Data & Methodology — Jefferson County

Full contaminant data, sample history, and sourcing for Jefferson County. For readers who want to go beyond the summary.

Contaminant Data — All Analytes

130 well testing events on record, covering 20 analytes. Data spans 1929 to 2022.

Contaminant Samples Years Detection Rate Distribution LowModHigh vs. Limit vs. PA Avg
Manganese 84 1964–1999 89%
1020% of limit ↑ 102% above
Iron 87 1929–1999 94%
567% of limit ~ typical
Sulfate 73 1929–1999 100%
14% of limit ↓ 21% below
Lead 54 1964–1999 19%
133% of limit ↑ 2783% above
Chloride 74 1929–1999 100%
4% of limit ↓ 59% below
Arsenic 47 1995–1999 13%
14% of limit ↓ 52% below
Fluoride 25 1964–1999 76%
5% of limit ~ typical
HFPO-DA (GenX) municipal 46 2023–2025 0%
— —
Nitrate 62 1929–1999 55%
2% of limit ↓ 91% below
Nitrite 50 1973–1999 4%
2% of limit ↑ 33% above
PFHxS municipal 16 2023–2024 0%
— —
PFNA municipal 16 2023–2024 0%
— —
PFOA municipal 51 2023–2025 2%
52% of limit ↓ 45% below
PFOS municipal 51 2023–2025 0%
— —
Radon 42 1995–1997 100%
7% of limit ↓ 95% below
Uranium 8 1996–1999 50%
0% of limit ↓ 78% below
Sodium 68 1929–1999 100%
— ↓ 76% below
pH 84 1964–1999 100%
— ~ typical
PFBS municipal 46 2023–2025 2%
— ↓ 89% below
Hardness 88 1929–1999 100%
— ~ typical

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 Jefferson County

Of the 47 arsenic tests on record for Jefferson County (1995–1999), 87% found none.

Of the 74 chloride tests on record for Jefferson County (1929–1999), 0% found none, and half were below 11 mg/L.

Of the 25 fluoride tests on record for Jefferson County (1964–1999), 24% found none, and half were below 200 µg/L.

Of the 87 iron tests on record for Jefferson County (1929–1999), 6% found none, and half were below 900 µg/L.

Of the 54 lead tests on record for Jefferson County (1964–1999), 81% found none.

Of the 84 manganese tests on record for Jefferson County (1964–1999), 11% found none, and half were below 390 µg/L.

Of the 62 nitrate tests on record for Jefferson County (1929–1999), 45% found none.

Of the 35 pfoa tests on record for Jefferson County (2025), 97% found none.

Of the 35 pfos tests on record for Jefferson County (2025), 100% found none.

Of the 73 sulfate tests on record for Jefferson County (1929–1999), 0% found none, and half were below 34 mg/L.

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Data Coverage & Gaps

Well-sampled analytes (15+ samples)

  • Manganese 84 samples
  • Iron 87 samples
  • Sulfate 73 samples
  • Lead 54 samples
  • Chloride 74 samples
  • Arsenic 47 samples
  • Fluoride 25 samples
  • HFPO-DA (GenX) 46 samples
  • Nitrate 62 samples
  • Nitrite 50 samples
  • PFOA 51 samples
  • PFOS 51 samples
  • Radon 42 samples
  • Sodium 68 samples
  • pH 84 samples
  • PFBS 46 samples
  • Hardness 88 samples

Limited data (<15 samples) — interpret with caution

  • Uranium 8 samples

Public vs. Private Water in Jefferson County

42 Active public water systems
30,935 Residents on public water
48% Households on private wells

Public water systems in Jefferson 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 Jefferson 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.

Contaminant Associated Condition Jefferson County Prevalence PA Average Source Year
Lead Heart disease rate 9.1% 7.2% 2020
Radon Cancer prevalence 8.2% 7.0% 2020

Source: CDC PLACES county-level estimates. Raw data: Download Jefferson County CDC PLACES data →

Data Sources

This report aggregates data from the following public databases:

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.

Last updated: 2026-08-04

Full methodology →