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Radon Levels in Walla Walla County, Washington

EPA puts Walla Walla County in Zone 2, its middle radon zone, and 20.6% of its 34 reported radon tests (2020) 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

    20.6%

    1.6 pts above WA

    Walla Walla
    20.6%
    Washington
    19.0%

    34 tests, 2020

  • Median result

    1.5pCi/L

    Below action level

    Walla Walla
    1.5 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2020

  • Tests reported

    34

    10th of 10 by tests

    Walla Walla
    34
    Spokane
    721

    Reported to CDC before any fix, 2020

  • 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 Washington

    3 of 10

    Top quarter

    Walla Walla
    20.6%
    Spokane
    40.6%

    By share, of 10 with 30+ tests

Read a result for Walla Walla County

Starts at Walla Walla County's median, 1.5 pCi/L

1.5pCi/L

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

EPA’s reading of 1.5 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. Walla Walla County's median reported result, 2020.

Interpret this reading

The data

Walla Walla County, At a glance

Walla Walla County at a glance

Predicted: EPA radon zone

EPA Zone 2: moderate predicted potential

Walla Walla 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 Walla Walla County, 2020

Share of reported tests at or above 4 pCi/L, by year, Walla Walla County
Share of reported tests at or above 4 pCi/L, by year, Walla Walla County
YearShare of reported tests at or above 4 pCi/L
201423.1%
20156.7%
201617.6%
201719.3%
201824.3%
201927.3%
202020.6%

2020: 20.6%. Across these years the share ran from 6.7% to 27.3%. Each column counts radon tests reported to CDC that year, not homes.

What these figures count

These are the 34 tests reported to CDC for Walla Walla County over 2020, 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: 2020. Measured data period: 2005 to 2020 (every CDC figure on file).

How to read these figures

Walla Walla County, Compared

Walla Walla County radon figures, compared

Calculated by Radon411

Walla Walla County's 34 reported tests in 2020 had a middle value of 1.5 pCi/L and a maximum of 15.2 pCi/L, and 20.6% reached 4 pCi/L. Washington as a whole (37 Washington counties, pooled) comes to 19.0%: 1.6 points lower than here.

Among its state's counties it ranks 3rd of 10 Washington counties with 30 or more tests for the same period. Statewide for the same period, Spokane County reported the highest share (40.6%) and Kitsap County the lowest (0.0%).

Below the action level, 18 tests (52.9%) came in under 2 pCi/L, against 67.6% statewide, and 9 tests (26.5%) fell between 2 and 4, against 13.3% statewide. The busiest year on file was 2017, with 57 tests reported; the quietest, 2014, had 13.

EPA's 1993 zone map puts Walla Walla County in Zone 2, a predicted county average between 2 and 4 pCi/L. USGS geology rates 100% of the county's land moderate radon potential.

Umatilla County, OR, the one bordering county with a figure for the same period, reported 20.0%. Over 5 years of annual figures the share rose 13.9 points, from 6.7% in 2015 to 20.6% in 2020; its peak was 27.3% in 2019.

Share of reported tests at or above 4 pCi/L by year, Walla Walla County against Washington2015 to 2020, years with 30 or more tests: Walla Walla County 6.7% to 20.6%, the state's pooled share 19.0% in 2020.
Walla Walla CountyWashington, pooled
Share of reported tests at or above 4 pCi/L by year, Walla Walla County against Washington: data table
YearTestsWalla Walla County, at or above 4 pCi/LWashington, pooled
2015456.7%17.4%
20175719.3%19.1%
20183724.3%16.1%
20193327.3%20.9%
20203420.6%19.0%
Walla Walla County against Washington, the United States and nearby counties, 2020
AreaTestsAt or above 4 pCi/LMedianDifference from Walla Walla County
Walla Walla County3420.6%1.5 pCi/LThis county
Washington, pooled37 counties, pooled2,78119.0%Not pooled−1.6 points
United States, pooled915 counties, pooled405,35525.5%Not pooled+4.9 points
Spokane Countyhighest in the state72140.6%2.7 pCi/L+20.0 points
Kitsap Countylowest in the state500.0%0.4 pCi/L−20.6 points
Franklin County, WAborders it425.0%1.9 pCi/L+4.4 points
Umatilla County, ORborders it4020.0%2.7 pCi/L−0.6 points
Benton County, WAborders it214.8%1.4 pCi/L−15.8 points
Where Walla Walla County's reported results fell, 2020, beside Washington and the United States
ResultWalla Walla County testsWalla Walla County shareWashington shareU.S. shareAgainst Washington
Under 2 pCi/L1852.9%67.6%51.6%−14.7 points
2 to 4 pCi/L926.5%13.3%22.9%+13.2 points
4 pCi/L and above720.6%19.0%25.5%+1.6 points
Walla Walla County ranked among the 10 Washington counties with 30 or more tests, by share at or above 4 pCi/L, 2020
CountyRankTestsAt or above 4 pCi/LMedian
Spokane County1 of 1072140.6%2.7 pCi/L
Stevens County2 of 104537.8%1.9 pCi/L
Walla Walla County3 of 103420.6%1.5 pCi/L
Clark County4 of 1049017.6%1.2 pCi/L
Thurston County5 of 10466.5%0.4 pCi/L
Yakima County6 of 10575.3%0.7 pCi/L
King County7 of 105035.0%0.3 pCi/L
Pierce County8 of 104204.3%0.7 pCi/L
Snohomish County9 of 101021.0%0.2 pCi/L
Kitsap County10 of 10500.0%0.4 pCi/L
Walla Walla County radon tests by year, against Washington's pooled share
YearTestsAt or above 4 pCi/LMedianHighestWashington, pooledChange from the row before
20203420.6%1.5 pCi/L15.2 pCi/L19.0%−6.7 points
20193327.3%2.0 pCi/L35.6 pCi/L20.9%+3.0 points
20183724.3%2.8 pCi/L26.2 pCi/L16.1%+5.0 points
20175719.3%1.6 pCi/L50.3 pCi/L19.1%+1.7 points
20161717.6%1.8 pCi/L24.0 pCi/L16.6%+10.9 points
2015456.7%1.0 pCi/L8.6 pCi/L17.4%−16.4 points
20141323.1%1.3 pCi/L8.2 pCi/L15.0%First on file

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

Walla Walla County, Geology

The ground under Walla Walla County

Predicted

USGS's geologic map puts all of Walla Walla County's mapped land in one class: moderate radon potential. 95.6% of it lies in the area the map calls Columbia Basin, to which USGS gives a radon index of 10, in the moderate band (9 to 11).

USGS's geologic areas under Walla Walla County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Columbia BasinBasaltic rocks low in uranium content. Uranium content of soils is moderately elevated.Moderate1095.6%
Blue MountainsTertiary basalt, andesite, tuffaceous sedimentary rocks, and tuff.Moderate93.8%
Deschutes Umatilla PlateauTertiary basalt, basaltic breccia, tuffaceous sedimentary rocks and tuff. Elevated uranium in soils.Moderate90.6%

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

Walla Walla County beside the ground around it

Across Washington 13.7% of the land is rated high; none of Walla Walla County's is. Of the 4 counties that border it, none has as large a share of moderate-potential ground; Benton County comes nearest at 100%.

Share of land by USGS radon potential: Walla Walla County, the 4 counties bordering it and Washington
AreaEPA zoneLow potentialModerate potentialHigh potential
Walla Walla CountyZone 2None100%None
Franklin CountyZone 2None100%None
Columbia CountyZone 2None100%None
Benton CountyZone 2None100%None
Umatilla County, ORZone 2None100%None
Washington38 counties, pooled by land areaVaries46.4%39.0%13.7%

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

Local help

Walla Walla County, Local resources

Radon testing and mitigation in Walla Walla County

What Washington's program says
Phone
360-236-3200
Email
doh.radon@doh.wa.gov

What it means

Walla Walla County, Questions

Questions about radon in Walla Walla County

Are radon levels high in Walla Walla County?

In 2020, 20.6% of the radon tests reported to CDC for Walla Walla County, Washington were at or above 4 pCi/L, and the median reported pre-mitigation result was 1.5 pCi/L. Of 10 Washington counties with 30 or more tests for the same period, 2 reported a higher share; pooled, the state comes to 19.0%.

Which counties border Walla Walla County?

Walla Walla County borders 4 counties: Franklin County, WA, Columbia County, WA, Benton County, WA and Umatilla County, OR.

Products

Walla Walla County, Products

Testing a home in Walla Walla County

In Walla Walla County, 20.6% of 34 tests reported to CDC in 2020 reached 4 pCi/L, against 19.0% pooled across Washington. In Zone 2 a short-term kit (2 to 90 days) is the quick first check in Walla Walla County; a long-term test tells the year-round average.

Test kits and monitors3

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Best radon monitors for Walla Walla County homes, compared

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Walla Walla County, Bordering counties

Counties bordering Walla Walla County

Calculated by Radon411

Walla Walla County, Cities and towns

Cities and towns in Walla Walla County

Walla Walla County's population has barely moved since 2020: 62,361 residents on July 1, 2025 against 62,620 then, by the Census Bureau's estimates. That works out to 49 people per square mile of land. Walla Walla alone is home to 34,058 of them, 54.6% of the total. Together its 4 incorporated places hold 73.0% of those residents; the other 27.0% live outside any of them. Testing is reported here more often than across the state: CDC's 34 reported tests for 2020 come to 0.5 for every 1,000 residents (2025 estimate), against 0.3 for Washington.

From Walla Walla to Prescott, CDC publishes no figure by town: each reads Walla Walla County's.

The cities and towns in Walla Walla County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Walla Walla34,058−0.6%54.6%
College Place9,923−0.4%15.9%
Waitsburg1,184+1.6%1.9%
Prescott369−1.3%0.6%

4 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).

Walla Walla County, Homes

Homes in Walla Walla County

Of Walla Walla County's 25,219 homes, 68% are detached houses, against 62% across Washington; 14% are in buildings of five or more homes. The homes are older than Washington's as a whole: half were built before 1973 (1984 for Washington), and 38% date from before 1960. 66% of occupied homes are lived in by their owner (Washington: 64%); in the rest a tenant can run a test, but a fix is the landlord's to make.

Homes in Walla Walla County, Washington, 2019 to 2023
HomesWalla Walla CountyWashington
Housing units25,2193,262,667
Detached houses68%62%
In buildings of 5 or more14%22%
Mobile homes7%6%
Built before 196038%21%
Built since 200022%28%
Middle year built19731984
Owner-occupied66%64%

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