Union County, IA radon potential
Union County is mapped as Zone 1 - Highest Potential by EPA — meaning the county-wide average indoor level is predicted above 4 pCi/L. Nationally, Union County ranks higher in radon potential than 77% of rated counties (the 77th percentile).
Union County by the numbers
Union County, Iowa is home to about 11,955 people across 423.645 square miles. That works out to roughly 28 people per square mile. Within its own EPA zone, Union County is bigger by population than 32% of the counties that share it. EPA's geology-based Region 7 groups Union County with 411 other counties nationally sharing its underlying rock and soil profile.
What this actually means for a house in Union County
Fixing a home becomes an EPA recommendation past 4 pCi/L, and that is precisely the side of the line Union County's Zone 1 prediction lands on, well above the roughly 1.3 pCi/L most US homes average. Being in Zone 1 raises the odds Union County homes test above the action level, but it does not mean any specific house does — EPA recommends every home be tested, in every zone, because the only way to know is to test.
Next steps for a home in Union County
A short-term test kit is the standard first step and typically costs far less than mitigation itself. If a test comes back at or above 4 pCi/L, a radon mitigation system for a typical home runs roughly $800–$2,500 (around $1,200 for a common single-family install), driven mainly by foundation type, not by county.
Find Iowa's state radon program
For Union County, an ongoing number beats a one-time test - a Airthings radon monitor tracks Union County's levels over time. RadonZoneCheck earns a commission there, at no extra cost to you. Use code RADONZONE-10OFF at checkout for 10% off.
Where Union County's figures come from
Union County's zone, rank and region all trace back to named EPA and Census sources — the methodology guide lists exactly which ones. The guide to what a radon zone actually means covers why testing matters in every zone, not just Zone 1.