Is Marion County, TX a radon risk area?

EPA's own radon map rates Marion County zone 3 - low potential, predicting a county-wide average indoor level below 2 pCi/L. Nationally that's the 6th percentile for radon potential — Marion County outranks 6% of every county EPA has rated.

Marion County by the numbers

About 9,704 people live in Marion County, Texas, spread over 380.902 square miles. Averaged across its land area, Marion County runs about 25 people per square mile. Rank 828 by population within its EPA zone puts Marion County at the 20th percentile among zone peers. Geologically, Marion County is grouped into EPA Region 6 alongside 502 other counties that share its rock and soil setting.

Zone vs. an actual test

Marion County's Zone 3 prediction undercuts the roughly 1.3 pCi/L most US homes average, nowhere near EPA's 4 pCi/L threshold for recommending mitigation. A Zone 3 rating means Marion 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.

Next steps for a home in Marion County

Nothing about Marion 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

Marion County's test kit answers today; a Airthings radon monitor keeps answering for Marion 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. The guide to what a radon zone actually means covers why testing matters in every zone, not just Zone 1.