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Radon Levels in Delaware County, Oklahoma

EPA puts Delaware County in Zone 2, its middle radon zone, and high results are common there: 41.9% of the 31 radon tests reported to CDC (2008 to 2017, laboratory totals) came back at or above 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

    41.9%

    29.2 pts above OK

    Delaware
    41.9%
    Oklahoma
    12.7%

    31 tests, 2008 to 2017

  • Median result

    2.3pCi/L

    Below action level

    Delaware
    2.3 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    31

    4th of 4 by tests

    Delaware
    31
    Tulsa
    306

    Reported to CDC before any fix, 2008 to 2017

  • EPA radon zone

    Zone 2

    Moderate potential

    1. 1
    2. Zone 2
    3. 3

    1 highest, 3 lowest

    EPA predicts 2 to 4 pCi/L indoors

  • Rank in Oklahoma

    1 of 4

    Top quarter

    Delaware
    41.9%
    Delaware
    41.9%

    By share, of 4 with 30+ tests

Read a result for Delaware County

Starts at Delaware County's median, 2.3 pCi/L

2.3pCi/L

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

EPA’s reading of 2.3 pCi/L

Between 2 and 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 between 2 and 4 pCi/L. EPA recommends considering a fix when the level is between 2 and 4 pCi/L. Delaware County's median reported result, 2008 to 2017.

Interpret this readingWhat a fix costs

The data

Delaware County, At a glance

Delaware County at a glance

Predicted: EPA radon zone

EPA Zone 2: moderate predicted potential

Delaware County is a county: EPA's forecast for it as a whole is an average indoor of 2 to 4 pCi/L (75 to 150 Bq/m³). It describes no single address, and homes above EPA's are found in every zone, this one included.

USGS geologic potential: Moderate across 100% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

Radon tests reported for Delaware County, 2008 to 2017, laboratory

Reported results by concentration band, Delaware County, 2008 to 2017, laboratory
Under 2 pCi/L: 35%2 to 4 pCi/L: 23%4 pCi/L and above: 42%

Of 31 pre-mitigation tests reported to CDC, not homes in this area.

Reported results by concentration band, Delaware County, 2008 to 2017, laboratory: data table
Result bandTests MeasuredShare Measured
Under 2 pCi/L1135.5%
2 to 4 pCi/L722.6%
4 pCi/L and above1341.9%
What these figures count

These are the 31 tests reported to CDC for Delaware County over 2008 to 2017 (laboratory totals), many from homes being sold or already suspected of a problem: they describe the county's reported tests, not 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

Delaware County, Compared

Delaware County radon figures, compared

Calculated by Radon411

In Delaware County, about 4 in 10 reported tests over the 2008 to 2017 laboratory totals (13 of 31) were at or above EPA's action level. Against the national pool of 35.7%, the gap is 6.2 points higher. Across 52 Oklahoma counties pooled together, 12.7% of tests reached that level, so Delaware County runs 29.2 points above its state.

Of 2 neighbours with a figure, none reported a larger share at or above 4 pCi/L; the spread is 31.4% (Cherokee County) to 34.0% (Benton County, AR). By share, Delaware County is 1st of 4 Oklahoma counties with 30 or more tests for the same period.

Half the tests came in under 2.3 pCi/L and half over it; the single highest reached 47.1 pCi/L. Below the action level, 11 tests (35.5%) came in under 2 pCi/L, against 68.7% statewide, and 7 tests (22.6%) fell between 2 and 4, against 18.7% statewide.

Zone 2 on EPA's map (predicted average between 2 and 4 pCi/L) and a 41.9% share point the same way here. USGS geology rates 100% of the county's land moderate radon potential.

CDC's ten-year totals for Delaware County went from 38 tests (2005 to 2014) to 31 (2008 to 2017), the share going from 44.7% to 41.9%.

Delaware County against Oklahoma, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Delaware County
Delaware County3141.9%2.3 pCi/LThis county
Oklahoma, pooled52 counties, pooled81412.7%Not pooled−29.2 points
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled−6.2 points
Oklahoma Countyhighest in the state1198.4%0.8 pCi/L−33.5 points
Tulsa Countylowest in the state3068.2%0.9 pCi/L−33.7 points
Adair County, OKborders it250.0%3.8 pCi/L+8.1 points
Benton County, ARborders it14734.0%2.2 pCi/L−7.9 points
Mayes County, OKborders it333.3%3.8 pCi/L−8.6 points
Cherokee County, OKborders it5131.4%1.9 pCi/L−10.5 points
McDonald County, MOborders it1921.1%1.9 pCi/L−20.8 points
Ottawa County, OKborders it30.0%0.2 pCi/L−41.9 points
Craig County, OKborders it20.0%2.6 pCi/L−41.9 points
Where Delaware County's reported results fell, 2008 to 2017, laboratory, beside Oklahoma and the United States
ResultDelaware County testsDelaware County shareOklahoma shareU.S. shareAgainst Oklahoma
Under 2 pCi/L1135.5%68.7%39.6%−33.2 points
2 to 4 pCi/L722.6%18.7%24.7%+3.9 points
4 pCi/L and above1341.9%12.7%35.7%+29.2 points
Delaware County ranked among the 4 Oklahoma counties with 30 or more tests, by share at or above 4 pCi/L, 2008 to 2017, laboratory
CountyRankTestsAt or above 4 pCi/LMedian
Delaware County1 of 43141.9%2.3 pCi/L
Cherokee County2 of 45131.4%1.9 pCi/L
Oklahoma County3 of 41198.4%0.8 pCi/L
Tulsa County4 of 43068.2%0.9 pCi/L
Delaware County ten-year laboratory totals, against Oklahoma's pooled share
PeriodTestsAt or above 4 pCi/LMedianHighestOklahoma, pooledChange from the row before
2008 to 20173141.9%2.3 pCi/L47.1 pCi/L12.7%+1.9 points
2007 to 20163540.0%2.2 pCi/L47.1 pCi/L12.1%−4.7 points
2006 to 20153844.7%2.5 pCi/L47.1 pCi/L12.6%Level
2005 to 20143844.7%2.5 pCi/L47.1 pCi/L12.0%First on file

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

Delaware County, Geology

The ground under Delaware County

Predicted

Most of the ground under Delaware County is one class on USGS's geologic map: 99.9% of its land is moderate radon potential, with 0.1% low. All of it lies in the area the map calls Ozark Plateau, to which USGS gives a radon index of 9, in the moderate band (9 to 11).

USGS's geologic areas under Delaware County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Ozark PlateauMississippian and Pennsylvanian limestone and shale.Moderate999.9%

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

Delaware County beside the ground around it

Across Oklahoma 0.6% of the land is rated high; none of Delaware County's is. Of the 7 counties that border it, 2 have more moderate-potential ground, Benton County, AR the most at 100%.

Share of land by USGS radon potential: Delaware County, the 7 counties bordering it and Oklahoma
AreaEPA zoneLow potentialModerate potentialHigh potential
Delaware CountyZone 20.1%99.9%None
Mayes CountyZone 258.8%41.2%None
McDonald County, MOZone 2None100%None
Benton County, ARZone 2None100%None
Ottawa CountyZone 352.0%48.0%None
Cherokee CountyZone 216.7%83.3%None
Craig CountyZone 394.1%5.9%None
Adair CountyZone 219.6%80.4%None
Oklahoma77 counties, pooled by land areaVaries84.8%14.6%0.6%

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

Local help

Delaware County, Local resources

Radon testing and mitigation in Delaware County

What it means

Delaware County, Questions

Questions about radon in Delaware County

Are radon levels high in Delaware County?

Over the 2008 to 2017 laboratory totals, 41.9% of the radon tests reported to CDC for Delaware County, Oklahoma were at or above 4 pCi/L, and the median reported pre-mitigation result was 2.3 pCi/L. Of 4 Oklahoma counties with 30 or more tests for the same period, none reported a higher share; pooled, the state comes to 12.7%.

Which counties border Delaware County?

Delaware County borders 7 counties: Mayes County, OK, McDonald County, MO, Benton County, AR, Ottawa County, OK, Cherokee County, OK, Craig County, OK and Adair County, OK.

Products

Delaware County, Products

Testing a home in Delaware County

In Delaware County, 41.9% of 31 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 12.7% pooled across Oklahoma. In Zone 2 a short-term kit (2 to 90 days) is the quick first check in Delaware County; a long-term test tells the year-round average.

Test kits and monitors3

See every kit and monitor

Best radon monitors for Delaware County homes, compared

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Delaware County, Bordering counties

Counties bordering Delaware County

Calculated by Radon411

Delaware County, Cities and towns

Cities and towns in Delaware County

The Census Bureau estimates 41,910 residents in Delaware County for July 1, 2025, 1,529 more than in 2020 (+3.8%). That works out to 57 people per square mile of land. No town dominates: Grove, the largest, has 7,399 residents, 17.7% of the total. Testing is reported here more often than across the state: CDC's 31 reported tests for 2008 to 2017 come to 0.7 for every 1,000 residents (2025 estimate), against 0.2 for Oklahoma.

From Grove to Oaks, CDC publishes no figure by town: each reads Delaware County's.

The cities and towns in Delaware County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Grove7,399+6.3%17.7%
Jay2,507+3.5%6.0%
West Siloam Springs1,066+3.3%2.5%
Colcord758+3.8%1.8%
Kansas756+6.9%1.8%
Ketchumextends beyond Delaware County514+2.6%Counted whole
Bernice434+3.3%1.0%
Oaksextends beyond Delaware County271+0.7%Counted whole

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

Delaware County, Homes

Homes in Delaware County

Of Delaware County's 24,282 homes, 65% are detached houses, against 73% across Oklahoma; 26% are mobile homes. Half of its homes were built before 1987, close to Oklahoma's 1980: 11% date from before 1960 and 26% from 2000 or later. Owners live in 76% of the occupied homes (Oklahoma: 66%), so for most households a test and a fix are their own to order.

Homes in Delaware County, Oklahoma, 2019 to 2023
HomesDelaware CountyOklahoma
Housing units24,2821,763,036
Detached houses65%73%
In buildings of 5 or more3%12%
Mobile homes26%9%
Built before 196011%21%
Built since 200026%25%
Middle year built19871980
Owner-occupied76%66%

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