What EPA's radon map says about Mercer County

EPA places Mercer 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, Mercer County ranks higher in radon potential than 74% of rated counties (the 74th percentile).

Where Mercer County sits nationally

About 8,348 people live in Mercer County, North Dakota, spread over 1,042.782 square miles. That works out to roughly 8 people per square mile. Among counties sharing Mercer County's EPA zone, it outranks 24% of them by population. EPA's geology-based Region 8 groups Mercer County with 290 other counties nationally sharing its underlying rock and soil profile.

What this actually means for a house in Mercer County

Fixing a home becomes an EPA recommendation past 4 pCi/L, and that is precisely the side of the line Mercer County's Zone 1 prediction lands on, well above the roughly 1.3 pCi/L most US homes average. Some Mercer County homes will test comfortably under the action level despite the county's Zone 1 rating — the only way to know which kind of home you have is an actual test.

If Mercer County tests above the action level

Mitigation cost doesn't depend on Mercer 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 North Dakota's state radon program

Mercer County's test kit answers today; a Airthings radon monitor keeps answering for Mercer 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 Mercer County carries, the zone explainer covers what it does and doesn't tell you about any one house.