What EPA's radon map says about Jefferson County

EPA's own radon map rates Jefferson County zone 3 - low potential, predicting a county-wide average indoor level below 2 pCi/L. That puts Jefferson County in the 30th percentile nationally for radon potential — higher than 30% of the counties EPA has rated.

How Jefferson County compares

About 253,948 people live in Jefferson County, Texas, spread over 876.736 square miles. Averaged across its land area, Jefferson County runs about 290 people per square mile. Among counties sharing Jefferson County's EPA zone, it outranks 90% of them by population. Jefferson County falls in EPA Radon Region 6, one of 503 counties nationally EPA assigns to that same geologic province.

What this actually means for a house in Jefferson County

At Zone 3, Jefferson County's predicted county average is under the national indoor average (~1.3 pCi/L) and well below EPA's 4 pCi/L action level — outdoor air nationally runs about 0.4 pCi/L for comparison. Even at Zone 3, Jefferson County homes are not guaranteed a low reading — zone is a county-wide average, and EPA recommends testing every home regardless of zone.

Next steps for a home in Jefferson County

Mitigation cost doesn't depend on Jefferson County's zone — it depends on the house's foundation. A typical system runs $800–$2,500 (about $1,200 typical), and testing first is what tells you whether that's needed at all.

Find Texas's state radon program

Jefferson County's test kit answers today; a Airthings radon monitor keeps answering for Jefferson County over time. Affiliate link, RadonZoneCheck earns a commission there, at no extra cost to you. Code RADONZONE-10OFF takes 10% off at checkout.

More on how this number was built

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