Jefferson County, NE: EPA's radon zone, explained

EPA's own radon map rates Jefferson County zone 1 - highest potential, predicting a county-wide average indoor level above 4 pCi/L. That puts Jefferson County in the 73rd percentile nationally for radon potential — higher than 73% of the counties EPA has rated.

Where Jefferson County sits nationally

Jefferson County, Nebraska is home to about 7,136 people across 570.182 square miles. That works out to roughly 13 people per square mile. By population, Jefferson County is the 840th largest of every county sharing its EPA zone — the 21st percentile by population within that zone. EPA's geology-based Region 7 groups Jefferson County with 411 other counties nationally sharing its underlying rock and soil profile.

What this actually means for a house in Jefferson County

Outdoor air nationally averages about 0.4 pCi/L, indoor air about 1.3 pCi/L — Jefferson 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 Jefferson County will test well under the action level, and EPA's guidance is to test regardless of zone.

If Jefferson County tests above the action level

For a Jefferson 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 Nebraska's state radon program

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

Where Jefferson County's figures come from

The methodology guide shows exactly which EPA and Census sources feed Jefferson County's numbers. If you're unsure why a low zone still deserves a test, the zone explainer covers that directly.