What EPA's radon map says about Allegheny County

EPA's own radon map rates Allegheny County zone 1 - highest potential, predicting a county-wide average indoor level above 4 pCi/L. Nationally that's the 100th percentile for radon potential — Allegheny County outranks 100% of every county EPA has rated.

Where Allegheny County sits nationally

About 1,231,814 people live in Allegheny County, Pennsylvania, spread over 729.952 square miles. That works out to roughly 1,688 people per square mile. Among counties sharing Allegheny County's EPA zone, it outranks 100% of them by population. EPA's geology-based Region 3 groups Allegheny County with 244 other counties nationally sharing its underlying rock and soil profile.

Why the zone isn't the answer by itself

Where the national indoor average runs about 1.3 pCi/L, Allegheny County's Zone 1 rating puts its predicted county average above EPA's 4 pCi/L action level itself. Being in Zone 1 raises the odds Allegheny County homes test above the action level, but it does not mean any specific house does — EPA recommends every home be tested, in every zone, because the only way to know is to test.

If Allegheny County tests above the action level

Mitigation cost doesn't depend on Allegheny County's zone — it depends on the house's foundation. A typical system runs $800–$2,500 (about $1,200 typical), and testing first is what tells you whether that's needed at all.

Find Pennsylvania's state radon program

Allegheny County's test kit answers today; a Airthings radon monitor keeps answering for Allegheny County over time. Affiliate link, RadonZoneCheck earns a commission there, at no extra cost to you. Use code RADONZONE-10OFF at checkout for 10% off.

More on how this number was built

The methodology guide shows exactly which EPA and Census sources feed Allegheny County's numbers. Whatever zone Allegheny County carries, the zone explainer covers what it does and doesn't tell you about any one house.