South Carolina: 46 counties covered
Of 46 rated South Carolina counties, 1 is 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.
- Greenville County
- Charleston County
- Richland County
- Horry County
- Spartanburg County
- Lexington County
- York County
- Berkeley County
- Anderson County
- Beaufort County
- Aiken County
- Dorchester County
- Pickens County
- Florence County
- Lancaster County
- Sumter County
- Orangeburg County
- Oconee County
- Kershaw County
- Laurens County
- Greenwood County
- Georgetown County
- Darlington County
- Cherokee County
- Chesterfield County
- Colleton County
- Newberry County
- Jasper County
- Chester County
- Clarendon County
- Williamsburg County
- Edgefield County
- Marion County
- Dillon County
- Union County
- Marlboro County
- Abbeville County
- Barnwell County
- Fairfield County
- Saluda County
- Hampton County
- Lee County
- Calhoun County
- Bamberg County
- McCormick County
- Allendale County