Short-term kitFirst Alert
RD1 short-term charcoal radon test kit
- Lab fee included
Method: Charcoal
In home: 2 to 4 days
Locations and reports
Radon Levels in Madison County, Missouri
EPA puts Madison County in Zone 2, its middle radon zone, and only 1 radon test from it is on file with CDC (2020). Homes with elevated levels occur in all three zones, so only a test measures yours.
Data checked By Radon411Methodology
Highest bordering
41.1%
St. Francois County
- St. Francois
- 41.1%
- Perry
- 37.8%
2 of 5 neighbours have 30+ tests, 2008 to 2017
Nearest county
41.1%
St. Francois County, 24 miles
- St. Francois
- 41.1%
- Missouri
- 30.6%
Share at 4+ pCi/L, 146 tests, 2008 to 2017
Ground above low
100.0%
5.8 pts above Missouri
- Madison
- 100.0%
- Missouri
- 94.2%
Share of land USGS rates moderate or high potential
Tests reported
23
Too few for a share
- Madison
- 23
- Needed
- 30
2008 to 2017, laboratory
EPA radon zone
Zone 2
Moderate potential
- 1
- Zone 2
- 3
1 highest, 3 lowest
EPA predicts 2 to 4 pCi/L indoors
Read a result for Madison County
Starts at EPA's action level
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 4.0 pCi/L
At or above 4 pCi/L
- Under 20 to 1.9 pCi/L
- 2 to 4consider a fix
- 4 and aboveEPA says fix it
This result is at or above 4 pCi/L. EPA recommends fixing a home when the radon level is 4 pCi/L or higher.
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
USGS geologic potential: High across 68% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for Madison County, 2020
| Year | Share of reported tests at or above 4 pCi/L |
|---|---|
| 2014 | 50.0% |
| 2015 | 0.0% |
| 2017 | 0.0% |
| 2020 | 0.0% |
2020: 0.0%. Across these years the share ran from 0.0% to 50.0%. Each column counts radon tests reported to CDC that year, not homes.
What these figures count
Only 1 test was reported to CDC for Madison County over 2020, and tests are often run on homes being sold or already suspected of a problem: so few describe neither the county nor this house.
Measured: CDC tracking data. Figure above: 2020. Measured data period: 2005 to 2020 (every CDC figure on file).
Madison County, Compared
Madison County radon figures, compared
Calculated by Radon411CDC's largest figure for Madison County rests on 23 tests over the 2008 to 2017 laboratory totals, 9 of them at or above 4 pCi/L, so each test moves its share by 4.3 points and no rank or comparison is drawn from it. Results reached as high as 52.5 pCi/L, with a middle value of 3.5 pCi/L.
Of the counties bordering it, 2 have a figure over the 2008 to 2017 laboratory totals: St. Francois County reported the largest share at or above 4 pCi/L, 41.1%, and Perry County the smallest, 37.8%. Farther out, Ste. Genevieve County (30 miles away) at 31.1%, Cape Girardeau County (37 miles away) at 35.2% and Washington County (44 miles away) at 26.3% have figures too. Pooled across 115 Missouri counties, 30.6% of reported tests reached that level; across every county in the country with a figure, 35.7%.
Statewide for the same period, Atchison County reported the highest share (69.9%) and Vernon County the lowest (8.8%). EPA's 1993 map puts Madison County in Zone 2, its middle label: a predicted county average between 2 and 4 pCi/L. USGS geology rates 68% of the county's land high radon potential.
Pooled shares: Radon411's sum of CDC's county counts for one period.
Madison County, Geology
The ground under Madison County
PredictedUSGS's geologic map splits Madison County: 68.2% of its land is high radon potential and 31.8% moderate. The map puts 68.2% of Madison County in the area it calls St. Francois Mountains and 31.8% in Salem Plateau. 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 |
|---|---|---|---|---|
| St. Francois Mountains | Granitic and volcanic rocks. Some soils have high uranium concentrations. | High | 13 | 68.2% |
| Salem Plateau | Ordovician dolomite, sandstone, limestone, and shale. | Moderate | 11 | 31.8% |
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 Missouri as a whole: 68.2% of its land against 8.2%. Of the 5 counties that border it, 1 has more high-potential ground, Iron County the most at 85.3%.
The map rates the ground, not the air in any home.
Local help
Madison County, Local resources
Radon testing and mitigation in Madison County
- Missouri Radon ProgramMissouri Radon Program, run by Missouri Department of Health and Senior Services, offers free or discounted test kits, and answers questions about testing and mitigation in Missouri.Visit the program’s page(opens in a new tab)
- Free and low-cost kitsThe program says:
Free radon test kits are available for Missouri residents (limit one per household).
- Compare kits
- Professionals in Missouri27 professionals are listed in Missouri.
What Missouri's program says
- Phone
- 573-751-6102
- radon@health.mo.gov
What it means
Madison County, Questions
Questions about radon in Madison County
Are radon levels high in Madison County?
In 2020, 0.0% of the radon tests reported to CDC for Madison County, Missouri were at or above 4 pCi/L, and the median reported pre-mitigation result was 2.4 pCi/L. Of the counties bordering it, 2 have a figure over the 2008 to 2017 laboratory totals: St. Francois County reported the largest share at or above 4 pCi/L, 41.1%, and Perry County the smallest, 37.8%.
Which counties border Madison County?
Madison County borders 5 counties: Iron County, Bollinger County, Wayne County, St. Francois County and Perry County.
Products
Madison County, Products
Testing a home in Madison County
No CDC figure names Madison County; the nearest county with one, St. Francois County (24 miles away), reported 41.1% of its tests at or above 4 pCi/L over the 2008 to 2017 laboratory totals, the only reading nearby until a test of this home. 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
Long-term kit
RL116 long-term radon test kit
- Lab fee extra
Method: Alpha track
In home: 90 days to 12 months
MonitorAEGTEST
HOUND-1011S rechargeable radon detector with a screen
- C-NRPP 2024/25: Not included
- Battery
- Alarm
- Screen
Method: Semiconductor sensor
First reading: Within 12 hours
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Explore
Madison County, Bordering counties
Counties bordering Madison County
Calculated by Radon411- Radon levels in Iron CountyEPA zone 1
50.0%at or above 4 pCi/L
Median 3.5 pCi/L · 14 tests
- Radon levels in St. Francois CountyEPA zone 2
41.1%at or above 4 pCi/L
Median 2.9 pCi/L · 146 tests
- Radon levels in Perry CountyEPA zone 2
37.8%at or above 4 pCi/L
Median 3.2 pCi/L · 82 tests
- Radon levels in Wayne CountyEPA zone 2
23.5%at or above 4 pCi/L
Median 1.9 pCi/L · 17 tests
- Radon levels in Bollinger CountyEPA zone 2
0.0%at or above 4 pCi/L
Median 1.4 pCi/L · 6 tests
Madison County, Cities and towns
Cities and towns in Madison County
The Census Bureau estimates 12,858 residents in Madison County for July 1, 2025, 235 more than in 2020 (+1.9%). That works out to 26 people per square mile of land. Its largest town, Fredericktown, has 4,584 residents, 35.7% of the total. Together its 4 incorporated places hold 41.4% of those residents; the other 58.6% live outside any of them. Reported testing is thin here: 23 tests over 2008 to 2017, or 1.8 for every 1,000 residents (2025 estimate), where Missouri as a whole comes to 9.3.
From Fredericktown to Marquand, CDC publishes no figure by town: each reads Madison County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Fredericktown | 4,584 | +3.4% | 35.7% |
| Junction City | 287 | +0.7% | 2.2% |
| Cobalt | 264 | +0.8% | 2.1% |
| Marquand | 190 | +1.1% | 1.5% |
4 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
Madison County is a place of houses on their own lots: 76% of its 5,853 homes are detached single-family houses, against 70% across Missouri. Half of its homes were built before 1977, close to Missouri's 1978: 30% date from before 1960 and 18% from 2000 or later. Owners live in 75% of the occupied homes (Missouri: 68%), so for most households a test and a fix are their own to order.
| Homes | Madison County | Missouri |
|---|---|---|
| Housing units | 5,853 | 2,809,501 |
| Detached houses | 76% | 70% |
| In buildings of 5 or more | 4% | 13% |
| Mobile homes | 13% | 5% |
| Built before 1960 | 30% | 28% |
| Built since 2000 | 18% | 21% |
| Middle year built | 1977 | 1978 |
| Owner-occupied | 75% | 68% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.