Is Tehama County, CA a radon risk area?

EPA's own radon map rates Tehama County zone 3 - low potential, predicting a county-wide average indoor level below 2 pCi/L. Nationally, Tehama County ranks higher in radon potential than 24% of rated counties (the 24th percentile).

How Tehama County compares

About 64,451 people live in Tehama County, California, spread over 2,949.137 square miles. That works out to roughly 22 people per square mile. Rank 292 by population within its EPA zone puts Tehama County at the 72nd percentile among zone peers. Geologically, Tehama County is grouped into EPA Region 9 alongside 94 other counties that share its rock and soil setting.

Why the zone isn't the answer by itself

At Zone 3, Tehama 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, Tehama County homes are not guaranteed a low reading — zone is a county-wide average, and EPA recommends testing every home regardless of zone.

Testing and mitigation in Tehama County

Nothing about Tehama County's EPA zone changes the mitigation number: $800–$2,500 nationally (around $1,200 typical), set by the house's foundation rather than the county it sits in — and only relevant once a test actually clears 4 pCi/L.

Find California's state radon program

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

More on how this number was built

Tehama County's zone, rank and region all trace back to named EPA and Census sources — the methodology guide lists exactly which ones. If you're unsure why a low zone still deserves a test, the zone explainer covers that directly.