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Radon Levels in Benton County, Arkansas

EPA puts Benton County in Zone 2, its middle radon zone, and 34.0% of its 147 reported radon tests (2008 to 2017, laboratory totals) were 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

    34.0%

    10.8 pts above AR

    Benton
    34.0%
    Arkansas
    23.2%

    147 tests, 2008 to 2017

  • Median result

    2.2pCi/L

    Below action level

    Benton
    2.2 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    147

    Most tested in Arkansas

    Benton
    147

    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 Arkansas

    3 of 5

    Middle half

    Benton
    34.0%
    Garland
    45.5%

    By share, of 5 with 30+ tests

Read a result for Benton County

Starts at Benton County's median, 2.2 pCi/L

2.2pCi/L

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

EPA’s reading of 2.2 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. Benton County's median reported result, 2008 to 2017.

Interpret this readingWhat a fix costs

The data

Benton County, At a glance

Benton County at a glance

Predicted: EPA radon zone

EPA Zone 2: moderate predicted potential

Benton 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 Benton County, 2008 to 2017, laboratory

Reported results by concentration band, Benton County, 2008 to 2017, laboratory
Under 2 pCi/L: 46%2 to 4 pCi/L: 20%4 pCi/L and above: 34%

Of 147 pre-mitigation tests reported to CDC, not homes in this area.

Reported results by concentration band, Benton County, 2008 to 2017, laboratory: data table
Result bandTests MeasuredShare Measured
Under 2 pCi/L6846.3%
2 to 4 pCi/L2919.7%
4 pCi/L and above5034.0%
What these figures count

These are the 147 tests reported to CDC for Benton 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

Benton County, Compared

Benton County radon figures, compared

Calculated by Radon411

In Benton County, about 3 in 10 reported tests over the 2008 to 2017 laboratory totals (50 of 147) were at or above EPA's action level. Against the national pool of 35.7%, the gap is 1.7 points lower. Across 58 Arkansas counties pooled together, 23.2% of tests reached that level, so Benton County runs 10.8 points above its state.

Of 3 neighbours with a figure, 2 reported a larger share at or above 4 pCi/L and 1 a smaller one; the spread is 13.0% (Washington County) to 41.9% (Delaware County, OK). By share, Benton County is 3rd of 5 Arkansas counties with 30 or more tests for the same period.

Half the tests came in under 2.2 pCi/L and half over it; the single highest reached 97.9 pCi/L. Below the action level, 68 tests (46.3%) came in under 2 pCi/L, against 55.5% statewide, and 29 tests (19.7%) fell between 2 and 4, against 21.3% statewide.

Zone 2 on EPA's map (predicted average between 2 and 4 pCi/L) and a 34.0% share point the same way here. USGS geology rates 100% of the county's land moderate radon potential.

CDC's ten-year totals for Benton County went from 117 tests (2005 to 2014) to 147 (2008 to 2017), the share going from 33.3% to 34.0%.

Benton County against Arkansas, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Benton County
Benton County14734.0%2.2 pCi/LThis county
Arkansas, pooled58 counties, pooled66823.2%Not pooled−10.8 points
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled+1.7 points
Garland Countyhighest in the state4445.5%2.7 pCi/L+11.5 points
Pulaski Countylowest in the state1106.4%0.9 pCi/L−27.6 points
Adair County, OKborders it250.0%3.8 pCi/L+16.0 points
Delaware County, OKborders it3141.9%2.3 pCi/L+7.9 points
Barry County, MOborders it5541.8%3.1 pCi/L+7.8 points
Carroll County, ARborders it1729.4%2.0 pCi/L−4.6 points
McDonald County, MOborders it1921.1%1.9 pCi/L−12.9 points
Madison County, ARborders it616.7%1.2 pCi/L−17.3 points
Washington County, ARborders it5413.0%2.2 pCi/L−21.0 points
Where Benton County's reported results fell, 2008 to 2017, laboratory, beside Arkansas and the United States
ResultBenton County testsBenton County shareArkansas shareU.S. shareAgainst Arkansas
Under 2 pCi/L6846.3%55.5%39.6%−9.2 points
2 to 4 pCi/L2919.7%21.3%24.7%−1.6 points
4 pCi/L and above5034.0%23.2%35.7%+10.8 points
Benton County ranked among the 5 Arkansas counties with 30 or more tests, by share at or above 4 pCi/L, 2008 to 2017, laboratory
CountyRankTestsAt or above 4 pCi/LMedian
Garland County1 of 54445.5%2.7 pCi/L
Saline County2 of 55335.8%2.4 pCi/L
Benton County3 of 514734.0%2.2 pCi/L
Washington County4 of 55413.0%2.2 pCi/L
Pulaski County5 of 51106.4%0.9 pCi/L
Benton County ten-year laboratory totals, against Arkansas' pooled share
PeriodTestsAt or above 4 pCi/LMedianHighestArkansas, pooledChange from the row before
2008 to 201714734.0%2.2 pCi/L97.9 pCi/L23.2%+3.0 points
2007 to 201614531.0%1.8 pCi/L97.9 pCi/L22.7%+0.2 points
2006 to 201513330.8%1.8 pCi/L53.8 pCi/L22.5%−2.5 points
2005 to 201411733.3%2.0 pCi/L75.1 pCi/L24.3%First on file

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

Benton County, Geology

The ground under Benton County

Predicted

USGS's geologic map puts all of Benton County's mapped land in one class: moderate radon potential. The map puts 82.5% of Benton County in the area it calls Springfield Plateau and 17.2% in Salem Plateau. USGS gives both a radon index of 9, in the moderate band (9 to 11).

USGS's geologic areas under Benton County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Springfield PlateauMississippian limestone, shale, and sandstone.Moderate982.5%
Salem PlateauOrdovician dolomite.Moderate917.2%

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

Benton County beside the ground around it

Benton County has more moderate-potential ground than Arkansas as a whole: 100% of its land against 21.3%. Of the 7 counties that border it, none has as large a share of moderate-potential ground; Barry County, MO comes nearest at 100%.

Share of land by USGS radon potential: Benton County, the 7 counties bordering it and Arkansas
AreaEPA zoneLow potentialModerate potentialHigh potential
Benton CountyZone 2None100%None
Washington CountyZone 334.8%65.2%None
McDonald County, MOZone 2None100%None
Barry County, MOZone 2None100%None
Delaware County, OKZone 20.1%99.9%None
Madison CountyZone 363.6%36.4%None
Carroll CountyZone 24.6%95.4%None
Adair County, OKZone 219.6%80.4%None
Arkansas75 counties, pooled by land areaVaries78.7%21.3%None

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

Local help

Benton County, Local resources

Radon testing and mitigation in Benton County

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

What it means

Benton County, Questions

Questions about radon in Benton County

Are radon levels high in Benton County?

Over the 2008 to 2017 laboratory totals, 34.0% of the radon tests reported to CDC for Benton County, Arkansas were at or above 4 pCi/L, and the median reported pre-mitigation result was 2.2 pCi/L. Of 5 Arkansas counties with 30 or more tests for the same period, 2 reported a higher share; pooled, the state comes to 23.2%.

Which counties border Benton County?

Benton County borders 7 counties: Washington County, AR, McDonald County, MO, Barry County, MO, Delaware County, OK, Madison County, AR, Carroll County, AR and Adair County, OK.

Products

Benton County, Products

Testing a home in Benton County

In Benton County, 34.0% of 147 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 23.2% pooled across Arkansas. In Zone 2 a short-term kit (2 to 90 days) is the quick first check in Benton County; a long-term test tells the year-round average.

Test kits and monitors3

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Best radon monitors for Benton County homes, compared

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Benton County, Bordering counties

Counties bordering Benton County

Calculated by Radon411

Benton County, Cities and towns

Cities and towns in Benton County

Benton County is growing: the Census Bureau puts it at 332,554 residents on July 1, 2025, up 16.0% from 286,597 in 2020. That works out to 392 people per square mile of land. Springdale, the largest place on its list (90,685 residents in all), extends beyond Benton County, so no share of the total is worked out for it. Testing is reported here more often than across the state: CDC's 147 reported tests for 2008 to 2017 come to 0.4 for every 1,000 residents (2025 estimate), against 0.2 for Arkansas.

From Springdale to Bethel Heights, CDC publishes no figure by town: each reads Benton County's.

The 12 largest cities and towns in Benton County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Springdaleextends beyond Benton County90,685+3.9%Counted whole
Rogers76,956+9.8%23.1%
Bentonville63,057+15.0%19.0%
Bella Vista34,518+14.2%10.4%
Centerton27,176+48.9%8.2%
Siloam Springs21,298+21.5%6.4%
Lowell12,184+22.5%3.7%
Pea Ridge11,233+68.3%3.4%
Cave Springs6,701+14.0%2.0%
Gentry4,899+27.2%1.5%
Gravette3,889+8.8%1.2%
Highfill3,676+119.9%1.1%
  • Little Flock
  • Elm Springs (part)
  • Decatur
  • Garfield
  • Avoca
  • Sulphur Springs
  • Gateway
  • Springtown
  • Bethel Heights

21 incorporated places, as listed in the U.S. Census Bureau’s 2020 place reference files. “(part)” marks a place that extends into another county. Residents: U.S. Census Bureau population estimates for July 1, 2025 (Vintage 2025). A place that extends beyond Benton County is counted whole, so it has no share.

Benton County, Homes

Homes in Benton County

Of Benton County's 118,496 homes, 74% are detached houses, against 70% across Arkansas; 11% are in buildings of five or more homes. Much of Benton County is recent building: 48% of its homes have gone up since 2000 and the middle year built is 1999, against 1987 for Arkansas. 67% 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 Benton County, Arkansas, 2019 to 2023
HomesBenton CountyArkansas
Housing units118,4961,382,664
Detached houses74%70%
In buildings of 5 or more11%10%
Mobile homes4%11%
Built before 19605%14%
Built since 200048%28%
Middle year built19991987
Owner-occupied67%66%

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