State radon data hub
Pennsylvania radon levels, county by county
67 Pennsylvania counties have published radon test data. Ranked worst-first below — the median county sees 49% of home tests reach the EPA action level of 4 pCi/L. Deep-dive pages (data + geology + housing stock) exist for 18 counties so far; more ship as coverage expands.
Costs, licensing, and how to read a quote: the Pennsylvania mitigation cost guide. Instant county lookup: radon by ZIP.
| # | County | % tests ≥ 4 pCi/L | Tests (10-yr) | EPA zone |
|---|---|---|---|---|
| 1 | Fulton | 69.7% | 90 | 1 |
| 2 | Juniata | 67.3% | 213 | 1 |
| 3 | Mifflin | 67.1% | 331 | 1 |
| 4 | Centre | 67% | 1,236 | 1 |
| 5 | Snyder | 64.8% | 306 | 1 |
| 6 | Franklin | 63.6% | 3,658 | 1 |
| 7 | Lebanon | 63.6% | 2,437 | 1 |
| 8 | Union | 62.9% | 320 | 1 |
| 9 | Perry | 62.5% | 548 | 1 |
| 10 | Montour | 61.6% | 165 | 1 |
| 11 | Cumberland | 61% | 4,713 | 1 |
| 12 | York | 59.7% | 7,893 | 1 |
| 13 | Northumberland | 59.5% | 658 | 1 |
| 14 | Clearfield | 57.8% | 552 | 1 |
| 15 | Jefferson | 57.7% | 413 | 2 |
| 16 | Armstrong | 57.6% | 595 | 1 |
| 17 | Huntingdon | 56.5% | 250 | 1 |
| 18 | Clinton | 56.1% | 346 | 1 |
| 19 | Schuylkill | 55.7% | 2,144 | 1 |
| 20 | Lancaster | 55.1% | 8,108 | 1 |
| 21 | Dauphin | 55% | 3,902 | 1 |
| 22 | Warren | 54.6% | 364 | 2 |
| 23 | Bedford | 54.4% | 495 | 1 |
| 24 | Carbon | 54.4% | 818 | 1 |
| 25 | Berks | 52.6% | 7,522 | 1 |
| 26 | Lycoming | 52.5% | 1,273 | 1 |
| 27 | Potter | 52.1% | 138 | 2 |
| 28 | Indiana | 51.5% | 745 | 1 |
| 29 | Columbia | 51% | 518 | 1 |
| 30 | Northampton | 50.4% | 5,798 | 1 |
| 31 | Beaver | 49.7% | 2,430 | 1 |
| 32 | Elk | 49.5% | 277 | 2 |
| 33 | Lehigh | 49.4% | 8,055 | 1 |
| 34 | Bradford | 49% | 374 | 1 |
| 35 | Butler | 48.5% | 5,305 | 1 |
| 36 | Venango | 48.4% | 669 | 1 |
| 37 | Clarion | 47.8% | 599 | 1 |
| 38 | Adams | 46.4% | 3,287 | 1 |
| 39 | Cambria | 45.5% | 944 | 2 |
| 40 | Somerset | 45.4% | 435 | 2 |
| 41 | Blair | 45.2% | 836 | 1 |
| 42 | Forest | 44.7% | 37 | 2 |
| 43 | Monroe | 44.6% | 870 | 1 |
| 44 | Cameron | 44.1% | 80 | 1 |
| 45 | Lawrence | 42.9% | 1,119 | 2 |
| 46 | Wyoming | 42.5% | 183 | 1 |
| 47 | Westmoreland | 41.1% | 4,396 | 1 |
| 48 | Pike | 40.3% | 331 | 2 |
| 49 | Tioga | 40.3% | 260 | 1 |
| 50 | Susquehanna | 40.1% | 173 | 1 |
| 51 | Greene | 39% | 142 | 2 |
| 52 | Sullivan | 38.8% | 43 | 1 |
| 53 | Washington | 37.9% | 2,504 | 2 |
| 54 | Allegheny | 37.3% | 17,929 | 1 |
| 55 | Mercer | 36.7% | 1,230 | 2 |
| 56 | Lackawanna | 36.3% | 1,103 | 1 |
| 57 | Fayette | 35.8% | 526 | 2 |
| 58 | Luzerne | 34.4% | 2,323 | 1 |
| 59 | Crawford | 33.4% | 878 | 2 |
| 60 | Wayne | 32.5% | 209 | 2 |
| 61 | Erie | 31.8% | 6,605 | 2 |
| 62 | Chester | 29.3% | 11,038 | 1 |
| 63 | Bucks | 27.5% | 9,078 | 1 |
| 64 | Montgomery | 27.2% | 14,749 | 1 |
| 65 | McKean | 26.4% | 144 | 2 |
| 66 | Delaware | 21% | 8,601 | 1 |
| 67 | Philadelphia | 12.4% | 8,973 | 3 |
Source: CDC EPHT (labs), 2008–2017; county rank by share of tests at or above 4 pCi/L (counties with too few reported tests are excluded — absence of data is not absence of radon). Zones: EPA Map of Radon Zones. Full sourcing on the methodology page.