Full contaminant data, sample history, and sourcing for Winona County. For readers who want to go beyond the summary.
Contaminant Data — All Analytes
210 well testing events on record, covering
20 analytes.
Data spans 1961 to 2025.
Contaminant
Samples
Years
Detection Rate
Distribution LowModHigh
vs. Limit
vs. MN Avg
Iron
153
1963–2024
54%
142% of limit
↓ 80% below
PFOS
municipal
21
2023–2025
19%
150% of limit
↓ 25% below
Nitrate
55
1963–2025
96%
46% of limit
↑ 90% above
Manganese
117
1963–2024
74%
40% of limit
↓ 92% below
Arsenic
134
1980–2024
36%
2% of limit
↓ 97% below
Lead
136
1980–2024
42%
2% of limit
↓ 95% below
Chloride
190
1963–2025
81%
4% of limit
↓ 50% below
Fluoride
168
1963–2025
85%
3% of limit
↓ 60% below
HFPO-DA (GenX)
municipal
18
2023–2025
0%
—
—
Nitrite
45
2013–2025
0%
—
—
PFHxS
municipal
16
2023–2024
0%
—
—
PFNA
municipal
18
2023–2025
0%
—
—
PFOA
municipal
20
2023–2025
15%
19% of limit
↓ 95% below
Radon
1
2013
100%
70% of limit
↑ 36% above
Sulfate
179
1963–2025
98%
7% of limit
↓ 64% below
Uranium
24
1980–2015
88%
2% of limit
↓ 58% below
Hardness
18
1963–2013
100%
—
↓ 21% below
PFBS
municipal
17
2023–2024
6%
—
↑ 200% above
pH
22
1963–2022
100%
—
~ typical
Sodium
156
1963–2024
94%
—
↓ 92% 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 Winona County
Of the 134 arsenic tests on record for Winona County (1980–2024),
64% found none.
Of the 190 chloride tests on record for Winona County (1963–2025),
19% found none, and half were below 5.21 mg/L.
Of the 168 fluoride tests on record for Winona County (1963–2025),
15% found none, and half were below 100 µg/L.
Of the 153 iron tests on record for Winona County (1963–2024),
46% found none, and half were below 50 µg/L.
Of the 136 lead tests on record for Winona County (1980–2024),
58% found none.
Of the 117 manganese tests on record for Winona County (1963–2024),
26% found none, and half were below 12.8 µg/L.
Of the 55 nitrate tests on record for Winona County (1963–2025),
4% found none, and half were below 4.5 mg/L.
Of the 179 sulfate tests on record for Winona County (1963–2025),
2% found none, and half were below 16.7 mg/L.
Of the 24 uranium tests on record for Winona County (1980–2015),
12% found none, and half were below 0.47 µg/L.
Data Coverage & Gaps
Well-sampled analytes (15+ samples)
Iron 153 samples
PFOS 21 samples
Nitrate 55 samples
Manganese 117 samples
Arsenic 134 samples
Lead 136 samples
Chloride 190 samples
Fluoride 168 samples
HFPO-DA (GenX) 18 samples
Nitrite 45 samples
PFNA 18 samples
PFOA 20 samples
Sulfate 179 samples
Uranium 24 samples
Hardness 18 samples
PFBS 17 samples
pH 22 samples
Sodium 156 samples
Limited data (<15 samples) — interpret with caution
Radon 1 sample
Public vs. Private Water in Winona County
79Active public water systems
51,369Residents on public water
21%Households on private wells
Public water systems in Winona 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 Winona 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 Winona 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 Winona County. Census data explorer →
USGS Aquifer Atlas — principal aquifer type underlying Winona 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 Winona County, used in contamination risk scoring. TRI Explorer →
EPA Superfund NPL — National Priorities List sites in or near Winona 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.