What EPA's radon map says about Worth County

Worth County is mapped as Zone 1 - Highest Potential by EPA — meaning the county-wide average indoor level is predicted above 4 pCi/L. Worth County sits at the 73rd percentile nationally for radon potential — above 73 of every 100 rated counties.

Where Worth County sits nationally

About 7,307 people live in Worth County, Iowa, spread over 400.123 square miles. Population density there runs about 18 people per square mile. Among counties sharing Worth County's EPA zone, it outranks 21% of them by population. EPA's geology-based Region 7 groups Worth County with 411 other counties nationally sharing its underlying rock and soil profile.

What this actually means for a house in Worth County

Outdoor air nationally averages about 0.4 pCi/L, indoor air about 1.3 pCi/L — Worth County's Zone 1 prediction clears both of those and EPA's fix-it threshold besides. A Zone 1 rating means testing is worth doing sooner rather than later, but it is still county-wide average, not a reading for any single house — some homes in Worth County will test well under the action level, and EPA's guidance is to test regardless of zone.

If Worth County tests above the action level

Mitigation cost doesn't depend on Worth 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

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

Worth 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.