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 Washington County, Tennessee
EPA puts Washington County in Zone 1, its highest radon zone, and 26.1% of its 46 reported radon tests (2023) 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
Share at 4+ pCi/L
26.1%
1.2 pts above TN
- Washington
- 26.1%
- Tennessee
- 24.9%
46 tests, 2023
Median result
2.3pCi/L
Below action level
- Washington
- 2.3 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2023
Tests reported
46
12th of 15 by tests
- Washington
- 46
- Hamblen
- 594
Reported to CDC before any fix, 2023
EPA radon zone
Zone 1
Highest potential
- Zone 1
- 2
- 3
1 highest, 3 lowest
EPA predicts over 4 pCi/L indoors
Rank in Tennessee
5 of 15
Middle half
- Washington
- 26.1%
- Blount
- 50.0%
By share, of 15 with 30+ tests
Read a result for Washington County
Starts at Washington County's median, 2.3 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 2.3 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. Washington County's median reported result, 2023.
The data
Washington County, At a glance
Washington County at a glance
Predicted: EPA radon zone
EPA Zone 1: highest predicted potential
EPA puts all of Washington 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 Washington County, 2023
| Year | Share of reported tests at or above 4 pCi/L |
|---|---|
| 2022 | 36.1% |
| 2023 | 26.1% |
2023: 26.1%. Across these years the share ran from 26.1% to 36.1%. Each column counts radon tests reported to CDC that year, not homes.
What these figures count
These are the 46 tests reported to CDC for Washington County over 2023, 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: 2023. Measured data period: 2005 to 2023 (every CDC figure on file).
Washington County, Compared
Washington County radon figures, compared
Calculated by Radon411Washington County's 46 reported tests in 2023 had a middle value of 2.3 pCi/L and a maximum of 27.4 pCi/L, and 26.1% reached 4 pCi/L. Tennessee as a whole (70 Tennessee counties, pooled) comes to 24.9%: 1.2 points lower than here.
Among its state's counties it ranks 5th of 15 Tennessee counties with 30 or more tests for the same period. Statewide for the same period, Blount County reported the highest share (50.0%) and Hamilton County the lowest (2.4%).
Below the action level, 15 tests (32.6%) came in under 2 pCi/L, against 49.4% statewide, and 19 tests (41.3%) fell between 2 and 4, against 25.7% statewide. The busiest year on file was 2022, with 249 tests reported; the quietest, 2023, had 46.
EPA's 1993 zone map puts Washington County in Zone 1, a predicted county average above 4 pCi/L. USGS geology rates 100% of the county's land high radon potential.
CDC also counts 24 tests taken after mitigation in Washington County for the same period: tests in homes where a fix was already in.
Pooled shares: Radon411's sum of CDC's county counts for one period.
Washington County, Geology
The ground under Washington County
PredictedUSGS's geologic map puts all of Washington County's mapped land in one class: high radon potential. All of it lies in the area the map calls Ridge and Valley, to which USGS gives a radon index of 14, in the high band (12 to 17).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Ridge and Valley | Paleozoic sandstone and cherty dolostone. | High | 14 | 100% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Washington County beside the ground around it
Washington County has more high-potential ground than Tennessee as a whole: 100% of its land against 47.2%. Of the 5 counties that border it, none has as large a share of high-potential ground; Hawkins County comes nearest at 100%.
The map rates the ground, not the air in any home.
Local help
Washington County, Local resources
Radon testing and mitigation in Washington County
- Tennessee Radon ProgramTennessee Radon Program, run by Department of Environment & Conservation, offers free or discounted test kits, and answers questions about testing and mitigation in Tennessee.Visit the program’s page(opens in a new tab)
- Free and low-cost kitsThe program says:
The Tennessee Radon Program provides free radon test kits and information assistance to residents, while also providing training opportunities to radon professionals across the state.
- Compare kits
- Professionals in Tennessee1 professional is listed in Tennessee.
What Tennessee's program says
- Phone
- 1-800-232-1139
- TDEC.Radon@tn.gov
What it means
Washington County, Questions
Questions about radon in Washington County
Are radon levels high in Washington County?
In 2023, 26.1% of the radon tests reported to CDC for Washington County, Tennessee were at or above 4 pCi/L, and the median reported pre-mitigation result was 2.3 pCi/L. Of 15 Tennessee counties with 30 or more tests for the same period, 4 reported a higher share; pooled, the state comes to 24.9%.
Which counties border Washington County?
Washington County borders 5 counties: Unicoi County, Sullivan County, Carter County, Greene County and Hawkins County.
Products
Washington County, Products
Testing a home in Washington County
In Washington County, 26.1% of 46 tests reported to CDC in 2023 reached 4 pCi/L, against 24.9% pooled across Tennessee. In Zone 1 the year-round level in Washington 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
RadonScan-Plus USB-powered radon monitor with Wi-Fi
- C-NRPP 2024/25: Not included
- Plug-in
- Wi-Fi
- Alarm
- Screen, app
First reading: Within 5 minutes
Short-term kit
RA100 short-term liquid scintillation radon test kit
- Lab fee extra
Method: Liquid scintillation
In home: 48 to 96 hours
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Washington County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like Washington County
Explore
Washington County, Bordering counties
Counties bordering Washington County
Calculated by Radon411- Radon levels in Unicoi CountyEPA zone 2
50.0%at or above 4 pCi/L
Median 3.9 pCi/L · 2 tests · 23.9 points above Washington County
- Radon levels in Greene CountyEPA zone 1
47.1%at or above 4 pCi/L
Median 2.9 pCi/L · 17 tests · 21.0 points above Washington County
- Radon levels in Sullivan CountyEPA zone 1
37.0%at or above 4 pCi/L
Median 2.6 pCi/L · 27 tests · 10.9 points above Washington County
- Radon levels in Hawkins CountyEPA zone 1
33.3%at or above 4 pCi/L
Median 3.8 pCi/L · 3 tests · 7.2 points above Washington County
- Radon levels in Carter CountyEPA zone 2
0.0%at or above 4 pCi/L
Median 1.2 pCi/L · 9 tests · 26.1 points below Washington County
Washington County, Cities and towns
Cities and towns in Washington County
Washington County is growing: the Census Bureau puts it at 141,199 residents on July 1, 2025, up 6.0% from 133,211 in 2020. That works out to 432 people per square mile of land. Johnson City, the largest place on its list (74,943 residents in all), extends beyond Washington County, so no share of the total is worked out for it. CDC's 46 reported tests for 2023 work out to 0.3 per 1,000 residents (2025 estimate), close to Tennessee's 0.3.
From Johnson City to Watauga, CDC publishes no figure by town: each reads Washington County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Johnson Cityextends beyond Washington County | 74,943 | +5.4% | Counted whole |
| Jonesborough | 6,990 | +18.3% | 5.0% |
| Wataugaextends beyond Washington County | 364 | +3.4% | Counted whole |
Places in Washington County with a city page: 1 of 1
3 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 Washington County is counted whole, so it has no share.
Washington County, Homes
Homes in Washington County
Of Washington County's 61,426 homes, 65% are detached houses, against 68% across Tennessee; 15% are in buildings of five or more homes. Half of its homes were built before 1986, close to Tennessee's 1986: 20% date from before 1960 and 28% from 2000 or later. 64% of occupied homes are lived in by their owner (Tennessee: 67%); in the rest a tenant can run a test, but a fix is the landlord's to make.
| Homes | Washington County | Tennessee |
|---|---|---|
| Housing units | 61,426 | 3,095,472 |
| Detached houses | 65% | 68% |
| In buildings of 5 or more | 15% | 14% |
| Mobile homes | 9% | 8% |
| Built before 1960 | 20% | 18% |
| Built since 2000 | 28% | 29% |
| Middle year built | 1986 | 1986 |
| Owner-occupied | 64% | 67% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.