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Radon Levels in Union County, North Carolina

EPA puts Union County in Zone 3, its lowest 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

    11.2%

    11.4 pts below NC

    Union
    11.2%
    NC
    22.6%

    836 tests, 2008 to 2017

  • Median result

    1.1pCi/L

    Below action level

    Union
    1.1 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    836

    22nd of 75 by tests

    Union
    836
    Wake
    9,694

    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 NC

    49 of 75

    Middle half

    Union
    11.2%
    Transylvania
    47.8%

    By share, of 75 with 30+ tests

Read a result for Union County

Starts at Union County's median, 1.1 pCi/L

1.1pCi/L

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

EPA’s reading of 1.1 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. Union County's median reported result, 2008 to 2017.

Interpret this reading

The data

Union County, At a glance

Union County at a glance

Predicted: EPA radon zone

EPA Zone 3: lower predicted potential

is EPA's lowest class, and its forecast for Union 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 Union County, 2022

Share of reported tests at or above 4 pCi/L, by year, Union County
Share of reported tests at or above 4 pCi/L, by year, Union County
YearShare of reported tests at or above 4 pCi/L
20144.7%
20207.5%
20219.8%
20220.0%

2022: 0.0%. Across these years the share ran from 0.0% to 9.8%. Each column counts radon tests reported to CDC that year, not homes.

What these figures count

Only 3 tests were reported to CDC for Union 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

Union County, Compared

Union County radon figures, compared

Calculated by Radon411

Union County reports fewer high tests than North Carolina overall. 11.2% of its 836 tests over the 2008 to 2017 laboratory totals were at or above 4 pCi/L. That is 11.4 points below the 22.6% pooled from 99 North Carolina counties.

The newest figure, in 2022, counts only 3 tests (0.0% at or above 4 pCi/L), too few to compare, so this reading uses the 836-test figure.

Ordered from highest share down, it comes 49th of 75 North Carolina counties with 30 or more tests for the same period. Nationally, every county with a figure for the same period pools to 35.7%; Union County sits 24.5 points below it.

Next door, the shares run from 8.5% in Mecklenburg County to 25.3% in Stanly County, with Cabarrus County and Mecklenburg County below Union County. Zone 3 on EPA's map (predicted average under 2 pCi/L) and a 11.2% share point the same way here.

Half the tests came in under 1.1 pCi/L and half over it; the single highest reached 38.4 pCi/L. The rest split 71.3% under 2 pCi/L and 17.5% from 2 to 4 (North Carolina: 55.6% and 21.8%). Year by year, 2014 opened at 4.7% and 2021 closed at 9.8% (up 5.1 points), with 2021 the high at 9.8%.

The busiest year on file was 2020, with 147 tests reported; the quietest, 2022, had 3.

Share of reported tests at or above 4 pCi/L by year, Union County against North Carolina2014 to 2021, years with 30 or more tests: Union County 4.7% to 9.8%, the state's pooled share 14.9% in 2021.
Union CountyNorth Carolina, pooled
Share of reported tests at or above 4 pCi/L by year, Union County against North Carolina: data table
YearTestsUnion County, at or above 4 pCi/LNorth Carolina, pooled
20141074.7%21.9%
20201477.5%21.1%
2021619.8%14.9%
Union County against North Carolina, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Union County
Union County83611.2%1.1 pCi/LThis county
North Carolina, pooled99 counties, pooled73,13922.6%Not pooled+11.4 points
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled+24.5 points
Transylvania Countyhighest in the state3,86247.8%3.7 pCi/L+36.6 points
Nash Countylowest in the state300.0%0.2 pCi/L−11.2 points
Stanly County, NCborders it22925.3%2.2 pCi/L+14.1 points
Lancaster County, SCborders it37413.6%1.6 pCi/L+2.4 points
Cabarrus County, NCborders it8808.8%1.0 pCi/L−2.4 points
Mecklenburg County, NCborders it3,7538.5%0.9 pCi/L−2.7 points
Chesterfield County, SCborders it100.0%0.6 pCi/L−11.2 points
Anson County, NCborders it180.0%0.6 pCi/L−11.2 points
Where Union County's reported results fell, 2008 to 2017, laboratory, beside North Carolina and the United States
ResultUnion County testsUnion County shareNorth Carolina shareU.S. shareAgainst North Carolina
Under 2 pCi/L59671.3%55.6%39.6%+15.7 points
2 to 4 pCi/L14617.5%21.8%24.7%−4.3 points
4 pCi/L and above9411.2%22.6%35.7%−11.4 points
Union 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
Person County44 of 7519017.4%1.3 pCi/L
Macon County45 of 751,35417.1%1.4 pCi/L
Madison County46 of 7522816.7%1.3 pCi/L
Caswell County47 of 754714.9%1.6 pCi/L
Vance County48 of 7510914.7%1.5 pCi/L
Union County49 of 7583611.2%1.1 pCi/L
Chatham County50 of 7558710.9%1.1 pCi/L
Orange County51 of 751,09510.7%1.1 pCi/L
Granville County52 of 7515310.5%0.8 pCi/L
Wake County53 of 759,6949.6%1.0 pCi/L
Cabarrus County54 of 758808.8%1.0 pCi/L
Union County radon tests by year, against North Carolina's pooled share
YearTestsAt or above 4 pCi/LMedianHighestNorth Carolina, pooledChange from the row before
202230.0%0.1 pCi/L1.0 pCi/L10.7%−9.8 points
2021619.8%0.1 pCi/L6.0 pCi/L14.9%+2.3 points
20201477.5%0.9 pCi/L11.2 pCi/L21.1%+2.8 points
20141074.7%0.6 pCi/L5.2 pCi/L21.9%First on file

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

Union County, Geology

The ground under Union County

Predicted

USGS's geologic map puts all of Union County's mapped land in one class: low radon potential. The map puts 92.0% of Union County in the area it calls Carolina Slate Belt and 7.0% in Charlotte Belt, with one smaller area beside them. USGS gives the first a radon index of 6 and the second 8, both in the low band (5 to 8).

USGS's geologic areas under Union County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Carolina Slate BeltFelsic metavolcanics, intermediate volcanics, metamudstone, argillite, and epiclastic rocks.Low692.0%
Charlotte BeltIgneous rocks, including granite, gabbro, and diorite.Low87.0%
Wadesboro SubbasinArkosic sandstone, siltstone and conglomerate.Low81.0%

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

Union County beside the ground around it

Across North Carolina 1.3% of the land is rated high; none of Union County's is. Of the 6 counties that border it, 3 have more moderate-potential ground, Anson County the most at 31.1%.

Share of land by USGS radon potential: Union County, the 6 counties bordering it and North Carolina
AreaEPA zoneLow potentialModerate potentialHigh potential
Union CountyZone 3100%NoneNone
Lancaster County, SCZone 383.7%16.3%None
Cabarrus CountyZone 3100%NoneNone
Mecklenburg CountyZone 3100%NoneNone
Anson CountyZone 368.9%31.1%None
Stanly CountyZone 3100%NoneNone
Chesterfield County, SCZone 393.0%7.0%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

Union County, Local resources

Radon testing and mitigation in Union 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

Union County, Questions

Questions about radon in Union County

Are radon levels high in Union County?

In 2022, 0.0% of the radon tests reported to CDC for Union County, North Carolina were at or above 4 pCi/L, and the median reported pre-mitigation result was 0.1 pCi/L. Of 75 North Carolina counties with 30 or more tests for the same period, 48 reported a higher share; pooled, the state comes to 22.6%.

Which counties border Union County?

Union County borders 6 counties: Lancaster County, SC, Cabarrus County, NC, Mecklenburg County, NC, Anson County, NC, Stanly County, NC and Chesterfield County, SC.

Products

Union County, Products

Testing a home in Union County

In Union County, 11.2% of 836 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 22.6% pooled across North 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 Union County.

Test kits and monitors3

See every kit and monitor

Best radon monitors for Union County homes, compared

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Union County, Bordering counties

Counties bordering Union County

Calculated by Radon411

Union County, Cities and towns

Cities and towns in Union County

Union County is growing: the Census Bureau puts it at 267,674 residents on July 1, 2025, up 11.7% from 239,615 in 2020. That works out to 423 people per square mile of land. No town dominates: Indian Trail, the largest, has 44,303 residents, 16.6% of the total. Reported testing is thin here: 836 tests over 2008 to 2017, or 3.1 for every 1,000 residents (2025 estimate), where North Carolina as a whole comes to 6.5.

From Indian Trail to Hemby Bridge, CDC publishes no figure by town: each reads Union County's.

The 12 largest cities and towns in Union County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Indian Trail44,303+9.7%16.6%
Monroe42,644+22.9%15.9%
Mint Hillextends beyond Union County29,476+11.1%Counted whole
Waxhaw23,140+11.4%8.6%
Stallingsextends beyond Union County17,760+9.7%Counted whole
Weddingtonextends beyond Union County14,517+9.6%Counted whole
Wesley Chapel9,566+9.7%3.6%
Unionville7,322+9.8%2.7%
Marvin7,040+9.7%2.6%
Wingate4,628+7.4%1.7%
Fairview3,805+9.4%1.4%
Lake Park3,609+9.3%1.3%
  • Mineral Springs
  • Marshville
  • Hemby Bridge

15 incorporated places, as listed in the U.S. Census Bureau’s 2020 place reference files. “(part)” marks a place that extends into another county. Residents: U.S. Census Bureau population estimates for July 1, 2025 (Vintage 2025). A place that extends beyond Union County is counted whole, so it has no share.

Union County, Homes

Homes in Union County

Union County is a place of houses on their own lots: 87% of its 86,730 homes are detached single-family houses, against 65% across North Carolina. Much of Union County is recent building: 47% of its homes have gone up since 2000 and the middle year built is 1999, against 1990 for North Carolina. Owners live in 82% of the occupied homes (North Carolina: 66%), so for most households a test and a fix are their own to order.

Homes in Union County, North Carolina, 2019 to 2023
HomesUnion CountyNorth Carolina
Housing units86,7304,815,195
Detached houses87%65%
In buildings of 5 or more4%14%
Mobile homes5%11%
Built before 19607%14%
Built since 200047%33%
Middle year built19991990
Owner-occupied82%66%

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