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Licenses on file: see the profile
Locations and reports
Radon in Portland, Oregon
Portland lies in 3 counties, in EPA Zones 2 and 3; 99.5% of it is in Multnomah County, where 27.8% of 792 reported tests (2023) were at or above 4 pCi/L. Homes with elevated levels occur in all three zones, so the only way to know your home's level is to test it.
Data checked By Radon411Methodology
Share at 4+ pCi/L
27.8%
8.9 pts above OR
- Multnomah
- 27.8%
- Oregon
- 18.9%
Multnomah, 3rd of 14 in OR, 2023
Median result
2.0pCi/L
Below action level
- Multnomah
- 2.0 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of Multnomah's tests, 2023
Highest county
27.8%
Multnomah
- Multnomah
- 27.8%
- Washington
- 11.4%
3 counties, 3 with 30+ tests, 2023
EPA radon zone
Zone 2
Moderate potential
- 1
- Zone 2
- 3
1 highest, 3 lowest
Multnomah; Clackamas Zone 3, Washington Zone 2
Tests reported
792
In Multnomah
- Multnomah
- 792
- Washington
- 396
Reported to CDC before any fix, 2023
Read a result for Portland
Starts at Multnomah County's median, 2.0 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 2.0 pCi/L
Between 2 and 4 pCi/L
- Under 20 to 1.9 pCi/L
- 2 to 4consider a fix
- 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. Multnomah County's median reported result, 2023.
The data
Portland, What is published
What is published for Portland
Information:
Every figure for Portland is a county's
Radon data is published by county, not by city, and Portland reaches into 3 counties: Multnomah County, Clackamas County and Washington County. Each has its own EPA zone and its own CDC test figures, set side by side below and each labelled with its county. Only a test tells you about one home.
Portland covers 133 square miles of land across 3 counties: 99.5% in Multnomah County, 0.4% in Clackamas County and 0.1% in Washington County. About 635,109 people live there, 4,759 to the square mile.
Portland, Counties
Portland's counties, side by side
MeasuredEach county's own EPA zone and its own published CDC figures for 2023, the newest period any of them has. A county without a figure for that period is shown without one, never with a figure from another year.
- Multnomah County
- EPA zone
- Zone 2: Moderate predicted potential
- At or above 4 pCi/L
- 27.8%
- Median result
- 2.0 pCi/L
- Tests reported
- 792 tests
- Annual years on file
- 10
- Clackamas County
- EPA zone
- Zone 3: Lower predicted potential
- At or above 4 pCi/L
- 15.9%
- Median result
- 1.6 pCi/L
- Tests reported
- 321 tests
- Annual years on file
- 10
- Washington County
- EPA zone
- Zone 2: Moderate predicted potential
- At or above 4 pCi/L
- 11.4%
- Median result
- 1.3 pCi/L
- Tests reported
- 396 tests
- Annual years on file
- 10
| County | EPA zone | Reported tests at or above 4 pCi/L | Median reported result | Tests reported | Annual years on file |
|---|---|---|---|---|---|
| Multnomah County | Zone 2: Moderate predicted potential | 27.8% | 2.0 pCi/L | 792 tests | 10 |
| Clackamas County | Zone 3: Lower predicted potential | 15.9% | 1.6 pCi/L | 321 tests | 10 |
| Washington County | Zone 2: Moderate predicted potential | 11.4% | 1.3 pCi/L | 396 tests | 10 |
Portland spans 3 counties, each with its own EPA zone and its own CDC figure: Multnomah County (Zone 2, 27.8% of 792 tests), Clackamas County (Zone 3, 15.9% of 321 tests) and Washington County (Zone 2, 11.4% of 396 tests).
Multnomah County ranks 3rd of 14 Oregon counties with 30 or more tests for that period, 8.9 points above the 18.9% pooled across Oregon's counties, 5.6 points below the national pool of 33.4%. Of the city's other counties, Clackamas County reported 15.9% and Washington County reported 11.4%.
The counties nearest Portland with a CDC figure for 2023, measured from the middle of the city: Yamhill County (38 miles, 21.2% of 33 tests), Marion County (44 miles, 16.0% of 194 tests) and Hood River County (49 miles, 39.0% of 41 tests). Across the 8 nearest, the share at or above 4 pCi/L runs from 4.9% to 39.0%; the farthest of them, Lane County, is 111 miles away at 15.5%.
The directory lists 10 businesses with an address in Portland, 9 for testing and 4 for mitigation. Oregon's other cities with a page of their own: Salem.
Against Oregon and its other counties
Shares of tests people chose to run and report, by county (2023); the state's is its counties' counts added up, calculated by Radon411. Only a test measures a home.
The counties around Portland
By distance from the middle of Portland; counties with 30 or more tests.
The median reported pre-mitigation result for 2023 was 2.0 pCi/L in Multnomah County, 1.6 pCi/L in Clackamas County and 1.3 pCi/L in Washington County.
Predicted: EPA Map of Radon Zones, by county. Measured: CDC tracking data, by county, 2023.
Portland, Geology
The ground under Portland
PredictedUSGS's geologic map puts all of Portland's mapped land in one class: moderate radon potential. The map puts 83.7% of Portland in the area it calls Columbia River Gorge and 11.8% in Wilamette Valley. USGS gives both a radon index of 9, in the moderate band (9 to 11).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Columbia River Gorge | River and lacustrine delta deposits and volcanic debris flows. | Moderate | 9 | 83.7% |
| Wilamette Valley | Gravelly to clayey alluvium with moderately elevated uranium content. | Moderate | 9 | 11.8% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Portland beside its counties and Oregon
The ground under Portland is close to Multnomah County's as a whole: 95.5% rated moderate against 88.3%. Portland has more moderate-potential ground than Oregon as a whole: 95.5% of its land against 62.3%.
The map rates the ground, not the air in any home.
Portland, Homes
Homes in Portland
Portland has 304,113 homes, and many share a building: 32% are in buildings of five or more, 53% are detached houses, against 54% across Multnomah County. Half of its homes were built before 1966, close to Multnomah County's 1971: 45% date from before 1960 and 22% from 2000 or later. 53% of occupied homes are lived in by their owner (Multnomah County: 54%); in the rest a tenant can run a test, but a fix is the landlord's to make.
| Homes | Portland | Multnomah County | Oregon |
|---|---|---|---|
| Housing units | 304,113 | 367,704 | 1,838,631 |
| Detached houses | 53% | 54% | 63% |
| In buildings of 5 or more | 32% | 31% | 17% |
| Mobile homes | 1% | 2% | 8% |
| Built before 1960 | 45% | 40% | 23% |
| Built since 2000 | 22% | 21% | 24% |
| Middle year built | 1966 | 1971 | 1980 |
| Owner-occupied | 53% | 54% | 63% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.
Local help
Portland, Professionals
Radon professionals listed in Portland
Businesses whose listed city is Portland, from the state registries and listings in the Radon411 directory, with the same business and certification status the directory shows.
Radon professionals listed in Portland: 1 of 6
10 listings with Portland as the city. See radon mitigation and testing in Portland, or all radon professionals in Oregon.
Portland, Local resources
Local resources for Portland
Who to ask in Oregon: its radon program, test kits and professionals.
- Oregon Radon Awareness ProgramRun by Oregon Health Authority.Visit the program’s page(opens in a new tab)
- Free and low-cost kitsThe program says:
Oregon Radon Awareness Program provides a FREE short-term radon test kit to those living in areas of Oregon where little radon testing has been done.
- Compare kits
- Professionals in Oregon10 listings cover Portland.
The program's own words on licensing are on the Oregon page.
What it means
Portland, Questions
Questions about radon in Portland
What radon zone is Portland in?
A zone line runs through Portland: Multnomah County and Washington County in Zone 2 and Clackamas County in Zone 3. 99.5% of the city's land is in Multnomah County, so Zone 2 covers most addresses. Which zone applies depends on the county an address is in.
What are radon levels in Portland?
A high result is no surprise around Portland: 27.8% of 792 tests reported from Multnomah County for 2023 reached 4 pCi/L or more. The median reported result was 2.0 pCi/L. Clackamas County reported 15.9% of 321 tests and Washington County reported 11.4% of 396 tests; the counties are kept apart.
Should I test my home in Portland?
Yes. About 220 of the 792 tests reported from Multnomah County were at or above 4 pCi/L. That is above Oregon's pooled 18.9%, and ranks Multnomah County 3rd of the 14 Oregon counties with 30 or more tests. No map says which homes those are. How to test a home.
What ground is Portland built on, as far as radon goes?
83.7% of Portland sits on what USGS's map calls "Columbia River Gorge", rated moderate for radon potential, radon index 9; another 11.8% is "Wilamette Valley", in the same class.
Is radon higher in the counties around Portland?
Some are and some are not. Against Multnomah County's 27.8%, 1 of the 8 nearest counties with a figure report more and 7 less, from Linn County (4.9%, 73 miles off) to Hood River County (39.0%, 49 miles off).
Who tests for or fixes radon in Portland?
Radon411's directory has 10 businesses with an address in Portland, 9 listed for testing and 4 for mitigation. Every entry names the public list it was taken from. Radon professionals in Portland.
The answers use the published figures of Multnomah County, Clackamas County and Washington County, the counties Portland lies in.
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