What EPA's radon map says about Los Angeles County

EPA's own radon map rates Los Angeles County zone 2 - moderate potential, predicting a county-wide average indoor level between 2 and 4 pCi/L. Los Angeles County sits at the 66th percentile nationally for radon potential — above 66 of every 100 rated counties.

How Los Angeles County compares

About 9,757,179 people live in Los Angeles County, California, spread over 4,060.29 square miles. That works out to roughly 2,403 people per square mile. Among counties sharing Los Angeles County's EPA zone, it outranks 100% of them by population. EPA's geology-based Region 9 groups Los Angeles County with 94 other counties nationally sharing its underlying rock and soil profile.

Zone vs. an actual test

Los Angeles County's Zone 2 prediction clears the 1.3 pCi/L national indoor average without reaching EPA's own 4 pCi/L point for recommending a fix. Middle-of-the-pack doesn't mean risk-free for any one Los Angeles County address — a moderate county average still leaves individual homes to test either side of it.

If Los Angeles County tests above the action level

Mitigation cost doesn't depend on Los Angeles 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

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

More on how this number was built

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