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Radon Levels in Alleghany County, North Carolina

EPA puts Alleghany County in Zone 1, its highest radon zone, and only 3 radon tests from it are on file with CDC (2022). 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

    41.1%

    18.5 pts above NC

    Alleghany
    41.1%
    NC
    22.6%

    285 tests, 2008 to 2017

  • Median result

    3.3pCi/L

    Below action level

    Alleghany
    3.3 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    285

    43rd of 75 by tests

    Alleghany
    285
    Wake
    9,694

    Reported to CDC before any fix, 2008 to 2017

  • EPA radon zone

    Zone 1

    Highest potential

    1. Zone 1
    2. 2
    3. 3

    1 highest, 3 lowest

    EPA predicts over 4 pCi/L indoors

  • Rank in NC

    11 of 75

    Top quarter

    Alleghany
    41.1%
    Transylvania
    47.8%

    By share, of 75 with 30+ tests

Read a result for Alleghany County

Starts at Alleghany County's median, 3.3 pCi/L

3.3pCi/L

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

EPA’s reading of 3.3 pCi/L

Between 2 and 4 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 between 2 and 4 pCi/L. EPA recommends considering a fix when the level is between 2 and 4 pCi/L. Alleghany County's median reported result, 2008 to 2017.

Interpret this readingWhat a fix costs

The data

Alleghany County, At a glance

Alleghany County at a glance

Predicted: EPA radon zone

EPA Zone 1: highest predicted potential

EPA puts all of Alleghany County in and predicts an average indoor of greater than 4 pCi/L (greater than 150 Bq/m³) across the county. That is one forecast for the whole county, not a reading of any address in it; homes above EPA's turn up in all three zones.

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

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

Radon tests reported for Alleghany County, 2022

Share of reported tests at or above 4 pCi/L, by year, Alleghany County
Share of reported tests at or above 4 pCi/L, by year, Alleghany County
YearShare of reported tests at or above 4 pCi/L
201441.0%
202040.8%
202125.0%
202266.7%

2022: 66.7%. Across these years the share ran from 25.0% to 66.7%. Each column counts radon tests reported to CDC that year, not homes.

What these figures count

Only 3 tests were reported to CDC for Alleghany County over 2022, and tests are often run on homes being sold or already suspected of a problem: so few describe neither the county nor this house.

Measured: CDC tracking data. Figure above: 2022. Measured data period: 2005 to 2022 (every CDC figure on file).

How to read these figures

Alleghany County, Compared

Alleghany County radon figures, compared

Calculated by Radon411

In Alleghany County, about 4 in 10 reported tests over the 2008 to 2017 laboratory totals (117 of 285) were at or above EPA's action level. Against the national pool of 35.7%, the gap is 5.4 points higher. Across 99 North Carolina counties pooled together, 22.6% of tests reached that level, so Alleghany County runs 18.5 points above its state.

The newest figure, in 2022, counts only 3 tests (66.7% at or above 4 pCi/L), too few to compare, so this reading uses the 285-test figure.

Of 4 neighbours with a figure, 2 reported a larger share at or above 4 pCi/L and 2 a smaller one; the spread is 33.3% (Surry County) to 44.7% (Grayson County, VA). By share, Alleghany County is 11th of 75 North Carolina counties with 30 or more tests for the same period.

Half the tests came in under 3.3 pCi/L and half over it; the single highest reached 364.4 pCi/L. Below the action level, 86 tests (30.2%) came in under 2 pCi/L, against 55.6% statewide, and 82 tests (28.8%) fell between 2 and 4, against 21.8% statewide.

Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 41.1% share point the same way here. USGS geology rates 100% of the county's land moderate radon potential. CDC also counts 32 tests taken after mitigation in Alleghany County for the same period: tests in homes where a fix was already in.

The busiest year on file was 2020, with 76 tests reported; the quietest, 2022, had 3.

Alleghany County against North Carolina, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Alleghany County
Alleghany County28541.1%3.3 pCi/LThis county
North Carolina, pooled99 counties, pooled73,13922.6%Not pooled−18.5 points
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled−5.4 points
Transylvania Countyhighest in the state3,86247.8%3.7 pCi/L+6.7 points
Nash Countylowest in the state300.0%0.2 pCi/L−41.1 points
Grayson County, VAborders it4744.7%3.8 pCi/L+3.6 points
Wilkes County, NCborders it40244.3%3.5 pCi/L+3.2 points
Ashe County, NCborders it68134.1%2.5 pCi/L−7.0 points
Surry County, NCborders it85533.3%2.4 pCi/L−7.8 points
Where Alleghany County's reported results fell, 2008 to 2017, laboratory, beside North Carolina and the United States
ResultAlleghany County testsAlleghany County shareNorth Carolina shareU.S. shareAgainst North Carolina
Under 2 pCi/L8630.2%55.6%39.6%−25.4 points
2 to 4 pCi/L8228.8%21.8%24.7%+7.0 points
4 pCi/L and above11741.1%22.6%35.7%+18.5 points
Alleghany County ranked among the 75 North 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
Clay County6 of 7532343.0%3.0 pCi/L
Warren County7 of 758242.7%3.0 pCi/L
Halifax County8 of 755942.4%2.6 pCi/L
Graham County9 of 756942.0%3.0 pCi/L
Henderson County10 of 754,09341.8%3.3 pCi/L
Alleghany County11 of 7528541.1%3.3 pCi/L
Northampton County12 of 756240.3%3.4 pCi/L
Cleveland County13 of 7551139.5%2.8 pCi/L
Avery County14 of 7516038.8%2.8 pCi/L
McDowell County15 of 7577637.5%2.7 pCi/L
Ashe County16 of 7568134.1%2.5 pCi/L
Alleghany County radon tests by year, against North Carolina's pooled share
YearTestsAt or above 4 pCi/LMedianHighestNorth Carolina, pooledChange from the row before
2022366.7%4.0 pCi/L5.0 pCi/L10.7%+41.7 points
20212025.0%0.6 pCi/L5.0 pCi/L14.9%−15.8 points
20207640.8%2.8 pCi/L32.0 pCi/L21.1%−0.2 points
20146141.0%3.0 pCi/L28.0 pCi/L21.9%First on file

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

Alleghany County, Geology

The ground under Alleghany County

Predicted

USGS's geologic map puts all of Alleghany County's mapped land in one class: moderate radon potential. All of it lies in the area the map calls Blue Ridge, to which USGS gives a radon index of 10, in the moderate band (9 to 11).

USGS's geologic areas under Alleghany County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Blue RidgeGranite, pegmatite, monazite, schist, and gneiss.Moderate10100%

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

Alleghany County beside the ground around it

Across North Carolina 1.3% of the land is rated high; none of Alleghany County's is. Of the 4 counties that border it, 1 has more high-potential ground, Grayson County, VA the most at 2.5%.

Share of land by USGS radon potential: Alleghany County, the 4 counties bordering it and North Carolina
AreaEPA zoneLow potentialModerate potentialHigh potential
Alleghany CountyZone 1None100%None
Grayson County, VAZone 2None97.5%2.5%
Wilkes CountyZone 2None100%None
Ashe CountyZone 2None100%None
Surry CountyZone 2None100%None
North Carolina100 counties, pooled by land areaVaries64.8%33.0%1.3%

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

Local help

Alleghany County, Local resources

Radon testing and mitigation in Alleghany County

What North Carolina's program says
Licensing of radon professionals
The North Carolina Radon Program is presently developing a Radon Proficiency Program as directed by Session Law 2023-91 House Bill 782 .

What it means

Alleghany County, Questions

Questions about radon in Alleghany County

Are radon levels high in Alleghany County?

In 2022, 66.7% of the radon tests reported to CDC for Alleghany County, North Carolina were at or above 4 pCi/L, and the median reported pre-mitigation result was 4.0 pCi/L. Of 75 North Carolina counties with 30 or more tests for the same period, 10 reported a higher share; pooled, the state comes to 22.6%.

Which counties border Alleghany County?

Alleghany County borders 4 counties: Grayson County, VA, Wilkes County, NC, Ashe County, NC and Surry County, NC.

Products

Alleghany County, Products

Testing a home in Alleghany County

In Alleghany County, 41.1% of 285 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 22.6% pooled across North Carolina. In Zone 1 the year-round level in Alleghany County is the one to know: a long-term test (more than 90 days) or a monitor, with a short-term kit for a first answer.

Test kits and monitors3

See every kit and monitor

Alleghany County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like Alleghany County

Explore

Alleghany County, Bordering counties

Counties bordering Alleghany County

Calculated by Radon411

Alleghany County, Cities and towns

Cities and towns in Alleghany County

Alleghany County is growing: the Census Bureau puts it at 11,479 residents on July 1, 2025, up 5.4% from 10,891 in 2020. That works out to 49 people per square mile of land. Sparta, its one incorporated place, has 1,918 residents, 16.7% of the total. Testing is reported here more often than across the state: CDC's 285 reported tests for 2008 to 2017 come to 24.8 for every 1,000 residents (2025 estimate), against 6.5 for North Carolina.

Sparta is the one incorporated place here; CDC publishes no figure by town, so it reads Alleghany County's.

Sparta, Alleghany County: residents on July 1, 2025
PlaceResidentsSince 2020Share of residents
Sparta1,918+4.8%16.7%

One incorporated place, 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).

Alleghany County, Homes

Homes in Alleghany County

Alleghany County is a place of houses on their own lots: 78% of its 7,752 homes are detached single-family houses, against 65% across North Carolina. The homes are older than North Carolina's as a whole: half were built before 1982 (1990 for North Carolina), and 16% date from before 1960. Owners live in 77% of the occupied homes (North Carolina: 66%), so for most households a test and a fix are their own to order.

Homes in Alleghany County, North Carolina, 2019 to 2023
HomesAlleghany CountyNorth Carolina
Housing units7,7524,815,195
Detached houses78%65%
In buildings of 5 or more4%14%
Mobile homes16%11%
Built before 196016%14%
Built since 200021%33%
Middle year built19821990
Owner-occupied77%66%

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