Every Tennessee county's actual test results, all 95 from state health data, set against the EPA's 1993 predictions. The short version: the rock under your ridge decides more than your zip code does, and East Tennessee drew the uranium-bearing rock.
Radon is a serious issue in Tennessee, and worst in East Tennessee: the EPA designates 38 of the state's 95 counties as Zone 1 (highest potential), and the heaviest concentration runs down the Ridge-and-Valley corridor from the Virginia line through Knoxville to Chattanooga. The test data backs the map and stays current: in CDC tracking data for 2023, Blount County averaged 6.7 pCi/L, the metro's current hot spot, while the state's 2020 compile put Sevier County, rated "moderate" Zone 2 in 1993, at the metro's highest long-run average (6.51). The EPA action level is 4.0 pCi/L. Tennessee mails free test kits to residents (about 6,000 a year), recommends retesting every two years, requires sellers to disclose known radon, yet licenses no one to fix it, which makes vetting your mitigator your job.
USGS mapped it in 1993; thirty years of homeowner tests have been grading their work since. East Tennessee's three physiographic provinces each tell a different story:
Every county, colored by average indoor radon. Hover or tap for the numbers. The east lights up because the rock does.
Counties with few tests swing hard. The table below carries test counts and stays the record. Sources: TDH 2020 compile · CDC EPHT through 2023.
Long-run averages from the state compile against the newest CDC year. Counties trending up in red, cooling in green. The reshuffle is the argument for testing on current data, not old reputations. Tennessee began CDC reporting in 2022, so the recent layer is young and worth watching.
Every county, sorted by long-run average. Readings in pCi/L; EPA action level 4.0. Zone = EPA 1993 designation (1 high / 2 moderate / 3 low). "Compile" columns are the state's 2020 dataset; "Recent" is CDC tracking data with the year in parentheses. Counties with few tests are honest anecdotes, not averages.
Zone census: 38 counties Zone 1 · 29 Zone 2 · 25 Zone 3. Sources: TDH state test data (through Oct 2020) · CDC EPHT county data (through 2023) · EPA Map of Radon Zones. Zip-level detail: the lookup.
| County | EPA Zone | Compile avg | Median | Max | Tests | Recent avg | CDC tests |
|---|---|---|---|---|---|---|---|
| Trousdale | 1 | 8.34 | 1.55 | 55.5 | 8 | 3.6 ('23) | 1 |
| Campbell | 3 | 7.99 | 3.5 | 36.9 | 18 | 3.8 ('23) | 23 |
| Claiborne | 1 | 7.24 | 1.8 | 40.3 | 28 | 5 ('23) | 19 |
| Decatur | 2 | 6.86 | 1.7 | 35.9 | 7 | n/a | n/a |
| Sullivan | 1 | 6.52 | 3.4 | 179.8 | 665 | 4 ('23) | 97 |
| Sevier | 2 | 6.51 | 3.7 | 113 | 150 | 4.6 ('23) | 82 |
| White | 2 | 6.15 | 3 | 36.6 | 45 | 3 ('23) | 13 |
| Overton | 2 | 5.64 | 3.1 | 48.9 | 32 | 13 ('23) | 8 |
| Hamblen | 1 | 5.62 | 3.1 | 31 | 54 | 3.8 ('23) | 72 |
| Loudon | 1 | 5.55 | 3.5 | 78.1 | 252 | 4.7 ('23) | 167 |
| Smith | 1 | 5.42 | 4.9 | 14.2 | 10 | 2.9 ('23) | 5 |
| Washington | 1 | 5.34 | 3.2 | 79.7 | 754 | 3.9 ('23) | 144 |
| Jefferson | 1 | 5.25 | 2.7 | 35.7 | 48 | 2.8 ('23) | 74 |
| Davidson | 1 | 5.12 | 2.8 | 121.5 | 1329 | 4 ('23) | 396 |
| Robertson | 2 | 5.12 | 2.45 | 43 | 62 | 1.3 ('23) | 15 |
| Marshall | 1 | 5.02 | 2.85 | 15.4 | 40 | 1.8 ('23) | 3 |
| Greene | 1 | 4.97 | 2.7 | 121.3 | 205 | 3.7 ('23) | 62 |
| Stewart | 2 | 4.97 | 2.35 | 28.4 | 14 | 2.7 ('23) | 1 |
| Carter | 2 | 4.79 | 2.5 | 45.7 | 202 | 1.3 ('23) | 18 |
| Blount | 1 | 4.78 | 2.6 | 90.3 | 160 | 6.7 ('23) | 142 |
| Anderson | 1 | 4.76 | 2.7 | 57.3 | 132 | 2.1 ('23) | 77 |
| Warren | 2 | 4.76 | 3.5 | 33.6 | 28 | 3.4 ('23) | 8 |
| Perry | 1 | 4.71 | 2.3 | 15.3 | 10 | n/a | n/a |
| Rhea | 3 | 4.7 | 1.5 | 41.6 | 20 | 4.2 ('23) | 8 |
| Lewis | 1 | 4.59 | 3.6 | 9.2 | 9 | n/a | n/a |
| Monroe | 1 | 4.53 | 3.2 | 15.3 | 53 | 2.4 ('23) | 50 |
| Macon | 2 | 4.48 | 1.6 | 16.9 | 16 | 4.1 ('23) | 3 |
| Roane | 1 | 4.43 | 2.3 | 45.4 | 131 | 2.8 ('23) | 53 |
| Johnson | 2 | 4.31 | 3.25 | 21.2 | 62 | 4.5 ('23) | 15 |
| Knox | 1 | 3.94 | 2.2 | 103.9 | 872 | 2.4 ('23) | 479 |
| Hawkins | 1 | 3.85 | 2.85 | 22 | 132 | 2.7 ('23) | 38 |
| Montgomery | 2 | 3.83 | 1.9 | 55.2 | 215 | 4.6 ('23) | 56 |
| Marion | 3 | 3.74 | 2.2 | 44.1 | 247 | 5.2 ('23) | 8 |
| Unicoi | 2 | 3.7 | 2.3 | 18 | 89 | 3.9 ('23) | 7 |
| Williamson | 1 | 3.57 | 2.1 | 48.9 | 739 | 2.2 ('23) | 161 |
| Hancock | 1 | 3.55 | 3.35 | 5.8 | 4 | n/a | n/a |
| Cheatham | 2 | 3.53 | 1.5 | 25.3 | 59 | 3.7 ('23) | 19 |
| Dickson | 2 | 3.5 | 2 | 38 | 70 | 5.1 ('23) | 13 |
| Polk | 2 | 3.5 | 1.65 | 15.7 | 8 | 3.1 ('23) | 11 |
| Hickman | 1 | 3.48 | 1.6 | 21.1 | 30 | 2.6 ('23) | 6 |
| Sumner | 2 | 3.47 | 2.1 | 42.1 | 330 | 2.4 ('23) | 68 |
| Meigs | 1 | 3.45 | 3.6 | 7.6 | 17 | 1.3 ('23) | 4 |
| Grainger | 1 | 3.37 | 2.05 | 9.5 | 14 | 11.7 ('23) | 9 |
| Lincoln | 1 | 3.2 | 2.1 | 17.9 | 49 | 3 ('23) | 5 |
| Bledsoe | 3 | 3.18 | 1.6 | 21.1 | 12 | 0.2 ('23) | 2 |
| Cocke | 2 | 3.18 | 2.4 | 11.3 | 25 | 2.7 ('23) | 25 |
| Fentress | 2 | 3.13 | 1.45 | 22.7 | 20 | 2.3 ('23) | 8 |
| Franklin | 3 | 3.11 | 1.8 | 22 | 35 | 2.6 ('23) | 15 |
| Giles | 1 | 3.08 | 2.2 | 14.7 | 33 | 4.3 ('23) | 7 |
| McMinn | 1 | 3.04 | 1.8 | 22.1 | 16 | 2.1 ('23) | 10 |
| Wilson | 1 | 3.03 | 1.8 | 27.1 | 259 | 1.4 ('23) | 50 |
| Putnam | 2 | 2.97 | 1.85 | 16.1 | 116 | 3.8 ('23) | 40 |
| Sequatchie | 3 | 2.92 | 2.1 | 11.4 | 25 | 0.8 ('23) | 6 |
| Henry | 3 | 2.88 | 1.7 | 13.8 | 30 | n/a | n/a |
| Pickett | n/a | 2.85 | 2.2 | 9.9 | 11 | n/a | 1 |
| Scott | 3 | 2.84 | 1.55 | 9.9 | 10 | 0.3 ('22) | 2 |
| Cannon | 2 | 2.72 | 2.2 | 7.4 | 13 | 1.3 ('23) | 5 |
| Rutherford | 1 | 2.72 | 1.65 | 24.1 | 342 | 2.5 ('23) | 90 |
| Hamilton | 2 | 2.69 | 1.5 | 72.7 | 482 | 1.4 ('23) | 133 |
| Weakley | 3 | 2.66 | 1.2 | 6.2 | 8 | n/a | n/a |
| Lawrence | 1 | 2.6 | 2 | 19.2 | 50 | 1.9 ('23) | 10 |
| Madison | 3 | 2.57 | 1.7 | 12.9 | 39 | 2 ('23) | 5 |
| Bradley | 1 | 2.51 | 1.85 | 15.6 | 94 | 4 ('23) | 27 |
| Gibson | 3 | 2.48 | 1.3 | 9.3 | 17 | 0.9 ('22) | 5 |
| Jackson | 1 | 2.47 | 1.8 | 5.2 | 10 | 3 ('23) | 5 |
| Bedford | 1 | 2.44 | 1.95 | 9 | 40 | 1.4 ('23) | 8 |
| Haywood | 3 | 2.4 | 2.4 | 2.4 | 1 | 1.1 ('22) | 1 |
| Coffee | 2 | 2.33 | 1.2 | 21.9 | 77 | 1.5 ('23) | 10 |
| Union | 1 | 2.31 | 1.6 | 8.9 | 8 | 3.4 ('23) | 10 |
| Humphreys | 1 | 2.26 | 1.7 | 12.4 | 36 | 1.4 ('23) | 5 |
| Carroll | 3 | 2.22 | 2.3 | 5 | 13 | 1.3 ('22) | 1 |
| McNairy | 2 | 2.19 | 1.4 | 9.7 | 19 | n/a | n/a |
| Clay | n/a | 2.15 | 1.9 | 5 | 14 | 2.5 ('23) | 7 |
| Obion | 3 | 2.14 | 0.5 | 11.7 | 11 | 1.6 ('22) | 1 |
| Wayne | 1 | 2.09 | 1.5 | 7.6 | 12 | 9.7 ('22) | 2 |
| DeKalb | 2 | 2.04 | 1.9 | 5.5 | 19 | 59.7 ('22) | 3 |
| Chester | 2 | 1.8 | 1.75 | 3.3 | 8 | 1.2 ('23) | 3 |
| Tipton | 3 | 1.73 | 1.35 | 4.5 | 16 | 3.2 ('23) | 2 |
| Van Buren | n/a | 1.66 | 1.2 | 4.4 | 5 | 2 ('22) | 1 |
| Shelby | 3 | 1.6 | 1.15 | 11.1 | 142 | 1 ('23) | 27 |
| Cumberland | 3 | 1.59 | 1.2 | 4.9 | 69 | 2.7 ('23) | 31 |
| Hardin | 2 | 1.43 | 0.8 | 5.2 | 11 | 1.8 ('22) | 1 |
| Henderson | 2 | 1.4 | 0.6 | 4.3 | 8 | n/a | n/a |
| Hardeman | 3 | 1.35 | 1.35 | 2 | 2 | n/a | n/a |
| Fayette | 3 | 1.34 | 0.95 | 3.2 | 14 | 2.3 ('23) | 5 |
| Crockett | 3 | 1.15 | 1.05 | 2.2 | 4 | 0.9 ('22) | 1 |
| Maury | 1 | 1.14 | 0.9 | 4.7 | 15 | 5.9 ('23) | 34 |
| Benton | 2 | 1.11 | 1.1 | 2.4 | 13 | 1.4 ('23) | 4 |
| Morgan | 3 | 1.06 | 0.6 | 3.8 | 18 | 23.2 ('23) | 5 |
| Dyer | 3 | 1.05 | 0.7 | 2.1 | 13 | n/a | n/a |
| Lauderdale | 3 | 1.04 | 0.8 | 2.5 | 5 | n/a | n/a |
| Grundy | 3 | 0.85 | 0.85 | 1.4 | 12 | 0.5 ('22) | 3 |
| Houston | 2 | 0.83 | 0.9 | 1 | 3 | 3.8 ('23) | 1 |
| Lake | 3 | 0.65 | 0.65 | 1 | 2 | n/a | n/a |
| Moore | 1 | 0.3 | 0.3 | 0.3 | 1 | n/a | n/a |
The Tennessee Radon Program mails about 6,000 free test kits a year and recommends every home retest every two years. Use it. It's the best free thing the state does for your lungs.
Sellers must disclose known radon on the residential property disclosure form, which is why testing is standard practice in East Tennessee transactions, and why the contract clock exists.
No state credential, no state standards for radon professionals. Per AARST's state report card, Tennessee requires nothing. Our answer is the vetting checklist every network pro passes.
AARST estimates roughly 900 radon-induced lung cancer cases a year in Tennessee. Radon is the leading cause of lung cancer in nonsmokers. Roughly 31,000 pre-mitigation tests on record statewide is a start, for a state of seven million.
Common enough that the EPA rates 38 of 95 counties at its highest potential, and concentrated enough that geography matters: the Ridge-and-Valley corridor through Knoxville is among the more serious radon regions in the country, while the Cumberland Plateau tests consistently low. The table above is the honest map; your own test is the honest answer.
By actual test averages in the state data, the top of the table mixes East Tennessee's karst counties with a few small-sample surprises. Treat any county with few tests carefully. In the Knoxville metro specifically: Sevier (6.51), Hamblen (5.62), Loudon (5.55), Jefferson (5.25), Blount (4.78), Anderson (4.76), with Knox's 872 tests averaging 3.94 and maxing at 103.9. "Worst," practically speaking, is whichever county contains your unsealed crawl space.
The map is a 1993 prediction at county scale, and its own fine print says every home should test regardless of zone. Our data shows why: Campbell County is mapped Zone 3 and averages 7.99 in real tests. Zones target public resources; they don't test houses. Radon varies house to house on the same street. The map gets you curious, the test gets you answered.
No and no: no mandatory testing, no new-construction requirement, no mitigator licensing; the only legal hook is seller disclosure of known radon. That laissez-faire posture is exactly why the practical standards here are private ones: certified testers on transactions, NRPP-credentialed mitigators, written under-4.0 guarantees. The state gives you a free kit and its blessing; the rest is on you and whoever you hire.
A real person answers, seven days a week
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