Greater Cincinnati & Northern Kentucky radon data
Radon Levels in Greater Cincinnati: What the Data Shows by County
Greater Cincinnati sits in a high-radon region, and the federal map proves it. This page lays out the EPA zone for every county in the metro, the one number every homeowner should know, and why a zone label — high or low — can never replace testing your own home.
Radon is a radioactive gas that seeps up from soil and rock and collects in the lowest lived-in level of a house, usually a basement. You cannot see it or smell it, and the geology under this region produces more of it than most of the country.
The EPA uses a single line to tell homeowners when to act. If your home tests at or above it, the recommendation is clear: fix it.
The federal risk map
What the EPA radon zones mean
The EPA sorts every U.S. county into one of three radon zones based on the predicted average indoor level before any mitigation. The zones are a planning tool — they flag how likely elevated radon is across a whole county, not what any single house will read.
- Zone 1 — predicted average indoor level above 4 pCi/L. The highest of the three zones.
- Zone 2 — predicted average between 2 and 4 pCi/L.
- Zone 3 — predicted average below 2 pCi/L. The lowest-risk category.
Greater Cincinnati has no Zone 3 counties. The Ohio side is Zone 1 and the Northern Kentucky side is Zone 2 — and, as the data below shows, a Zone 2 label here does not mean a home is in the clear.
County-by-county
EPA radon zones across the metro counties
Below is the EPA zone for each county in the Greater Cincinnati and Northern Kentucky market, plus Dearborn County across the Indiana line. The zone is a county-wide prediction, so the guidance in the last column is the same everywhere: test every home.
| County | State | EPA Zone | What it means |
|---|---|---|---|
| Hamilton | OH | Zone 1 | Predicted indoor average above 4.0 pCi/L. Test every home. |
| Butler | OH | Zone 1 | Predicted indoor average above 4.0 pCi/L. Test every home. |
| Warren | OH | Zone 1 | Predicted indoor average above 4.0 pCi/L. Test every home. |
| Clermont | OH | Zone 1 | Predicted indoor average above 4.0 pCi/L. Test every home. |
| Brown | OH | Zone 1 | Predicted indoor average above 4.0 pCi/L. Test every home. |
| Boone | KY | Zone 2 | Predicted average 2–4 pCi/L, but local tests often exceed 4.0. Test every home. |
| Kenton | KY | Zone 2 | Predicted average 2–4 pCi/L, but local tests often exceed 4.0. Test every home. |
| Campbell | KY | Zone 2 | Predicted average 2–4 pCi/L, but local tests often exceed 4.0. Test every home. |
| Dearborn | IN | Zone 1 | Predicted indoor average above 4.0 pCi/L. Test every home. |
Zone assignments come from the EPA Map of Radon Zones. Each zone is a predicted county average, not a measured level for any specific address. The EPA does not publish a single per-county pCi/L number, and individual homes vary widely.
Local geology
Why radon levels vary house to house
Radon starts as uranium breaking down in soil and rock, then rises through the ground into homes. The dirt and bedrock under Greater Cincinnati release more of it than most of the country, and the Ohio River valley is the reason.
The valley left behind glacial till — a dense, uneven mix of clay, sand, and rock fragments that traps and channels the gas. Beneath and around it runs fractured limestone and shale, and those cracks give radon a direct path toward the surface. That geology sits on both sides of the river, which is why Ohio and Northern Kentucky counties share the same underlying risk even with different zone labels.
What varies is the last few feet. How your foundation was poured, its age, whether it has a basement or a slab, where the cracks and sump pit sit, and how air moves through the house all decide how much of that gas ends up inside. Two homes over the same soil can read very differently because they were built differently.
Why the map is not enough
The house-next-door reality
Two nearly identical homes on the same street — even side by side — can test on opposite sides of the action level. One reads low, the other reads high, over the same ground. The difference comes down to construction details and how each house pulls air from the soil below it.
That is why a zone map, a county average, or a neighbor's result cannot tell you what to do about your home. They describe the odds for the area. Only a test measures your house.
A county map tells you the odds. A test tells you your number. Only one of those lets you decide what to do about your home.
Read the Kentucky data carefully
Zone 2 in Northern Kentucky does not mean safe
Boone, Kenton, and Campbell counties carry an EPA Zone 2 rating, which predicts a county average between 2 and 4 pCi/L. On paper that sounds lower than the Ohio side. In practice it does not play out that way.
Real-world test results across Northern Kentucky frequently come back above the 4.0 action level, despite the Zone 2 label. A zone is a broad prediction for an entire county; it was never meant to clear an individual home. The fractured-limestone geology that drives radon here does not stop at the state line.
The takeaway is the same as everywhere else in the metro: the zone tells you elevated radon is plausible, and only a test tells you your home's level. If you own a home in Boone, Kenton, or Campbell county, test it. See local detail for Florence or the wider Northern Kentucky area.
First step
How to get your home tested
Testing is inexpensive and straightforward, and it is the only way to learn your home's radon level. You can start with a do-it-yourself kit or hire a licensed professional for a documented measurement.
Both the Ohio Department of Health and the EPA point homeowners toward free or low-cost test-kit programs. If you want a starting point that costs little or nothing, ask about a test kit through the Ohio DOH radon program — availability changes over time, so it is worth checking directly.
Need a documented reading for a home sale or a mitigation decision? Here is how professional radon testing works.
If your test is high
What to do if you are above 4.0 pCi/L
A reading at or above 4.0 does not mean something is wrong with your house — it is common across this region. It means it is time to fix it, and radon is one of the more straightforward home problems to solve.
A mitigation system vents the gas from under your slab to above the roofline before it enters your living space. A well-built system usually brings a home under 2.0 pCi/L. Get a free quote from a licensed contractor and compare it against the going rates for the area.
Common questions
Cincinnati radon level questions
The EPA maps radon by county, not by zip code. The Ohio counties around Cincinnati sit in Zone 1 and the Northern Kentucky counties sit in Zone 2. A zip-code map can only show general area risk, because radon varies house to house. It cannot tell you your home's level — only a test can.
Hamilton, Butler, Warren, Clermont, and Brown counties in Ohio are EPA Radon Zone 1, the highest of the three zones, with a predicted average indoor level above 4 pCi/L. Dearborn County, Indiana is also Zone 1. The Northern Kentucky counties of Boone, Kenton, and Campbell are Zone 2, with a predicted 2 to 4 pCi/L average.
No. Zone 2 predicts a county average between 2 and 4 pCi/L, but real-world test results in Boone, Kenton, and Campbell counties frequently exceed the 4.0 action level. A zone is a prediction, not a reading for your house, so every Northern Kentucky home should be tested.
Yes. Radon depends on the soil and rock under each foundation, how the home was built, its foundation type, and how air moves through it. Two houses next door to each other can test very differently, which is why a neighbor's result does not tell you your number.
The EPA sets its action level at 4.0 pCi/L and recommends fixing any home that tests at or above it. Radon carries some risk below 4.0 too, since no level is considered fully safe, and many homeowners choose to mitigate in the 2 to 4 range as well. A properly built system usually brings a home under 2.0.
Free, no obligation
Know your number, then know your options
If your test came back above 4 pCi/L — or you are ready to test — we will connect you with an Ohio ODH-licensed radon contractor who covers your county. The licensed contractor handles the testing and the mitigation; we make the match. It works the same across our full service area, in West Chester, Florence, and every community in between.