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Radon Levels in Union County, Arkansas

EPA puts Union County in Zone 3, its lowest radon zone, and only 2 radon tests from it are on file with CDC (2008 to 2017, laboratory totals). Homes with elevated levels occur in all three zones, so only a test measures yours.

Data checked By Radon411Methodology

How to test this homeFind a certified tester

  • Nearest county

    31.9%

    Saline County, 102 miles

    Saline
    31.9%
    Arkansas
    22.7%

    Share at 4+ pCi/L, 47 tests, 2007 to 2016

  • Ground above low

    None

    21.3 pts below Arkansas

    Union
    0.0%
    Arkansas
    21.3%

    Share of land USGS rates moderate or high potential

  • Tests reported

    3

    Too few for a share

    Union
    3
    Needed
    30

    2007 to 2016, laboratory

  • 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

Read a result for Union County

Starts at EPA's action level

4.0pCi/L

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

EPA’s reading of 4.0 pCi/L

At or above 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 at or above 4 pCi/L. EPA recommends fixing a home when the radon level is 4 pCi/L or higher.

Interpret this readingWhat a fix costs

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, 2008 to 2017, laboratory

CDC holds 2 reported tests for Union County over the 2008 to 2017 laboratory totals, with a median of 0.1 pCi/L: too few to describe a county (Radon411 reads a share from 30 tests up). Union County beside the counties around it is how this page reads it.

What these figures count

Only 2 tests were reported to CDC for Union County over 2008 to 2017 (laboratory totals), 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: 2008 to 2017, laboratory. Measured data period: 2005 to 2017 (every CDC figure on file).

How to read these figures

Union County, Compared

Union County radon figures, compared

Calculated by Radon411

CDC's largest figure for Union County rests on 3 tests over the 2007 to 2016 laboratory totals, 0 of them at or above 4 pCi/L, so each test moves its share by 33.3 points and no rank or comparison is drawn from it. Results reached as high as 0.1 pCi/L, with a middle value of 0.1 pCi/L.

The nearest counties with a figure are Saline County (102 miles away) at 31.9%, Garland County (102 miles away) at 45.8% and Pulaski County (111 miles away) at 6.8%. Pooled across 60 Arkansas counties, 22.7% of reported tests reached that level; across every county in the country with a figure, 35.8%.

Statewide for the same period, Garland County reported the highest share (45.8%) and Pulaski County the lowest (6.8%). EPA's 1993 map puts Union County in Zone 3, its lowest label: a predicted county average under 2 pCi/L. USGS geology rates 100% of the county's land low radon potential.

Arkansas, the United States and the counties around Union County, 2007 to 2016, laboratory
AreaTestsAt or above 4 pCi/LMedian
Arkansas, pooled60 counties, pooled68722.7%Not pooled
United States, pooled2,666 counties, pooled1,939,02535.8%Not pooled
Garland Countyhighest in the state4845.8%2.9 pCi/L
Pulaski Countylowest in the state1036.8%0.9 pCi/L
Union Parish, LAborders it10.0%2.8 pCi/L
Bradley County, ARborders it10.0%0.1 pCi/L
Ashley County, ARborders it10.0%1.3 pCi/L
Columbia County, ARborders it20.0%0.6 pCi/L
The nearest Arkansas counties to Union County with 30 or more tests, 2007 to 2016, laboratory
CountyDistanceTestsAt or above 4 pCi/LMedian
Saline County102 mi4731.9%2.2 pCi/L
Garland County102 mi4845.8%2.9 pCi/L
Pulaski County111 mi1036.8%0.9 pCi/L
Washington County214 mi5614.3%2.2 pCi/L
Benton County238 mi14531.0%1.8 pCi/L
Union County ten-year laboratory totals, against Arkansas' pooled share
PeriodTestsAt or above 4 pCi/LMedianHighestArkansas, pooledChange from the row before
2008 to 201720.0%0.1 pCi/L0.1 pCi/L23.2%Level
2007 to 201630.0%0.1 pCi/L0.1 pCi/L22.7%Level
2006 to 201530.0%0.1 pCi/L0.1 pCi/L22.5%Level
2005 to 201430.0%0.1 pCi/L0.1 pCi/L24.3%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. All of it lies in the area the map calls West Gulf Coastal Plain, to which USGS gives a radon index of 7, in the low band (5 to 8).

USGS's geologic areas under Union County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
West Gulf Coastal PlainGlauconitic, phosphatic, and carbonaceous sediments.Low799.8%

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 Arkansas 21.3% of the land is rated moderate; none of Union County's is. None of the 8 counties that border it has any moderate-potential ground either.

Share of land by USGS radon potential: Union County, the 8 counties bordering it and Arkansas
AreaEPA zoneLow potentialModerate potentialHigh potential
Union CountyZone 3100%NoneNone
Calhoun CountyZone 3100%NoneNone
Union Parish, LAZone 3100%NoneNone
Bradley CountyZone 3100%NoneNone
Claiborne Parish, LAZone 3100%NoneNone
Ouachita CountyZone 3100%NoneNone
Columbia CountyZone 3100%NoneNone
Ashley CountyZone 3100%NoneNone
Morehouse Parish, LAZone 3100%NoneNone
Arkansas75 counties, pooled by land areaVaries78.7%21.3%None

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 Arkansas's program says
Phone
501-661-2621
Email
ADH.EPI.Radon@arkansas.gov

What it means

Union County, Questions

Questions about radon in Union County

Are radon levels high in Union County?

Over the 2008 to 2017 laboratory totals, 0.0% of the radon tests reported to CDC for Union County, Arkansas were at or above 4 pCi/L, and the median reported pre-mitigation result was 0.1 pCi/L. Of the 5 nearest counties with a figure, within 238 miles, the share of tests at or above 4 pCi/L runs from 6.8% to 45.8%.

Which counties border Union County?

Union County borders 8 counties: Calhoun County, AR, Union Parish, LA, Bradley County, AR, Claiborne Parish, LA, Ouachita County, AR, Columbia County, AR, Ashley County, AR and Morehouse Parish, LA.

Products

Union County, Products

Testing a home in Union County

No CDC figure names Union County; the nearest county with one, Saline County (102 miles away), reported 31.9% of its tests at or above 4 pCi/L over the 2007 to 2016 laboratory totals, the only reading nearby until a test of this home. 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 has been losing residents: from 38,942 in 2020 to 36,926 on July 1, 2025, a fall of 5.2% by the Census Bureau's estimates. That works out to 36 people per square mile of land. Its largest town, El Dorado, has 16,609 residents, 45.0% of the total. Together its 8 incorporated places hold 56.1% of those residents; the other 43.9% live outside any of them. Reported testing is thin here: 3 tests over 2007 to 2016, or 0.1 for every 1,000 residents (2025 estimate), where Arkansas as a whole comes to 0.2.

From El Dorado to Felsenthal, CDC publishes no figure by town: each reads Union County's.

The cities and towns in Union County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
El Dorado16,609−6.2%45.0%
Smackover1,584−2.6%4.3%
Norphlet717−5.5%1.9%
Junction City476−5.2%1.3%
Huttig427−5.5%1.2%
Calion409−4.9%1.1%
Strong400−4.1%1.1%
Felsenthal83−1.2%0.2%

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).

Union County, Homes

Homes in Union County

Of Union County's 18,663 homes, 71% are detached houses, against 70% across Arkansas; 21% are mobile homes. The homes are older than Arkansas' as a whole: half were built before 1977 (1987 for Arkansas), and 23% date from before 1960. 73% of occupied homes are lived in by their owner (Arkansas: 66%); in the rest a tenant can run a test, but a fix is the landlord's to make.

Homes in Union County, Arkansas, 2019 to 2023
HomesUnion CountyArkansas
Housing units18,6631,382,664
Detached houses71%70%
In buildings of 5 or more4%10%
Mobile homes21%11%
Built before 196023%14%
Built since 200020%28%
Middle year built19771987
Owner-occupied73%66%

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