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Radon Levels in Chatham County, North Carolina

EPA puts Chatham County in Zone 3, its lowest radon zone, and only 1 radon test from it is 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

    10.9%

    11.7 pts below NC

    Chatham
    10.9%
    NC
    22.6%

    587 tests, 2008 to 2017

  • Median result

    1.1pCi/L

    Below action level

    Chatham
    1.1 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    587

    33rd of 75 by tests

    Chatham
    587
    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

    50 of 75

    Middle half

    Chatham
    10.9%
    Transylvania
    47.8%

    By share, of 75 with 30+ tests

Read a result for Chatham County

Starts at Chatham 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. Chatham County's median reported result, 2008 to 2017.

Interpret this reading

The data

Chatham County, At a glance

Chatham County at a glance

Predicted: EPA radon zone

EPA Zone 3: lower predicted potential

is EPA's lowest class, and its forecast for Chatham 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 99% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

Radon tests reported for Chatham County, 2022

Share of reported tests at or above 4 pCi/L, by year, Chatham County
Share of reported tests at or above 4 pCi/L, by year, Chatham County
YearShare of reported tests at or above 4 pCi/L
201415.0%
20200.0%
20210.0%
20220.0%

2022: 0.0%. Across these years the share ran from 0.0% to 15.0%. Each column counts radon tests reported to CDC that year, not homes.

What these figures count

Only 1 test was reported to CDC for Chatham 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

Chatham County, Compared

Chatham County radon figures, compared

Calculated by Radon411

Chatham County reports fewer high tests than North Carolina overall. 10.9% of its 587 tests over the 2008 to 2017 laboratory totals were at or above 4 pCi/L. That is 11.7 points below the 22.6% pooled from 99 North Carolina counties.

The newest figure, in 2022, counts only 1 test (0.0% at or above 4 pCi/L), too few to compare, so this reading uses the 587-test figure.

Ordered from highest share down, it comes 50th 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%; Chatham County sits 24.8 points below it.

Next door, the shares run from 0.6% in Harnett County to 19.2% in Moore County, with Orange County, Wake County and Randolph County below Chatham County. Zone 3 on EPA's map (predicted average under 2 pCi/L) and a 10.9% share point the same way here.

Half the tests came in under 1.1 pCi/L and half over it; the single highest reached 27.5 pCi/L. The rest split 69.7% under 2 pCi/L and 19.4% from 2 to 4 (North Carolina: 55.6% and 21.8%). Year by year, 2014 opened at 15.0% and 2021 closed at 0.0% (down 15.0 points), with 2014 the high at 15.0%.

The busiest year on file was 2021, with 151 tests reported; the quietest, 2022, had 1.

Share of reported tests at or above 4 pCi/L by year, Chatham County against North Carolina2014 to 2021, years with 30 or more tests: Chatham County 15.0% to 0.0%, the state's pooled share 14.9% in 2021.
Chatham CountyNorth Carolina, pooled
Share of reported tests at or above 4 pCi/L by year, Chatham County against North Carolina: data table
YearTestsChatham County, at or above 4 pCi/LNorth Carolina, pooled
20144015.0%21.9%
2020430.0%21.1%
20211510.0%14.9%
Chatham County against North Carolina, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Chatham County
Chatham County58710.9%1.1 pCi/LThis county
North Carolina, pooled99 counties, pooled73,13922.6%Not pooled+11.7 points
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled+24.8 points
Transylvania Countyhighest in the state3,86247.8%3.7 pCi/L+36.9 points
Nash Countylowest in the state300.0%0.2 pCi/L−10.9 points
Moore County, NCborders it9919.2%1.3 pCi/L+8.3 points
Orange County, NCborders it1,09510.7%1.1 pCi/L−0.2 points
Wake County, NCborders it9,6949.6%1.0 pCi/L−1.3 points
Randolph County, NCborders it4227.1%0.9 pCi/L−3.8 points
Durham County, NCborders it1,5704.3%0.7 pCi/L−6.6 points
Alamance County, NCborders it5203.7%0.5 pCi/L−7.2 points
Lee County, NCborders it931.1%0.9 pCi/L−9.8 points
Harnett County, NCborders it1810.6%0.6 pCi/L−10.3 points
Where Chatham County's reported results fell, 2008 to 2017, laboratory, beside North Carolina and the United States
ResultChatham County testsChatham County shareNorth Carolina shareU.S. shareAgainst North Carolina
Under 2 pCi/L40969.7%55.6%39.6%+14.1 points
2 to 4 pCi/L11419.4%21.8%24.7%−2.4 points
4 pCi/L and above6410.9%22.6%35.7%−11.7 points
Chatham 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
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
Mecklenburg County55 of 753,7538.5%0.9 pCi/L
Chatham County radon tests by year, against North Carolina's pooled share
YearTestsAt or above 4 pCi/LMedianHighestNorth Carolina, pooledChange from the row before
202210.0%3.0 pCi/L3.0 pCi/L10.7%Level
20211510.0%1.0 pCi/L3.0 pCi/L14.9%Level
2020430.0%0.8 pCi/L3.9 pCi/L21.1%−15.0 points
20144015.0%1.0 pCi/L6.9 pCi/L21.9%First on file

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

Chatham County, Geology

The ground under Chatham County

Predicted

Most of the ground under Chatham County is one class on USGS's geologic map: 98.6% of its land is low radon potential, with 1.4% moderate. The map puts 72.3% of Chatham County in the area it calls Carolina Slate Belt and 25.9% in Sanford-Durham Sub-Basins, 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 Chatham County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Carolina Slate BeltFelsic metavolcanics, intermediate volcanics, metamudstone, argillite, and epiclastic rocks.Low672.3%
Sanford-Durham Sub-BasinsArkosic sandstone, siltstone and conglomerate.Low825.9%
Raleigh BeltProterozoic through Cambrian biotite gneiss and mica schist.Moderate111.4%

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

Chatham County beside the ground around it

Across North Carolina 1.3% of the land is rated high; none of Chatham County's is. Of the 8 counties that border it, 4 have more moderate-potential ground, Wake County the most at 79.4%.

Share of land by USGS radon potential: Chatham County, the 8 counties bordering it and North Carolina
AreaEPA zoneLow potentialModerate potentialHigh potential
Chatham CountyZone 398.6%1.4%None
Orange CountyZone 3100%NoneNone
Lee CountyZone 389.3%10.7%None
Alamance CountyZone 3100%NoneNone
Durham CountyZone 396.7%3.3%None
Randolph CountyZone 3100%NoneNone
Harnett CountyZone 388.1%11.9%None
Moore CountyZone 3100%NoneNone
Wake CountyZone 220.6%79.4%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

Chatham County, Local resources

Radon testing and mitigation in Chatham 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

Chatham County, Questions

Questions about radon in Chatham County

Are radon levels high in Chatham County?

In 2022, 0.0% of the radon tests reported to CDC for Chatham County, North Carolina were at or above 4 pCi/L, and the median reported pre-mitigation result was 3.0 pCi/L. Of 75 North Carolina counties with 30 or more tests for the same period, 49 reported a higher share; pooled, the state comes to 22.6%.

Which counties border Chatham County?

Chatham County borders 8 counties: Orange County, Lee County, Alamance County, Durham County, Randolph County, Harnett County, Moore County and Wake County.

Products

Chatham County, Products

Testing a home in Chatham County

In Chatham County, 10.9% of 587 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 Chatham County.

Test kits and monitors3

See every kit and monitor

Best radon monitors for Chatham County homes, compared

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Chatham County, Bordering counties

Counties bordering Chatham County

Calculated by Radon411

Chatham County, Cities and towns

Cities and towns in Chatham County

Chatham County is growing: the Census Bureau puts it at 85,111 residents on July 1, 2025, up 11.0% from 76,663 in 2020. That works out to 125 people per square mile of land. Cary, the largest place on its list (183,582 residents in all), extends beyond Chatham County, so no share of the total is worked out for it. CDC's 587 reported tests for 2008 to 2017 work out to 6.9 per 1,000 residents (2025 estimate), close to North Carolina's 6.5.

From Cary to Goldston, CDC publishes no figure by town: each reads Chatham County's.

The cities and towns in Chatham County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Caryextends beyond Chatham County183,582+5.0%Counted whole
Siler City8,155+5.1%9.6%
Pittsboro5,054+10.8%5.9%
Goldston268+11.2%0.3%

4 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). A place that extends beyond Chatham County is counted whole, so it has no share.

Chatham County, Homes

Homes in Chatham County

Chatham County is a place of houses on their own lots: 76% of its 35,013 homes are detached single-family houses, against 65% across North Carolina. Half of its homes were built before 1997, close to North Carolina's 1990: 11% date from before 1960 and 43% from 2000 or later. Owners live in 80% of the occupied homes (North Carolina: 66%), so for most households a test and a fix are their own to order.

Homes in Chatham County, North Carolina, 2019 to 2023
HomesChatham CountyNorth Carolina
Housing units35,0134,815,195
Detached houses76%65%
In buildings of 5 or more4%14%
Mobile homes13%11%
Built before 196011%14%
Built since 200043%33%
Middle year built19971990
Owner-occupied80%66%

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