Ohio · county radon data
Radon in Butler County, Ohio
54.3% of the 1,552 home radon tests on record here reached the EPA action level — mid-pack for the state, ranked #43 of 88 tested Ohio counties.
What the numbers say
Butler County sits 0.5 points above the Ohio median (53.8% of tests over the limit across the state's counties). The median reading among its 1,552 reported tests was 4.4 pCi/L — and the single highest test on record reached 143.8 pCi/L, more than 35× the action level. EPA maps place the county in Radon Zone 1 — its highest-potential category, where average indoor screening levels are predicted above 4 pCi/L.
Why: the ground under Butler County
Covered by glacial till that ground up and redistributed Ohio's shale and carbonate bedrock. The till concentrates fine radioactive minerals while outwash sands provide fast pathways for soil gas — the reason most of Ohio is EPA Zone 1 or 2.
Geology sources: USGS WRI 98-4169 · EPA OH zone documentation.
The housing stock factor
The median Butler County home dates to 1979 — decades before radon-resistant new construction entered building codes. With 392,876 residents largely housed in that older stock, testing is the only way any individual household knows where it stands.
ZIP codes in Butler County
Ohio doesn't publish ZIP-level test results, so these ZIPs share the county figures above — the roster is here so you can confirm your address is covered by this data.
| ZIP | Place |
|---|---|
| 45011 | Hamilton |
| 45013 | Hamilton |
| 45014 | Fairfield |
| 45015 | Hamilton |
| 45042 | Middletown |
| 45044 | Middletown |
| 45050 | Monroe |
| 45053 | Okeana |
| 45055 | Overpeck |
| 45056 | Oxford |
| 45062 | Seven Mile |
| 45064 | Somerville |
| 45067 | Trenton |
| 45069 | West Chester |
Butler County in the Ohio picture
| Butler County | 54.3% over the limit | 1,552 tests |
| Ohio's highest: Pickaway County | 81.4% | 154 tests |
| Ohio county median | 53.8% | 88 counties ranked |
| Share of all Ohio tests from this county | 1.8% | |
Ranked nearby in Ohio
- Muskingum County — #40, 56.3% of 339 tests over the limit
- Pike County — #41, 56.1% of 33 tests over the limit
- Erie County — #42, 54.5% of 1,436 tests over the limit
- Van Wert County — #44, 53.8% of 18 tests over the limit
- Hocking County — #45, 53.3% of 41 tests over the limit
- Warren County — #46, 52.5% of 2,076 tests over the limit
(Ranking neighbors — counties adjacent in the Ohio test ranking, not necessarily on the map.)
High test? Fixes and real pricing: the Ohio mitigation cost guide. Every statistic here traces to the methodology (CDC EPHT (labs), 2008–2017; zones: EPA; year built & population: ACS 5-year).
Butler County radon FAQ
- Is radon high in Butler County?
- 54.3% of 1,552 home tests reported to the CDC came back at or above the EPA action level of 4 pCi/L — 0.5 points above the Ohio county median of 53.8%, ranking #43 of 88 tested counties. EPA classifies the county as Zone 1.
- Does an older home in Butler County mean more radon risk?
- The county's median home was built in 1979 — before radon-resistant construction practices entered building codes in the 1990s, so most of the housing stock has no built-in radon protection. Construction age changes the odds, not the answer: only a test tells you about your house.
- Where do these Butler County numbers come from?
- 1,552 aggregated home tests in the CDC's Environmental Public Health Tracking dataset (CDC EPHT 2008-2017). Median reading: 4.4 pCi/L; the highest recorded test hit 143.8 pCi/L. How we handle the data, including its limits, is documented on our methodology page.
- What's the highest radon reading recorded in Butler County?
- 143.8 pCi/L — 35× the EPA action level — against a county median of 4.4 pCi/L across 1,552 tests. That spread is the point: neighboring homes routinely test wildly differently.