Data & Methodology — Somerset County

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

Contaminant Data — All Analytes

141 well testing events on record, covering 20 analytes. Data spans 1923 to 2025.

Contaminant Samples Years Detection Rate Distribution LowModHigh vs. Limit vs. NJ Avg
PFOA municipal 55 2021–2025 69%
138% of limit ↓ 31% below
Manganese 81 1968–2021 60%
8% of limit ↓ 98% below
Iron 82 1954–2021 54%
12% of limit ↓ 98% below
Arsenic 64 1987–2021 81%
47% of limit ↑ 183% above
Sulfate 83 1954–2021 100%
9% of limit ↓ 46% below
Chloride 83 1954–2021 100%
6% of limit ↓ 79% below
PFOS municipal 55 2021–2025 13%
108% of limit ↓ 37% below
Nitrate 75 1954–2021 84%
26% of limit ~ typical
Lead 66 1985–2021 14%
1% of limit ↓ 98% below
Fluoride 69 1954–2021 75%
3% of limit ↓ 50% below
HFPO-DA (GenX) municipal 55 2021–2025 0%
— —
Nitrite 70 1987–2021 11%
1% of limit ↓ 56% below
PFHxS municipal 53 2021–2025 6%
31% of limit ↓ 29% below
PFNA municipal 54 2021–2025 0%
— —
Radon 2 1989–1997 100%
43% of limit ~ typical
Uranium 19 1985–2010 89%
13% of limit ↑ 184% above
Hardness 82 1954–2021 100%
— ↑ 22% above
PFBS municipal 52 2021–2025 10%
— ↓ 25% below
pH 108 1954–2021 100%
— ~ typical
Sodium 81 1968–2021 100%
— ↓ 68% 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 NJ.

Compare your result with Somerset County

Of the 64 arsenic tests on record for Somerset County (1987–2021), 19% found none, and half were below 2.55 µg/L.

Of the 83 chloride tests on record for Somerset County (1954–2021), 0% found none, and half were below 15.2 mg/L.

Of the 69 fluoride tests on record for Somerset County (1954–2021), 25% found none, and half were below 100 µg/L.

Of the 82 iron tests on record for Somerset County (1954–2021), 46% found none, and half were below 3.35 µg/L.

Of the 66 lead tests on record for Somerset County (1985–2021), 86% found none.

Of the 81 manganese tests on record for Somerset County (1968–2021), 40% found none, and half were below 0.79 µg/L.

Of the 75 nitrate tests on record for Somerset County (1954–2021), 16% found none, and half were below 2.2 mg/L.

Of the 83 sulfate tests on record for Somerset County (1954–2021), 0% found none, and half were below 22.4 mg/L.

Have a number from your lab? Enter it to see where it falls. Nothing is sent anywhere.

Want the full picture for your well? Check all your results.

Data Coverage & Gaps

Well-sampled analytes (15+ samples)

  • PFOA 55 samples
  • Manganese 81 samples
  • Iron 82 samples
  • Arsenic 64 samples
  • Sulfate 83 samples
  • Chloride 83 samples
  • PFOS 55 samples
  • Nitrate 75 samples
  • Lead 66 samples
  • Fluoride 69 samples
  • HFPO-DA (GenX) 55 samples
  • Nitrite 70 samples
  • PFHxS 53 samples
  • PFNA 54 samples
  • Uranium 19 samples
  • Hardness 82 samples
  • PFBS 52 samples
  • pH 108 samples
  • Sodium 81 samples

Limited data (<15 samples) — interpret with caution

  • Radon 2 samples

Public vs. Private Water in Somerset County

92 Active public water systems
72,721 Residents on public water
18% Households on private wells

Public water systems in Somerset 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 Somerset 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 Somerset County Prevalence NJ Average Source Year
Arsenic Cancer prevalence 6.6% 6.2% 2020
Arsenic Kidney disease rate 2.1% 2.7% 2020
Lead Heart disease rate 5.5% 5.8% 2020

Source: CDC PLACES county-level estimates. Raw data: Download Somerset 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 NJ with at least one sample for that analyte.

Last updated: 2026-08-04

Full methodology →