Is Mercer County, MO a radon risk area?

EPA's own radon map rates Mercer County zone 2 - moderate potential, predicting a county-wide average indoor level between 2 and 4 pCi/L. That puts Mercer County in the 35th percentile nationally for radon potential — higher than 35% of the counties EPA has rated.

Where Mercer County sits nationally

About 3,452 people live in Mercer County, Missouri, spread over 453.835 square miles. Population density there runs about 8 people per square mile. Rank 977 by population within its EPA zone puts Mercer County at the 5th percentile among zone peers. Mercer County falls in EPA Radon Region 7, one of 412 counties nationally EPA assigns to that same geologic province.

What this actually means for a house in Mercer County

Mercer County's predicted average falls between EPA's 4 pCi/L action level and the national indoor average of about 1.3 pCi/L (outdoor air runs roughly 0.4 pCi/L). A Zone 2 rating is a moderate county-wide average, not a guarantee about any one house in Mercer County — testing is the only way to know an individual home's actual level.

Testing and mitigation in Mercer County

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 Missouri'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

Every figure on this page traces to EPA's own Map of Radon Zones and Census data, documented in the methodology guide. If you're unsure why a low zone still deserves a test, the zone explainer covers that directly.