Radon in Pennsylvania: radon map by county
EPA's Map of Radon Zones puts 49 of Pennsylvania's 67 counties in Zone 1 (predicted average indoor radon above 4 pCi/L), 17 in Zone 2 and 1 in Zone 3. Of 173,284 building tests that radon laboratories reported for 2008 to 2017, 41.1% were at or above EPA's 4 pCi/L action level, against 36.5% nationally (number 14 of 42 states with 1,000+ tests). The highest county share is Fulton County (69.7% of 90 tests).
Radon by county in Pennsylvania
| County | EPA zone | Lab tests | Median | 4+ pCi/L | PA agency data |
|---|---|---|---|---|---|
| Adams County | Zone 1 | 3,287 | 3.6 | 46.4% | median 2.8 pCi/L, 38.2% of 22,270 |
| Allegheny County | Zone 1 | 17,929 | 2.9 | 37.3% | median 2.6 pCi/L, 32.4% of 356,401 |
| Armstrong County | Zone 1 | 595 | 4.8 | 57.6% | median 3.7 pCi/L, 47.7% of 5,834 |
| Beaver County | Zone 1 | 2,430 | 3.9 | 49.7% | median 3.6 pCi/L, 46.6% of 33,920 |
| Bedford County | Zone 1 | 495 | 4.8 | 54.4% | median 4.1 pCi/L, 51.4% of 4,936 |
| Berks County | Zone 1 | 7,522 | 4.3 | 52.6% | median 3.7 pCi/L, 48.2% of 92,206 |
| Blair County | Zone 1 | 836 | 3.5 | 45.2% | median 3.0 pCi/L, 40.2% of 19,892 |
| Bradford County | Zone 1 | 374 | 3.8 | 49% | median 3.1 pCi/L, 43.1% of 6,355 |
| Bucks County | Zone 1 | 9,078 | 2.1 | 27.5% | median 2.0 pCi/L, 25.1% of 292,079 |
| Butler County | Zone 1 | 5,305 | 3.8 | 48.5% | median 3.4 pCi/L, 44.8% of 52,826 |
| Cambria County | Zone 2 | 944 | 3.5 | 45.5% | median 3.3 pCi/L, 41.4% of 18,797 |
| Cameron County | Zone 1 | 80 | 3.4 | 44.1% | median 3.6 pCi/L, 45.8% of 535 |
| Carbon County | Zone 1 | 818 | 4.5 | 54.4% | median 3.1 pCi/L, 43.1% of 13,987 |
| Centre County | Zone 1 | 1,236 | 7.2 | 67% | median 4.6 pCi/L, 53.6% of 48,355 |
| Chester County | Zone 1 | 11,038 | 2.2 | 29.3% | median 2.2 pCi/L, 29.3% of 261,523 |
| Clarion County | Zone 1 | 599 | 3.8 | 47.8% | median 3.4 pCi/L, 43.5% of 4,347 |
| Clearfield County | Zone 1 | 552 | 5.1 | 57.8% | median 4.0 pCi/L, 50.1% of 12,136 |
| Clinton County | Zone 1 | 346 | 4.5 | 56.1% | median 2.9 pCi/L, 40.4% of 5,873 |
| Columbia County | Zone 1 | 518 | 4.2 | 51% | median 3.3 pCi/L, 44.3% of 13,444 |
| Crawford County | Zone 2 | 878 | 2.7 | 33.4% | median 2.4 pCi/L, 30.1% of 7,039 |
| Cumberland County | Zone 1 | 4,713 | 5.8 | 61% | median 3.9 pCi/L, 49.9% of 103,102 |
| Dauphin County | Zone 1 | 3,902 | 4.8 | 55% | median 3.0 pCi/L, 43.3% of 96,399 |
| Delaware County | Zone 1 | 8,601 | 1.9 | 21% | median 1.8 pCi/L, 17.7% of 193,590 |
| Elk County | Zone 2 | 277 | 3.9 | 49.5% | median 3.6 pCi/L, 45.5% of 4,039 |
| Erie County | Zone 2 | 6,605 | 2.6 | 31.8% | median 2.0 pCi/L, 26.2% of 50,053 |
| Fayette County | Zone 2 | 526 | 2.8 | 35.8% | median 2.7 pCi/L, 31% of 8,896 |
| Forest County | Zone 2 | 37 | 3.6 | 44.7% | median 3.0 pCi/L, 41.3% of 361 |
| Franklin County | Zone 1 | 3,658 | 6.0 | 63.6% | median 4.3 pCi/L, 52.4% of 28,191 |
| Fulton County | Zone 1 | 90 | 7.9 | 69.7% | median 7.0 pCi/L, 66.3% of 879 |
| Greene County | Zone 2 | 142 | 3.3 | 39% | median 2.6 pCi/L, 30.3% of 1,864 |
| Huntingdon County | Zone 1 | 250 | 5.0 | 56.5% | median 3.8 pCi/L, 49% of 4,734 |
| Indiana County | Zone 1 | 745 | 4.2 | 51.5% | median 3.4 pCi/L, 43.4% of 10,500 |
| Jefferson County | Zone 2 | 413 | 4.9 | 57.7% | median 4.0 pCi/L, 50.2% of 5,572 |
| Juniata County | Zone 1 | 213 | 6.5 | 67.3% | median 5.4 pCi/L, 59.5% of 2,056 |
| Lackawanna County | Zone 1 | 1,103 | 2.7 | 36.3% | median 2.1 pCi/L, 25.2% of 43,297 |
| Lancaster County | Zone 1 | 8,108 | 4.8 | 55.1% | median 4.1 pCi/L, 51.3% of 134,696 |
| Lawrence County | Zone 2 | 1,119 | 3.3 | 42.9% | median 3.0 pCi/L, 36.8% of 10,322 |
| Lebanon County | Zone 1 | 2,437 | 7.5 | 63.6% | median 5.1 pCi/L, 55.7% of 33,304 |
| Lehigh County | Zone 1 | 8,055 | 3.9 | 49.4% | median 3.1 pCi/L, 43.4% of 109,567 |
| Luzerne County | Zone 1 | 2,323 | 2.6 | 34.4% | median 2.1 pCi/L, 27.4% of 65,979 |
| Lycoming County | Zone 1 | 1,273 | 4.3 | 52.5% | median 3.1 pCi/L, 42% of 18,920 |
| McKean County | Zone 2 | 144 | 1.6 | 26.4% | median 1.6 pCi/L, 21.5% of 2,246 |
| Mercer County | Zone 2 | 1,230 | 3.0 | 36.7% | median 2.6 pCi/L, 31.4% of 11,929 |
| Mifflin County | Zone 1 | 331 | 7.0 | 67.1% | median 5.0 pCi/L, 56.7% of 4,907 |
| Monroe County | Zone 1 | 870 | 3.4 | 44.6% | median 2.5 pCi/L, 35.8% of 61,895 |
| Montgomery County | Zone 1 | 14,749 | 2.2 | 27.2% | median 2.1 pCi/L, 24.5% of 391,126 |
| Montour County | Zone 1 | 165 | 5.5 | 61.6% | median 2.8 pCi/L, 38.4% of 5,238 |
| Northampton County | Zone 1 | 5,798 | 4.0 | 50.4% | median 3.2 pCi/L, 43.6% of 99,957 |
| Northumberland County | Zone 1 | 658 | 5.6 | 59.5% | median 2.9 pCi/L, 40% of 12,729 |
| Perry County | Zone 1 | 548 | 6.6 | 62.5% | median 5.4 pCi/L, 57.7% of 7,069 |
| Philadelphia County | Zone 3 | 8,973 | 1.5 | 12.4% | median 1.5 pCi/L, 10.9% of 193,339 |
| Pike County | Zone 2 | 331 | 3.0 | 40.3% | median 2.2 pCi/L, 29.9% of 33,275 |
| Potter County | Zone 2 | 138 | 4.4 | 52.1% | median 3.0 pCi/L, 43.1% of 2,224 |
| Schuylkill County | Zone 1 | 2,144 | 5.0 | 55.7% | median 3.8 pCi/L, 49.1% of 24,017 |
| Snyder County | Zone 1 | 306 | 7.6 | 64.8% | median 3.3 pCi/L, 44.5% of 5,853 |
| Somerset County | Zone 2 | 435 | 3.5 | 45.4% | median 3.1 pCi/L, 40.9% of 7,078 |
| Sullivan County | Zone 1 | 43 | 3.3 | 38.8% | median 2.5 pCi/L, 33.8% of 820 |
| Susquehanna County | Zone 1 | 173 | 3.3 | 40.1% | median 2.7 pCi/L, 35.1% of 4,736 |
| Tioga County | Zone 1 | 260 | 3.0 | 40.3% | median 2.4 pCi/L, 34% of 4,535 |
| Union County | Zone 1 | 320 | 5.1 | 62.9% | median 3.0 pCi/L, 41% of 9,905 |
| Venango County | Zone 1 | 669 | 3.8 | 48.4% | median 3.2 pCi/L, 42% of 6,416 |
| Warren County | Zone 2 | 364 | 4.4 | 54.6% | median 3.2 pCi/L, 42.8% of 4,968 |
| Washington County | Zone 2 | 2,504 | 3.0 | 37.9% | median 2.8 pCi/L, 33% of 43,589 |
| Wayne County | Zone 2 | 209 | 2.8 | 32.5% | median 2.0 pCi/L, 24.6% of 19,511 |
| Westmoreland County | Zone 1 | 4,396 | 3.1 | 41.1% | median 3.1 pCi/L, 38.3% of 74,297 |
| Wyoming County | Zone 1 | 183 | 3.5 | 42.5% | median 3.1 pCi/L, 39.5% of 4,700 |
| York County | Zone 1 | 7,893 | 5.4 | 59.7% | median 4.3 pCi/L, 52.5% of 98,845 |
Lab tests: buildings tested by radon laboratories, 2008 to 2017; median in pCi/L; “4+ pCi/L” is the share of tests at or above EPA's action level. n/a: no value on file (no tests, or too few to report).
Pennsylvania state radon data
The state environmental protection agency reports every radon test result reported to the state since 1986, by county and ZIP code. The county pages show these results next to the laboratory results. Pennsylvania county pages also list every ZIP code with 10 or more tests.
What the zones mean
Zone 1 counties have a predicted average indoor radon screening level above 4 pCi/L, Zone 2 from 2 to 4 pCi/L and Zone 3 below 2 pCi/L. The prediction is from 1993 indoor measurements, geology, aerial radioactivity, soils and foundation types. EPA: “This map should not be used to determine if individual homes need to be tested.” EPA recommends fixing a home at 4 pCi/L or more and considering a fix between 2 and 4 pCi/L, because there is no known safe level of exposure.
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Radon in Pennsylvania: questions
What radon zone is Pennsylvania?
EPA's 1993 map does not give states one zone; it zones each county. In Pennsylvania, 49 counties are Zone 1, 17 Zone 2 and 1 Zone 3. EPA says the map "should not be used to determine if individual homes need to be tested".
Which Pennsylvania counties have the highest radon levels?
By the share of laboratory tests at or above 4 pCi/L for 2008 to 2017 (counties with 20 or more tests): Fulton County 69.7% (median 7.9 pCi/L, 90 tests); Juniata County 67.3% (median 6.5 pCi/L, 213 tests); Mifflin County 67.1% (median 7.0 pCi/L, 331 tests); Centre County 67% (median 7.2 pCi/L, 1,236 tests); Snyder County 64.8% (median 7.6 pCi/L, 306 tests).
How common is high radon in Pennsylvania?
41.1% of the 173,284 tests in the laboratory data for Pennsylvania (2008 to 2017) were at or above 4 pCi/L; the national share was 36.5%. Buildings are tested by choice, often because of a sale or a concern, so the share describes the tests on file, not every home.
Does Pennsylvania publish its own radon test data?
Yes. The state environmental protection agency reports every radon test result reported to the state since 1986, by county and ZIP code. Each Pennsylvania county page here shows those results beside the laboratory results.
Should I test for radon in Pennsylvania?
Yes. EPA recommends testing every home no matter where it is, fixing it at 4 pCi/L or more and considering a fix between 2 and 4 pCi/L, because there is no known safe level of radon exposure.
States bordering Pennsylvania
Other free hazard lookups
- Radon by county and ZIP codeEPA radon zone and the radon test results on file for any county, ZIP code or address.
- Fault lines near an addressUSGS-mapped earthquake faults within 5 miles, their age and slip rate, and the USGS seismic hazard value.
- Power lines near an addressHigh-voltage transmission lines within 1 mile from federal maps, with voltage and distance.
- Flood zone lookupThe FEMA flood zone mapped at any US address. Not an official flood zone determination.
- Superfund sites near an addressThe nearest EPA Superfund (NPL) sites and their status.
All of these, plus wetlands, FEMA hazard ratings and the federal contamination lists, are in the Environmental Records Report for any US address ($29).
Superfund sites in Pennsylvania · Radon map of every state
Data compiled 2026-10-20. County-level screening information, not a radon measurement of any building.