Data & Methodology — Middlesex County

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

Contaminant Data — All Analytes

3555 well testing events on record, covering 20 analytes. Data spans 1923 to 2023.

Contaminant Samples Years Detection Rate Distribution LowModHigh vs. Limit vs. NJ Avg
Manganese 463 1933–2022 95%
200% of limit ↓ 58% below
Iron 473 1923–2022 92%
167% of limit ↓ 65% below
PFOA municipal 102 2021–2025 54%
158% of limit ↓ 21% below
Radon 43 1985–2006 100%
21% of limit ↓ 49% below
PFOS municipal 99 2021–2025 20%
122% of limit ↓ 28% below
Chloride 3351 1923–2022 100%
6% of limit ↓ 78% below
Lead 391 1970–2022 29%
67% of limit ↑ 183% above
Nitrate 435 1933–2022 63%
21% of limit ~ typical
Sulfate 484 1923–2022 98%
8% of limit ↓ 50% below
HFPO-DA (GenX) municipal 102 2021–2025 5%
131% of limit ~ typical
PFHxS municipal 101 2021–2025 10%
40% of limit ~ typical
Arsenic 165 1984–2022 52%
6% of limit ↓ 62% below
Fluoride 331 1942–2022 46%
2% of limit ↓ 52% below
Nitrite 389 1973–2022 17%
1% of limit ↓ 41% below
PFNA municipal 99 2021–2025 1%
21% of limit ↓ 52% below
Uranium 51 1985–2011 57%
2% of limit ↓ 53% below
Sodium 523 1933–2022 99%
— ↓ 77% below
pH 980 1942–2022 100%
— ~ typical
PFBS municipal 101 2021–2025 5%
— ↓ 27% below
Hardness 476 1923–2022 99%
— ↓ 72% 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 Middlesex County

Of the 165 arsenic tests on record for Middlesex County (1984–2022), 48% found none, and half were below 60 ng/L.

Of the 3351 chloride tests on record for Middlesex County (1923–2022), 0% found none, and half were below 16 mg/L.

Of the 331 fluoride tests on record for Middlesex County (1942–2022), 54% found none.

Of the 473 iron tests on record for Middlesex County (1923–2022), 8% found none, and half were below 400 µg/L.

Of the 391 lead tests on record for Middlesex County (1970–2022), 71% found none.

Of the 463 manganese tests on record for Middlesex County (1933–2022), 5% found none, and half were below 90 µg/L.

Of the 435 nitrate tests on record for Middlesex County (1933–2022), 37% found none, and half were below 160 µg/L.

Of the 484 sulfate tests on record for Middlesex County (1923–2022), 2% found none, and half were below 20.6 mg/L.

Of the 51 uranium tests on record for Middlesex County (1985–2011), 43% found none, and half were below 20 ng/L.

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Data Coverage & Gaps

Well-sampled analytes (15+ samples)

  • Manganese 463 samples
  • Iron 473 samples
  • PFOA 102 samples
  • Radon 43 samples
  • PFOS 99 samples
  • Chloride 3351 samples
  • Lead 391 samples
  • Nitrate 435 samples
  • Sulfate 484 samples
  • HFPO-DA (GenX) 102 samples
  • PFHxS 101 samples
  • Arsenic 165 samples
  • Fluoride 331 samples
  • Nitrite 389 samples
  • PFNA 99 samples
  • Uranium 51 samples
  • Sodium 523 samples
  • pH 980 samples
  • PFBS 101 samples
  • Hardness 476 samples

Public vs. Private Water in Middlesex County

35 Active public water systems
668,615 Residents on public water
2% Households on private wells

Public water systems in Middlesex 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 Middlesex 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 Middlesex County Prevalence NJ Average Source Year
Lead Heart disease rate 5.1% 5.8% 2020
Arsenic Cancer prevalence 5.8% 6.2% 2020
Arsenic Kidney disease rate 2.5% 2.7% 2020

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