Long-term kit
RL416 long-term radon test kit, lab fee included
- Lab fee included
Method: Alpha track
In home: 90 days to 12 months
Locations and reports
Radon Levels in Mercer County, Kentucky
EPA puts Mercer County in Zone 1, its highest radon zone, and 38.2% of its 288 reported radon tests (2008 to 2017, laboratory totals) were at or above 4 pCi/L. Homes with elevated levels occur in all three zones, so only a test measures yours.
Data checked By Radon411Methodology
Share at 4+ pCi/L
38.2%
5.5 pts below KY
- Mercer
- 38.2%
- Kentucky
- 43.7%
288 tests, 2008 to 2017
Median result
2.7pCi/L
Below action level
- Mercer
- 2.7 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2008 to 2017
Tests reported
288
19th of 69 by tests
- Mercer
- 288
- Jefferson
- 6,590
Reported to CDC before any fix, 2008 to 2017
EPA radon zone
Zone 1
Highest potential
- Zone 1
- 2
- 3
1 highest, 3 lowest
EPA predicts over 4 pCi/L indoors
Rank in Kentucky
31 of 69
Middle half
- Mercer
- 38.2%
- Meade
- 68.4%
By share, of 69 with 30+ tests
Read a result for Mercer County
Starts at Mercer County's median, 2.7 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 2.7 pCi/L
Between 2 and 4 pCi/L
- Under 20 to 1.9 pCi/L
- 2 to 4consider a fix
- 4 and aboveEPA says fix it
This result is between 2 and 4 pCi/L. EPA recommends considering a fix when the level is between 2 and 4 pCi/L. Mercer County's median reported result, 2008 to 2017.
The data
Mercer County, At a glance
Mercer County at a glance
Predicted: EPA radon zone
EPA Zone 1: highest predicted potential
EPA puts all of Mercer County in
USGS geologic potential: High across 60% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for Mercer County, 2008 to 2017, laboratory
Under 2 pCi/L: 39%2 to 4 pCi/L: 23%4 pCi/L and above: 38%
Of 288 pre-mitigation tests reported to CDC, not homes in this area.
| Result band | Tests Measured | Share Measured |
|---|---|---|
| Under 2 pCi/L | 112 | 38.9% |
| 2 to 4 pCi/L | 66 | 22.9% |
| 4 pCi/L and above | 110 | 38.2% |
What these figures count
These are the 288 tests reported to CDC for Mercer County over 2008 to 2017 (laboratory totals), many from homes being sold or already suspected of a problem: they describe the county's reported tests, not this house.
Measured: CDC tracking data. Figure above: 2008 to 2017, laboratory. Measured data period: 2005 to 2017 (every CDC figure on file).
Mercer County, Compared
Mercer County radon figures, compared
Calculated by Radon411In Mercer County, about 4 in 10 reported tests over the 2008 to 2017 laboratory totals (110 of 288) were at or above EPA's action level. Against the national pool of 35.7%, the gap is 2.5 points higher. Across 120 Kentucky counties pooled together, 43.7% of tests reached that level, so Mercer County runs 5.5 points below its state.
Of 6 neighbours with a figure, 4 reported a larger share at or above 4 pCi/L and 2 a smaller one; the spread is 25.2% (Anderson County) to 57.9% (Woodford County). By share, Mercer County is 31st of 69 Kentucky counties with 30 or more tests for the same period.
Half the tests came in under 2.7 pCi/L and half over it; the single highest reached 42.8 pCi/L. Below the action level, 112 tests (38.9%) came in under 2 pCi/L, against 33.2% statewide, and 66 tests (22.9%) fell between 2 and 4, against 23.1% statewide.
Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 38.2% share point the same way here. USGS geology rates 60% of the county's land high radon potential. CDC also counts 16 tests taken after mitigation in Mercer County for the same period: tests in homes where a fix was already in.
CDC's ten-year totals for Mercer County went from 296 tests (2005 to 2014) to 288 (2008 to 2017), the share going from 39.5% to 38.2%.
Pooled shares: Radon411's sum of CDC's county counts for one period.
Mercer County, Geology
The ground under Mercer County
PredictedUSGS's geologic map splits Mercer County: 60.2% of its land is high radon potential and 39.8% moderate. The map puts 60.2% of Mercer County in the area it calls Inner Bluegrass and 39.8% in Outer Bluegrass. USGS gives the first a radon index of 13, in the high band (12 to 17), and the second 11, in the moderate band (9 to 11).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Inner Bluegrass | Ordovician limestones, dolomites and shales. | High | 13 | 60.2% |
| Outer Bluegrass | Ordovician-Devonian limestone and shale. | Moderate | 11 | 39.8% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Mercer County beside the ground around it
Mercer County has more high-potential ground than Kentucky as a whole: 60.2% of its land against 18.2%. Of the 6 counties that border it, 2 have more high-potential ground, Woodford County the most at 100%.
The map rates the ground, not the air in any home.
Local help
Mercer County, Local resources
Radon testing and mitigation in Mercer County
- Kentucky's radon programKentucky Board of Radon SafetyKentucky's radon program answers questions about testing, mitigation and the rules in Kentucky.Visit the program’s page(opens in a new tab)
- Free and low-cost kitsAsk the program whether it has free or discounted kits, or compare kits you can buy.
- Compare kits
- Professionals in Kentucky8 professionals are listed in Kentucky.
What Kentucky's program says
- Phone
- 502-782-2782
- Radon@ky.gov
What it means
Mercer County, Questions
Questions about radon in Mercer County
Are radon levels high in Mercer County?
Over the 2008 to 2017 laboratory totals, 38.2% of the radon tests reported to CDC for Mercer County, Kentucky were at or above 4 pCi/L, and the median reported pre-mitigation result was 2.7 pCi/L. Of 69 Kentucky counties with 30 or more tests for the same period, 30 reported a higher share; pooled, the state comes to 43.7%.
Which counties border Mercer County?
Mercer County borders 6 counties: Anderson County, Boyle County, Woodford County, Jessamine County, Washington County and Garrard County.
Products
Mercer County, Products
Testing a home in Mercer County
In Mercer County, 38.2% of 288 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 43.7% pooled across Kentucky. In Zone 1 the year-round level in Mercer County is the one to know: a long-term test (more than 90 days) or a monitor, with a short-term kit for a first answer.
Test kits and monitors3
See every kit and monitor
MonitorKidde
Radon Detector (RAB) battery digital radon detector with an alarm
- C-NRPP 2024/25: Not included
- Battery
- Alarm
- Screen
Method: Semiconductor sensor
First reading: Within 12 hours
Short-term kit
Air Chek Short-Term radon test kit you hang, lab fee included
- Lab fee included
In home: 72 to 168 hours
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Mercer County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like Mercer County
Explore
Mercer County, Bordering counties
Counties bordering Mercer County
Calculated by Radon411- Radon levels in Woodford CountyEPA zone 1
57.9%at or above 4 pCi/L
Median 4.9 pCi/L · 342 tests · 19.7 points above Mercer County
- Radon levels in Jessamine CountyEPA zone 1
55.5%at or above 4 pCi/L
Median 4.7 pCi/L · 789 tests · 17.3 points above Mercer County
- Radon levels in Boyle CountyEPA zone 1
53.9%at or above 4 pCi/L
Median 4.4 pCi/L · 492 tests · 15.7 points above Mercer County
- Radon levels in Garrard CountyEPA zone 2
39.6%at or above 4 pCi/L
Median 2.6 pCi/L · 164 tests · 1.4 points above Mercer County
- Radon levels in Washington CountyEPA zone 2
27.3%at or above 4 pCi/L
Median 2.4 pCi/L · 44 tests · 10.9 points below Mercer County
- Radon levels in Anderson CountyEPA zone 2
25.2%at or above 4 pCi/L
Median 2.2 pCi/L · 226 tests · 13.0 points below Mercer County
Mercer County, Cities and towns
Cities and towns in Mercer County
The Census Bureau estimates 23,733 residents in Mercer County for July 1, 2025, 1,079 more than in 2020 (+4.8%). That works out to 95 people per square mile of land. Its largest town, Harrodsburg, has 9,576 residents, 40.3% of the total. Together its 2 incorporated places hold 44.7% of those residents; the other 55.3% live outside any of them. Testing is reported here more often than across the state: CDC's 288 reported tests for 2008 to 2017 come to 12.1 for every 1,000 residents (2025 estimate), against 6.3 for Kentucky.
From Harrodsburg to Burgin, CDC publishes no figure by town: each reads Mercer County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Harrodsburg | 9,576 | +4.4% | 40.3% |
| Burgin | 1,027 | +4.6% | 4.3% |
2 incorporated places, as listed in the U.S. Census Bureau’s 2020 place reference files. Residents: U.S. Census Bureau population estimates for July 1, 2025 (Vintage 2025).
Mercer County, Homes
Homes in Mercer County
Mercer County is a place of houses on their own lots: 80% of its 10,410 homes are detached single-family houses, against 68% across Kentucky. Half of its homes were built before 1978, close to Kentucky's 1982: 25% date from before 1960 and 24% from 2000 or later. Owners live in 77% of the occupied homes (Kentucky: 68%), so for most households a test and a fix are their own to order.
| Homes | Mercer County | Kentucky |
|---|---|---|
| Housing units | 10,410 | 2,010,655 |
| Detached houses | 80% | 68% |
| In buildings of 5 or more | 6% | 12% |
| Mobile homes | 7% | 11% |
| Built before 1960 | 25% | 22% |
| Built since 2000 | 24% | 24% |
| Middle year built | 1978 | 1982 |
| Owner-occupied | 77% | 68% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.