What EPA's radon map says about Shasta County

EPA places Shasta County in Zone 3 - Low Potential — a predicted county-wide average indoor radon level below 2 pCi/L, based on the geology, soil and aerial radioactivity data behind EPA's national map. Nationally, Shasta County ranks higher in radon potential than 28% of rated counties (the 28th percentile).

How Shasta County compares

About 181,121 people live in Shasta County, California, spread over 3,775.651 square miles. Averaged across its land area, Shasta County runs about 48 people per square mile. Among counties sharing Shasta County's EPA zone, it outranks 86% of them by population. Geologically, Shasta County is grouped into EPA Region 9 alongside 94 other counties that share its rock and soil setting.

What this actually means for a house in Shasta County

Shasta County's predicted average sits below the national indoor average of about 1.3 pCi/L, well under EPA's 4 pCi/L action level. A Zone 3 label describes Shasta County's average, not any one basement or slab in it — testing is still the only way an individual homeowner actually finds out.

Next steps for a home in Shasta County

Mitigation cost doesn't depend on Shasta 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 California's state radon program

Shasta County's test kit answers today; a Airthings radon monitor keeps answering for Shasta 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

Shasta County's zone, rank and region all trace back to named EPA and Census sources — the methodology guide lists exactly which ones. Whatever zone Shasta County carries, the zone explainer covers what it does and doesn't tell you about any one house.