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Radon Levels in Madison County, Kentucky

EPA puts Madison County in Zone 2, its middle radon zone, and 38.7% of its 604 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

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  • Share at 4+ pCi/L

    38.7%

    5.0 pts below KY

    Madison
    38.7%
    Kentucky
    43.7%

    604 tests, 2008 to 2017

  • Median result

    2.9pCi/L

    Below action level

    Madison
    2.9 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    604

    10th of 69 by tests

    Madison
    604
    Jefferson
    6,590

    Reported to CDC before any fix, 2008 to 2017

  • EPA radon zone

    Zone 2

    Moderate potential

    1. 1
    2. Zone 2
    3. 3

    1 highest, 3 lowest

    EPA predicts 2 to 4 pCi/L indoors

  • Rank in Kentucky

    30 of 69

    Middle half

    Madison
    38.7%
    Meade
    68.4%

    By share, of 69 with 30+ tests

Read a result for Madison County

Starts at Madison County's median, 2.9 pCi/L

2.9pCi/L

EPA’s own thresholds; the figures are the area’s, never this home’s.

EPA’s reading of 2.9 pCi/L

Between 2 and 4 pCi/L

  1. Under 20 to 1.9 pCi/L
  2. 2 to 4consider a fix
  3. 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. Madison County's median reported result, 2008 to 2017.

Interpret this readingWhat a fix costs

The data

Madison County, At a glance

Madison County at a glance

Predicted: EPA radon zone

EPA Zone 2: moderate predicted potential

Madison County is a county: EPA's forecast for it as a whole is an average indoor of 2 to 4 pCi/L (75 to 150 Bq/m³). It describes no single address, and homes above EPA's are found in every zone, this one included.

USGS geologic potential: Moderate across 61% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

Radon tests reported for Madison County, 2008 to 2017, laboratory

Reported results by concentration band, Madison County, 2008 to 2017, laboratory
Under 2 pCi/L: 36%2 to 4 pCi/L: 25%4 pCi/L and above: 39%

Of 604 pre-mitigation tests reported to CDC, not homes in this area.

Reported results by concentration band, Madison County, 2008 to 2017, laboratory: data table
Result bandTests MeasuredShare Measured
Under 2 pCi/L21936.3%
2 to 4 pCi/L15125.0%
4 pCi/L and above23438.7%
What these figures count

These are the 604 tests reported to CDC for Madison 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).

How to read these figures

Madison County, Compared

Madison County radon figures, compared

Calculated by Radon411

In Madison County, about 4 in 10 reported tests over the 2008 to 2017 laboratory totals (234 of 604) were at or above EPA's action level. Against the national pool of 35.7%, the gap is 3.0 points higher. Across 120 Kentucky counties pooled together, 43.7% of tests reached that level, so Madison County runs 5.0 points below its state.

Of 5 neighbours with a figure, 4 reported a larger share at or above 4 pCi/L and 1 a smaller one; the spread is 29.0% (Clark County) to 55.5% (Jessamine County). By share, Madison County is 30th of 69 Kentucky counties with 30 or more tests for the same period.

Half the tests came in under 2.9 pCi/L and half over it; the single highest reached 101.2 pCi/L. Below the action level, 219 tests (36.3%) came in under 2 pCi/L, against 33.2% statewide, and 151 tests (25.0%) fell between 2 and 4, against 23.1% statewide.

Zone 2 on EPA's map (predicted average between 2 and 4 pCi/L) and a 38.7% share point the same way here. USGS geology rates 61% of the county's land moderate radon potential. CDC also counts 31 tests taken after mitigation in Madison County for the same period: tests in homes where a fix was already in.

CDC's ten-year totals for Madison County went from 381 tests (2005 to 2014) to 604 (2008 to 2017), the share going from 42.0% to 38.7%.

Madison County against Kentucky, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Madison County
Madison County60438.7%2.9 pCi/LThis county
Kentucky, pooled120 counties, pooled28,79343.7%Not pooled+5.0 points
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled−3.0 points
Meade Countyhighest in the state11768.4%8.2 pCi/L+29.7 points
Hopkins Countylowest in the state429.5%1.7 pCi/L−29.2 points
Jessamine County, KYborders it78955.5%4.7 pCi/L+16.8 points
Fayette County, KYborders it5,26354.5%4.5 pCi/L+15.8 points
Estill County, KYborders it17744.1%3.2 pCi/L+5.4 points
Rockcastle County, KYborders it1442.9%3.0 pCi/L+4.2 points
Garrard County, KYborders it16439.6%2.6 pCi/L+0.9 points
Clark County, KYborders it23129.0%2.4 pCi/L−9.7 points
Jackson County, KYborders it110.0%1.8 pCi/L−38.7 points
Where Madison County's reported results fell, 2008 to 2017, laboratory, beside Kentucky and the United States
ResultMadison County testsMadison County shareKentucky shareU.S. shareAgainst Kentucky
Under 2 pCi/L21936.3%33.2%39.6%+3.1 points
2 to 4 pCi/L15125.0%23.1%24.7%+1.9 points
4 pCi/L and above23438.7%43.7%35.7%−5.0 points
Madison County ranked among the 69 Kentucky counties with 30 or more tests, by share at or above 4 pCi/L, 2008 to 2017, laboratory
CountyRankTestsAt or above 4 pCi/LMedian
Adair County25 of 695343.4%3.8 pCi/L
Franklin County26 of 6981043.1%3.3 pCi/L
Boone County27 of 691,43442.9%3.5 pCi/L
Garrard County28 of 6916439.6%2.6 pCi/L
Jefferson County29 of 696,59039.4%2.7 pCi/L
Madison County30 of 6960438.7%2.9 pCi/L
Mercer County31 of 6928838.2%2.7 pCi/L
Shelby County32 of 6940737.6%3.0 pCi/L
Oldham County33 of 6980337.1%2.7 pCi/L
Henry County34 of 694136.6%3.2 pCi/L
Owen County35 of 695836.2%2.5 pCi/L
Madison County ten-year laboratory totals, against Kentucky's pooled share
PeriodTestsAt or above 4 pCi/LMedianHighestKentucky, pooledChange from the row before
2008 to 201760438.7%2.9 pCi/L101.2 pCi/L43.7%−0.7 points
2007 to 201651339.4%3.1 pCi/L101.2 pCi/L45.1%−1.4 points
2006 to 201545140.8%3.1 pCi/L101.2 pCi/L46.4%−1.2 points
2005 to 201438142.0%3.1 pCi/L101.2 pCi/L47.3%First on file

Pooled shares: Radon411's sum of CDC's county counts for one period.

Madison County, Geology

The ground under Madison County

Predicted

USGS's geologic map splits Madison County: 61.3% of its land is moderate radon potential and 38.7% high. The map puts 55.2% of Madison County in the area it calls Outer Bluegrass and 31.7% in New Albany-Chattanooga Shale, with 3 smaller areas beside them. USGS gives the first a radon index of 11, in the moderate band (9 to 11), and the second 14, in the high band (12 to 17).

USGS's geologic areas under Madison County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Outer BluegrassOrdovician-Devonian limestone and shale.Moderate1155.2%
New Albany-Chattanooga ShaleDevonian/Mississippian Black shale.High1431.7%
Mississippian PlateauMississippian marine limestones, dolomites, marine sandstones, siltstones, and shales.Moderate116.1%
Inner BluegrassOrdovician limestones, dolomites and shales.High134.7%
Eastern PennyroyalMarine shale, sandstone and limestone.High122.4%

Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.

Madison County beside the ground around it

Madison County has more high-potential ground than Kentucky as a whole: 38.7% of its land against 18.2%. Of the 7 counties that border it, 4 have more high-potential ground, Jessamine County the most at 100%.

Share of land by USGS radon potential: Madison County, the 7 counties bordering it and Kentucky
AreaEPA zoneLow potentialModerate potentialHigh potential
Madison CountyZone 2None61.3%38.7%
Garrard CountyZone 2None50.3%49.7%
Estill CountyZone 2None57.3%42.7%
Jessamine CountyZone 1NoneNone100%
Clark CountyZone 1None73.0%27.0%
Rockcastle CountyZone 2None85.7%14.3%
Fayette CountyZone 1None23.2%76.8%
Jackson CountyZone 2None100%None
Kentucky120 counties, pooled by land areaVaries5.7%76.1%18.2%

The map rates the ground, not the air in any home.

Local help

Madison County, Local resources

Radon testing and mitigation in Madison County

What Kentucky's program says
Phone
502-782-2782
Email
Radon@ky.gov

What it means

Madison County, Questions

Questions about radon in Madison County

Are radon levels high in Madison County?

Over the 2008 to 2017 laboratory totals, 38.7% of the radon tests reported to CDC for Madison County, Kentucky were at or above 4 pCi/L, and the median reported pre-mitigation result was 2.9 pCi/L. Of 69 Kentucky counties with 30 or more tests for the same period, 29 reported a higher share; pooled, the state comes to 43.7%.

Which counties border Madison County?

Madison County borders 7 counties: Garrard County, Estill County, Jessamine County, Clark County, Rockcastle County, Fayette County and Jackson County.

Products

Madison County, Products

Testing a home in Madison County

In Madison County, 38.7% of 604 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 43.7% pooled across Kentucky. In Zone 2 a short-term kit (2 to 90 days) is the quick first check in Madison County; a long-term test tells the year-round average.

Test kits and monitors3

See every kit and monitor

Best radon monitors for Madison County homes, compared

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Madison County, Bordering counties

Counties bordering Madison County

Calculated by Radon411

Madison County, Cities and towns

Cities and towns in Madison County

Madison County is growing: the Census Bureau puts it at 101,696 residents on July 1, 2025, up 9.3% from 93,002 in 2020. That works out to 233 people per square mile of land. Its largest town, Richmond, has 40,663 residents, 40.0% of the total. Together its 2 incorporated places hold 56.4% of those residents; the other 43.6% live outside any of them. CDC's 604 reported tests for 2008 to 2017 work out to 5.9 per 1,000 residents (2025 estimate), close to Kentucky's 6.3.

From Richmond to Berea, CDC publishes no figure by town: each reads Madison County's.

The cities and towns in Madison County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Richmond40,663+15.1%40.0%
Berea16,662+6.9%16.4%

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).

Madison County, Homes

Homes in Madison County

Of Madison County's 39,920 homes, 63% are detached houses, against 68% across Kentucky; 15% are in buildings of five or more homes. Much of Madison County is recent building: 37% of its homes have gone up since 2000 and the middle year built is 1993, against 1982 for Kentucky. 62% of occupied homes are lived in by their owner (Kentucky: 68%); in the rest a tenant can run a test, but a fix is the landlord's to make.

Homes in Madison County, Kentucky, 2019 to 2023
HomesMadison CountyKentucky
Housing units39,9202,010,655
Detached houses63%68%
In buildings of 5 or more15%12%
Mobile homes7%11%
Built before 196010%22%
Built since 200037%24%
Middle year built19931982
Owner-occupied62%68%

Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.