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Radon Levels in Union Parish, Louisiana

EPA puts Union Parish in Zone 3, its lowest radon zone, and most reported tests there come back low, though 0.0% of 192 (2022) 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

    0.0%

    0.4 pts below LA

    Union Parish
    0.0%
    Louisiana
    0.4%

    192 tests, 2022

  • Median result

    0.2pCi/L

    Below action level

    Union Parish
    0.2 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2022

  • Tests reported

    192

    6th of 9 by tests

    Union Parish
    192
    Caddo Parish
    486

    Reported to CDC before any fix, 2022

  • 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 Louisiana

    2 of 9

    Top quarter

    Union Parish
    0.0%
    Caddo Parish
    1.9%

    By share, of 9 with 30+ tests

Read a result for Union Parish

Starts at Union Parish's median, 0.2 pCi/L

0.2pCi/L

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

EPA’s reading of 0.2 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 Parish's median reported result, 2022.

Interpret this reading

The data

Union Parish, At a glance

Union Parish at a glance

Predicted: EPA radon zone

EPA Zone 3: lower predicted potential

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

Share of reported tests at or above 4 pCi/L, by year, Union Parish
Share of reported tests at or above 4 pCi/L, by year, Union Parish
YearShare of reported tests at or above 4 pCi/L
20180.0%
20190.0%
20220.0%

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

What these figures count

These are the 192 tests reported to CDC for Union Parish over 2022, many from homes being sold or already suspected of a problem: they describe the parish's reported tests, not 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 Parish, Compared

Union Parish radon figures, compared

Calculated by Radon411

Only 0 of 192 radon tests reported for Union Parish in 2022 reached 4 pCi/L (0.0%). The median result, 0.2 pCi/L, sits below 2, well under EPA's 4 pCi/L action level, and the top reported result was 1.0 pCi/L.

Across 12 Louisiana counties pooled together, 0.4% of tests reached that level, so Union Parish runs 0.4 points below its state. Against the national pool of 23.9%, the gap is 23.9 points lower. Its place in the state: 2nd of 9 Louisiana counties with 30 or more tests for the same period.

Zone 3 on EPA's map (predicted average under 2 pCi/L) and a 0.0% share point the same way here.

Below the action level, 192 tests (100.0%) came in under 2 pCi/L, against 98.1% statewide, and 0 tests (0.0%) fell between 2 and 4, against 1.5% statewide. USGS geology rates 100% of the county's land low radon potential.

The busiest year on file was 2022, with 192 tests reported; the quietest, 2019, had 3.

Union Parish against Louisiana, the United States and nearby counties, 2022
AreaTestsAt or above 4 pCi/LMedianDifference from Union Parish
Union Parish1920.0%0.2 pCi/LThis county
Louisiana, pooled12 counties, pooled2,0220.4%Not pooled+0.4 points
United States, pooled853 counties, pooled333,14023.9%Not pooled+23.9 points
Caddo Parishhighest in the state4861.9%0.4 pCi/L+1.9 points
West Baton Rouge Parishlowest in the state420.0%0.6 pCi/LLevel
Ouachita Parish, LAborders it30.0%1.0 pCi/LLevel
Where Union Parish's reported results fell, 2022, beside Louisiana and the United States
ResultUnion Parish testsUnion Parish shareLouisiana shareU.S. shareAgainst Louisiana
Under 2 pCi/L192100.0%98.1%54.5%+1.9 points
2 to 4 pCi/L00.0%1.5%21.7%−1.5 points
4 pCi/L and above00.0%0.4%23.9%−0.4 points
Union Parish ranked among the 9 Louisiana counties with 30 or more tests, by share at or above 4 pCi/L, 2022
CountyRankTestsAt or above 4 pCi/LMedian
Caddo Parish1 of 94861.9%0.4 pCi/L
East Baton Rouge Parish2 of 94470.0%0.2 pCi/L
Rapides Parish2 of 92040.0%0.4 pCi/L
Lafayette Parish2 of 92010.0%0.2 pCi/L
Orleans Parish2 of 91980.0%0.3 pCi/L
Union Parish2 of 91920.0%0.2 pCi/L
Webster Parish2 of 91380.0%0.2 pCi/L
Assumption Parish2 of 91020.0%0.2 pCi/L
West Baton Rouge Parish2 of 9420.0%0.6 pCi/L
Union Parish radon tests by year, against Louisiana's pooled share
YearTestsAt or above 4 pCi/LMedianHighestLouisiana, pooledChange from the row before
20221920.0%0.2 pCi/L1.0 pCi/L0.4%Level
201930.0%1.7 pCi/L1.7 pCi/L2.0%Level
201830.0%0.2 pCi/L0.2 pCi/L0.5%First on file

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

Union Parish, Geology

The ground under Union Parish

Predicted

USGS's geologic map puts all of Union Parish's mapped land in one class: low radon potential. All of it lies in the area the map calls Old Uplands, to which USGS gives a radon index of 7, in the low band (5 to 8).

USGS's geologic areas under Union Parish
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Old UplandsClays, silts, sands, and ironstone.Low7100%

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

Union Parish beside the ground around it

Neither Union Parish nor Louisiana as a whole has any land USGS rates above low potential. None of the 6 counties that border it has any moderate-potential ground either.

Share of land by USGS radon potential: Union Parish, the 6 counties bordering it and Louisiana
AreaEPA zoneLow potentialModerate potentialHigh potential
Union ParishZone 3100%NoneNone
Lincoln ParishZone 3100%NoneNone
Ouachita ParishZone 3100%NoneNone
Union County, ARZone 3100%NoneNone
Morehouse ParishZone 3100%NoneNone
Claiborne ParishZone 3100%NoneNone
Ashley County, ARZone 3100%NoneNone
Louisiana64 parishes, pooled by land areaVaries98.4%NoneNone

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

Local help

Union Parish, Local resources

Radon testing and mitigation in Union Parish

What it means

Union Parish, Questions

Questions about radon in Union Parish

Are radon levels high in Union Parish?

In 2022, 0.0% of the radon tests reported to CDC for Union Parish, Louisiana were at or above 4 pCi/L, and the median reported pre-mitigation result was 0.2 pCi/L. Of 9 Louisiana counties with 30 or more tests for the same period, 1 reported a higher share; pooled, the state comes to 0.4%.

Which counties border Union Parish?

Union Parish borders 6 counties: Lincoln Parish, LA, Ouachita Parish, LA, Union County, AR, Morehouse Parish, LA, Claiborne Parish, LA and Ashley County, AR.

Products

Union Parish, Products

Testing a home in Union Parish

In Union Parish, 0.0% of 192 tests reported to CDC in 2022 reached 4 pCi/L, against 0.4% pooled across Louisiana. 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 Parish.

Test kits and monitors3

See every kit and monitor

Best radon monitors for Union Parish homes, compared

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Union Parish, Bordering counties

Counties bordering Union Parish

Calculated by Radon411

Union Parish, Cities and towns

Cities and towns in Union Parish

About 20,561 people live in Union Parish by the Census Bureau's estimate for July 1, 2025, 536 fewer than in 2020 (−2.5%). That works out to 23 people per square mile of land. No town dominates: Farmerville, the largest, has 3,432 residents, 16.7% of the total. Testing is reported here more often than across the state: CDC's 192 reported tests for 2022 come to 9.3 for every 1,000 residents (2025 estimate), against 0.4 for Louisiana.

From Farmerville to Lillie, CDC publishes no figure by town: each reads Union Parish's.

The cities and towns in Union Parish by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Farmerville3,432−0.6%16.7%
Bernice1,305−3.8%6.3%
Marion595−4.5%2.9%
Junction Cityextends beyond Union Parish412−5.3%Counted whole
Spearsville123−4.7%0.6%
Downsvilleextends beyond Union Parish113−6.6%Counted whole
Lillie109−0.9%0.5%

7 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 Union Parish is counted whole, so it has no share.

Union Parish, Homes

Homes in Union Parish

Of Union Parish's 10,416 homes, 58% are detached houses, against 65% across Louisiana; 37% are mobile homes. Half of its homes were built before 1988, close to Louisiana's 1982: 11% date from before 1960 and 27% from 2000 or later. Owners live in 76% of the occupied homes (Louisiana: 67%), so for most households a test and a fix are their own to order.

Homes in Union Parish, Louisiana, 2019 to 2023
HomesUnion ParishLouisiana
Housing units10,4162,094,002
Detached houses58%65%
In buildings of 5 or more3%11%
Mobile homes37%13%
Built before 196011%19%
Built since 200027%27%
Middle year built19881982
Owner-occupied76%67%

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