Is Marion County, MS a radon risk area?

Marion County is mapped as Zone 3 - Low Potential by EPA — meaning the county-wide average indoor level is predicted below 2 pCi/L. That puts Marion County in the 15th percentile nationally for radon potential — higher than 15% of the counties EPA has rated.

How Marion County compares

About 24,008 people live in Marion County, Mississippi, spread over 542.326 square miles. Averaged across its land area, Marion County runs about 44 people per square mile. Rank 552 by population within its EPA zone puts Marion County at the 47th percentile among zone peers. Geologically, Marion County is grouped into EPA Region 4 alongside 735 other counties that share its rock and soil setting.

Zone vs. an actual test

Marion County's predicted average sits below the national indoor average of about 1.3 pCi/L, well under EPA's 4 pCi/L action level. A Zone 3 rating means Marion County's county-wide average is predicted low, but EPA is explicit that a meaningful share of homes in low-potential zones still test above the action level — a low zone is not a reason to skip testing.

If Marion County tests above the action level

Nothing about Marion 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

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