Is Mercer County, KY a radon risk area?

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. That puts Mercer County in the 83rd percentile nationally for radon potential — higher than 83% of the counties EPA has rated.

How Mercer County compares

About 23,515 people live in Mercer County, Kentucky, spread over 249.383 square miles. That works out to roughly 94 people per square mile. Rank 527 by population within its EPA zone puts Mercer County at the 51st percentile among zone peers. Mercer County falls in EPA Radon Region 4, one of 736 counties nationally EPA assigns to that same geologic province.

Why the zone isn't the answer by itself

Outdoor air nationally averages about 0.4 pCi/L, indoor air about 1.3 pCi/L — Mercer County's Zone 1 prediction clears both of those and EPA's fix-it threshold besides. EPA's guidance doesn't change because of a Zone 1 label: test the house. What changes is the reason to not put it off in Mercer County specifically.

If Mercer County tests above the action level

Nothing about Mercer 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 Kentucky'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

Mercer County's zone, rank and region all trace back to named EPA and Census sources — the methodology guide lists exactly which ones. Whatever zone Mercer County carries, the zone explainer covers what it does and doesn't tell you about any one house.