What EPA's radon map says about Greene County

Greene County is mapped as Zone 1 - Highest Potential by EPA — meaning the county-wide average indoor level is predicted above 4 pCi/L. Nationally, Greene County ranks higher in radon potential than 74% of rated counties (the 74th percentile).

How Greene County compares

About 8,662 people live in Greene County, Iowa, spread over 569.558 square miles. Population density there runs about 15 people per square mile. Among counties sharing Greene County's EPA zone, it outranks 24% of them by population. Greene County falls in EPA Radon Region 7, one of 412 counties nationally EPA assigns to that same geologic province.

What this actually means for a house in Greene County

Where the national indoor average runs about 1.3 pCi/L, Greene County's Zone 1 rating puts its predicted county average above EPA's 4 pCi/L action level itself. That doesn't mean every Greene County house tests high — a zone is a county-wide prediction, never a single-home reading — but it's a reason to test sooner rather than let it wait.

If Greene County tests above the action level

Mitigation cost doesn't depend on Greene 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 Iowa's state radon program

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

Every figure on this page traces to EPA's own Map of Radon Zones and Census data, documented in the methodology guide. The guide to what a radon zone actually means covers why testing matters in every zone, not just Zone 1.