What EPA's radon map says about Cass County

Cass County is mapped as Zone 1 - Highest Potential by EPA — meaning the county-wide average indoor level is predicted above 4 pCi/L. Nationally that's the 78th percentile for radon potential — Cass County outranks 78% of every county EPA has rated.

How Cass County compares

About 13,024 people live in Cass County, Iowa, spread over 564.258 square miles. That works out to roughly 23 people per square mile. Among counties sharing Cass County's EPA zone, it outranks 34% of them by population. Cass 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 Cass County

Cass 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. Being in Zone 1 raises the odds Cass 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 Cass County tests above the action level

Mitigation cost doesn't depend on Cass 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

Cass County's test kit answers today; a Airthings radon monitor keeps answering for Cass 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. Whatever zone Cass County carries, the zone explainer covers what it does and doesn't tell you about any one house.