Data & Methodology — Lancaster County

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

Contaminant Data — All Analytes

3224 well testing events on record, covering 22 analytes. Data spans 1904 to 2025.

Contaminant Samples Years Detection Rate Distribution LowModHigh vs. Limit vs. PA Avg
Nitrate 2071 1925–2022 98%
110% of limit ↑ 519% above
Radon 167 1986–2021 100%
18% of limit ↓ 86% below
Manganese 409 1961–2022 89%
40% of limit ↓ 92% below
PFOA municipal 872 2023–2025 41%
103% of limit ~ typical
PFOS municipal 872 2023–2025 32%
105% of limit ~ typical
Iron 429 1925–2022 66%
27% of limit ↓ 95% below
Chloride 854 1925–2022 100%
10% of limit ~ typical
Sulfate 768 1925–2022 97%
13% of limit ↓ 25% below
Nitrite 1955 1938–2022 48%
1% of limit ↓ 33% below
Arsenic 237 1976–2022 22%
10% of limit ↓ 66% below
Fluoride 513 1961–2022 81%
3% of limit ↓ 27% below
HFPO-DA (GenX) municipal 871 2023–2025 0%
— —
Lead 229 1976–2022 16%
13% of limit ↑ 188% above
PFHxS municipal 136 2023–2025 10%
38% of limit ~ typical
PFNA municipal 136 2023–2025 0%
— —
Uranium 232 1986–2022 80%
27% of limit ↑ 1057% above
Total Coliform 5 1993–2022 53%
— ~ typical
Sodium 652 1925–2022 100%
— ↓ 54% below
pH 2252 1938–2022 100%
— ~ typical
PFBS municipal 870 2023–2025 39%
— ~ typical
Hardness 666 1925–2022 100%
— ↑ 84% above
E. coli 5 1994–2022 9%
— ~ 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 Lancaster County

Of the 237 arsenic tests on record for Lancaster County (1976–2022), 78% found none.

Of the 854 chloride tests on record for Lancaster County (1925–2022), 0% found none, and half were below 24 mg/L.

Of the 513 fluoride tests on record for Lancaster County (1961–2022), 19% found none, and half were below 100 µg/L.

Of the 429 iron tests on record for Lancaster County (1925–2022), 34% found none, and half were below 30 µg/L.

Of the 229 lead tests on record for Lancaster County (1976–2022), 84% found none.

Of the 409 manganese tests on record for Lancaster County (1961–2022), 11% found none, and half were below 20 µg/L.

Of the 2071 nitrate tests on record for Lancaster County (1925–2022), 2% found none, and half were below 10.4 mg/L.

Of the 736 pfoa tests on record for Lancaster County (2025), 56% found none.

Of the 736 pfos tests on record for Lancaster County (2025), 66% found none.

Of the 768 sulfate tests on record for Lancaster County (1925–2022), 3% found none, and half were below 31.2 mg/L.

Of the 232 uranium tests on record for Lancaster County (1986–2022), 20% found none, and half were below 5 µg/L.

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Data Coverage & Gaps

Well-sampled analytes (15+ samples)

  • Nitrate 2071 samples
  • Radon 167 samples
  • Manganese 409 samples
  • PFOA 872 samples
  • PFOS 872 samples
  • Iron 429 samples
  • Chloride 854 samples
  • Sulfate 768 samples
  • Nitrite 1955 samples
  • Arsenic 237 samples
  • Fluoride 513 samples
  • HFPO-DA (GenX) 871 samples
  • Lead 229 samples
  • Uranium 232 samples
  • Sodium 652 samples
  • pH 2252 samples
  • PFBS 870 samples
  • Hardness 666 samples

Limited data (<15 samples) — interpret with caution

  • Total Coliform 5 samples
  • E. coli 5 samples

Public vs. Private Water in Lancaster County

431 Active public water systems
409,282 Residents on public water
44% Households on private wells

Public water systems in Lancaster 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 Lancaster 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 Lancaster County Prevalence PA Average Source Year
Nitrate Cancer prevalence 6.1% 7.0% 2020
Lead Heart disease rate 7.3% 7.2% 2020

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