What EPA's radon map says about Pierce County

Pierce County is mapped as Zone 1 - Highest Potential by EPA — meaning the county-wide average indoor level is predicted above 4 pCi/L. Pierce County sits at the 89th percentile nationally for radon potential — above 89 of every 100 rated counties.

Pierce County by the numbers

About 43,380 people live in Pierce County, Wisconsin, spread over 574.018 square miles. Averaged across its land area, Pierce County runs about 76 people per square mile. Among counties sharing Pierce County's EPA zone, it outranks 67% of them by population. EPA's geology-based Region 5 groups Pierce County with 523 other counties nationally sharing its underlying rock and soil profile.

Why the zone isn't the answer by itself

Outdoor air nationally averages about 0.4 pCi/L, indoor air about 1.3 pCi/L — Pierce County's Zone 1 prediction clears both of those and EPA's fix-it threshold besides. That doesn't mean every Pierce 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.

Next steps for a home in Pierce County

Mitigation cost doesn't depend on Pierce 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

Pierce County's test kit answers today; a Airthings radon monitor keeps answering for Pierce 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 Pierce County's numbers. If you're unsure why a low zone still deserves a test, the zone explainer covers that directly.