Short-term kitempowerDX
Standard Radon Test short-term mail-in radon test kit
- Lab fee included
Method: Passive sampler
In home: 48 to 96 hours
Locations and reports
Radon Levels in Johnston County, Oklahoma
EPA puts Johnston County in Zone 3, its lowest radon zone. Homes with elevated levels occur in all three zones, so only a test measures yours.
Data checked By Radon411Methodology
Nearest county
8.9%
Oklahoma County, 95 miles
- Oklahoma
- 8.9%
- Oklahoma
- 12.6%
Share at 4+ pCi/L, 135 tests, 2006 to 2015
Ground above low
None
15.2 pts below Oklahoma
- Johnston
- 0.0%
- Oklahoma
- 15.2%
Share of land USGS rates moderate or high potential
Tests reported
0
None published
A home here needs its own test
EPA radon zone
Zone 3
Lower potential
- 1
- 2
- Zone 3
1 highest, 3 lowest
EPA predicts under 2 pCi/L indoors
Read a result for Johnston 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
Johnston County, At a glance
Johnston County at a glance
Predicted: EPA radon zone
EPA Zone 3: lower predicted potential
USGS geologic potential: Low across 100% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
No CDC test figures here
CDC has published no radon test figures for Johnston County. Oklahoma County, 95 miles away, is the nearest county with a figure over the 2006 to 2015 laboratory totals.
Johnston County, Compared
Johnston County radon figures, compared
Calculated by Radon411CDC's county radon counts over the 2006 to 2015 laboratory totals cover 53 Oklahoma counties, and Johnston County is not among them: no year's figure and no ten-year laboratory total names it. Pooled across 53 Oklahoma counties, 12.6% of reported tests reached that level; across every county in the country with a figure, 36.3%.
The nearest counties with a figure are Oklahoma County (95 miles away) at 8.9%, Tulsa County (131 miles away) at 6.0% and Cherokee County (144 miles away) at 32.0%. Statewide for the same period, Delaware County reported the highest share (44.7%) and Tulsa County the lowest (6.0%).
EPA's 1993 map puts Johnston County in Zone 3, its lowest label: a predicted county average under 2 pCi/L. USGS geology rates 100% of the county's land low radon potential.
Pooled shares: Radon411's sum of CDC's county counts for one period.
Johnston County, Geology
The ground under Johnston County
PredictedUSGS's geologic map puts all of Johnston County's mapped land in one class: low radon potential. The map puts 65.4% of Johnston County in the area it calls Central Oklahoma Plains and Hills and 30.6% in Gulf Coast Plain, with one smaller area beside them. USGS gives the first a radon index of 7 and the second 8, both in the low band (5 to 8).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Central Oklahoma Plains and Hills | Nonmarine Permian and Tertiary rocks, including shale, sandstone, and conglomerate in the western part, and Mississippian and Pennsylvanian rocks in the eastern part. | Low | 7 | 65.4% |
| Gulf Coast Plain | Cretaceous shale, nonmarine sand and clay and marine limestone and clay. | Low | 8 | 30.6% |
| Ouachita Mountains | Mississippian and Pennsylvanian limestone, sandstone, siltstone, shale, conglomerate. | Low | 8 | 4.0% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Johnston County beside the ground around it
Across Oklahoma 0.6% of the land is rated high; none of Johnston County's is. Of the 7 counties that border it, 1 has more moderate-potential ground, Bryan County the most at 54.3%.
The map rates the ground, not the air in any home.
Local help
Johnston County, Local resources
Radon testing and mitigation in Johnston County
- Oklahoma's radon programDepartment of Environmental QualityOklahoma's radon program answers questions about testing, mitigation and the rules in Oklahoma.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
- See the Oklahoma directoryNo professionals are listed in Oklahoma yet. The state program can point you to registered testers and mitigators.
What it means
Johnston County, Questions
Questions about radon in Johnston County
Are radon levels high in Johnston County?
No CDC testing statistics are published here for Johnston County, Oklahoma yet. Of the 5 nearest counties with a figure, within 178 miles, the share of tests at or above 4 pCi/L runs from 6.0% to 44.7%.
Which counties border Johnston County?
Johnston County borders 7 counties: Marshall County, Murray County, Coal County, Pontotoc County, Bryan County, Carter County and Atoka County.
Products
Johnston County, Products
Testing a home in Johnston County
No CDC figure names Johnston County; the nearest county with one, Oklahoma County (95 miles away), reported 8.9% of its tests at or above 4 pCi/L over the 2006 to 2015 laboratory totals, the only reading nearby until a test of this home. Zone 3 is the lowest label, yet homes at or above 4 pCi/L occur in every zone: a short-term kit (2 to 90 days) is the quick first check in Johnston County.
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
EcoQube Wi-Fi continuous radon monitor
- C-NRPP 2024/25: Approved
- Plug-in
- Wi-Fi
- App only
Method: Ion chamber
First reading: Within 10 minutes
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Explore
Johnston County, Bordering counties
Counties bordering Johnston County
Calculated by Radon411- Radon levels in Carter CountyEPA zone 3
25.0%at or above 4 pCi/L
Median 1.5 pCi/L · 8 tests
- Radon levels in Pontotoc CountyEPA zone 3
0.0%at or above 4 pCi/L
Median 0.6 pCi/L · 3 tests
- Radon levels in Bryan CountyEPA zone 3
0.0%at or above 4 pCi/L
Median 0.6 pCi/L · 1 test
- Radon levels in Marshall CountyEPA zone 3
No CDC figure for 2006 to 2015; its page reads it against its own neighbours.
- Radon levels in Murray CountyEPA zone 3
No CDC figure for 2006 to 2015; its page reads it against its own neighbours.
- Radon levels in Coal CountyEPA zone 3
No CDC figure for 2006 to 2015; its page reads it against its own neighbours.
- Radon levels in Atoka CountyEPA zone 3
No CDC figure for 2006 to 2015; its page reads it against its own neighbours.
Johnston County, Cities and towns
Cities and towns in Johnston County
The Census Bureau estimates 10,448 residents in Johnston County for July 1, 2025, 206 more than in 2020 (+2.0%). That works out to 16 people per square mile of land. Its largest town, Tishomingo, has 3,123 residents, 29.9% of the total. CDC publishes no radon test count for Johnston County; across Oklahoma its counts for 2006 to 2015 come to 0.2 tests for every 1,000 residents (2025 estimate).
From Tishomingo to Bromide, CDC publishes no figure by town: each reads Johnston County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Tishomingo | 3,123 | +0.8% | 29.9% |
| Mannsville | 753 | +3.9% | 7.2% |
| Ravia | 472 | +1.9% | 4.5% |
| Wapanucka | 397 | +2.8% | 3.8% |
| Mill Creek | 296 | +1.7% | 2.8% |
| Milburn | 253 | +1.6% | 2.4% |
| Bromideextends beyond Johnston County | 121 | +1.7% | Counted whole |
7 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). A place that extends beyond Johnston County is counted whole, so it has no share.
Johnston County, Homes
Homes in Johnston County
Of Johnston County's 4,710 homes, 73% are detached houses, against 73% across Oklahoma; 19% are mobile homes. Half of its homes were built before 1983, close to Oklahoma's 1980: 19% date from before 1960 and 26% from 2000 or later. 70% of occupied homes are lived in by their owner (Oklahoma: 66%); in the rest a tenant can run a test, but a fix is the landlord's to make.
| Homes | Johnston County | Oklahoma |
|---|---|---|
| Housing units | 4,710 | 1,763,036 |
| Detached houses | 73% | 73% |
| In buildings of 5 or more | 2% | 12% |
| Mobile homes | 19% | 9% |
| Built before 1960 | 19% | 21% |
| Built since 2000 | 26% | 25% |
| Middle year built | 1983 | 1980 |
| Owner-occupied | 70% | 66% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.