Which Pennsylvania counties have the highest radon levels?
Lebanon, Schuylkill and York have the highest average radon of the Pennsylvania counties with at least 20,000 recorded tests, at 12.25, 11.77 and 10.75 pCi/L. The counties below are those with at least 20,000 recorded tests, ranked by average reading. The concentration in the south and east follows the Reading Prong and the fractured limestone belt that runs through the middle of the state.
| County | Tests | Median | Average | At or above 4 |
|---|---|---|---|---|
| Lebanon | 33,304 | 5.13 | 12.25 | 55.7% |
| Schuylkill | 24,017 | 3.80 | 11.77 | 49.1% |
| York | 98,845 | 4.30 | 10.75 | 52.5% |
| Lancaster | 134,696 | 4.13 | 9.92 | 51.3% |
| Berks | 92,206 | 3.70 | 9.70 | 48.2% |
| Centre | 48,355 | 4.60 | 9.28 | 53.6% |
| Lehigh | 109,569 | 3.10 | 9.13 | 43.4% |
| Cumberland | 103,102 | 3.90 | 8.83 | 49.9% |
| Dauphin | 96,399 | 3.00 | 8.82 | 43.3% |
| Franklin | 28,191 | 4.30 | 8.51 | 52.4% |
| Northampton | 99,957 | 3.20 | 8.09 | 43.6% |
| Beaver | 33,921 | 3.60 | 7.53 | 46.6% |
Three columns rather than one, because they disagree, and the disagreement is the point. Radon readings are not distributed evenly: most houses cluster low and a small number run extremely high, which drags every average upward. Pennsylvania averages 6.00 pCi/L and has a median of 2.50, so the typical house in this state sits well under the action level while the average suggests it scrapes just below.
Schuylkill County shows what that does to a ranking. It places second on average at 11.77 and seventh on median at 3.80, because a handful of extreme readings lift its mean without moving its middle. Centre County runs the other way: sixth on average, second on median.
What does radon mitigation cost across Pennsylvania?
Radon mitigation in Pennsylvania averaged $1,390 per system across 22,552 installations recorded from 2024 to 2026, and York County averaged $1,203. The state requires its certified contractors to report the cost of every system they install, which makes Pennsylvania one of the few places where the price of radon mitigation is a matter of public record rather than an estimate.
That puts York County roughly 13 percent below the state figure.
Treat national cost guides with that spread in mind. A range drawn from metropolitan markets overstates what most of Pennsylvania pays, and a single national midpoint hides a gap of several hundred dollars between counties. The county level detail is on the page about what radon mitigation costs in York County.
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Which radon rule applies everywhere in Pennsylvania?
DEP certification applies everywhere in Pennsylvania: anyone who tests for radon or mitigates it in a building must be certified or work for a certified firm. Pennsylvania runs a certification program covering radon testing, mitigation and laboratory analysis, for individuals and firms alike. It applies wherever in the state the work happens, and it is the single check worth doing before any contractor starts.
Ask for the certification number and verify it rather than taking the claim. How the program works and where to look it up is set out on the page about PA DEP radon certification.
Common questions about radon in Pennsylvania
Which Pennsylvania county has the most radon?
Lebanon is highest on both measures, at 12.25 pCi/L average and 5.13 median, among counties with at least 20,000 tests. York is third on both, at 10.75 and 4.30. Schuylkill is second on average but seventh on median, because extreme readings lift its mean.
What is the average radon level in Pennsylvania?
Across 3,334,286 certified test results the median reading is 2.50 pCi/L and the average is 6.00, with 33.7 percent of tests at or above the 4 pCi/L action level. The typical Pennsylvania house therefore sits under the action level while the average sits just below it.
How much does radon mitigation cost in Pennsylvania?
Across 22,552 installations recorded between 2024 and 2026 the average came to $1,390. York County averaged $1,203 over the same period, about 13 percent below the state figure.
Do I need a certified contractor in Pennsylvania?
The state certifies individuals and firms for radon testing, mitigation and laboratory analysis, and the requirement applies anywhere in Pennsylvania. Ask for the number and verify it before work starts.
Why is Pennsylvania radon so high?
Geology. The Reading Prong and the fractured limestone belt running through the south and east of the state both produce radon and give it easy paths upward into foundations.