Is Webster County, IA a radon risk area?

EPA places Webster 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. Rank it against the rest of the country and Webster County lands in the 87th percentile for radon potential.

Where Webster County sits nationally

About 36,909 people live in Webster County, Iowa, spread over 715.704 square miles. That works out to roughly 52 people per square mile. Rank 407 by population within its EPA zone puts Webster County at the 62nd percentile among zone peers. Geologically, Webster County is grouped into EPA Region 7 alongside 411 other counties that share its rock and soil setting.

What this actually means for a house in Webster County

Where the national indoor average runs about 1.3 pCi/L, Webster County's Zone 1 rating puts its predicted county average above EPA's 4 pCi/L action level itself. That doesn't mean every Webster 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 Webster County tests above the action level

Nothing about Webster County's EPA zone changes the mitigation number: $800–$2,500 nationally (around $1,200 typical), set by the house's foundation rather than the county it sits in — and only relevant once a test actually clears 4 pCi/L.

Find Iowa's state radon program

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

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.