Radon levels by Pennsylvania county
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 | Average | At or above 4 |
|---|---|---|---|
| Lebanon | 33,304 | 12.25 | 55.7% |
| Schuylkill | 24,017 | 11.77 | 49.1% |
| York | 98,845 | 10.75 | 52.5% |
| Lancaster | 134,696 | 9.92 | 51.3% |
| Berks | 92,206 | 9.70 | 48.2% |
| Centre | 48,355 | 9.28 | 53.6% |
| Lehigh | 109,569 | 9.13 | 43.4% |
| Cumberland | 103,102 | 8.83 | 49.9% |
| Dauphin | 96,399 | 8.82 | 43.3% |
| Franklin | 28,191 | 8.51 | 52.4% |
| Northampton | 99,957 | 8.09 | 43.6% |
| Beaver | 33,921 | 7.53 | 46.6% |
Two columns rather than one, because they do not always agree. Centre County averages 9.28, below Berks at 9.70, yet a larger share of its tests exceed the action level. An average can be pulled up by a handful of extreme readings, while the percentage above 4 describes how many households actually face a decision.
What mitigation costs across Pennsylvania
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.
Across 22,552 installations recorded statewide between 2024 and 2026, the average came to 1,390 dollars. York County averaged 1,203 over the same period, 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.
The rule that applies everywhere in the state
Pennsylvania runs a certification programme 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 programme 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?
Among counties with at least 20,000 recorded tests, Lebanon averages highest at 12.25 pCi/L, followed by Schuylkill at 11.77 and York at 10.75. All three run well above the state average of 6.00.
What is the average radon level in Pennsylvania?
Across 3,334,286 certified test results the state averages 6.00 pCi/L, with 33.7 percent of tests at or above the 4 pCi/L action level. The DEP information page puts the statewide share nearer 40 percent.
How much does radon mitigation cost in Pennsylvania?
Across 22,552 installations recorded between 2024 and 2026 the average came to 1,390 dollars. 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.