What EPA's radon map says about Monona County

EPA places Monona 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. Nationally that's the 74th percentile for radon potential — Monona County outranks 74% of every county EPA has rated.

Monona County by the numbers

About 8,429 people live in Monona County, Iowa, spread over 694.072 square miles. Population density there runs about 12 people per square mile. Among counties sharing Monona County's EPA zone, it outranks 24% of them by population. EPA's geology-based Region 7 groups Monona County with 411 other counties nationally sharing its underlying rock and soil profile.

Zone vs. an actual test

Monona 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. Some Monona County homes will test comfortably under the action level despite the county's Zone 1 rating — the only way to know which kind of home you have is an actual test.

If Monona County tests above the action level

Mitigation cost doesn't depend on Monona 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

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

More on how this number was built

Monona County's zone, rank and region all trace back to named EPA and Census sources — the methodology guide lists exactly which ones. The guide to what a radon zone actually means covers why testing matters in every zone, not just Zone 1.