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 Johnson County, Nebraska
EPA puts Johnson County in Zone 1, its highest radon zone, and only 18 radon tests from it are 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
65.3%
17.6 pts above NE
- Johnson
- 65.3%
- Nebraska
- 47.7%
216 tests, 2017
Median result
4.8pCi/L
Action level reached
- Johnson
- 4.8 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2017
Tests reported
216
40th of 74 by tests
- Johnson
- 216
- Douglas
- 18,306
Reported to CDC before any fix, 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 Nebraska
16 of 74
Top quarter
- Johnson
- 65.3%
- Webster
- 84.6%
By share, of 74 with 30+ tests
Read a result for Johnson County
Starts at Johnson County's median, 4.8 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 4.8 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. Johnson County's median reported result, 2017.
The data
Johnson County, At a glance
Johnson County at a glance
Predicted: EPA radon zone
EPA Zone 1: highest predicted potential
EPA puts all of Johnson County in
USGS geologic potential: High across 100% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for Johnson County, 2023
| Year | Share of reported tests at or above 4 pCi/L |
|---|---|
| 2014 | 37.5% |
| 2015 | 70.6% |
| 2016 | 56.7% |
| 2017 | 65.3% |
| 2018 | 72.7% |
| 2019 | 48.0% |
| 2020 | 53.6% |
| 2021 | 60.0% |
| 2022 | 57.1% |
| 2023 | 61.1% |
2023: 61.1%. Across these years the share ran from 37.5% to 72.7%. Each column counts radon tests reported to CDC that year, not homes.
What these figures count
Only 18 tests were reported to CDC for Johnson 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).
Johnson County, Compared
Johnson County radon figures, compared
Calculated by Radon411More than half: 65.3% of the 216 radon tests reported to CDC for Johnson County in 2017 read at least 4 pCi/L. That places it 16th of 74 Nebraska counties with 30 or more tests for the same period. That is 17.6 points above the 47.7% pooled from 92 Nebraska counties.
The newest figure, in 2023, counts only 18 tests (61.1% at or above 4 pCi/L), too few to compare, so this reading uses the 216-test figure.
The median result, 4.8 pCi/L, sits above EPA's 4 pCi/L action level, and the top reported result was 22.5 pCi/L. The rest split 18.1% under 2 pCi/L and 16.7% from 2 to 4 (Nebraska: 25.6% and 26.7%). Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 65.3% share point the same way here.
No bordering county with a figure for the same period reported a higher share; the closest is Nemaha County at 61.9%, the lowest Lancaster County at 44.5%. Statewide for the same period, Webster County reported the highest share (84.6%) and Cherry County the lowest (15.4%).
The busiest year on file was 2017, with 216 tests reported; the quietest, 2022, had 7.
Over 7 years of annual figures the share fell 10.6 points, from 70.6% in 2015 to 60.0% in 2021; its peak was 72.7% in 2018. Nationally, every county with a figure for the same period pools to 31.7%; Johnson County sits 33.6 points above it.
Johnson CountyNebraska, pooled
60.0% % of tests34.9% % of tests
| Year | Tests | Johnson County, at or above 4 pCi/L | Nebraska, pooled |
|---|---|---|---|
| 2015 | 51 | 70.6% | 53.3% |
| 2016 | 90 | 56.7% | 47.4% |
| 2017 | 216 | 65.3% | 47.7% |
| 2018 | 99 | 72.7% | 44.5% |
| 2019 | 75 | 48.0% | 44.3% |
| 2020 | 84 | 53.6% | 42.2% |
| 2021 | 45 | 60.0% | 34.9% |
Pooled shares: Radon411's sum of CDC's county counts for one period.
Johnson County, Geology
The ground under Johnson County
PredictedUSGS's geologic map puts all of Johnson County's mapped land in one class: high radon potential. All of it lies in the area the map calls Pre-Wisconsin glacial deposits, to which USGS gives a radon index of 13, in the high band (12 to 17).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Pre-Wisconsin glacial deposits | Loess-mantled glacial drift. | High | 13 | 100% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Johnson County beside the ground around it
Johnson County has more high-potential ground than Nebraska as a whole: 100% of its land against 40.9%. Of the 5 counties that border it, none has as large a share of high-potential ground; Gage County comes nearest at 100%.
The map rates the ground, not the air in any home.
Local help
Johnson County, Local resources
Radon testing and mitigation in Johnson County
- Office of Environmental Health Hazards & Indoor AirOffice of Environmental Health Hazards & Indoor Air, run by Nebraska Department of Health and Human Services, licenses or certifies radon professionals and offers free or discounted test kits, and answers questions about testing and mitigation in Nebraska.Visit the program’s page(opens in a new tab)
- Free and low-cost kitsThe program says:
Some local programs distribute radon kits for free or a reduced cost.
- Compare kits
- Professionals in Nebraska116 professionals are listed in Nebraska.
What Nebraska's program says
- Phone
- (402) 471-1005
- Licensing of radon professionals
If radon testing is done in schools, offices, or other places of work, it must be done by a licensed radon measurement business.
What it means
Johnson County, Questions
Questions about radon in Johnson County
Are radon levels high in Johnson County?
In 2023, 61.1% of the radon tests reported to CDC for Johnson County, Nebraska were at or above 4 pCi/L, and the median reported pre-mitigation result was 4.7 pCi/L. Of 74 Nebraska counties with 30 or more tests for the same period, 15 reported a higher share; pooled, the state comes to 47.7%.
Which counties border Johnson County?
Johnson County borders 5 counties: Pawnee County, Otoe County, Nemaha County, Gage County and Lancaster County.
Products
Johnson County, Products
Testing a home in Johnson County
In Johnson County, 65.3% of 216 tests reported to CDC in 2017 reached 4 pCi/L, against 47.7% pooled across Nebraska. In Zone 1 the year-round level in Johnson 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
Monitor
RadonEye RD200 plug-in continuous radon monitor
- C-NRPP 2024/25: Approved
- Plug-in
- Bluetooth
- Alarm
- Screen, app
Method: Ion chamber
First reading: Within 10 minutes
Short-term kit
Radon Short Term Test Kit short-term charcoal radon test kit, lab fee included
- Lab fee included
Method: Charcoal
In home: 2 to 7 days
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Johnson County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like Johnson County
Explore
Johnson County, Bordering counties
Counties bordering Johnson County
Calculated by Radon411- Radon levels in Nemaha CountyEPA zone 1
61.9%at or above 4 pCi/L
Median 7.5 pCi/L · 252 tests · 3.4 points below Johnson County
- Radon levels in Gage CountyEPA zone 1
57.3%at or above 4 pCi/L
Median 5.0 pCi/L · 801 tests · 8.0 points below Johnson County
- Radon levels in Otoe CountyEPA zone 1
52.2%at or above 4 pCi/L
Median 4.5 pCi/L · 834 tests · 13.1 points below Johnson County
- Radon levels in Pawnee CountyEPA zone 1
46.9%at or above 4 pCi/L
Median 3.7 pCi/L · 96 tests · 18.4 points below Johnson County
- Radon levels in Lancaster CountyEPA zone 1
44.5%at or above 4 pCi/L
Median 3.5 pCi/L · 13,947 tests · 20.8 points below Johnson County
Johnson County, Cities and towns
Cities and towns in Johnson County
About 5,218 people live in Johnson County by the Census Bureau's estimate for July 1, 2025, 74 fewer than in 2020 (−1.4%). That works out to 14 people per square mile of land. Its largest town, Tecumseh, has 1,695 residents, 32.5% of the total. Together its 5 incorporated places hold 49.9% of those residents; the other 50.1% live outside any of them. CDC's 216 reported tests for 2017 work out to 41.4 per 1,000 residents (2025 estimate), close to Nebraska's 32.5.
From Tecumseh to Crab Orchard, CDC publishes no figure by town: each reads Johnson County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Tecumseh | 1,695 | −1.6% | 32.5% |
| Sterling | 481 | −0.2% | 9.2% |
| Cook | 314 | −1.9% | 6.0% |
| Elk Creek | 67 | −1.5% | 1.3% |
| Crab Orchard | 45 | −2.2% | 0.9% |
5 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).
Johnson County, Homes
Homes in Johnson County
Johnson County is a place of houses on their own lots: 89% of its 2,090 homes are detached single-family houses, against 72% across Nebraska. The homes are older than Nebraska's as a whole: half were built before 1953 (1975 for Nebraska), and 57% date from before 1960. 68% of occupied homes are lived in by their owner (Nebraska: 67%); in the rest a tenant can run a test, but a fix is the landlord's to make.
| Homes | Johnson County | Nebraska |
|---|---|---|
| Housing units | 2,090 | 855,631 |
| Detached houses | 89% | 72% |
| In buildings of 5 or more | 5% | 17% |
| Mobile homes | 3% | 3% |
| Built before 1960 | 57% | 32% |
| Built since 2000 | 11% | 22% |
| Middle year built | 1953 | 1975 |
| Owner-occupied | 68% | 67% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.