Louisiana: 64 counties covered
Of 64 rated Louisiana counties, 0 are in EPA's highest radon-potential zone (Zone 1) — but every county page links to testing guidance regardless of zone, because a county rating is a county-wide average, not a reading for any one house.
- East Baton Rouge Parish
- Jefferson Parish
- Orleans Parish
- St. Tammany Parish
- Lafayette Parish
- Caddo Parish
- Calcasieu Parish
- Ouachita Parish
- Livingston Parish
- Tangipahoa Parish
- Ascension Parish
- Bossier Parish
- Rapides Parish
- Terrebonne Parish
- Lafourche Parish
- St. Landry Parish
- Iberia Parish
- Vermilion Parish
- Acadia Parish
- St. Martin Parish
- St. Charles Parish
- Lincoln Parish
- St. Mary Parish
- Vernon Parish
- Washington Parish
- St. Bernard Parish
- St. John the Baptist Parish
- Avoyelles Parish
- Beauregard Parish
- Natchitoches Parish
- Webster Parish
- Evangeline Parish
- Jefferson Davis Parish
- Iberville Parish
- West Baton Rouge Parish
- De Soto Parish
- Morehouse Parish
- Allen Parish
- Plaquemines Parish
- Grant Parish
- Sabine Parish
- Union Parish
- Assumption Parish
- Pointe Coupee Parish
- Richland Parish
- East Feliciana Parish
- St. James Parish
- Franklin Parish
- Concordia Parish
- West Feliciana Parish
- Jackson Parish
- LaSalle Parish
- Claiborne Parish
- Winn Parish
- Bienville Parish
- St. Helena Parish
- Caldwell Parish
- West Carroll Parish
- Madison Parish
- Catahoula Parish
- Red River Parish
- East Carroll Parish
- Cameron Parish
- Tensas Parish