What EPA's radon map says about Castro County

EPA's own radon map rates Castro County zone 2 - moderate potential, predicting a county-wide average indoor level between 2 and 4 pCi/L. Nationally, Castro County ranks higher in radon potential than 38% of rated counties (the 38th percentile).

Where Castro County sits nationally

About 7,380 people live in Castro County, Texas, spread over 894.444 square miles. Averaged across its land area, Castro County runs about 8 people per square mile. Among counties sharing Castro County's EPA zone, it outranks 14% of them by population. Castro County falls in EPA Radon Region 6, one of 503 counties nationally EPA assigns to that same geologic province.

Zone vs. an actual test

EPA's Zone 2 rating for Castro County sits below its own 4 pCi/L action level but above the national indoor average of about 1.3 pCi/L. A county-wide moderate average, like Castro County's, can still hide a specific house well above or below it — testing is what actually answers the question.

Testing and mitigation in Castro County

Mitigation cost doesn't depend on Castro 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

Castro County's test kit answers today; a Airthings radon monitor keeps answering for Castro County over time. Affiliate link, RadonZoneCheck earns a commission there, at no extra cost to you. RADONZONE-10OFF at checkout knocks 10% off.

More on how this number was built

Every figure on this page traces to EPA's own Map of Radon Zones and Census data, documented in the methodology guide. Whatever zone Castro County carries, the zone explainer covers what it does and doesn't tell you about any one house.