If you live in Aiken County, you have likely heard radon come up during a home inspection, seen it mentioned in a local news investigation, or noticed that Aiken keeps appearing on elevated radon lists across South Carolina. The question that follows is a reasonable one: why does Aiken seem to have consistently higher radon levels than many surrounding areas, including parts of Georgia just across the river?
The answer involves geology, soil type, and ongoing local discussion about industrial history. Here is a clear explanation of each factor.
What Radon Is and How It Gets Into Homes
Radon is a naturally occurring radioactive gas produced when uranium in soil and rock decays over geological time. It seeps upward through the ground and enters structures through foundation cracks, crawl space openings, slab joints, plumbing penetrations, and basement walls. The Environmental Protection Agency identifies radon as the second leading cause of lung cancer in the United States, behind smoking. The EPA action level is 4.0 pCi/L (picocuries per liter) — above this threshold, action to reduce indoor radon is recommended.
The Centers for Disease Control and Prevention notes that approximately 21,000 Americans die from radon-induced lung cancer annually, and that the risk can be substantially reduced by testing and acting when levels are elevated.
Documented Radon Levels in Aiken County
A 2020 WRDW I-Team investigation found radon readings in Aiken County reaching as high as 74 pCi/L — far above the EPA action level. The investigation also reported that some zip codes near New Ellenton and the Savannah River Site showed especially elevated readings, and that certain areas in Aiken tested higher than neighboring counties in Georgia. This was not isolated anecdotal data; the investigation drew on testing results compiled across the county over time.
Aiken County consistently appears in South Carolina’s higher radon data, and that pattern has a geological explanation.
The Primary Cause: Aiken’s Geology
The dominant factor in Aiken’s elevated radon levels is its underlying geology. Aiken sits near what geologists call the Fall Line, the geological transition zone between South Carolina’s Coastal Plain and the Piedmont region. This transition matters for radon because:
- The Piedmont region contains uranium-bearing granite and metamorphic rock formations
- Uranium naturally and continuously breaks down into radon gas
- Aiken’s position near this geological boundary means its soils have meaningful uranium content
In simple terms: the geology beneath Aiken has both the source material that generates radon and the proximity to Piedmont formations that amplifies that generation compared to areas farther into the coastal plain.
The Sandhills Factor
Aiken is also part of South Carolina’s Sandhills region, an area composed of ancient coastal dune formations and loose sandy soils. Sandy soil is more porous and less compact than clay-heavy soil, which makes it easier for gases to move through. Radon generated beneath the surface can migrate upward more readily through sandy Sandhills soil than through denser soils that would slow its movement.
Compare this to areas with heavy clay soils, which act as a partial natural barrier to radon migration. Clay soils do not eliminate radon risk, but they slow the rate at which radon moves from the subsoil into structures. The Sandhills soil composition gives radon a more direct pathway into homes.
Why Homes in the Same Neighborhood Test Differently
Even within Aiken County, two homes on the same street can have significantly different radon levels. Factors that create this variation include:
- Foundation type: Homes with basements or crawl spaces have more soil contact area than slab-on-grade homes, creating more potential radon entry points.
- Foundation condition: Older homes or homes that have settled may have more cracks and gaps around the foundation perimeter.
- HVAC operation: Different heating and cooling configurations create different pressure differentials inside the home, which affects how strongly radon is drawn in from the soil.
- Building tightness: Energy-efficient homes that are well-sealed reduce air exchange with the outdoors, which can allow radon to accumulate at higher concentrations than in leakier older homes.
The Savannah River Site Question
Some Aiken residents have raised questions about whether the Savannah River Site (SRS) contributes to elevated residential radon levels. SRS historically handled radioactive materials and nuclear weapons production, including uranium processing, and has a documented history of radioactive material in soil and groundwater. The WRDW investigation noted that some of the highest radon readings were found in zip codes near SRS.
However, no definitive scientific study has established that SRS operations directly cause elevated radon in residential homes. Most environmental scientists point to the underlying natural geology — the uranium-bearing Piedmont rock formations and Sandhills soil — as the primary driver. The question continues to come up in the community, and the absence of a definitive answer does not resolve the concern for residents in affected zip codes. What is clear is that testing your specific home is the only way to know your actual radon level.
Why Winter Testing Often Produces Higher Results in Aiken
Radon levels in any home are not constant throughout the year. Winter conditions typically produce higher indoor radon concentrations because homes are sealed more tightly, reducing natural air exchange. Heating systems also create pressure differences — the stack effect — where warm indoor air rising through the structure draws outside air and soil gases (including radon) upward from below. In Aiken, where baseline radon potential is already higher than average, this seasonal amplification can push levels significantly above the EPA action threshold even in homes that tested acceptable in summer.
Testing in Aiken County
Given Aiken’s documented radon profile, testing is not a precaution — it is a baseline step every homeowner, buyer, and renter in the county should take. Even homes that appear low-risk based on general assumptions about new construction or upper-floor position should be confirmed with an actual measurement.
EnviroPro 360 provides professional radon testing for homeowners throughout Aiken, North Augusta, Augusta, Evans, Martinez, Grovetown, and the broader CSRA. Testing follows EPA measurement protocols with calibrated equipment. Results are provided with a plain-language explanation of what the number means and what the appropriate next steps are if levels are elevated.
Contact EnviroPro 360 to schedule radon testing for your Aiken County home and get a result you can act on.
