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Radon Levels in Sullivan County, Tennessee

EPA puts Sullivan County in Zone 1, its highest radon zone, and only 27 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

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  • Share at 4+ pCi/L

    51.5%

    18.2 pts above TN

    Sullivan
    51.5%
    Tennessee
    33.3%

    1,799 tests, 2008 to 2017

  • Median result

    4.2pCi/L

    Action level reached

    Sullivan
    4.2 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    1,799

    4th of 80 by tests

    Sullivan
    1,799
    Davidson
    5,592

    Reported to CDC before any fix, 2008 to 2017

  • EPA radon zone

    Zone 1

    Highest potential

    1. Zone 1
    2. 2
    3. 3

    1 highest, 3 lowest

    EPA predicts over 4 pCi/L indoors

  • Rank in Tennessee

    5 of 80

    Top quarter

    Sullivan
    51.5%
    Jefferson
    56.8%

    By share, of 80 with 30+ tests

Read a result for Sullivan County

Starts at Sullivan County's median, 4.2 pCi/L

4.2pCi/L

EPA’s own thresholds; the figures are the area’s, never this home’s.

EPA’s reading of 4.2 pCi/L

At or above 4 pCi/L

  1. Under 20 to 1.9 pCi/L
  2. 2 to 4consider a fix
  3. 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. Sullivan County's median reported result, 2008 to 2017.

Interpret this readingWhat a fix costs

The data

Sullivan County, At a glance

Sullivan County at a glance

Predicted: EPA radon zone

EPA Zone 1: highest predicted potential

EPA puts all of Sullivan County in and predicts an average indoor of greater than 4 pCi/L (greater than 150 Bq/m³) across the county. That is one forecast for the whole county, not a reading of any address in it; homes above EPA's turn up in all three zones.

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 Sullivan County, 2023

Share of reported tests at or above 4 pCi/L, by year, Sullivan County
Share of reported tests at or above 4 pCi/L, by year, Sullivan County
YearShare of reported tests at or above 4 pCi/L
202226.9%
202337.0%

2023: 37.0%. Across these years the share ran from 26.9% to 37.0%. Each column counts radon tests reported to CDC that year, not homes.

What these figures count

Only 27 tests were reported to CDC for Sullivan 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).

How to read these figures

Sullivan County, Compared

Sullivan County radon figures, compared

Calculated by Radon411

More than half: 51.5% of the 1,799 radon tests reported to CDC for Sullivan County over the 2008 to 2017 laboratory totals read at least 4 pCi/L. That places it 5th of 80 Tennessee counties with 30 or more tests for the same period. That is 18.2 points above the 33.3% pooled from 95 Tennessee counties.

The newest figure, in 2023, counts only 27 tests (37.0% at or above 4 pCi/L), too few to compare, so this reading uses the 1,799-test figure.

The median result, 4.2 pCi/L, sits above EPA's 4 pCi/L action level, and the top reported result was 104.3 pCi/L. The rest split 23.2% under 2 pCi/L and 25.3% from 2 to 4 (Tennessee: 42.4% and 24.3%). Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 51.5% share point the same way here.

1 of its 7 bordering counties with figures ran higher, led by Washington County, VA at 58.1%; Johnson County reported 34.4%. Statewide for the same period, Jefferson County reported the highest share (56.8%) and Chester County the lowest (0.0%).

The busiest year on file was 2022, with 156 tests reported; the quietest, 2023, had 27.

Nationally, every county with a figure for the same period pools to 35.7%; Sullivan County sits 15.8 points above it. CDC also counts 86 tests taken after mitigation in Sullivan County for the same period: tests in homes where a fix was already in.

Sullivan County against Tennessee, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Sullivan County
Sullivan County1,79951.5%4.2 pCi/LThis county
Tennessee, pooled95 counties, pooled31,06633.3%Not pooled−18.2 points
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled−15.8 points
Jefferson Countyhighest in the state14656.8%4.7 pCi/L+5.3 points
Chester Countylowest in the state440.0%1.1 pCi/L−51.5 points
Washington County, VAborders it38458.1%4.8 pCi/L+6.6 points
Bristol city, VAborders it11050.9%4.2 pCi/L−0.6 points
Scott County, VAborders it7550.7%4.0 pCi/L−0.8 points
Washington County, TNborders it1,59049.6%3.9 pCi/L−1.9 points
Carter County, TNborders it34547.2%3.7 pCi/L−4.3 points
Hawkins County, TNborders it28938.4%2.7 pCi/L−13.1 points
Johnson County, TNborders it15734.4%2.3 pCi/L−17.1 points
Where Sullivan County's reported results fell, 2008 to 2017, laboratory, beside Tennessee and the United States
ResultSullivan County testsSullivan County shareTennessee shareU.S. shareAgainst Tennessee
Under 2 pCi/L41823.2%42.4%39.6%−19.2 points
2 to 4 pCi/L45525.3%24.3%24.7%+1.0 points
4 pCi/L and above92651.5%33.3%35.7%+18.2 points
Sullivan County ranked among the 80 Tennessee counties with 30 or more tests, by share at or above 4 pCi/L, 2008 to 2017, laboratory
CountyRankTestsAt or above 4 pCi/LMedian
Jefferson County1 of 8014656.8%4.7 pCi/L
Loudon County2 of 8085954.5%4.4 pCi/L
Campbell County3 of 807153.5%4.5 pCi/L
Sevier County4 of 8032853.0%4.4 pCi/L
Sullivan County5 of 801,79951.5%4.2 pCi/L
Washington County6 of 801,59049.6%3.9 pCi/L
White County7 of 8014749.0%3.9 pCi/L
Anderson County8 of 8026948.3%3.8 pCi/L
Grainger County9 of 805648.2%3.8 pCi/L
Carter County10 of 8034547.2%3.7 pCi/L
Jackson County11 of 804946.9%3.9 pCi/L
Sullivan County radon tests by year, against Tennessee's pooled share
YearTestsAt or above 4 pCi/LMedianHighestTennessee, pooledChange from the row before
20232737.0%2.6 pCi/L20.3 pCi/L24.9%+10.1 points
202215626.9%2.5 pCi/L18.5 pCi/L23.8%First on file

Pooled shares: Radon411's sum of CDC's county counts for one period.

Sullivan County, Geology

The ground under Sullivan County

Predicted

USGS's geologic map puts all of Sullivan 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).

USGS's geologic areas under Sullivan County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Ridge and ValleyPaleozoic sandstone and cherty dolostone.High1499.9%

Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.

Sullivan County beside the ground around it

Sullivan County has more high-potential ground than Tennessee as a whole: 100% of its land against 47.2%. Of the 7 counties that border it, none has as large a share of high-potential ground; Bristol city, VA comes nearest at 100%.

Share of land by USGS radon potential: Sullivan County, the 7 counties bordering it and Tennessee
AreaEPA zoneLow potentialModerate potentialHigh potential
Sullivan CountyZone 1NoneNone100%
Bristol city, VAZone 1NoneNone100%
Carter CountyZone 2None39.5%60.5%
Washington CountyZone 1NoneNone100%
Scott County, VAZone 1None5.9%94.1%
Washington County, VAZone 1None1.4%98.6%
Johnson CountyZone 2None14.9%85.1%
Hawkins CountyZone 1NoneNone100%
Tennessee95 counties, pooled by land areaVaries30.5%22.3%47.2%

The map rates the ground, not the air in any home.

Local help

Sullivan County, Local resources

Radon testing and mitigation in Sullivan County

What Tennessee's program says
Phone
1-800-232-1139
Email
TDEC.Radon@tn.gov

What it means

Sullivan County, Questions

Questions about radon in Sullivan County

Are radon levels high in Sullivan County?

In 2023, 37.0% of the radon tests reported to CDC for Sullivan County, Tennessee were at or above 4 pCi/L, and the median reported pre-mitigation result was 2.6 pCi/L. Of 80 Tennessee counties with 30 or more tests for the same period, 4 reported a higher share; pooled, the state comes to 33.3%.

Which counties border Sullivan County?

Sullivan County borders 7 counties: Bristol city, VA, Carter County, TN, Washington County, TN, Scott County, VA, Washington County, VA, Johnson County, TN and Hawkins County, TN.

Products

Sullivan County, Products

Testing a home in Sullivan County

In Sullivan County, 51.5% of 1,799 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 33.3% pooled across Tennessee. In Zone 1 the year-round level in Sullivan 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

Sullivan County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like Sullivan County

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Sullivan County, Bordering counties

Counties bordering Sullivan County

Calculated by Radon411

Sullivan County, Cities and towns

Cities and towns in Sullivan County

The Census Bureau estimates 163,759 residents in Sullivan County for July 1, 2025, 5,521 more than in 2020 (+3.5%). That works out to 396 people per square mile of land. Johnson City, the largest place on its list (74,943 residents in all), extends beyond Sullivan County, so no share of the total is worked out for it. Testing is reported here more often than across the state: CDC's 1,799 reported tests for 2008 to 2017 come to 11.0 for every 1,000 residents (2025 estimate), against 4.2 for Tennessee.

From Johnson City to Bluff City, CDC publishes no figure by town: each reads Sullivan County's.

The cities and towns in Sullivan County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Johnson Cityextends beyond Sullivan County74,943+5.4%Counted whole
Kingsportextends beyond Sullivan County57,530+3.6%Counted whole
Bristol28,107+3.5%17.2%
Bluff City1,836+1.2%1.1%

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). A place that extends beyond Sullivan County is counted whole, so it has no share.

Sullivan County, Homes

Homes in Sullivan County

Of Sullivan County's 75,917 homes, 70% are detached houses, against 68% across Tennessee; 11% are mobile homes. The homes are older than Tennessee's as a whole: half were built before 1976 (1986 for Tennessee), and 28% date from before 1960. 73% 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 in Sullivan County, Tennessee, 2019 to 2023
HomesSullivan CountyTennessee
Housing units75,9173,095,472
Detached houses70%68%
In buildings of 5 or more10%14%
Mobile homes11%8%
Built before 196028%18%
Built since 200018%29%
Middle year built19761986
Owner-occupied73%67%

Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.