Clinton County, IA: EPA's radon zone, explained

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 89% of rated counties (the 89th percentile).

Where Clinton County sits nationally

Clinton County, Iowa is home to about 46,015 people across 694.959 square miles. Population density there runs about 66 people per square mile. By population, Clinton County is the 338th largest of every county sharing its EPA zone — the 68th percentile by population within that zone. Clinton County falls in EPA Radon Region 7, one of 412 counties nationally EPA assigns to that same geologic province.

Zone vs. an actual test

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. 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 Clinton County specifically.

Testing and mitigation in Clinton County

For a Clinton County homeowner, the order is simple: test first, since a kit costs a small fraction of what mitigation would. Only if the result clears 4 pCi/L does a system — typically $800–$2,500, about $1,200 for a common install — become worth pricing out.

Find Iowa's state radon program

For Clinton County, an ongoing number beats a one-time test - a Airthings radon monitor tracks Clinton County's levels over time. RadonZoneCheck earns a commission there, at no extra cost to you. RADONZONE-10OFF at checkout knocks 10% off.

Where Clinton County's figures come from

The methodology guide shows exactly which EPA and Census sources feed Clinton County's numbers. Whatever zone Clinton County carries, the zone explainer covers what it does and doesn't tell you about any one house.