What EPA's radon map says about Walworth County

EPA's own radon map rates Walworth County zone 1 - highest potential, predicting a county-wide average indoor level above 4 pCi/L. Nationally that's the 94th percentile for radon potential — Walworth County outranks 94% of every county EPA has rated.

Walworth County by the numbers

About 106,029 people live in Walworth County, Wisconsin, spread over 555.436 square miles. Averaged across its land area, Walworth County runs about 191 people per square mile. Among counties sharing Walworth County's EPA zone, it outranks 83% of them by population. Geologically, Walworth County is grouped into EPA Region 5 alongside 523 other counties that share its rock and soil setting.

What this actually means for a house in Walworth County

Walworth 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. 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 Walworth County will test well under the action level, and EPA's guidance is to test regardless of zone.

Next steps for a home in Walworth County

Mitigation cost doesn't depend on Walworth 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 Wisconsin's state radon program

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

Every figure on this page traces to EPA's own Map of Radon Zones and Census data, documented in the methodology guide. Whatever zone Walworth County carries, the zone explainer covers what it does and doesn't tell you about any one house.