Short-term kit
RA400 short-term liquid scintillation radon test kit, lab fee included
- Lab fee included
Method: Liquid scintillation
In home: 48 to 96 hours
Locations and reports
Radon Levels in Lewis County, Missouri
EPA puts Lewis County in Zone 2, its middle radon zone, and only 1 radon test from it is on file with CDC (2023). Homes with elevated levels occur in all three zones, so only a test measures yours.
Data checked By Radon411Methodology
Share at 4+ pCi/L
32.4%
1.8 pts above MO
- Lewis
- 32.4%
- Missouri
- 30.6%
71 tests, 2008 to 2017
Median result
2.6pCi/L
Below action level
- Lewis
- 2.6 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2008 to 2017
Tests reported
71
47th of 72 by tests
- Lewis
- 71
- St. Louis
- 17,747
Reported to CDC before any fix, 2008 to 2017
EPA radon zone
Zone 2
Moderate potential
- 1
- Zone 2
- 3
1 highest, 3 lowest
EPA predicts 2 to 4 pCi/L indoors
Rank in Missouri
33 of 72
Middle half
- Lewis
- 32.4%
- Atchison
- 69.9%
By share, of 72 with 30+ tests
Read a result for Lewis County
Starts at Lewis County's median, 2.6 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 2.6 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. Lewis County's median reported result, 2008 to 2017.
The data
Lewis County, At a glance
Lewis County at a glance
Predicted: EPA radon zone
EPA Zone 2: moderate predicted potential
Lewis County is a
USGS geologic potential: Moderate across 91% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for Lewis County, 2023
| Year | Share of reported tests at or above 4 pCi/L |
|---|---|
| 2014 | 100.0% |
| 2015 | 25.0% |
| 2016 | 0.0% |
| 2017 | 25.0% |
| 2018 | 0.0% |
| 2021 | 0.0% |
| 2022 | 0.0% |
| 2023 | 0.0% |
2023: 0.0%. Across these years the share ran from 0.0% to 100.0%. Each column counts radon tests reported to CDC that year, not homes.
What these figures count
Only 1 test was reported to CDC for Lewis County over 2023, 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: 2023. Measured data period: 2005 to 2023 (every CDC figure on file).
Lewis County, Compared
Lewis County radon figures, compared
Calculated by Radon411In Lewis County, about 3 in 10 reported tests over the 2008 to 2017 laboratory totals (23 of 71) were at or above EPA's action level. Against the national pool of 35.7%, the gap is 3.3 points lower. Across 115 Missouri counties pooled together, 30.6% of tests reached that level, so Lewis County runs 1.8 points above its state.
The newest figure, in 2023, counts only 1 test (0.0% at or above 4 pCi/L), too few to compare, so this reading uses the 71-test figure.
Of 3 neighbours with a figure, all 3 reported a larger share at or above 4 pCi/L; the spread is 41.8% (Marion County) to 55.2% (Adams County, IL). By share, Lewis County is 33rd of 72 Missouri counties with 30 or more tests for the same period.
Half the tests came in under 2.6 pCi/L and half over it; the single highest reached 16.9 pCi/L. Below the action level, 32 tests (45.1%) came in under 2 pCi/L, against 41.2% statewide, and 16 tests (22.5%) fell between 2 and 4, against 28.1% statewide.
Zone 2 on EPA's map (predicted average between 2 and 4 pCi/L) and a 32.4% share point the same way here. USGS geology rates 91% of the county's land moderate radon potential.
The busiest year on file was 2015, with 4 tests reported; the quietest, 2023, had 1.
Pooled shares: Radon411's sum of CDC's county counts for one period.
Lewis County, Geology
The ground under Lewis County
PredictedMost of the ground under Lewis County is one class on USGS's geologic map: 90.9% of its land is moderate radon potential, with 9.1% high. The map puts 90.9% of Lewis County in the area it calls Dissected Till Plains and 9.1% in Galesburg Plain. USGS gives the first a radon index of 11, in the moderate band (9 to 11), and the second 13, in the high band (12 to 17).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Dissected Till Plains | Till-covered Pennsylvanian sandstone, shale, and limestone. | Moderate | 11 | 90.9% |
| Galesburg Plain | Illinoian glacial deposits and loess over Paleozoic sedimentary rocks. | High | 13 | 9.1% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Lewis County beside the ground around it
On high-potential ground Lewis County is close to Missouri as a whole: 9.1% of its land against 8.2%. Of the 6 counties that border it, 2 have more high-potential ground, Hancock County, IL the most at 100%.
The map rates the ground, not the air in any home.
Local help
Lewis County, Local resources
Radon testing and mitigation in Lewis 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
Lewis County, Questions
Questions about radon in Lewis County
Are radon levels high in Lewis County?
In 2023, 0.0% of the radon tests reported to CDC for Lewis County, Missouri were at or above 4 pCi/L, and the median reported pre-mitigation result was 3.7 pCi/L. Of 72 Missouri counties with 30 or more tests for the same period, 32 reported a higher share; pooled, the state comes to 30.6%.
Which counties border Lewis County?
Lewis County borders 6 counties: Knox County, MO, Clark County, MO, Marion County, MO, Shelby County, MO, Adams County, IL and Hancock County, IL.
Products
Lewis County, Products
Testing a home in Lewis County
In Lewis County, 32.4% of 71 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 30.6% pooled across Missouri. In Zone 2 a short-term kit (2 to 90 days) is the quick first check in Lewis County; a long-term test tells the year-round average.
Test kits and monitors3
See every kit and monitor
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
Monitor
Wave Radon battery smart radon monitor
- C-NRPP 2024/25: Not included
- Battery
- Bluetooth
- App only
Method: Alpha spectrometry
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Explore
Lewis County, Bordering counties
Counties bordering Lewis County
Calculated by Radon411- Radon levels in Adams County, ILEPA zone 1
55.2%at or above 4 pCi/L
Median 4.5 pCi/L · 3,677 tests · 22.8 points above Lewis County
- Radon levels in Hancock County, ILEPA zone 1
43.5%at or above 4 pCi/L
Median 3.5 pCi/L · 177 tests · 11.1 points above Lewis County
- Radon levels in Marion County, MOEPA zone 2
41.8%at or above 4 pCi/L
Median 3.2 pCi/L · 282 tests · 9.4 points above Lewis County
- Radon levels in Clark County, MOEPA zone 2
29.4%at or above 4 pCi/L
Median 2.2 pCi/L · 17 tests · 3.0 points below Lewis County
- Radon levels in Shelby County, MOEPA zone 2
24.1%at or above 4 pCi/L
Median 1.7 pCi/L · 29 tests · 8.3 points below Lewis County
- Radon levels in Knox County, MOEPA zone 2
0.0%at or above 4 pCi/L
Median 1.9 pCi/L · 10 tests · 32.4 points below Lewis County
Lewis County, Cities and towns
Cities and towns in Lewis County
About 9,879 people live in Lewis County by the Census Bureau's estimate for July 1, 2025, 163 fewer than in 2020 (−1.6%). That works out to 20 people per square mile of land. Its largest town, Canton, has 2,763 residents, 28.0% of the total. Together its 6 incorporated places hold 53.0% of those residents; the other 47.0% live outside any of them. CDC's 71 reported tests for 2008 to 2017 work out to 7.2 per 1,000 residents (2025 estimate), close to Missouri's 9.3.
From Canton to Monticello, CDC publishes no figure by town: each reads Lewis County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Canton | 2,763 | −0.5% | 28.0% |
| La Grange | 806 | −2.2% | 8.2% |
| La Belle | 654 | −2.2% | 6.6% |
| Lewistown | 512 | −2.1% | 5.2% |
| Ewing | 394 | −1.7% | 4.0% |
| Monticello | 105 | −1.9% | 1.1% |
6 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).
Lewis County, Homes
Homes in Lewis County
Of Lewis County's 4,315 homes, 75% are detached houses, against 70% across Missouri; 10% are mobile homes. The homes are older than Missouri's as a whole: half were built before 1968 (1978 for Missouri), and 34% date from before 1960. Owners live in 77% of the occupied homes (Missouri: 68%), so for most households a test and a fix are their own to order.
| Homes | Lewis County | Missouri |
|---|---|---|
| Housing units | 4,315 | 2,809,501 |
| Detached houses | 75% | 70% |
| In buildings of 5 or more | 4% | 13% |
| Mobile homes | 10% | 5% |
| Built before 1960 | 34% | 28% |
| Built since 2000 | 14% | 21% |
| Middle year built | 1968 | 1978 |
| 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.