Is Hillsborough County, FL a radon risk area?

EPA's own radon map rates Hillsborough County zone 2 - moderate potential, predicting a county-wide average indoor level between 2 and 4 pCi/L. Nationally that's the 66th percentile for radon potential — Hillsborough County outranks 66% of every county EPA has rated.

Hillsborough County by the numbers

About 1,581,426 people live in Hillsborough County, Florida, spread over 1,022.539 square miles. That works out to roughly 1,547 people per square mile. Rank 9 by population within its EPA zone puts Hillsborough County at the 99th percentile among zone peers. Hillsborough 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 Hillsborough County

EPA's Zone 2 rating for Hillsborough County sits below its own 4 pCi/L action level but above the national indoor average of about 1.3 pCi/L. Middle-of-the-pack doesn't mean risk-free for any one Hillsborough County address — a moderate county average still leaves individual homes to test either side of it.

Testing and mitigation in Hillsborough County

Nothing about Hillsborough 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 Florida's state radon program

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

The methodology guide shows exactly which EPA and Census sources feed Hillsborough County's numbers. The guide to what a radon zone actually means covers why testing matters in every zone, not just Zone 1.