Data & Methodology — Oakland County

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

Contaminant Data — All Analytes

687 well testing events on record, covering 22 analytes. Data spans 1901 to 2023.

Contaminant Samples Years Detection Rate Distribution LowModHigh vs. Limit vs. MI Avg
Iron 393 1901–2023 93%
326% of limit ~ typical
Arsenic 138 1975–2023 81%
20% of limit ↓ 33% below
Manganese 270 1956–2023 91%
40% of limit ↓ 55% below
Chloride 453 1901–2023 100%
9% of limit ↓ 53% below
Radon 29 1996–2013 100%
7% of limit ~ typical
Nitrate 381 1938–2016 73%
0% of limit ↓ 93% below
PFHxS municipal 198 2023–2025 3%
65% of limit ~ typical
PFOS municipal 198 2023–2025 2%
168% of limit ↑ 44% above
PFOA municipal 198 2023–2025 2%
88% of limit ~ typical
Sulfate 451 1901–2023 100%
10% of limit ↓ 54% below
Fluoride 381 1901–2023 93%
6% of limit ↓ 22% below
HFPO-DA (GenX) municipal 196 2023–2025 1%
54% of limit ~ typical
Lead 93 1975–2023 37%
0% of limit ↓ 98% below
Nitrite 178 1975–2016 34%
1% of limit ~ typical
PFNA municipal 198 2023–2025 0%
— —
Uranium 94 1929–2023 88%
2% of limit ↑ 123% above
E. coli 4 1997–2016 3%
— ~ typical
Hardness 461 1901–2023 100%
— ~ typical
PFBS municipal 198 2023–2025 3%
— ~ typical
pH 503 1901–2023 100%
— ~ typical
Sodium 355 1901–2023 100%
— ↓ 45% below
Total Coliform 4 1997–2016 7%
— ~ 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 MI.

Compare your result with Oakland County

Of the 138 arsenic tests on record for Oakland County (1975–2023), 19% found none, and half were below 0.99 µg/L.

Of the 453 chloride tests on record for Oakland County (1901–2023), 0% found none, and half were below 22 mg/L.

Of the 381 fluoride tests on record for Oakland County (1901–2023), 7% found none, and half were below 210 µg/L.

Of the 393 iron tests on record for Oakland County (1901–2023), 7% found none, and half were below 900 µg/L.

Of the 93 lead tests on record for Oakland County (1975–2023), 63% found none.

Of the 270 manganese tests on record for Oakland County (1956–2023), 9% found none, and half were below 15.6 µg/L.

Of the 381 nitrate tests on record for Oakland County (1938–2016), 27% found none.

Of the 451 sulfate tests on record for Oakland County (1901–2023), 0% found none, and half were below 24 mg/L.

Of the 94 uranium tests on record for Oakland County (1929–2023), 12% found none, and half were below 0.555 µg/L.

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Data Coverage & Gaps

Well-sampled analytes (15+ samples)

  • Iron 393 samples
  • Arsenic 138 samples
  • Manganese 270 samples
  • Chloride 453 samples
  • Radon 29 samples
  • Nitrate 381 samples
  • PFHxS 198 samples
  • PFOS 198 samples
  • PFOA 198 samples
  • Sulfate 451 samples
  • Fluoride 381 samples
  • Lead 93 samples
  • Nitrite 178 samples
  • PFNA 198 samples
  • Uranium 94 samples
  • Hardness 461 samples
  • PFBS 198 samples
  • pH 503 samples
  • Sodium 355 samples

Limited data (<15 samples) — interpret with caution

  • E. coli 4 samples
  • Total Coliform 4 samples

Public vs. Private Water in Oakland County

741 Active public water systems
1,148,236 Residents on public water
18% Households on private wells

Public water systems in Oakland 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 Oakland 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 Oakland County Prevalence MI Average Source Year
Arsenic Cancer prevalence 7.1% 7.2% 2023
Arsenic Cancer prevalence 6.0% 7.2% 2020
Arsenic Kidney disease rate 2.4% 3.2% 2020

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

Full methodology →