What EPA's radon map says about McPherson County

EPA places McPherson 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. Nationally, McPherson County ranks higher in radon potential than 68% of rated counties (the 68th percentile).

Where McPherson County sits nationally

About 2,307 people live in McPherson County, South Dakota, spread over 1,136.668 square miles. That works out to roughly 2 people per square mile. Among counties sharing McPherson County's EPA zone, it outranks 5% of them by population. EPA's geology-based Region 8 groups McPherson County with 290 other counties nationally sharing its underlying rock and soil profile.

What this actually means for a house in McPherson County

Fixing a home becomes an EPA recommendation past 4 pCi/L, and that is precisely the side of the line McPherson County's Zone 1 prediction lands on, well above the roughly 1.3 pCi/L most US homes average. 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 McPherson County will test well under the action level, and EPA's guidance is to test regardless of zone.

Next steps for a home in McPherson County

Mitigation cost doesn't depend on McPherson 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 South Dakota's state radon program

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

McPherson 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.