Data & Methodology — Roseau County

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

Contaminant Data — All Analytes

58 well testing events on record, covering 16 analytes. Data spans 1954 to 2024.

Contaminant Samples Years Detection Rate Distribution LowModHigh vs. Limit vs. MN Avg
Iron 52 1954–1995 100%
312% of limit ↓ 56% below
Manganese 49 1954–1995 100%
140% of limit ↓ 71% below
Arsenic 15 1995 80%
79% of limit ~ typical
PFOS 6 — 100%
15% of limit ↓ 93% below
PFOA 22 — 100%
37% of limit ↓ 91% below
PFHxS 7 — 100%
11% of limit ↓ 86% below
Lead 15 1995 60%
1% of limit ↓ 97% below
Nitrate 52 1954–1995 77%
3% of limit ↓ 87% below
Fluoride 28 1954–1995 100%
10% of limit ↑ 41% above
Sulfate 57 1954–1995 98%
5% of limit ↓ 75% below
Chloride 56 1954–1995 100%
2% of limit ↓ 73% below
PFNA 2 — 100%
20% of limit ↑ 21% above
Hardness 42 1954–1972 100%
— ~ typical
PFBS 14 — 100%
— ↓ 89% below
pH 42 1954–1972 100%
— ~ typical
Sodium 57 1954–1995 100%
— ↓ 29% 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 MN.

Compare your result with Roseau County

Of the 56 chloride tests on record for Roseau County (1954–1995), 0% found none, and half were below 5.1 mg/L.

Of the 28 fluoride tests on record for Roseau County (1954–1995), 0% found none, and half were below 390 µg/L.

Of the 52 iron tests on record for Roseau County (1954–1995), 0% found none, and half were below 935 µg/L.

Of the 49 manganese tests on record for Roseau County (1954–1995), 0% found none, and half were below 70 µg/L.

Of the 52 nitrate tests on record for Roseau County (1954–1995), 23% found none, and half were below 90 µg/L.

Of the 22 pfoa tests on record for Roseau County, 0% found none, and half were below 1.47 ng/L.

Of the 57 sulfate tests on record for Roseau County (1954–1995), 2% found none, and half were below 11.8 mg/L.

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Data Coverage & Gaps

Well-sampled analytes (15+ samples)

  • Iron 52 samples
  • Manganese 49 samples
  • Arsenic 15 samples
  • PFOA 22 samples
  • Lead 15 samples
  • Nitrate 52 samples
  • Fluoride 28 samples
  • Sulfate 57 samples
  • Chloride 56 samples
  • Hardness 42 samples
  • pH 42 samples
  • Sodium 57 samples

Limited data (<15 samples) — interpret with caution

  • PFOS 6 samples
  • PFHxS 7 samples
  • PFNA 2 samples
  • PFBS 14 samples

Public vs. Private Water in Roseau County

45 Active public water systems
8,619 Residents on public water
65% Households on private wells

Public water systems in Roseau 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 Roseau 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 Roseau County Prevalence MN Average Source Year
Arsenic Cancer prevalence 6.1% 7.0% 2020
Arsenic Kidney disease rate 2.5% 2.9% 2020
Lead Heart disease rate 5.6% 6.6% 2020

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

Last updated: 2026-08-04

Full methodology →