What EPA's radon map says about Cumberland County

EPA places Cumberland County in Zone 2 - Moderate Potential — a predicted county-wide average indoor radon level between 2 and 4 pCi/L, based on the geology, soil and aerial radioactivity data behind EPA's national map. Nationally that's the 40th percentile for radon potential — Cumberland County outranks 40% of every county EPA has rated.

How Cumberland County compares

About 10,305 people live in Cumberland County, Illinois, spread over 345.946 square miles. Averaged across its land area, Cumberland County runs about 30 people per square mile. Among counties sharing Cumberland County's EPA zone, it outranks 21% of them by population. Geologically, Cumberland County is grouped into EPA Region 5 alongside 523 other counties that share its rock and soil setting.

What this actually means for a house in Cumberland County

Cumberland County's Zone 2 prediction clears the 1.3 pCi/L national indoor average without reaching EPA's own 4 pCi/L point for recommending a fix. A county-wide moderate average, like Cumberland County's, can still hide a specific house well above or below it — testing is what actually answers the question.

Testing and mitigation in Cumberland County

Mitigation cost doesn't depend on Cumberland 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 Illinois's state radon program

Cumberland County's test kit answers today; a Airthings radon monitor keeps answering for Cumberland 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

The methodology guide shows exactly which EPA and Census sources feed Cumberland County's numbers. If you're unsure why a low zone still deserves a test, the zone explainer covers that directly.