Is Cobb County, GA a radon risk area?

EPA places Cobb County in Zone 1 - Highest Potential — a predicted county-wide average indoor radon level above 4 pCi/L, based on the geology, soil and aerial radioactivity data behind EPA's national map. That puts Cobb County in the 99th percentile nationally for radon potential — higher than 99% of the counties EPA has rated.

Cobb County by the numbers

About 787,538 people live in Cobb County, Georgia, spread over 339.701 square miles. Population density there runs about 2,318 people per square mile. Rank 18 by population within its EPA zone puts Cobb County at the 98th percentile among zone peers. Cobb County falls in EPA Radon Region 4, one of 736 counties nationally EPA assigns to that same geologic province.

What this actually means for a house in Cobb County

Outdoor air nationally averages about 0.4 pCi/L, indoor air about 1.3 pCi/L — Cobb County's Zone 1 prediction clears both of those and EPA's fix-it threshold besides. Being in Zone 1 raises the odds Cobb County homes test above the action level, but it does not mean any specific house does — EPA recommends every home be tested, in every zone, because the only way to know is to test.

If Cobb County tests above the action level

Nothing about Cobb 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 Georgia's state radon program

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

Cobb County's zone, rank and region all trace back to named EPA and Census sources — the methodology guide lists exactly which ones. The guide to what a radon zone actually means covers why testing matters in every zone, not just Zone 1.