What EPA's radon map says about Guthrie County

Guthrie County is mapped as Zone 1 - Highest Potential by EPA — meaning the county-wide average indoor level is predicted above 4 pCi/L. Nationally, Guthrie County ranks higher in radon potential than 76% of rated counties (the 76th percentile).

Where Guthrie County sits nationally

About 10,774 people live in Guthrie County, Iowa, spread over 590.614 square miles. Population density there runs about 18 people per square mile. Among counties sharing Guthrie County's EPA zone, it outranks 30% of them by population. Geologically, Guthrie County is grouped into EPA Region 7 alongside 411 other counties that share its rock and soil setting.

Zone vs. an actual test

Guthrie County's predicted average sits above EPA's own action level of 4 pCi/L — the concentration at which EPA recommends fixing a home — versus a national average around 1.3 pCi/L indoors and 0.4 pCi/L outdoors. 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 Guthrie County specifically.

Testing and mitigation in Guthrie County

Mitigation cost doesn't depend on Guthrie 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

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

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