What EPA's radon map says about Washington Parish

EPA places Washington Parish 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. That puts Washington Parish in the 21st percentile nationally for radon potential — higher than 21% of the counties EPA has rated.

How Washington Parish compares

About 45,090 people live in Washington Parish, Louisiana, spread over 669.637 square miles. That works out to roughly 67 people per square mile. Among counties sharing Washington Parish's EPA zone, it outranks 64% of them by population. Washington Parish falls in EPA Radon Region 6, one of 503 counties nationally EPA assigns to that same geologic province.

Zone vs. an actual test

A Zone 3 county like Washington Parish is predicted closer to the 0.4 pCi/L typical outdoors than to EPA's 4 pCi/L action level. Don't read Zone 3 as a pass for Washington Parish — EPA's guidance to test every home makes no exception for counties predicted low.

Testing and mitigation in Washington Parish

Mitigation cost doesn't depend on Washington Parish'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 Louisiana's state radon program

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

The methodology guide shows exactly which EPA and Census sources feed Washington Parish's numbers. If you're unsure why a low zone still deserves a test, the zone explainer covers that directly.