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Radon Levels in St. Tammany Parish, Louisiana

EPA puts St. Tammany Parish in Zone 3, its lowest radon zone, and most reported tests there come back low, though 0.0% of 93 (2021) 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%

    3.9 pts below LA

    St. Tammany Parish
    0.0%
    Louisiana
    3.9%

    93 tests, 2021

  • Median result

    0.9pCi/L

    Below action level

    St. Tammany Parish
    0.9 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2021

  • Tests reported

    93

    11th of 14 by tests

    St. Tammany Parish
    93
    Ascension Parish
    522

    Reported to CDC before any fix, 2021

  • 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

    3 of 14

    Top quarter

    St. Tammany Parish
    0.0%
    Caddo Parish
    20.1%

    By share, of 14 with 30+ tests

Read a result for St. Tammany Parish

Starts at St. Tammany Parish's median, 0.9 pCi/L

0.9pCi/L

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

EPA’s reading of 0.9 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. St. Tammany Parish's median reported result, 2021.

Interpret this reading

The data

St. Tammany Parish, At a glance

St. Tammany Parish at a glance

Predicted: EPA radon zone

EPA Zone 3: lower predicted potential

is EPA's lowest class, and its forecast for St. Tammany 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 St. Tammany Parish, 2021

Share of reported tests at or above 4 pCi/L, by year, St. Tammany Parish
Share of reported tests at or above 4 pCi/L, by year, St. Tammany Parish
YearShare of reported tests at or above 4 pCi/L
20140.0%
20150.0%
201615.4%
20170.0%
20180.0%
20195.3%
20200.0%
20210.0%

2021: 0.0%. Across these years the share ran from 0.0% to 15.4%. Each column counts radon tests reported to CDC that year, not homes.

What these figures count

These are the 93 tests reported to CDC for St. Tammany Parish over 2021, 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: 2021. Measured data period: 2005 to 2021 (every CDC figure on file).

How to read these figures

St. Tammany Parish, Compared

St. Tammany Parish radon figures, compared

Calculated by Radon411

Only 0 of 93 radon tests reported for St. Tammany Parish in 2021 reached 4 pCi/L (0.0%). The median result, 0.9 pCi/L, sits below 2, well under EPA's 4 pCi/L action level, and the top reported result was 2.5 pCi/L.

Across 21 Louisiana counties pooled together, 3.9% of tests reached that level, so St. Tammany Parish runs 3.9 points below its state. Against the national pool of 24.4%, the gap is 24.4 points lower. Its place in the state: 3rd of 14 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. Of 2 neighbours with a figure, all 2 reported a larger share at or above 4 pCi/L; the spread is 0.0% (Orleans Parish) to 0.0% (Tangipahoa Parish).

Below the action level, 87 tests (93.5%) came in under 2 pCi/L, against 92.3% statewide, and 6 tests (6.5%) fell between 2 and 4, against 3.8% statewide. Over 5 years of annual figures the share fell 15.4 points, from 15.4% in 2016 to 0.0% in 2021; its peak was 15.4% in 2016. USGS geology rates 100% of the county's land low radon potential.

The busiest year on file was 2021, with 93 tests reported; the quietest, 2014, had 3.

Share of reported tests at or above 4 pCi/L by year, St. Tammany Parish against Louisiana2016 to 2021, years with 30 or more tests: St. Tammany Parish 15.4% to 0.0%, the state's pooled share 3.9% in 2021.
St. Tammany ParishLouisiana, pooled
Share of reported tests at or above 4 pCi/L by year, St. Tammany Parish against Louisiana: data table
YearTestsSt. Tammany Parish, at or above 4 pCi/LLouisiana, pooled
20163915.4%2.0%
2017360.0%2.6%
2019575.3%2.0%
2020630.0%0.8%
2021930.0%3.9%
St. Tammany Parish against Louisiana, the United States and nearby counties, 2021
AreaTestsAt or above 4 pCi/LMedianDifference from St. Tammany Parish
St. Tammany Parish930.0%0.9 pCi/LThis county
Louisiana, pooled21 counties, pooled3,3273.9%Not pooled+3.9 points
United States, pooled807 counties, pooled344,60424.4%Not pooled+24.4 points
Caddo Parishhighest in the state47720.1%1.1 pCi/L+20.1 points
Catahoula Parishlowest in the state630.0%0.2 pCi/LLevel
Tangipahoa Parish, LAborders it420.0%0.9 pCi/LLevel
Jefferson Parish, LAborders it120.0%0.9 pCi/LLevel
Orleans Parish, LAborders it450.0%1.1 pCi/LLevel
Where St. Tammany Parish's reported results fell, 2021, beside Louisiana and the United States
ResultSt. Tammany Parish testsSt. Tammany Parish shareLouisiana shareU.S. shareAgainst Louisiana
Under 2 pCi/L8793.5%92.3%54.4%+1.2 points
2 to 4 pCi/L66.5%3.8%21.2%+2.7 points
4 pCi/L and above00.0%3.9%24.4%−3.9 points
St. Tammany Parish ranked among the 14 Louisiana counties with 30 or more tests, by share at or above 4 pCi/L, 2021
CountyRankTestsAt or above 4 pCi/LMedian
West Baton Rouge Parish3 of 144530.0%0.4 pCi/L
East Baton Rouge Parish3 of 144200.0%0.4 pCi/L
Avoyelles Parish3 of 142160.0%0.2 pCi/L
Calcasieu Parish3 of 142160.0%0.6 pCi/L
Rapides Parish3 of 141920.0%0.3 pCi/L
Natchitoches Parish3 of 141680.0%0.5 pCi/L
Ouachita Parish3 of 141590.0%0.7 pCi/L
St. Tammany Parish3 of 14930.0%0.9 pCi/L
Catahoula Parish3 of 14630.0%0.2 pCi/L
Orleans Parish3 of 14450.0%1.1 pCi/L
Tangipahoa Parish3 of 14420.0%0.9 pCi/L
St. Tammany Parish radon tests by year, against Louisiana's pooled share
YearTestsAt or above 4 pCi/LMedianHighestLouisiana, pooledChange from the row before
2021930.0%0.9 pCi/L2.5 pCi/L3.9%Level
2020630.0%0.5 pCi/L2.3 pCi/L0.8%−5.3 points
2019575.3%1.2 pCi/L11.2 pCi/L2.0%+5.3 points
2018150.0%1.0 pCi/L1.3 pCi/L0.5%Level
2017360.0%0.5 pCi/L2.1 pCi/L2.6%−15.4 points
20163915.4%0.9 pCi/L59.2 pCi/L2.0%+15.4 points
2015240.0%0.9 pCi/L1.8 pCi/L7.2%Level
201430.0%1.4 pCi/L1.4 pCi/L10.5%First on file

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

St. Tammany Parish, Geology

The ground under St. Tammany Parish

Predicted

USGS's geologic map puts all of St. Tammany Parish's mapped land in one class: low radon potential. The map puts 52.6% of St. Tammany Parish in the area it calls Terraces and 46.9% in Delta. USGS gives the first a radon index of 8 and the second 6, both in the low band (5 to 8).

USGS's geologic areas under St. Tammany Parish
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
TerracesClays, siltstone, and sandstone.Low852.6%
DeltaAlluvium and marsh.Low646.9%

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

St. Tammany Parish beside the ground around it

Neither St. Tammany Parish nor Louisiana as a whole has any land USGS rates above low potential. None of the 7 counties that border it has any moderate-potential ground either.

Share of land by USGS radon potential: St. Tammany Parish, the 7 counties bordering it and Louisiana
AreaEPA zoneLow potentialModerate potentialHigh potential
St. Tammany ParishZone 399.7%NoneNone
Hancock County, MSZone 399.5%NoneNone
Orleans ParishZone 3100%NoneNone
Tangipahoa ParishZone 3100%NoneNone
Washington ParishZone 3100%NoneNone
Pearl River County, MSZone 3100%NoneNone
St. John the Baptist ParishZone 3100%NoneNone
Jefferson ParishZone 384.8%NoneNone
Louisiana64 parishes, pooled by land areaVaries98.4%NoneNone

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

Local help

St. Tammany Parish, Local resources

Radon testing and mitigation in St. Tammany Parish

What it means

St. Tammany Parish, Questions

Questions about radon in St. Tammany Parish

Are radon levels high in St. Tammany Parish?

In 2021, 0.0% of the radon tests reported to CDC for St. Tammany Parish, Louisiana were at or above 4 pCi/L, and the median reported pre-mitigation result was 0.9 pCi/L. Of 14 Louisiana counties with 30 or more tests for the same period, 2 reported a higher share; pooled, the state comes to 3.9%.

Which counties border St. Tammany Parish?

St. Tammany Parish borders 7 counties: Hancock County, MS, Orleans Parish, LA, Tangipahoa Parish, LA, Washington Parish, LA, Pearl River County, MS, St. John the Baptist Parish, LA and Jefferson Parish, LA.

Products

St. Tammany Parish, Products

Testing a home in St. Tammany Parish

In St. Tammany Parish, 0.0% of 93 tests reported to CDC in 2021 reached 4 pCi/L, against 3.9% 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 St. Tammany Parish.

Test kits and monitors3

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Best radon monitors for St. Tammany Parish homes, compared

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St. Tammany Parish, Bordering counties

Counties bordering St. Tammany Parish

Calculated by Radon411

St. Tammany Parish, Cities and towns

Cities and towns in St. Tammany Parish

St. Tammany Parish is growing: the Census Bureau puts it at 279,108 residents on July 1, 2025, up 5.3% from 264,989 in 2020. That works out to 330 people per square mile of land. No town dominates: Slidell, the largest, has 28,341 residents, 10.2% of the total. Together its 8 incorporated places hold 21.7% of those residents; the other 78.3% live outside any of them. Reported testing is thin here: 93 tests over 2021, or 0.3 for every 1,000 residents (2025 estimate), where Louisiana as a whole comes to 0.7.

From Slidell to Sun, CDC publishes no figure by town: each reads St. Tammany Parish's.

The cities and towns in St. Tammany Parish by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Slidell28,341−0.9%10.2%
Mandeville12,918+0.7%4.6%
Covington11,721+1.2%4.2%
Abita Springs2,753+5.0%1.0%
Pearl River2,715+6.3%1.0%
Madisonville877+3.4%0.3%
Folsom846+9.2%0.3%
Sun401+1.5%0.1%

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).

St. Tammany Parish, Homes

Homes in St. Tammany Parish

St. Tammany Parish is a place of houses on their own lots: 77% of its 112,414 homes are detached single-family houses, against 65% across Louisiana. Much of St. Tammany Parish is recent building: 40% of its homes have gone up since 2000 and the middle year built is 1995, against 1982 for Louisiana. Owners live in 79% of the occupied homes (Louisiana: 67%), so for most households a test and a fix are their own to order.

Homes in St. Tammany Parish, Louisiana, 2019 to 2023
HomesSt. Tammany ParishLouisiana
Housing units112,4142,094,002
Detached houses77%65%
In buildings of 5 or more9%11%
Mobile homes7%13%
Built before 19605%19%
Built since 200040%27%
Middle year built19951982
Owner-occupied79%67%

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