓ 84% below
Iron
72
1967–2011
68%
67% of limit
↓ 89% below
Arsenic
30
1980–2017
40%
51% of limit
↑ 74% above
PFOS
municipal
87
2023–2025
16%
74% of limit
↓ 42% below
Chloride
83
1933–2011
100%
5% of limit
↓ 55% below
Fluoride
72
1967–2011
46%
5% of limit
~ typical
Sulfate
74
1933–2011
95%
10% of limit
↓ 43% below
PFOA
municipal
87
2023–2025
14%
66% of limit
↓ 29% below
HFPO-DA (GenX)
municipal
73
2023–2025
0%
—
—
Lead
21
1980–2011
5%
5% of limit
~ typical
Nitrite
102
1980–2017
26%
1% of limit
↓ 33% below
PFHxS
municipal
16
2023–2025
0%
—
—
PFNA
municipal
16
2023–2025
0%
—
—
Uranium
8
1994–2011
25%
1% of limit
↓ 37% below
Sodium
58
1969–2011
100%
—
↓ 56% below
pH
122
1967–2017
100%
—
~ typical
PFBS
municipal
73
2023–2025
8%
—
↓ 29% below
Hardness
65
1933–2011
100%
—
↑ 30% above
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 Blair County
Of the 30 arsenic tests on record for Blair County (1980–2017),
60% found none.
Of the 83 chloride tests on record for Blair County (1933–2011),
0% found none, and half were below 12 mg/L.
Of the 72 fluoride tests on record for Blair County (1967–2011),
54% found none.
Of the 72 iron tests on record for Blair County (1967–2011),
32% found none, and half were below 40 µg/L.
Of the 21 lead tests on record for Blair County (1980–2011),
95% found none.
Of the 56 manganese tests on record for Blair County (1967–2011),
45% found none, and half were below 9.36 µg/L.
Of the 108 nitrate tests on record for Blair County (1933–2017),
1% found none, and half were below 7.26 mg/L.
Of the 71 pfoa tests on record for Blair County (2025),
83% found none.
Of the 71 pfos tests on record for Blair County (2025),
80% found none.
Of the 74 sulfate tests on record for Blair County (1933–2011),
5% found none, and half were below 22.6 mg/L.
Data Coverage & Gaps
Well-sampled analytes (15+ samples)
Nitrate 108 samples
Manganese 56 samples
Iron 72 samples
Arsenic 30 samples
PFOS 87 samples
Chloride 83 samples
Fluoride 72 samples
Sulfate 74 samples
PFOA 87 samples
HFPO-DA (GenX) 73 samples
Lead 21 samples
Nitrite 102 samples
Sodium 58 samples
pH 122 samples
PFBS 73 samples
Hardness 65 samples
Limited data (<15 samples) — interpret with caution
Radon 14 samples
Uranium 8 samples
Public vs. Private Water in Blair County
53Active public water systems
101,979Residents on public water
31%Households on private wells
Public water systems in Blair 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 Blair 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 Blair 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 Blair County. Census data explorer →
USGS Aquifer Atlas — principal aquifer type underlying Blair 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 Blair County, used in contamination risk scoring. TRI Explorer →
EPA Superfund NPL — National Priorities List sites in or near Blair 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.