What EPA's radon map says about Webster County

EPA places Webster County in Zone 2 - Moderate Potential — a predicted county-wide average indoor radon level between 2 and 4 pCi/L, based on the geology, soil and aerial radioactivity data behind EPA's national map. Nationally that's the 54th percentile for radon potential — Webster County outranks 54% of every county EPA has rated.

Where Webster County sits nationally

About 42,041 people live in Webster County, Missouri, spread over 592.563 square miles. Averaged across its land area, Webster County runs about 71 people per square mile. Among counties sharing Webster County's EPA zone, it outranks 63% of them by population. 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

Webster County's predicted average falls between EPA's 4 pCi/L action level and the national indoor average of about 1.3 pCi/L (outdoor air runs roughly 0.4 pCi/L). A county-wide moderate average, like Webster County's, can still hide a specific house well above or below it — testing is what actually answers the question.

If Webster County tests above the action level

Mitigation cost doesn't depend on Webster 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 Missouri'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. 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 Webster County's numbers. If you're unsure why a low zone still deserves a test, the zone explainer covers that directly.