Data & Methodology — Franklin County

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

Contaminant Data — All Analytes

706 well testing events on record, covering 20 analytes. Data spans 1951 to 2018.

Contaminant Samples Years Detection Rate Distribution LowModHigh vs. Limit vs. OH Avg
Iron 653 1972–2014 97%
667% of limit ↑ 52% above
Manganese 652 1974–2014 98%
160% of limit ~ typical
Arsenic 268 1975–2014 94%
60% of limit ↑ 281% above
Sulfate 484 1974–2014 100%
44% of limit ~ typical
Lead 558 1975–2014 40%
0% of limit ↓ 100% below
PFOA municipal 51 2018–2025 8%
136% of limit ~ typical
Nitrate 290 1974–2006 37%
2% of limit ↓ 65% below
Chloride 654 1972–2014 100%
12% of limit ↓ 21% below
Fluoride 621 1974–2014 98%
8% of limit ↓ 27% below
HFPO-DA (GenX) municipal 50 2023–2025 0%
— —
Nitrite 301 1974–2006 35%
1% of limit ↑ 57% above
PFHxS municipal 50 2023–2025 0%
— —
PFNA municipal 51 2018–2025 0%
— —
PFOS municipal 50 2023–2025 0%
— —
Radon 3 2006 100%
6% of limit ↓ 73% below
Uranium 3 2006 100%
9% of limit ↑ 287% above
Sodium 652 1974–2014 100%
— ↓ 58% below
pH 619 1974–2007 100%
— ~ typical
PFBS municipal 50 2023–2025 10%
— ↑ 95% above
Hardness 628 1974–2014 100%
— ~ 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 Franklin County

Of the 268 arsenic tests on record for Franklin County (1975–2014), 6% found none, and half were below 6 µg/L.

Of the 654 chloride tests on record for Franklin County (1972–2014), 0% found none, and half were below 30 mg/L.

Of the 621 fluoride tests on record for Franklin County (1974–2014), 2% found none, and half were below 300 µg/L.

Of the 653 iron tests on record for Franklin County (1972–2014), 3% found none, and half were below 1.92 mg/L.

Of the 558 lead tests on record for Franklin County (1975–2014), 60% found none.

Of the 652 manganese tests on record for Franklin County (1974–2014), 2% found none, and half were below 79 µg/L.

Of the 290 nitrate tests on record for Franklin County (1974–2006), 63% found none.

Of the 484 sulfate tests on record for Franklin County (1974–2014), 0% found none, and half were below 110 mg/L.

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Data Coverage & Gaps

Well-sampled analytes (15+ samples)

  • Iron 653 samples
  • Manganese 652 samples
  • Arsenic 268 samples
  • Sulfate 484 samples
  • Lead 558 samples
  • PFOA 51 samples
  • Nitrate 290 samples
  • Chloride 654 samples
  • Fluoride 621 samples
  • Nitrite 301 samples
  • PFNA 51 samples
  • Sodium 652 samples
  • pH 619 samples
  • Hardness 628 samples

Limited data (<15 samples) — interpret with caution

  • Radon 3 samples
  • Uranium 3 samples

Public vs. Private Water in Franklin County

96 Active public water systems
1,502,361 Residents on public water
1% Households on private wells

Public water systems in Franklin 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 Franklin 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 Franklin County Prevalence OH Average Source Year
Lead Heart disease rate 5.9% 7.6% 2020
Arsenic Cancer prevalence 5.8% 6.8% 2020
Arsenic Kidney disease rate 2.8% 3.1% 2020

Source: CDC PLACES county-level estimates. Raw data: Download Franklin 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: 2026-08-04

Full methodology →