Radon in South Carolina: radon map by county
EPA's Map of Radon Zones puts 1 of South Carolina's 46 counties in Zone 1 (predicted average indoor radon above 4 pCi/L), 8 in Zone 2 and 37 in Zone 3. Of 15,855 building tests that radon laboratories reported for 2008 to 2017, 18.1% were at or above EPA's 4 pCi/L action level, against 36.5% nationally (number 37 of 42 states with 1,000+ tests). The highest county share is Oconee County (42.6% of 1,035 tests).
Radon by county in South Carolina
| County | EPA zone | Lab tests | Median | 4+ pCi/L |
|---|---|---|---|---|
| Abbeville County | Zone 2 | 46 | 1.8 | 22.7% |
| Aiken County | Zone 3 | 194 | 1.3 | 13.3% |
| Allendale County | Zone 3 | 1 | 0.1 | 0% |
| Anderson County | Zone 2 | 959 | 1.1 | 11.1% |
| Bamberg County | Zone 3 | 5 | 1.0 | 5% |
| Barnwell County | Zone 3 | 6 | 1.9 | 0% |
| Beaufort County | Zone 3 | 203 | 0.7 | 2% |
| Berkeley County | Zone 3 | 78 | 0.7 | 4% |
| Calhoun County | Zone 3 | 10 | 0.6 | 0% |
| Charleston County | Zone 3 | 233 | 0.6 | 1.5% |
| Cherokee County | Zone 2 | 118 | 1.6 | 13.7% |
| Chester County | Zone 3 | 22 | 1.1 | 22.2% |
| Chesterfield County | Zone 3 | 8 | 0.6 | 0% |
| Clarendon County | Zone 3 | 3 | 0.8 | 0% |
| Colleton County | Zone 3 | 11 | 0.1 | 9.1% |
| Darlington County | Zone 3 | 25 | 0.6 | 0% |
| Dillon County | Zone 3 | 16 | 0.3 | 0% |
| Dorchester County | Zone 3 | 85 | 1.0 | 4.8% |
| Edgefield County | Zone 3 | 10 | 1.2 | 25% |
| Fairfield County | Zone 3 | 23 | 0.9 | 7.4% |
| Florence County | Zone 3 | 56 | 0.7 | 0% |
| Georgetown County | Zone 3 | 26 | 0.1 | 0% |
| Greenville County | Zone 1 | 7,077 | 1.7 | 19.6% |
| Greenwood County | Zone 3 | 96 | 1.0 | 7.1% |
| Hampton County | Zone 3 | 3 | 0.1 | 0% |
| Horry County | Zone 3 | 87 | 0.6 | 0.9% |
| Jasper County | Zone 3 | 9 | 0.6 | 0% |
| Kershaw County | Zone 3 | 64 | 0.7 | 5% |
| Lancaster County | Zone 3 | 278 | 1.6 | 13.6% |
| Laurens County | Zone 2 | 175 | 1.3 | 13.9% |
| Lee County | Zone 3 | 3 | 1.1 | 0% |
| Lexington County | Zone 3 | 488 | 0.9 | 12.5% |
| Marion County | Zone 3 | 8 | 0.9 | 0% |
| Marlboro County | Zone 3 | 7 | 0.9 | 0% |
| McCormick County | Zone 3 | 10 | 1.1 | 0% |
| Newberry County | Zone 3 | 77 | 1.1 | 16% |
| Oconee County | Zone 2 | 1,035 | 3.3 | 42.6% |
| Orangeburg County | Zone 3 | 59 | 0.9 | 5.7% |
| Pickens County | Zone 2 | 969 | 1.8 | 23.6% |
| Richland County | Zone 3 | 589 | 0.7 | 4.9% |
| Saluda County | Zone 3 | 11 | 1.1 | 16.7% |
| Spartanburg County | Zone 2 | 1,665 | 1.7 | 19.1% |
| Sumter County | Zone 3 | 37 | 1.3 | 11.9% |
| Union County | Zone 3 | 24 | 1.0 | 0% |
| Williamsburg County | Zone 3 | 13 | 0.6 | 0% |
| York County | Zone 2 | 933 | 1.2 | 13.6% |
Lab tests: buildings tested by radon laboratories, 2008 to 2017; median in pCi/L; “4+ pCi/L” is the share of tests at or above EPA's action level. n/a: no value on file (no tests, or too few to report).
What the zones mean
Zone 1 counties have a predicted average indoor radon screening level above 4 pCi/L, Zone 2 from 2 to 4 pCi/L and Zone 3 below 2 pCi/L. The prediction is from 1993 indoor measurements, geology, aerial radioactivity, soils and foundation types. EPA: “This map should not be used to determine if individual homes need to be tested.” EPA recommends fixing a home at 4 pCi/L or more and considering a fix between 2 and 4 pCi/L, because there is no known safe level of exposure.
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Radon in South Carolina: questions
What radon zone is South Carolina?
EPA's 1993 map does not give states one zone; it zones each county. In South Carolina, 1 county is Zone 1, 8 Zone 2 and 37 Zone 3. EPA says the map "should not be used to determine if individual homes need to be tested".
Which South Carolina counties have the highest radon levels?
By the share of laboratory tests at or above 4 pCi/L for 2008 to 2017 (counties with 20 or more tests): Oconee County 42.6% (median 3.3 pCi/L, 1,035 tests); Pickens County 23.6% (median 1.8 pCi/L, 969 tests); Abbeville County 22.7% (median 1.8 pCi/L, 46 tests); Chester County 22.2% (median 1.1 pCi/L, 22 tests); Greenville County 19.6% (median 1.7 pCi/L, 7,077 tests).
How common is high radon in South Carolina?
18.1% of the 15,855 tests in the laboratory data for South Carolina (2008 to 2017) were at or above 4 pCi/L; the national share was 36.5%. Buildings are tested by choice, often because of a sale or a concern, so the share describes the tests on file, not every home.
Should I test for radon in South Carolina?
Yes. EPA recommends testing every home no matter where it is, fixing it at 4 pCi/L or more and considering a fix between 2 and 4 pCi/L, because there is no known safe level of radon exposure.
States bordering South Carolina
Other free hazard lookups
- Radon by county and ZIP codeEPA radon zone and the radon test results on file for any county, ZIP code or address.
- Fault lines near an addressUSGS-mapped earthquake faults within 5 miles, their age and slip rate, and the USGS seismic hazard value.
- Power lines near an addressHigh-voltage transmission lines within 1 mile from federal maps, with voltage and distance.
- Flood zone lookupThe FEMA flood zone mapped at any US address. Not an official flood zone determination.
- Superfund sites near an addressThe nearest EPA Superfund (NPL) sites and their status.
All of these, plus wetlands, FEMA hazard ratings and the federal contamination lists, are in the Environmental Records Report for any US address ($29).
Superfund sites in South Carolina · Radon map of every state
Data compiled 2026-10-20. County-level screening information, not a radon measurement of any building.