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Radon Levels in Horry County, South Carolina

EPA puts Horry County in Zone 3, its lowest radon zone, and most reported tests there come back low, though 0.9% of 106 (2008 to 2017, laboratory totals) reached 4 pCi/L. Homes with elevated levels occur in all three zones, so only a test measures yours.

Data checked By Radon411Methodology

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  • Share at 4+ pCi/L

    0.9%

    18.5 pts below SC

    Horry
    0.9%
    SC
    19.4%

    106 tests, 2008 to 2017

  • Median result

    0.6pCi/L

    Below action level

    Horry
    0.6 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    106

    16th of 24 by tests

    Horry
    106
    Greenville
    12,004

    Reported to CDC before any fix, 2008 to 2017

  • EPA radon zone

    Zone 3

    Lower potential

    1. 1
    2. 2
    3. Zone 3

    1 highest, 3 lowest

    EPA predicts under 2 pCi/L indoors

  • Rank in SC

    23 of 24

    Lowest quarter

    Horry
    0.9%
    Oconee
    42.6%

    By share, of 24 with 30+ tests

Read a result for Horry County

Starts at Horry County's median, 0.6 pCi/L

0.6pCi/L

EPA’s own thresholds; the figures are the area’s, never this home’s.

EPA’s reading of 0.6 pCi/L

Below 2 pCi/L

  1. Under 20 to 1.9 pCi/L
  2. 2 to 4consider a fix
  3. 4 and aboveEPA says fix it

This result is below 2 pCi/L, the level at which EPA says a fix should be considered. Horry County's median reported result, 2008 to 2017.

Interpret this reading

The data

Horry County, At a glance

Horry County at a glance

Predicted: EPA radon zone

EPA Zone 3: lower predicted potential

is EPA's lowest class, and its forecast for Horry County as a whole is an average indoor of less than 2 pCi/L (less than 75 Bq/m³). A low zone clears no address in it: homes above EPA's turn up in all three zones.

USGS geologic potential: Low across 100% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

Radon tests reported for Horry County, 2008 to 2017, laboratory

Reported results by concentration band, Horry County, 2008 to 2017, laboratory
Under 2 pCi/L: 98%2 to 4 pCi/L: 1%4 pCi/L and above: 1%

Of 106 pre-mitigation tests reported to CDC, not homes in this area.

Reported results by concentration band, Horry County, 2008 to 2017, laboratory: data table
Result bandTests MeasuredShare Measured
Under 2 pCi/L10498.1%
2 to 4 pCi/L10.9%
4 pCi/L and above10.9%
What these figures count

These are the 106 tests reported to CDC for Horry County over 2008 to 2017 (laboratory totals), many from homes being sold or already suspected of a problem: they describe the county's reported tests, not this house.

Measured: CDC tracking data. Figure above: 2008 to 2017, laboratory. Measured data period: 2005 to 2017 (every CDC figure on file).

How to read these figures

Horry County, Compared

Horry County radon figures, compared

Calculated by Radon411

Only 1 of 106 radon tests reported for Horry County over the 2008 to 2017 laboratory totals reached 4 pCi/L (0.9%). The median result, 0.6 pCi/L, sits below 2, well under EPA's 4 pCi/L action level, and the top reported result was 22.2 pCi/L.

Across 46 South Carolina counties pooled together, 19.4% of tests reached that level, so Horry County runs 18.5 points below its state. Against the national pool of 35.7%, the gap is 34.8 points lower. Its place in the state: 23rd of 24 South Carolina counties with 30 or more tests for the same period.

Zone 3 on EPA's map (predicted average under 2 pCi/L) and a 0.9% share point the same way here. Of 3 neighbours with a figure, 1 reported a larger share at or above 4 pCi/L and 2 a smaller one; the spread is 0.0% (Columbus County, NC) to 3.8% (Robeson County, NC).

Below the action level, 104 tests (98.1%) came in under 2 pCi/L, against 57.4% statewide, and 1 tests (0.9%) fell between 2 and 4, against 23.1% statewide. USGS geology rates 100% of the county's land low radon potential.

CDC's ten-year totals for Horry County went from 89 tests (2005 to 2014) to 106 (2008 to 2017), the share going from 1.1% to 0.9%.

Horry County against South Carolina, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Horry County
Horry County1060.9%0.6 pCi/LThis county
South Carolina, pooled46 counties, pooled26,48119.4%Not pooled+18.5 points
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled+34.8 points
Oconee Countyhighest in the state2,46942.6%3.3 pCi/L+41.7 points
Florence Countylowest in the state590.0%0.7 pCi/L−0.9 points
Robeson County, NCborders it533.8%0.8 pCi/L+2.9 points
Dillon County, SCborders it180.0%0.3 pCi/L−0.9 points
Georgetown County, SCborders it290.0%0.1 pCi/L−0.9 points
Brunswick County, NCborders it620.0%0.5 pCi/L−0.9 points
Columbus County, NCborders it310.0%0.1 pCi/L−0.9 points
Marion County, SCborders it90.0%0.9 pCi/L−0.9 points
Where Horry County's reported results fell, 2008 to 2017, laboratory, beside South Carolina and the United States
ResultHorry County testsHorry County shareSouth Carolina shareU.S. shareAgainst South Carolina
Under 2 pCi/L10498.1%57.4%39.6%+40.7 points
2 to 4 pCi/L10.9%23.1%24.7%−22.2 points
4 pCi/L and above10.9%19.4%35.7%−18.5 points
Horry County ranked among the 24 South Carolina counties with 30 or more tests, by share at or above 4 pCi/L, 2008 to 2017, laboratory
CountyRankTestsAt or above 4 pCi/LMedian
Anderson County14 of 241,73311.1%1.1 pCi/L
Greenwood County15 of 241137.1%1.0 pCi/L
Orangeburg County16 of 24535.7%0.9 pCi/L
Kershaw County17 of 24605.0%0.7 pCi/L
Richland County18 of 246714.9%0.7 pCi/L
Dorchester County19 of 241044.8%1.0 pCi/L
Berkeley County20 of 24994.0%0.7 pCi/L
Beaufort County21 of 242462.0%0.7 pCi/L
Charleston County22 of 242721.5%0.6 pCi/L
Horry County23 of 241060.9%0.6 pCi/L
Florence County24 of 24590.0%0.7 pCi/L
Horry County ten-year laboratory totals, against South Carolina's pooled share
PeriodTestsAt or above 4 pCi/LMedianHighestSouth Carolina, pooledChange from the row before
2008 to 20171060.9%0.6 pCi/L22.2 pCi/L19.4%−0.2 points
2007 to 2016911.1%0.6 pCi/L22.2 pCi/L19.3%Level
2006 to 2015921.1%0.5 pCi/L22.2 pCi/L19.8%Level
2005 to 2014891.1%0.5 pCi/L22.2 pCi/L19.8%First on file

Pooled shares: Radon411's sum of CDC's county counts for one period.

Horry County, Geology

The ground under Horry County

Predicted

USGS's geologic map puts all of Horry County's mapped land in one class: low radon potential. The map puts 65.9% of Horry County in the area it calls Lower Coastal Plain and 33.6% in Upper and Middle Coastal Plain. USGS gives the first a radon index of 7 and the second 8, both in the low band (5 to 8).

USGS's geologic areas under Horry County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Lower Coastal PlainDune, beach, and marine sediments.Low765.9%
Upper and Middle Coastal PlainTertiary coastal plain sandy and silty sediments and marsh deposits.Low833.6%

Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.

Horry County beside the ground around it

Across South Carolina 0.2% of the land is rated high; none of Horry County's is. None of the 6 counties that border it has any moderate-potential ground either.

Share of land by USGS radon potential: Horry County, the 6 counties bordering it and South Carolina
AreaEPA zoneLow potentialModerate potentialHigh potential
Horry CountyZone 399.6%NoneNone
Marion CountyZone 3100%NoneNone
Columbus County, NCZone 3100%NoneNone
Georgetown CountyZone 393.9%NoneNone
Dillon CountyZone 3100%NoneNone
Brunswick County, NCZone 393.4%NoneNone
Robeson County, NCZone 3100%NoneNone
South Carolina46 counties, pooled by land areaVaries80.8%18.2%0.2%

The map rates the ground, not the air in any home.

Local help

Horry County, Local resources

Radon testing and mitigation in Horry County

Listed radon businesses with an address in Horry County:

Listed radon professionals by town: Myrtle Beach

What South Carolina's program says
Phone
1-800-768-0362
Email
radon@des.sc.gov

What it means

Horry County, Questions

Questions about radon in Horry County

Are radon levels high in Horry County?

Over the 2008 to 2017 laboratory totals, 0.9% of the radon tests reported to CDC for Horry County, South Carolina were at or above 4 pCi/L, and the median reported pre-mitigation result was 0.6 pCi/L. Of 24 South Carolina counties with 30 or more tests for the same period, 22 reported a higher share; pooled, the state comes to 19.4%.

Which counties border Horry County?

Horry County borders 6 counties: Marion County, SC, Columbus County, NC, Georgetown County, SC, Dillon County, SC, Brunswick County, NC and Robeson County, NC.

Products

Horry County, Products

Testing a home in Horry County

In Horry County, 0.9% of 106 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 19.4% pooled across South Carolina. Zone 3 is the lowest label, yet homes at or above 4 pCi/L occur in every zone: a short-term kit (2 to 90 days) is the quick first check in Horry County.

Test kits and monitors3

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Best radon monitors for Horry County homes, compared

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Horry County, Bordering counties

Counties bordering Horry County

Calculated by Radon411

Horry County, Cities and towns

Cities and towns in Horry County

Horry County is growing: the Census Bureau puts it at 427,551 residents on July 1, 2025, up 20.9% from 353,774 in 2020. That works out to 377 people per square mile of land. No town dominates: Myrtle Beach, the largest, has 40,937 residents, 9.6% of the total. Together its 8 incorporated places hold 23.9% of those residents; the other 76.1% live outside any of them. Reported testing is thin here: 106 tests over 2008 to 2017, or 0.2 for every 1,000 residents (2025 estimate), where South Carolina as a whole comes to 4.8.

From Myrtle Beach to Atlantic Beach, CDC publishes no figure by town: each reads Horry County's.

The cities and towns in Horry County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Myrtle Beach40,937+13.8%9.6%
Conway30,627+21.5%7.2%
North Myrtle Beach21,346+12.7%5.0%
Surfside Beach4,392+5.5%1.0%
Loris2,935+19.0%0.7%
Aynor1,068+8.8%0.2%
Briarcliffe Acres585+21.4%0.1%
Atlantic Beach472+134.8%0.1%

8 incorporated places, as listed in the U.S. Census Bureau’s 2020 place reference files. Residents: U.S. Census Bureau population estimates for July 1, 2025 (Vintage 2025).

Horry County, Homes

Homes in Horry County

Fewer than six in ten of Horry County's 211,686 homes are detached houses (52%, against 64% across South Carolina); the rest are attached, in shared buildings or mobile. Half of its homes were built before 1998, close to South Carolina's 1991: 5% date from before 1960 and 46% from 2000 or later. Owners live in 76% of the occupied homes (South Carolina: 71%), so for most households a test and a fix are their own to order.

Homes in Horry County, South Carolina, 2019 to 2023
HomesHorry CountySouth Carolina
Housing units211,6862,401,638
Detached houses52%64%
In buildings of 5 or more26%13%
Mobile homes13%15%
Built before 19605%13%
Built since 200046%35%
Middle year built19981991
Owner-occupied76%71%

Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.