Santa Cruz County, AZ: EPA's radon zone, explained

EPA places Santa Cruz County in Zone 2 - Moderate Potential — a predicted county-wide average indoor radon level between 2 and 4 pCi/L, based on the geology, soil and aerial radioactivity data behind EPA's national map. Santa Cruz County sits at the 55th percentile nationally for radon potential — above 55 of every 100 rated counties.

Where Santa Cruz County sits nationally

Santa Cruz County, Arizona is home to about 50,508 people across 1,236.26 square miles. Population density there runs about 41 people per square mile. By population, Santa Cruz County is the 342nd largest of every county sharing its EPA zone — the 67th percentile by population within that zone. Geologically, Santa Cruz 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 Santa Cruz County

Santa Cruz County's predicted average falls between EPA's 4 pCi/L action level and the national indoor average of about 1.3 pCi/L (outdoor air runs roughly 0.4 pCi/L). A county-wide moderate average, like Santa Cruz County's, can still hide a specific house well above or below it — testing is what actually answers the question.

If Santa Cruz County tests above the action level

For a Santa Cruz County homeowner, the order is simple: test first, since a kit costs a small fraction of what mitigation would. Only if the result clears 4 pCi/L does a system — typically $800–$2,500, about $1,200 for a common install — become worth pricing out.

Find Arizona's state radon program

For Santa Cruz County, an ongoing number beats a one-time test - a Airthings radon monitor tracks Santa Cruz County's levels over time. RadonZoneCheck earns a commission there, at no extra cost to you. Code RADONZONE-10OFF takes 10% off at checkout.

Where Santa Cruz County's figures come from

The methodology guide shows exactly which EPA and Census sources feed Santa Cruz County's numbers. If you're unsure why a low zone still deserves a test, the zone explainer covers that directly.