Is Clinton County, IL a radon risk area?

Clinton County is mapped as Zone 2 - Moderate Potential by EPA — meaning the county-wide average indoor level is predicted between 2 and 4 pCi/L. Nationally, Clinton County ranks higher in radon potential than 52% of rated counties (the 52nd percentile).

Clinton County by the numbers

About 37,087 people live in Clinton County, Illinois, spread over 473.941 square miles. Population density there runs about 78 people per square mile. Rank 422 by population within its EPA zone puts Clinton County at the 59th percentile among zone peers. Geologically, Clinton County is grouped into EPA Region 5 alongside 523 other counties that share its rock and soil setting.

Zone vs. an actual test

Call it a middle case: above the 1.3 pCi/L most US homes average, below the 4 pCi/L line EPA uses to recommend mitigation — that's Clinton County's Zone 2 prediction. A county-wide moderate average, like Clinton County's, can still hide a specific house well above or below it — testing is what actually answers the question.

Testing and mitigation in Clinton County

Nothing about Clinton 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 Illinois's state radon program

Clinton County's test kit answers today; a Airthings radon monitor keeps answering for Clinton 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. The guide to what a radon zone actually means covers why testing matters in every zone, not just Zone 1.