Is Pima County, AZ a radon risk area?

Pima County is mapped as Zone 2 - Moderate Potential by EPA — meaning the county-wide average indoor level is predicted between 2 and 4 pCi/L. Pima County sits at the 65th percentile nationally for radon potential — above 65 of every 100 rated counties.

Pima County by the numbers

About 1,080,149 people live in Pima County, Arizona, spread over 9,188.692 square miles. Population density there runs about 118 people per square mile. Rank 15 by population within its EPA zone puts Pima County at the 99th percentile among zone peers. EPA's geology-based Region 9 groups Pima County with 94 other counties nationally sharing its underlying rock and soil profile.

Why the zone isn't the answer by itself

Neither at the 4 pCi/L action level nor down at the roughly 1.3 pCi/L national indoor norm, Pima County's Zone 2 prediction lands in the gap between the two. A Zone 2 rating is a moderate county-wide average, not a guarantee about any one house in Pima County — testing is the only way to know an individual home's actual level.

Testing and mitigation in Pima County

Nothing about Pima 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 Arizona's state radon program

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

Pima 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.