Marion County, AR: EPA's radon zone, explained

EPA's own radon map rates Marion County zone 2 - moderate potential, predicting a county-wide average indoor level between 2 and 4 pCi/L. Marion County sits at the 45th percentile nationally for radon potential — above 45 of every 100 rated counties.

How Marion County compares

Marion County, Arkansas is home to about 17,593 people across 596.598 square miles. That works out to roughly 29 people per square mile. By population, Marion County is the 667th largest of every county sharing its EPA zone — the 35th percentile by population within that zone. Geologically, Marion County is grouped into EPA Region 6 alongside 502 other counties that share its rock and soil setting.

Why the zone isn't the answer by itself

Call it a middle case: above the 1.3 pCi/L most US homes average, below the 4 pCi/L line EPA uses to recommend mitigation — that's Marion County's Zone 2 prediction. Marion County's Zone 2 rating sits in the middle nationally; EPA's guidance is unchanged by that — test every home regardless of its zone.

If Marion County tests above the action level

For a Marion County homeowner, the order is simple: test first, since a kit costs a small fraction of what mitigation would. Only if the result clears 4 pCi/L does a system — typically $800–$2,500, about $1,200 for a common install — become worth pricing out.

Find Arkansas's state radon program

For Marion County, an ongoing number beats a one-time test - a Airthings radon monitor tracks Marion County's levels over time. RadonZoneCheck earns a commission there, at no extra cost to you. Use code RADONZONE-10OFF at checkout for 10% off.

Where Marion County's figures come from

The methodology guide shows exactly which EPA and Census sources feed Marion County's numbers. The guide to what a radon zone actually means covers why testing matters in every zone, not just Zone 1.