Is Marshall County, MS a radon risk area?

EPA's own radon map rates Marshall County zone 3 - low potential, predicting a county-wide average indoor level below 2 pCi/L. Marshall County sits at the 19th percentile nationally for radon potential — above 19 of every 100 rated counties.

Where Marshall County sits nationally

About 34,374 people live in Marshall County, Mississippi, spread over 706.192 square miles. Population density there runs about 49 people per square mile. Rank 443 by population within its EPA zone puts Marshall County at the 57th percentile among zone peers. EPA's geology-based Region 4 groups Marshall County with 735 other counties nationally sharing its underlying rock and soil profile.

What this actually means for a house in Marshall County

At Zone 3, Marshall County's predicted county average is under the national indoor average (~1.3 pCi/L) and well below EPA's 4 pCi/L action level — outdoor air nationally runs about 0.4 pCi/L for comparison. Low doesn't mean zero: EPA's own data shows homes in Zone 3 counties like Marshall County testing above the action level often enough that skipping a test isn't the safe assumption.

Next steps for a home in Marshall County

Nothing about Marshall County's EPA zone changes the mitigation number: $800–$2,500 nationally (around $1,200 typical), set by the house's foundation rather than the county it sits in — and only relevant once a test actually clears 4 pCi/L.

Find Mississippi's state radon program

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