What EPA's radon map says about Clarke County

EPA places Clarke County in Zone 3 - Low Potential — a predicted county-wide average indoor radon level below 2 pCi/L, based on the geology, soil and aerial radioactivity data behind EPA's national map. Rank it against the rest of the country and Clarke County lands in the 10th percentile for radon potential.

Where Clarke County sits nationally

About 15,155 people live in Clarke County, Mississippi, spread over 691.576 square miles. Averaged across its land area, Clarke County runs about 22 people per square mile. Among counties sharing Clarke County's EPA zone, it outranks 31% of them by population. Clarke County falls in EPA Radon Region 4, one of 736 counties nationally EPA assigns to that same geologic province.

What this actually means for a house in Clarke County

A Zone 3 county like Clarke County is predicted closer to the 0.4 pCi/L typical outdoors than to EPA's 4 pCi/L action level. Even at Zone 3, Clarke County homes are not guaranteed a low reading — zone is a county-wide average, and EPA recommends testing every home regardless of zone.

If Clarke County tests above the action level

Mitigation cost doesn't depend on Clarke 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 Mississippi's state radon program

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

Clarke 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.