Full contaminant data, sample history, and sourcing for Mille Lacs County. For readers who want to go beyond the summary.
Contaminant Data — All Analytes
121 well testing events on record, covering
18 analytes.
Data spans 1957 to 2024.
Contaminant
Samples
Years
Detection Rate
Distribution LowModHigh
vs. Limit
vs. MN Avg
Manganese
62
1965–2025
85%
260% of limit
↓ 47% below
PFOS
municipal
8
2024–2025
62%
532% of limit
↑ 165% above
Iron
62
1965–2025
84%
163% of limit
↓ 77% below
PFOA
municipal
14
2006–2025
50%
300% of limit
↓ 30% below
Chloride
105
1965–2025
100%
7% of limit
~ typical
Nitrite
47
1992–1997
36%
2% of limit
↑ 66% above
Nitrate
66
1965–2006
55%
1% of limit
↓ 94% below
Arsenic
28
1995–2025
21%
14% of limit
↓ 83% below
Fluoride
47
1965–2025
79%
5% of limit
↓ 28% below
HFPO-DA (GenX)
municipal
10
2022–2025
0%
—
—
Lead
30
1993–2025
13%
2% of limit
↓ 95% below
PFHxS
municipal
5
2024
20%
40% of limit
↓ 50% below
PFNA
municipal
13
2006–2025
23%
82% of limit
↑ 394% above
Sulfate
87
1965–2025
94%
5% of limit
↓ 72% below
Sodium
59
1968–2025
100%
—
↓ 61% below
pH
54
1965–1998
100%
—
~ typical
PFBS
municipal
4
2024
0%
—
—
Hardness
33
1965–1993
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 Mille Lacs County
Of the 28 arsenic tests on record for Mille Lacs County (1995–2025),
79% found none.
Of the 105 chloride tests on record for Mille Lacs County (1965–2025),
0% found none, and half were below 18 mg/L.
Of the 47 fluoride tests on record for Mille Lacs County (1965–2025),
21% found none, and half were below 200 µg/L.
Of the 62 iron tests on record for Mille Lacs County (1965–2025),
16% found none, and half were below 255 µg/L.
Of the 30 lead tests on record for Mille Lacs County (1993–2025),
87% found none.
Of the 62 manganese tests on record for Mille Lacs County (1965–2025),
15% found none, and half were below 110 µg/L.
Of the 66 nitrate tests on record for Mille Lacs County (1965–2006),
45% found none.
Of the 87 sulfate tests on record for Mille Lacs County (1965–2025),
6% found none, and half were below 11 mg/L.
Data Coverage & Gaps
Well-sampled analytes (15+ samples)
Manganese 62 samples
Iron 62 samples
Chloride 105 samples
Nitrite 47 samples
Nitrate 66 samples
Arsenic 28 samples
Fluoride 47 samples
Lead 30 samples
Sulfate 87 samples
Sodium 59 samples
pH 54 samples
Hardness 33 samples
Limited data (<15 samples) — interpret with caution
PFOS 8 samples
PFOA 14 samples
HFPO-DA (GenX) 10 samples
PFHxS 5 samples
PFNA 13 samples
Public vs. Private Water in Mille Lacs County
93Active public water systems
20,644Residents on public water
65%Households on private wells
Public water systems in Mille Lacs 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 Mille Lacs 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.
This report aggregates data from the following public databases:
Water Quality Portal (WQP) — groundwater sample results for Mille Lacs County from EPA, USGS, and state agencies. Browse WQP data →
EPA Safe Drinking Water Information System (SDWIS) — public water system inventory used to estimate the share of residents on private wells. Browse SDWIS →
Census ACS 5-Year Estimates — well and cistern household counts (variable DP04_0074E) used to calculate the private-well percentage for Mille Lacs County. Census data explorer →
USGS Aquifer Atlas — principal aquifer type underlying Mille Lacs County, which informs which contaminants are geologically likely. USGS Aquifer Atlas →
EPA UCMR 5 (2023–2025) — PFAS occurrence data from public water systems, used as a proxy indicator for aquifer PFAS exposure. Rows marked "municipal" in the table above come from this source. About UCMR 5 →
EPA Toxics Release Inventory (TRI) — industrial facility chemical releases near Mille Lacs County, used in contamination risk scoring. TRI Explorer →
EPA Superfund NPL — National Priorities List sites in or near Mille Lacs County, used in contamination risk scoring. Superfund site search →
CDC PLACES — county-level health outcome prevalence (kidney disease, cancer, heart disease) correlated with detected contaminants. About CDC PLACES →
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.