What EPA's radon map says about St. Charles Parish

St. Charles Parish is mapped as Zone 3 - Low Potential by EPA — meaning the county-wide average indoor level is predicted below 2 pCi/L. That puts St. Charles Parish in the 22nd percentile nationally for radon potential — higher than 22% of the counties EPA has rated.

How St. Charles Parish compares

About 50,400 people live in St. Charles Parish, Louisiana, spread over 277.742 square miles. That works out to roughly 181 people per square mile. Among counties sharing St. Charles Parish's EPA zone, it outranks 67% of them by population. EPA's geology-based Region 6 groups St. Charles Parish with 502 other counties nationally sharing its underlying rock and soil profile.

Zone vs. an actual test

St. Charles Parish'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 label describes St. Charles Parish's average, not any one basement or slab in it — testing is still the only way an individual homeowner actually finds out.

If St. Charles Parish tests above the action level

Mitigation cost doesn't depend on St. Charles 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

St. Charles Parish's test kit answers today; a Airthings radon monitor keeps answering for St. Charles Parish 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

St. Charles Parish's zone, rank and region all trace back to named EPA and Census sources — the methodology guide lists exactly which ones. If you're unsure why a low zone still deserves a test, the zone explainer covers that directly.