What EPA's radon map says about Northumberland County

EPA places Northumberland County in Zone 1 - Highest Potential — a predicted county-wide average indoor radon level above 4 pCi/L, based on the geology, soil and aerial radioactivity data behind EPA's national map. That puts Northumberland County in the 93rd percentile nationally for radon potential — higher than 93% of the counties EPA has rated.

Where Northumberland County sits nationally

About 90,027 people live in Northumberland County, Pennsylvania, spread over 457.678 square miles. Averaged across its land area, Northumberland County runs about 197 people per square mile. Among counties sharing Northumberland County's EPA zone, it outranks 80% of them by population. EPA's geology-based Region 3 groups Northumberland County with 244 other counties nationally sharing its underlying rock and soil profile.

What this actually means for a house in Northumberland County

Northumberland County carries a Zone 1 label because its predicted average clears 4 pCi/L outright — three-plus times the 0.4 pCi/L typical outdoors and above the 1.3 pCi/L most homes see. EPA's guidance doesn't change because of a Zone 1 label: test the house. What changes is the reason to not put it off in Northumberland County specifically.

Testing and mitigation in Northumberland County

Mitigation cost doesn't depend on Northumberland 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

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

More on how this number was built

Every figure on this page traces to EPA's own Map of Radon Zones and Census data, documented in the methodology guide. If you're unsure why a low zone still deserves a test, the zone explainer covers that directly.