Full contaminant data, sample history, and sourcing for Madison County. For readers who want to go beyond the summary.
Contaminant Data — All Analytes
78 well testing events on record, covering
23 analytes.
Data spans 1955 to 2023.
Contaminant
Samples
Years
Detection Rate
Distribution LowModHigh
vs. Limit
vs. NY Avg
Manganese
29
1961–2022
86%
40% of limit
↓ 87% below
Iron
29
1961–2022
90%
22% of limit
↓ 89% below
Radon
18
2002–2022
100%
21% of limit
↓ 81% below
Sulfate
29
1961–2022
100%
10% of limit
↓ 30% below
Chloride
29
1961–2022
100%
7% of limit
↓ 77% below
Arsenic
27
1972–2022
67%
8% of limit
↓ 56% below
Fluoride
29
1961–2022
100%
3% of limit
↓ 47% below
HFPO-DA (GenX)
municipal
16
2024–2025
0%
—
—
Lead
27
1972–2022
52%
1% of limit
↓ 66% below
Nitrate
29
1961–2022
62%
12% of limit
~ typical
Nitrite
21
1973–2022
24%
0% of limit
↓ 63% below
PFHxS
municipal
16
2024–2025
0%
—
—
PFNA
municipal
16
2024–2025
0%
—
—
PFOA
municipal
16
2024–2025
0%
—
—
PFOS
municipal
16
2024–2025
0%
—
—
Uranium
18
2002–2022
94%
2% of limit
~ typical
Total Coliform
39
2005–2022
35%
—
~ typical
Sodium
27
1972–2022
100%
—
↓ 60% below
pH
63
1961–2022
100%
—
~ typical
PFBS
municipal
16
2024–2025
0%
—
—
Hardness
29
1961–2022
100%
—
~ typical
Fecal Coliform
5
2005–2022
6%
—
~ typical
E. coli
36
2005–2022
21%
—
~ 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 NY.
Compare your result with Madison County
Of the 27 arsenic tests on record for Madison County (1972–2022),
33% found none, and half were below 0.25 µg/L.
Of the 29 chloride tests on record for Madison County (1961–2022),
0% found none, and half were below 17 mg/L.
Of the 29 fluoride tests on record for Madison County (1961–2022),
0% found none, and half were below 120 µg/L.
Of the 29 iron tests on record for Madison County (1961–2022),
10% found none, and half were below 50 µg/L.
Of the 27 lead tests on record for Madison County (1972–2022),
48% found none, and half were below 30 ng/L.
Of the 29 manganese tests on record for Madison County (1961–2022),
14% found none, and half were below 10.1 µg/L.
Of the 29 nitrate tests on record for Madison County (1961–2022),
38% found none, and half were below 600 µg/L.
Of the 29 sulfate tests on record for Madison County (1961–2022),
0% found none, and half were below 23.8 mg/L.
Data Coverage & Gaps
Well-sampled analytes (15+ samples)
Manganese 29 samples
Iron 29 samples
Radon 18 samples
Sulfate 29 samples
Chloride 29 samples
Arsenic 27 samples
Fluoride 29 samples
Lead 27 samples
Nitrate 29 samples
Nitrite 21 samples
Uranium 18 samples
Total Coliform 39 samples
Sodium 27 samples
pH 63 samples
Hardness 29 samples
E. coli 36 samples
Limited data (<15 samples) — interpret with caution
Fecal Coliform 5 samples
No private-well PFAS data for Madison County
We have no private well sampling data for PFAS compounds (PFOA, PFOS, PFNA, and related chemicals) in Madison County.
PFAS testing for private wells requires a dedicated lab panel (~$300–$500). If you are near a military base, airport, or industrial site, consider testing proactively. Learn more about PFAS →
CDC Health Outcome Correlations
Where contaminants detected in Madison 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 Madison 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 Madison County. Census data explorer →
USGS Aquifer Atlas — principal aquifer type underlying Madison 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 Madison County, used in contamination risk scoring. TRI Explorer →
EPA Superfund NPL — National Priorities List sites in or near Madison 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 NY with at least one sample for that analyte.