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Radon Levels in Marion County, Oregon

EPA puts Marion County in Zone 3, its lowest radon zone, and 16.0% of its 194 reported radon tests (2023) 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

How to test this homeFind a certified tester

  • Share at 4+ pCi/L

    16.0%

    2.9 pts below OR

    Marion
    16.0%
    Oregon
    18.9%

    194 tests, 2023

  • Median result

    1.4pCi/L

    Below action level

    Marion
    1.4 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2023

  • Tests reported

    194

    4th of 14 by tests

    Marion
    194
    Multnomah
    792

    Reported to CDC before any fix, 2023

  • 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 Oregon

    6 of 14

    Middle half

    Marion
    16.0%
    Hood River
    39.0%

    By share, of 14 with 30+ tests

Read a result for Marion County

Starts at Marion County's median, 1.4 pCi/L

1.4pCi/L

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

EPA’s reading of 1.4 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. Marion County's median reported result, 2023.

Interpret this reading

The data

Marion County, At a glance

Marion County at a glance

Predicted: EPA radon zone

EPA Zone 3: lower predicted potential

is EPA's lowest class, and its forecast for Marion County 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 59% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

Radon tests reported for Marion County, 2023

Share of reported tests at or above 4 pCi/L, by year, Marion County
Share of reported tests at or above 4 pCi/L, by year, Marion County
YearShare of reported tests at or above 4 pCi/L
201428.4%
201529.7%
201619.7%
201717.1%
201820.3%
201929.7%
202015.0%
202114.6%
202227.0%
202316.0%

2023: 16.0%. Across these years the share ran from 14.6% to 29.7%. Each column counts radon tests reported to CDC that year, not homes.

What these figures count

These are the 194 tests reported to CDC for Marion County over 2023, 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: 2023. Measured data period: 2005 to 2023 (every CDC figure on file).

How to read these figures

Marion County, Compared

Marion County radon figures, compared

Calculated by Radon411

Marion County's 194 reported tests in 2023 had a middle value of 1.4 pCi/L and a maximum of 19.2 pCi/L, and 16.0% reached 4 pCi/L. Oregon as a whole (28 Oregon counties, pooled) comes to 18.9%: 2.9 points higher than here.

Among its state's counties it ranks 6th of 14 Oregon counties with 30 or more tests for the same period. Statewide for the same period, Hood River County reported the highest share (39.0%) and Deschutes County the lowest (1.7%).

Below the action level, 130 tests (67.0%) came in under 2 pCi/L, against 59.5% statewide, and 33 tests (17.0%) fell between 2 and 4, against 21.6% statewide. The busiest year on file was 2016, with 508 tests reported; the quietest, 2019, had 182.

EPA's 1993 zone map puts Marion County in Zone 3, a predicted county average under 2 pCi/L. USGS geology rates 59% of the county's land low radon potential.

Next door, the shares run from 4.9% in Linn County to 21.2% in Yamhill County, with Clackamas County, Polk County and Linn County below Marion County. Over 10 years of annual figures the share fell 12.4 points, from 28.4% in 2014 to 16.0% in 2023; its peak was 29.7% in 2015.

Share of reported tests at or above 4 pCi/L by year, Marion County against Oregon2014 to 2023, years with 30 or more tests: Marion County 28.4% to 16.0%, the state's pooled share 18.9% in 2023.
Marion CountyOregon, pooled
Share of reported tests at or above 4 pCi/L by year, Marion County against Oregon: data table
YearTestsMarion County, at or above 4 pCi/LOregon, pooled
201446428.4%25.1%
201547829.7%27.4%
201650819.7%21.5%
201735617.1%19.2%
201840020.3%19.6%
201918229.7%20.2%
202037315.0%16.8%
202132914.6%16.3%
202234527.0%20.2%
202319416.0%18.9%
Marion County against Oregon, the United States and nearby counties, 2023
AreaTestsAt or above 4 pCi/LMedianDifference from Marion County
Marion County19416.0%1.4 pCi/LThis county
Oregon, pooled28 counties, pooled2,32918.9%Not pooled+2.9 points
United States, pooled642 counties, pooled128,74033.4%Not pooled+17.4 points
Hood River Countyhighest in the state4139.0%2.2 pCi/L+23.0 points
Deschutes Countylowest in the state601.7%0.9 pCi/L−14.3 points
Wasco County, ORborders it1637.5%1.4 pCi/L+21.5 points
Yamhill County, ORborders it3321.2%1.6 pCi/L+5.2 points
Clackamas County, ORborders it32115.9%1.6 pCi/L−0.1 points
Polk County, ORborders it7910.1%1.4 pCi/L−5.9 points
Linn County, ORborders it414.9%0.8 pCi/L−11.1 points
Where Marion County's reported results fell, 2023, beside Oregon and the United States
ResultMarion County testsMarion County shareOregon shareU.S. shareAgainst Oregon
Under 2 pCi/L13067.0%59.5%41.4%+7.5 points
2 to 4 pCi/L3317.0%21.6%25.2%−4.6 points
4 pCi/L and above3116.0%18.9%33.4%−2.9 points
Marion County ranked among the 14 Oregon counties with 30 or more tests, by share at or above 4 pCi/L, 2023
CountyRankTestsAt or above 4 pCi/LMedian
Hood River County1 of 144139.0%2.2 pCi/L
Douglas County2 of 143333.3%1.8 pCi/L
Multnomah County3 of 1479227.8%2.0 pCi/L
Yamhill County4 of 143321.2%1.6 pCi/L
Jackson County5 of 144916.3%0.7 pCi/L
Marion County6 of 1419416.0%1.4 pCi/L
Clackamas County7 of 1432115.9%1.6 pCi/L
Benton County8 of 143215.6%0.9 pCi/L
Lane County9 of 145815.5%1.0 pCi/L
Washington County10 of 1439611.4%1.3 pCi/L
Polk County11 of 147910.1%1.4 pCi/L
Marion County radon tests by year, against Oregon's pooled share
YearTestsAt or above 4 pCi/LMedianHighestOregon, pooledChange from the row before
202319416.0%1.4 pCi/L19.2 pCi/L18.9%−11.0 points
202234527.0%2.0 pCi/L41.3 pCi/L20.2%+12.4 points
202132914.6%1.5 pCi/L15.4 pCi/L16.3%−0.4 points
202037315.0%1.3 pCi/L18.5 pCi/L16.8%−14.7 points
201918229.7%2.0 pCi/L74.7 pCi/L20.2%+9.4 points
201840020.3%1.6 pCi/L23.5 pCi/L19.6%+3.2 points
201735617.1%1.6 pCi/L65.6 pCi/L19.2%−2.6 points
201650819.7%1.8 pCi/L36.6 pCi/L21.5%−10.0 points
201547829.7%2.2 pCi/L49.8 pCi/L27.4%+1.3 points
201446428.4%2.3 pCi/L40.1 pCi/L25.1%First on file

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

Marion County, Geology

The ground under Marion County

Predicted

USGS's geologic map splits Marion County: 58.6% of its land is low radon potential and 41.4% moderate. The map puts 58.6% of Marion County in the area it calls Cascade Range and 41.4% in Wilamette Valley. USGS gives the first a radon index of 7, in the low band (5 to 8), and the second 9, in the moderate band (9 to 11).

USGS's geologic areas under Marion County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Cascade RangeWestern Cascade Range is Tertiary andesite, basalt flows, and pyroclastic rocks. Eastern Cascades are late Tertiary to Quaternary basaltic and andesitic volcanic rocks.Low758.6%
Wilamette ValleyGravelly to clayey alluvium with moderately elevated uranium content.Moderate941.4%

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

Marion County beside the ground around it

Oregon as a whole has more moderate-potential ground than Marion County: 62.3% of its land, against 41.4% here. Of the 6 counties that border it, 3 have more moderate-potential ground, Wasco County the most at 95.0%.

Share of land by USGS radon potential: Marion County, the 6 counties bordering it and Oregon
AreaEPA zoneLow potentialModerate potentialHigh potential
Marion CountyZone 358.6%41.4%None
Yamhill CountyZone 252.4%47.6%None
Clackamas CountyZone 386.6%13.4%None
Polk CountyZone 371.9%28.1%None
Linn CountyZone 376.6%23.4%None
Wasco CountyZone 25.0%95.0%None
Jefferson CountyZone 214.5%85.5%None
Oregon36 counties, pooled by land areaVaries37.5%62.3%None

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

Local help

Marion County, Local resources

Radon testing and mitigation in Marion County

Listed radon businesses with an address in Marion County:

Listed radon professionals by town: Salem, Silverton

What Oregon's program says
Email
Radon.program@dhsoha.state.or.us

What it means

Marion County, Questions

Questions about radon in Marion County

Are radon levels high in Marion County?

In 2023, 16.0% of the radon tests reported to CDC for Marion County, Oregon were at or above 4 pCi/L, and the median reported pre-mitigation result was 1.4 pCi/L. Of 14 Oregon counties with 30 or more tests for the same period, 5 reported a higher share; pooled, the state comes to 18.9%.

Which counties border Marion County?

Marion County borders 6 counties: Yamhill County, Clackamas County, Polk County, Linn County, Wasco County and Jefferson County.

Products

Marion County, Products

Testing a home in Marion County

In Marion County, 16.0% of 194 tests reported to CDC in 2023 reached 4 pCi/L, against 18.9% pooled across Oregon. 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 Marion County.

Test kits and monitors3

See every kit and monitor

Best radon monitors for Marion County homes, compared

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Marion County, Bordering counties

Counties bordering Marion County

Calculated by Radon411

Marion County, Cities and towns

Cities and towns in Marion County

The Census Bureau estimates 355,777 residents in Marion County for July 1, 2025, 9,493 more than in 2020 (+2.7%). That works out to 301 people per square mile of land. Salem, the largest place on its list (181,779 residents in all), extends beyond Marion County, so no share of the total is worked out for it. CDC's 194 reported tests for 2023 work out to 0.5 per 1,000 residents (2025 estimate), close to Oregon's 0.5.

From Salem to Idanha, CDC publishes no figure by town: each reads Marion County's.

The 12 largest cities and towns in Marion County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Salemextends beyond Marion County181,779+3.3%Counted whole
Keizer39,140−0.5%11.0%
Woodburn31,948+22.6%9.0%
Silverton10,450−0.2%2.9%
Stayton8,488+3.1%2.4%
Aumsville4,241−0.3%1.2%
Mount Angel3,454+2.0%1.0%
Hubbard3,399−1.2%1.0%
Jefferson3,299−1.3%0.9%
Sublimity2,882−2.9%0.8%
Gervais2,572−1.0%0.7%
Turner2,412−1.6%0.7%
  • Mill City (part)
  • Aurora
  • Donald
  • Gates (part)
  • St. Paul
  • Scotts Mills
  • Detroit
  • Idanha (part)

20 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 Marion County is counted whole, so it has no share.

Marion County, Homes

Homes in Marion County

Of Marion County's 130,600 homes, 63% are detached houses, against 63% across Oregon; 18% are in buildings of five or more homes. Half of its homes were built before 1979, close to Oregon's 1980: 20% date from before 1960 and 22% from 2000 or later. 62% of occupied homes are lived in by their owner (Oregon: 63%); in the rest a tenant can run a test, but a fix is the landlord's to make.

Homes in Marion County, Oregon, 2019 to 2023
HomesMarion CountyOregon
Housing units130,6001,838,631
Detached houses63%63%
In buildings of 5 or more18%17%
Mobile homes8%8%
Built before 196020%23%
Built since 200022%24%
Middle year built19791980
Owner-occupied62%63%

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