What EPA's radon map says about Starr County

EPA places Starr County in Zone 3 - Low Potential — a predicted county-wide average indoor radon level below 2 pCi/L, based on the geology, soil and aerial radioactivity data behind EPA's national map. Starr County sits at the 24th percentile nationally for radon potential — above 24 of every 100 rated counties.

Where Starr County sits nationally

About 66,587 people live in Starr County, Texas, spread over 1,223.179 square miles. Averaged across its land area, Starr County runs about 54 people per square mile. Among counties sharing Starr County's EPA zone, it outranks 73% of them by population. Starr County falls in EPA Radon Region 6, one of 503 counties nationally EPA assigns to that same geologic province.

What this actually means for a house in Starr County

Starr County's predicted average sits below the national indoor average of about 1.3 pCi/L, well under EPA's 4 pCi/L action level. A Zone 3 rating means Starr County's county-wide average is predicted low, but EPA is explicit that a meaningful share of homes in low-potential zones still test above the action level — a low zone is not a reason to skip testing.

If Starr County tests above the action level

Mitigation cost doesn't depend on Starr 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 Texas's state radon program

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

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