Full contaminant data, sample history, and sourcing for Onondaga County. For readers who want to go beyond the summary.
Contaminant Data — All Analytes
347 well testing events on record, covering
23 analytes.
Data spans 1953 to 2022.
Contaminant
Samples
Years
Detection Rate
Distribution LowModHigh
vs. Limit
vs. NY Avg
Chloride
270
1953–2022
100%
93% of limit
↑ 216% above
Sulfate
258
1953–2022
100%
16% of limit
~ typical
Manganese
218
1953–2022
82%
54% of limit
↓ 83% below
Iron
255
1953–2022
75%
50% of limit
↓ 74% below
Radon
17
2005–2022
100%
12% of limit
↓ 89% below
Arsenic
29
1971–2022
48%
11% of limit
↓ 41% below
Nitrate
97
1953–2022
75%
7% of limit
↓ 37% below
Fluoride
88
1953–2022
95%
6% of limit
~ typical
HFPO-DA (GenX)
municipal
40
2023–2025
0%
—
—
Lead
29
1971–2022
52%
1% of limit
↓ 76% below
Nitrite
56
2005–2022
57%
0% of limit
↓ 69% below
PFHxS
municipal
40
2023–2025
0%
—
—
PFNA
municipal
40
2023–2025
0%
—
—
PFOA
municipal
40
2023–2025
0%
—
—
PFOS
municipal
40
2023–2025
0%
—
—
Uranium
17
2005–2022
88%
1% of limit
↓ 45% below
E. coli
7
2005–2022
0%
—
—
Fecal Coliform
7
2005–2022
18%
—
~ typical
Hardness
249
1953–2023
98%
—
↑ 72% above
PFBS
municipal
40
2023–2025
2%
—
~ typical
pH
271
1953–2022
100%
—
~ typical
Sodium
243
1953–2022
100%
—
↑ 132% above
Total Coliform
7
2005–2022
18%
—
~ 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 Onondaga County
Of the 29 arsenic tests on record for Onondaga County (1971–2022),
52% found none.
Of the 270 chloride tests on record for Onondaga County (1953–2022),
0% found none, and half were below 233 mg/L.
Of the 88 fluoride tests on record for Onondaga County (1953–2022),
5% found none, and half were below 225 µg/L.
Of the 255 iron tests on record for Onondaga County (1953–2022),
25% found none, and half were below 100 µg/L.
Of the 29 lead tests on record for Onondaga County (1971–2022),
48% found none, and half were below 40 ng/L.
Of the 218 manganese tests on record for Onondaga County (1953–2022),
18% found none, and half were below 20 µg/L.
Of the 97 nitrate tests on record for Onondaga County (1953–2022),
25% found none, and half were below 400 µg/L.
Of the 258 sulfate tests on record for Onondaga County (1953–2022),
0% found none, and half were below 39.9 mg/L.
Data Coverage & Gaps
Well-sampled analytes (15+ samples)
Chloride 270 samples
Sulfate 258 samples
Manganese 218 samples
Iron 255 samples
Radon 17 samples
Arsenic 29 samples
Nitrate 97 samples
Fluoride 88 samples
Lead 29 samples
Nitrite 56 samples
Uranium 17 samples
Hardness 249 samples
pH 271 samples
Sodium 243 samples
Limited data (<15 samples) — interpret with caution
E. coli 7 samples
Fecal Coliform 7 samples
Total Coliform 7 samples
No private-well PFAS data for Onondaga County
We have no private well sampling data for PFAS compounds (PFOA, PFOS, PFNA, and related chemicals) in Onondaga 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 Onondaga 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 Onondaga 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 Onondaga County. Census data explorer →
USGS Aquifer Atlas — principal aquifer type underlying Onondaga 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 Onondaga County, used in contamination risk scoring. TRI Explorer →
EPA Superfund NPL — National Priorities List sites in or near Onondaga 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.