Data & Methodology — Marquette County

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

Contaminant Data — All Analytes

167 well testing events on record, covering 20 analytes. Data spans 1961 to 2017.

Contaminant Samples Years Detection Rate Distribution LowModHigh vs. Limit vs. MI Avg
Iron 67 1975–2015 96%
45% of limit ↓ 87% below
Manganese 67 1975–2015 93%
20% of limit ↓ 77% below
Arsenic 41 1975–2015 80%
10% of limit ↓ 67% below
Nitrate 147 1970–2015 95%
1% of limit ↓ 77% below
Chloride 148 1970–2015 100%
1% of limit ↓ 97% below
Fluoride 66 1975–2015 59%
2% of limit ↓ 70% below
HFPO-DA (GenX) municipal 10 2023–2024 0%
— —
Lead 43 1975–2015 12%
0% of limit ↓ 98% below
Nitrite 63 1975–2015 48%
0% of limit ↓ 100% below
PFHxS municipal 10 2023–2024 0%
— —
PFNA municipal 10 2023–2024 0%
— —
PFOA municipal 12 2010–2024 0%
— —
PFOS municipal 10 2023–2024 0%
— —
Radon 8 1990–2003 100%
8% of limit ~ typical
Sulfate 148 1970–2015 100%
3% of limit ↓ 86% below
Uranium 28 1976–2015 93%
0% of limit ↓ 61% below
Hardness 147 1970–2015 100%
— ↓ 62% below
PFBS municipal 10 2023–2024 0%
— —
pH 153 1970–2015 100%
— ~ typical
Sodium 65 1975–2015 100%
— ↓ 94% 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 MI.

Compare your result with Marquette County

Of the 41 arsenic tests on record for Marquette County (1975–2015), 20% found none, and half were below 1 µg/L.

Of the 148 chloride tests on record for Marquette County (1970–2015), 0% found none, and half were below 1.45 mg/L.

Of the 66 fluoride tests on record for Marquette County (1975–2015), 41% found none, and half were below 45 µg/L.

Of the 67 iron tests on record for Marquette County (1975–2015), 4% found none, and half were below 120 µg/L.

Of the 43 lead tests on record for Marquette County (1975–2015), 88% found none.

Of the 67 manganese tests on record for Marquette County (1975–2015), 7% found none, and half were below 10 µg/L.

Of the 147 nitrate tests on record for Marquette County (1970–2015), 5% found none, and half were below 50 µg/L.

Of the 148 sulfate tests on record for Marquette County (1970–2015), 0% found none, and half were below 7.45 mg/L.

Of the 28 uranium tests on record for Marquette County (1976–2015), 7% found none, and half were below 0.102 µg/L.

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Data Coverage & Gaps

Well-sampled analytes (15+ samples)

  • Iron 67 samples
  • Manganese 67 samples
  • Arsenic 41 samples
  • Nitrate 147 samples
  • Chloride 148 samples
  • Fluoride 66 samples
  • Lead 43 samples
  • Nitrite 63 samples
  • Sulfate 148 samples
  • Uranium 28 samples
  • Hardness 147 samples
  • pH 153 samples
  • Sodium 65 samples

Limited data (<15 samples) — interpret with caution

  • PFOA 12 samples
  • Radon 8 samples

Public vs. Private Water in Marquette County

95 Active public water systems
57,092 Residents on public water
30% Households on private wells

Public water systems in Marquette 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 Marquette 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 Marquette County Prevalence MI Average Source Year
Arsenic Cancer prevalence 6.3% 7.2% 2020
Arsenic Kidney disease rate 2.7% 3.2% 2020

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

Last updated: 2026-08-04

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