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

EPA places Howard 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, Howard County ranks higher in radon potential than 75% of rated counties (the 75th percentile).

Howard County by the numbers

Howard County, Iowa is home to about 9,360 people across 473.247 square miles. That works out to roughly 20 people per square mile. By population, Howard County is the 784th largest of every county sharing its EPA zone — the 26th percentile by population within that zone. Geologically, Howard County is grouped into EPA Region 7 alongside 411 other counties that share its rock and soil setting.

Zone vs. an actual test

Howard County carries a Zone 1 label because its predicted average clears 4 pCi/L outright — three-plus times the 0.4 pCi/L typical outdoors and above the 1.3 pCi/L most homes see. That doesn't mean every Howard County house tests high — a zone is a county-wide prediction, never a single-home reading — but it's a reason to test sooner rather than let it wait.

Testing and mitigation in Howard County

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

Where Howard County's figures come from

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