What EPA's radon map says about Clinton County

EPA places Clinton 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. Nationally, Clinton County ranks higher in radon potential than 86% of rated counties (the 86th percentile).

Clinton County by the numbers

About 32,895 people live in Clinton County, Indiana, spread over 405.067 square miles. Averaged across its land area, Clinton County runs about 81 people per square mile. Among counties sharing Clinton County's EPA zone, it outranks 58% of them by population. Geologically, Clinton County is grouped into EPA Region 5 alongside 523 other counties that share its rock and soil setting.

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 — Clinton County's Zone 1 prediction clears both of those and EPA's fix-it threshold besides. A Zone 1 rating means testing is worth doing sooner rather than later, but it is still county-wide average, not a reading for any single house — some homes in Clinton County will test well under the action level, and EPA's guidance is to test regardless of zone.

If Clinton County tests above the action level

Mitigation cost doesn't depend on Clinton 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 Indiana'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

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