Ohio · county radon data
Radon in Hamilton County, Ohio
34.7% of the 3,085 home radon tests on record here reached the EPA action level — toward the lower end of the state's tested counties, ranked #75 of 88 tested Ohio counties.
What the numbers say
Hamilton County sits 19.1 points below the Ohio median (53.8% of tests over the limit across the state's counties). The median reading among its 3,085 reported tests was 2.8 pCi/L — and the single highest test on record reached 81.4 pCi/L, more than 20× 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 Hamilton 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 Hamilton County home dates to 1963 — decades before radon-resistant new construction entered building codes. With 830,774 residents largely housed in that older stock, testing is the only way any individual household knows where it stands.
ZIP codes in Hamilton 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 |
|---|---|
| 45001 | Addyston |
| 45002 | Cleves |
| 45030 | Harrison |
| 45033 | Hooven |
| 45041 | Miamitown |
| 45051 | Mount Saint Joseph |
| 45052 | North Bend |
| 45111 | Camp Dennison |
| 45174 | Terrace Park |
| 45202 | Cincinnati |
| 45203 | Cincinnati |
| 45204 | Cincinnati |
| 45205 | Cincinnati |
| 45206 | Cincinnati |
| 45207 | Cincinnati |
| 45208 | Cincinnati |
| 45209 | Cincinnati |
| 45211 | Cincinnati |
| 45212 | Cincinnati |
| 45213 | Cincinnati |
| 45214 | Cincinnati |
| 45215 | Cincinnati |
| 45216 | Cincinnati |
| 45217 | Cincinnati |
| 45218 | Cincinnati |
| 45219 | Cincinnati |
| 45220 | Cincinnati |
| 45223 | Cincinnati |
| 45224 | Cincinnati |
| 45225 | Cincinnati |
| 45226 | Cincinnati |
| 45227 | Cincinnati |
| 45229 | Cincinnati |
| 45230 | Cincinnati |
| 45231 | Cincinnati |
| 45232 | Cincinnati |
| 45233 | Cincinnati |
| 45236 | Cincinnati |
| 45237 | Cincinnati |
| 45238 | Cincinnati |
| 45239 | Cincinnati |
| 45240 | Cincinnati |
| 45241 | Cincinnati |
| 45242 | Cincinnati |
| 45243 | Cincinnati |
| 45244 | Cincinnati |
| 45246 | Cincinnati |
| 45247 | Cincinnati |
| 45248 | Cincinnati |
| 45249 | Cincinnati |
| 45251 | Cincinnati |
| 45252 | Cincinnati |
| 45255 | Cincinnati |
| 45267 | Cincinnati |
Hamilton County in the Ohio picture
| Hamilton County | 34.7% over the limit | 3,085 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 | 3.7% | |
Ranked nearby in Ohio
- Athens County — #72, 38.1% of 181 tests over the limit
- Washington County — #73, 38.1% of 290 tests over the limit
- Scioto County — #74, 37% of 48 tests over the limit
- Trumbull County — #76, 34.6% of 377 tests over the limit
- Ashtabula County — #77, 34.4% of 282 tests over the limit
- Gallia County — #78, 33.3% of 16 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).
Hamilton County radon FAQ
- Is radon high in Hamilton County?
- 34.7% of 3,085 home tests reported to the CDC came back at or above the EPA action level of 4 pCi/L — 19.1 points below the Ohio county median of 53.8%, ranking #75 of 88 tested counties. EPA classifies the county as Zone 1.
- Does an older home in Hamilton County mean more radon risk?
- The county's median home was built in 1963 — 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 Hamilton County numbers come from?
- 3,085 aggregated home tests in the CDC's Environmental Public Health Tracking dataset (CDC EPHT 2008-2017). Median reading: 2.8 pCi/L; the highest recorded test hit 81.4 pCi/L. How we handle the data, including its limits, is documented on our methodology page.
- What's the highest radon reading recorded in Hamilton County?
- 81.4 pCi/L — 20× the EPA action level — against a county median of 2.8 pCi/L across 3,085 tests. That spread is the point: neighboring homes routinely test wildly differently.