Is Washington County, TX a radon risk area?

EPA places Washington 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. Nationally that's the 20th percentile for radon potential — Washington County outranks 20% of every county EPA has rated.

How Washington County compares

About 37,810 people live in Washington County, Texas, spread over 604.196 square miles. That works out to roughly 63 people per square mile. Rank 421 by population within its EPA zone puts Washington County at the 59th percentile among zone peers. Geologically, Washington County is grouped into EPA Region 6 alongside 502 other counties that share its rock and soil setting.

What this actually means for a house in Washington County

At Zone 3, Washington County's predicted county average is under the national indoor average (~1.3 pCi/L) and well below EPA's 4 pCi/L action level — outdoor air nationally runs about 0.4 pCi/L for comparison. Even at Zone 3, Washington County homes are not guaranteed a low reading — zone is a county-wide average, and EPA recommends testing every home regardless of zone.

Next steps for a home in Washington County

Nothing about Washington 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 Texas's state radon program

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

Every figure on this page traces to EPA's own Map of Radon Zones and Census data, documented in the methodology guide. The guide to what a radon zone actually means covers why testing matters in every zone, not just Zone 1.