Is Washington County, MS a radon risk area?

Washington County is mapped as Zone 3 - Low Potential by EPA — meaning the county-wide average indoor level is predicted below 2 pCi/L. Nationally that's the 20th percentile for radon potential — Washington County outranks 20% of every county EPA has rated.

Washington County by the numbers

About 41,181 people live in Washington County, Mississippi, spread over 724.147 square miles. Averaged across its land area, Washington County runs about 57 people per square mile. Rank 399 by population within its EPA zone puts Washington County at the 61st percentile among zone peers. Geologically, Washington County is grouped into EPA Region 4 alongside 735 other counties that share its rock and soil setting.

Zone vs. an actual test

Well clear of both the 1.3 pCi/L national indoor average and EPA's 4 pCi/L action level, Washington County's Zone 3 prediction is the low end of the scale. A Zone 3 label describes Washington County's average, not any one basement or slab in it — testing is still the only way an individual homeowner actually finds out.

If Washington County tests above the action level

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 Mississippi'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. RADONZONE-10OFF at checkout knocks 10% off.

More on how this number was built

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