Data & Methodology — Monroe County

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

Contaminant Data — All Analytes

46 well testing events on record, covering 16 analytes. Data spans 1945 to 2023.

Contaminant Samples Years Detection Rate Distribution LowModHigh vs. Limit vs. WI Avg
Manganese 22 1945–1991 100%
60% of limit ↓ 56% below
Iron 23 1945–1991 100%
24% of limit ↓ 90% below
Nitrate 23 1962–1991 70%
34% of limit ↑ 102% above
Nitrite 13 1966–1991 69%
1% of limit ~ typical
PFOA municipal 41 2022–2025 10%
8% of limit ↓ 47% below
Chloride 22 1945–1991 100%
3% of limit ↓ 39% below
Fluoride 14 1945–1991 100%
2% of limit ↓ 47% below
HFPO-DA (GenX) municipal 41 2022–2025 0%
— —
PFHxS municipal 41 2022–2025 10%
38% of limit ↑ 172% above
PFNA municipal 41 2022–2025 0%
— —
PFOS municipal 41 2022–2025 0%
— —
Sulfate 22 1945–1991 100%
6% of limit ~ typical
Hardness 22 1945–1991 100%
— ~ typical
PFBS municipal 41 2022–2025 5%
— ↑ 79% above
pH 27 1945–1991 100%
— ~ typical
Sodium 8 1966–1991 100%
— ↓ 76% 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 WI.

Compare your result with Monroe County

Of the 22 chloride tests on record for Monroe County (1945–1991), 0% found none, and half were below 6.9 mg/L.

Of the 23 iron tests on record for Monroe County (1945–1991), 0% found none, and half were below 73 µg/L.

Of the 22 manganese tests on record for Monroe County (1945–1991), 0% found none, and half were below 30 µg/L.

Of the 23 nitrate tests on record for Monroe County (1962–1991), 30% found none, and half were below 980 µg/L.

Of the 22 sulfate tests on record for Monroe County (1945–1991), 0% found none, and half were below 15 mg/L.

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Data Coverage & Gaps

Well-sampled analytes (15+ samples)

  • Manganese 22 samples
  • Iron 23 samples
  • Nitrate 23 samples
  • PFOA 41 samples
  • Chloride 22 samples
  • HFPO-DA (GenX) 41 samples
  • PFHxS 41 samples
  • PFNA 41 samples
  • PFOS 41 samples
  • Sulfate 22 samples
  • Hardness 22 samples
  • PFBS 41 samples
  • pH 27 samples

Limited data (<15 samples) — interpret with caution

  • Nitrite 13 samples
  • Fluoride 14 samples
  • Sodium 8 samples

CDC Health Outcome Correlations

Where contaminants detected in Monroe 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 Monroe County Prevalence WI Average Source Year
Nitrate Cancer prevalence 6.0% 7.0% 2020

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

Last updated: 2026-07-15

Full methodology →