Data & Methodology — Hamilton County

Full contaminant data, sample history, and sourcing for Hamilton County. For readers who want to go beyond the summary.

Contaminant Data — All Analytes

347 well testing events on record, covering 22 analytes. Data spans 1957 to 2023.

Contaminant Samples Years Detection Rate Distribution LowModHigh vs. Limit vs. OH Avg
Manganese 275 1972–2020 91%
406% of limit ~ typical
Iron 289 1972–2020 91%
27% of limit ↓ 95% below
Arsenic 198 1972–2020 73%
0% of limit ↓ 100% below
PFOS municipal 36 2008–2025 11%
212% of limit —
Uranium 51 1982–2020 73%
2% of limit ~ typical
Lead 226 1972–2020 56%
0% of limit ↓ 100% below
Nitrate 153 1972–2020 94%
16% of limit ↑ 751% above
Chloride 286 1972–2020 100%
18% of limit ↓ 58% below
Sulfate 164 1972–2020 100%
28% of limit ↓ 52% below
Fluoride 181 1972–2020 98%
6% of limit ↓ 64% below
HFPO-DA (GenX) municipal 35 2023–2025 9%
62% of limit —
Nitrite 139 1973–2020 72%
2% of limit ↓ 38% below
PFHxS municipal 35 2023–2025 0%
— —
PFNA municipal 37 2008–2025 0%
— —
PFOA municipal 38 2008–2025 0%
— —
Radon 8 1999–2019 100%
8% of limit ↓ 91% below
Total Coliform 2 2000–2019 86%
— —
Sodium 247 1972–2020 100%
— ↓ 73% below
pH 280 1972–2020 100%
— ~ typical
PFBS municipal 35 2023–2025 11%
— —
Hardness 262 1972–2020 100%
— ~ typical
E. coli 2 2000–2019 14%
— —

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.

Data Coverage & Gaps

Well-sampled analytes (15+ samples)

  • Manganese 275 samples
  • Iron 289 samples
  • Arsenic 198 samples
  • PFOS 36 samples
  • Uranium 51 samples
  • Lead 226 samples
  • Nitrate 153 samples
  • Chloride 286 samples
  • Sulfate 164 samples
  • Fluoride 181 samples
  • Nitrite 139 samples
  • PFNA 37 samples
  • PFOA 38 samples
  • Sodium 247 samples
  • pH 280 samples
  • Hardness 262 samples

Limited data (<15 samples) — interpret with caution

  • Radon 8 samples
  • Total Coliform 2 samples
  • E. coli 2 samples

Public vs. Private Water in Hamilton County

28 Active public water systems
842,267 Residents on public water

Public water systems in Hamilton 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 Hamilton 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.

Contaminant Associated Condition Hamilton County Prevalence OH Average Source Year
Arsenic Cancer prevalence 5.8% 6.8% 2020
Arsenic Kidney disease rate 2.8% 3.1% 2020
Lead Heart disease rate 7.0% 7.6% 2020

Source: CDC PLACES county-level estimates. Raw data: Download Hamilton County CDC PLACES data →

Data Sources

This report aggregates data from the following public databases:

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.

Last updated: 2026-07-15

Full methodology →