What Lancaster County's 3.6 pCi/L Radon Average Means for One House
September 1, 2026
The county average is a description of nineteen thousand tests piled together. A Lincoln house reads whatever its own soil, slab and airflow produce, and the only way to know is to measure that house.
The number and where it comes from
Nebraska law requires the state to publish five years of radon measurements by county. The most recent report puts Lancaster County at 3.6 pCi/L across 19,828 pre-mitigation tests recorded between October 2018 and September 2023. That is below the EPA action level of 4 and above the 2.7 pCi/L reporting line written into the statute.
It is a real, well-populated number. It is also nearly useless for deciding whether to test a particular house, and the reason is the shape of the data behind it.
Why averages hide the houses that matter
Radon readings are not spread evenly around the average. Most homes read low, and a long tail reads high. Statewide, the original screening survey found about 54 percent of single-family homes above 4 pCi/L and about 2 percent above 20. A county can average 3.6 while a third of its houses need mitigation and a handful read ten times the action level.
Two homes on the same Lincoln street can differ by a factor of ten. The soil under one slab is more permeable, one basement has an unsealed sump pit, one furnace pulls harder on the house. None of that shows in the county figure.
- Soil: gravel and fractured material under the slab moves radon freely; tight clay slows it.
- Foundation: cracks, floor-wall joints, sump pits and crawl spaces are the entry points.
- Airflow: a tight house in the heating season pulls soil gas in through every gap.
- Level: basements read highest; the test belongs on the lowest lived-in floor.
How Lincoln compares with the counties around it
The same report gives Douglas County 3.9, Sarpy 4.8, Seward 7.0, Saunders 6.7, Cass 7.5, Otoe 7.3 and Gage 7.9. Lancaster sits in the milder band of southeast Nebraska. The county data page lays the whole table out with sources.
That comparison matters for anyone buying in Seward, Crete, Wahoo or Beatrice, where the county averages run roughly double Lincoln's. It matters less for a Lincoln homeowner, because a personal reading of 9 is not softened by a county average of 3.6.
What the average is actually good for
It answers a different question: is radon a real issue in this area at all. In Lancaster County, yes. The county is EPA Zone 1, the state is among the highest-radon states in the country, and the Legislature wrote radon-resistant construction into the building code for that reason.
So the average justifies testing every house. It does not predict any house. That is the whole use of it.
The county figure also explains why real estate agents in Lincoln treat a radon contingency as routine rather than alarming: in a Zone 1 county the test is expected, the result is negotiated calmly, and a mitigation system is a normal line item rather than a red flag on the property.
From the average to a decision
A radon test under closed-house conditions gives the number that belongs to the address. Under 2, retest in two years. Between 2 and 4, EPA says consider fixing; the 2-to-4 guide covers that band. At or above 4, mitigate.
For a Lincoln homeowner deciding whether radon mitigation in Lincoln is worth pursuing, the county average settles that it is worth a test. Everything after that comes from the test.
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Quick Answers
Is 3.6 pCi/L a safe radon level?
There is no known safe level. EPA sets 4 as the action level and recommends considering mitigation between 2 and 4. The World Health Organization uses 2.7 as its reference. A county average near those lines means many individual homes are above them.
Are newer Lincoln neighborhoods lower in radon?
Not reliably. Newer homes built to the current state code include passive radon-resistant features that reduce entry, but they are also tighter, which concentrates whatever gets in. New homes should be tested like any other.
Where does the 19,828 figure come from?
Licensed Nebraska measurement businesses must report every test to the state monthly. The Department of Health and Human Services compiles five years of those reports by county and sends them to the Legislature each January.