Data & Methodology — Washington County

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

Contaminant Data — All Analytes

185 well testing events on record, covering 22 analytes. Data spans 1963 to 2024.

Contaminant Samples Years Detection Rate Distribution LowModHigh vs. Limit vs. OH Avg
Radon 1 2019 100%
137% of limit ↑ 518% above
PFOA municipal 13 2013–2025 38%
340% of limit ↑ 151% above
Manganese 147 1973–2019 80%
40% of limit ↓ 77% below
PFOS municipal 12 2023–2025 17%
124% of limit ↓ 39% below
Iron 165 1973–2019 85%
7% of limit ↓ 98% below
Sulfate 32 1978–2019 100%
22% of limit ↓ 50% below
Lead 116 1973–2019 81%
0% of limit ↓ 100% below
Arsenic 109 1974–2019 76%
0% of limit ↓ 100% below
Chloride 173 1973–2019 100%
14% of limit ~ typical
Fluoride 99 1973–2019 83%
5% of limit ↓ 51% below
HFPO-DA (GenX) municipal 12 2023–2025 0%
— —
Nitrate 58 1973–2019 100%
15% of limit ↑ 212% above
Nitrite 3 1973–2019 33%
1% of limit ~ typical
PFHxS municipal 12 2023–2025 17%
32% of limit ↓ 39% below
PFNA municipal 13 2013–2025 0%
— —
Uranium 1 2019 100%
1% of limit ↓ 39% below
E. coli 1 2019 0%
— —
Hardness 81 1973–2019 100%
— ~ typical
PFBS municipal 12 2023–2025 50%
— ↑ 27% above
pH 73 1973–2019 100%
— ~ typical
Sodium 171 1973–2019 100%
— ↓ 36% below
Total Coliform 1 2019 0%
— —

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 Washington County

Of the 109 arsenic tests on record for Washington County (1974–2019), 24% found none.

Of the 173 chloride tests on record for Washington County (1973–2019), 0% found none, and half were below 34 mg/L.

Of the 99 fluoride tests on record for Washington County (1973–2019), 17% found none, and half were below 180 µg/L.

Of the 165 iron tests on record for Washington County (1973–2019), 15% found none.

Of the 116 lead tests on record for Washington County (1973–2019), 19% found none.

Of the 147 manganese tests on record for Washington County (1973–2019), 20% found none.

Of the 58 nitrate tests on record for Washington County (1973–2019), 0% found none, and half were below 1.5 mg/L.

Of the 32 sulfate tests on record for Washington County (1978–2019), 0% found none, and half were below 55 mg/L.

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Data Coverage & Gaps

Well-sampled analytes (15+ samples)

  • Manganese 147 samples
  • Iron 165 samples
  • Sulfate 32 samples
  • Lead 116 samples
  • Arsenic 109 samples
  • Chloride 173 samples
  • Fluoride 99 samples
  • Nitrate 58 samples
  • Hardness 81 samples
  • pH 73 samples
  • Sodium 171 samples

Limited data (<15 samples) — interpret with caution

  • Radon 1 sample
  • PFOA 13 samples
  • Nitrite 3 samples
  • PFNA 13 samples
  • Uranium 1 sample
  • E. coli 1 sample
  • Total Coliform 1 sample

Public vs. Private Water in Washington County

18 Active public water systems
61,007 Residents on public water
1% Households on private wells

Public water systems in Washington 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 Washington 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 Washington County Prevalence OH Average Source Year
Arsenic Kidney disease rate 2.8% 3.1% 2020
PFOA Cancer prevalence 6.1% 6.8% 2020
Lead Heart disease rate 9.1% 7.6% 2020

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