Full contaminant data, sample history, and sourcing for Lyon County. For readers who want to go beyond the summary.
Contaminant Data — All Analytes
89 well testing events on record, covering
18 analytes.
Data spans 1955 to 2025.
Contaminant
Samples
Years
Detection Rate
Distribution LowModHigh
vs. Limit
vs. MN Avg
Sulfate
76
1955–2025
100%
293% of limit
↑ 1451% above
Manganese
72
1955–2025
96%
200% of limit
↓ 59% below
Iron
76
1955–2025
78%
500% of limit
↓ 30% below
Arsenic
24
1979–2025
50%
67% of limit
↓ 21% below
Lead
24
1979–2025
25%
92% of limit
↑ 106% above
Nitrate
56
1955–2006
95%
0% of limit
↓ 99% below
Chloride
85
1955–2025
99%
9% of limit
~ typical
Fluoride
58
1955–2025
100%
10% of limit
↑ 44% above
HFPO-DA (GenX)
municipal
4
2024–2025
0%
—
—
Nitrite
19
1994–1998
89%
0% of limit
↓ 75% below
PFHxS
municipal
2
2024
100%
42% of limit
↓ 48% below
PFNA
municipal
4
2024–2025
0%
—
—
PFOA
municipal
4
2024–2025
0%
—
—
PFOS
municipal
4
2024–2025
50%
20% of limit
↓ 90% below
Sodium
73
1955–2025
100%
—
↑ 415% above
pH
28
1955–2010
100%
—
~ typical
PFBS
municipal
2
2024
0%
—
—
Hardness
30
1955–1979
100%
—
↑ 92% above
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 Lyon County
Of the 24 arsenic tests on record for Lyon County (1979–2025),
50% found none, and half were below 0.43 µg/L.
Of the 85 chloride tests on record for Lyon County (1955–2025),
1% found none, and half were below 13.8 mg/L.
Of the 58 fluoride tests on record for Lyon County (1955–2025),
0% found none, and half were below 400 µg/L.
Of the 76 iron tests on record for Lyon County (1955–2025),
22% found none, and half were below 458 µg/L.
Of the 24 lead tests on record for Lyon County (1979–2025),
75% found none.
Of the 72 manganese tests on record for Lyon County (1955–2025),
4% found none, and half were below 93.2 µg/L.
Of the 56 nitrate tests on record for Lyon County (1955–2006),
5% found none, and half were below 23 µg/L.
Of the 76 sulfate tests on record for Lyon County (1955–2025),
0% found none, and half were below 733 mg/L.
Data Coverage & Gaps
Well-sampled analytes (15+ samples)
Sulfate 76 samples
Manganese 72 samples
Iron 76 samples
Arsenic 24 samples
Lead 24 samples
Nitrate 56 samples
Chloride 85 samples
Fluoride 58 samples
Nitrite 19 samples
Sodium 73 samples
pH 28 samples
Hardness 30 samples
Limited data (<15 samples) — interpret with caution
HFPO-DA (GenX) 4 samples
PFNA 4 samples
PFOA 4 samples
PFOS 4 samples
Public vs. Private Water in Lyon County
16Active public water systems
21,039Residents on public water
15%Households on private wells
Public water systems in Lyon 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 Lyon 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 Lyon 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 Lyon County. Census data explorer →
USGS Aquifer Atlas — principal aquifer type underlying Lyon 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 Lyon County, used in contamination risk scoring. TRI Explorer →
EPA Superfund NPL — National Priorities List sites in or near Lyon 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.