Full contaminant data, sample history, and sourcing for Clark County. For readers who want to go beyond the summary.
Contaminant Data — All Analytes
926 well testing events on record, covering
22 analytes.
Data spans 1965 to 2020.
Contaminant
Samples
Years
Detection Rate
Distribution LowModHigh
vs. Limit
vs. OH Avg
Manganese
193
1972–2020
88%
219% of limit
↑ 24% above
Iron
196
1972–2020
78%
88% of limit
↓ 80% below
Radon
15
1999–2013
100%
8% of limit
↓ 62% below
Nitrate
79
1972–2020
90%
22% of limit
↑ 356% above
Arsenic
169
1986–2020
75%
0% of limit
↓ 100% below
Chloride
878
1972–2020
100%
9% of limit
↓ 39% below
Fluoride
141
1972–2020
96%
6% of limit
↓ 39% below
HFPO-DA (GenX)
municipal
10
2023–2025
0%
—
—
Lead
187
1972–2020
57%
0% of limit
↓ 100% below
Nitrite
68
1973–2020
21%
1% of limit
↑ 135% above
PFHxS
municipal
10
2023–2025
0%
—
—
PFNA
municipal
10
2023–2025
0%
—
—
PFOA
municipal
10
2023–2025
0%
—
—
PFOS
municipal
10
2023–2025
0%
—
—
Sulfate
105
1972–2020
100%
14% of limit
↓ 67% below
Uranium
34
1999–2020
91%
4% of limit
↑ 85% above
Total Coliform
6
2013–2019
43%
—
~ typical
Sodium
815
1972–2020
100%
—
↓ 67% below
pH
465
1972–2020
100%
—
~ typical
PFBS
municipal
10
2023–2025
20%
—
~ typical
Hardness
186
1972–2020
100%
—
~ typical
E. coli
6
2013–2019
14%
—
~ 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 OH.
Compare your result with Clark County
Of the 169 arsenic tests on record for Clark County (1986–2020),
25% found none.
Of the 878 chloride tests on record for Clark County (1972–2020),
0% found none, and half were below 23 mg/L.
Of the 141 fluoride tests on record for Clark County (1972–2020),
4% found none, and half were below 240 µg/L.
Of the 196 iron tests on record for Clark County (1972–2020),
22% found none, and half were below 147 µg/L.
Of the 187 lead tests on record for Clark County (1972–2020),
43% found none.
Of the 193 manganese tests on record for Clark County (1972–2020),
12% found none, and half were below 95 µg/L.
Of the 79 nitrate tests on record for Clark County (1972–2020),
10% found none, and half were below 2 mg/L.
Of the 105 sulfate tests on record for Clark County (1972–2020),
0% found none, and half were below 36 mg/L.
Of the 34 uranium tests on record for Clark County (1999–2020),
9% found none, and half were below 1.24 µg/L.
Data Coverage & Gaps
Well-sampled analytes (15+ samples)
Manganese 193 samples
Iron 196 samples
Radon 15 samples
Nitrate 79 samples
Arsenic 169 samples
Chloride 878 samples
Fluoride 141 samples
Lead 187 samples
Nitrite 68 samples
Sulfate 105 samples
Uranium 34 samples
Sodium 815 samples
pH 465 samples
Hardness 186 samples
Limited data (<15 samples) — interpret with caution
Total Coliform 6 samples
E. coli 6 samples
No private-well PFAS data for Clark County
We have no private well sampling data for PFAS compounds (PFOA, PFOS, PFNA, and related chemicals) in Clark 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 Clark 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 Clark 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 Clark County. Census data explorer →
USGS Aquifer Atlas — principal aquifer type underlying Clark 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 Clark County, used in contamination risk scoring. TRI Explorer →
EPA Superfund NPL — National Priorities List sites in or near Clark 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 OH with at least one sample for that analyte.