Short-term kitKidde
442020 short-term charcoal radon test kit
- Lab fee included
Method: Charcoal
In home: 3 days
Locations and reports
Radon Levels in Whatcom County, Washington
EPA puts Whatcom County in Zone 3, its lowest radon zone, and only 25 radon tests from it are on file with CDC (2020). Homes with elevated levels occur in all three zones, so only a test measures yours.
Data checked By Radon411Methodology
Share at 4+ pCi/L
5.3%
20.2 pts below WA
- Whatcom
- 5.3%
- Washington
- 25.5%
113 tests, 2007 to 2016
Median result
0.9pCi/L
Below action level
- Whatcom
- 0.9 pCi/L
- EPA
- 4.0 pCi/L
Midpoint of the tests, 2007 to 2016
Tests reported
113
8th of 19 by tests
- Whatcom
- 113
- Spokane
- 2,979
Reported to CDC before any fix, 2007 to 2016
EPA radon zone
Zone 3
Lower potential
- 1
- 2
- Zone 3
1 highest, 3 lowest
EPA predicts under 2 pCi/L indoors
Rank in Washington
14 of 19
Middle half
- Whatcom
- 5.3%
- Pend Oreille
- 59.5%
By share, of 19 with 30+ tests
Read a result for Whatcom County
Starts at Whatcom County's median, 0.9 pCi/L
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 0.9 pCi/L
Below 2 pCi/L
- Under 20 to 1.9 pCi/L
- 2 to 4consider a fix
- 4 and aboveEPA says fix it
This result is below 2 pCi/L, the level at which EPA says a fix should be considered. Whatcom County's median reported result, 2007 to 2016.
The data
Whatcom County, At a glance
Whatcom County at a glance
Predicted: EPA radon zone
EPA Zone 3: lower predicted potential
USGS geologic potential: Low across 99% of the county's area
Predicted: EPA Map of Radon Zones
Measured: tests reported to CDC
Radon tests reported for Whatcom County, 2020
| Year | Share of reported tests at or above 4 pCi/L |
|---|---|
| 2014 | 1.2% |
| 2015 | 0.0% |
| 2016 | 2.6% |
| 2017 | 7.2% |
| 2018 | 7.7% |
| 2019 | 17.1% |
| 2020 | 20.0% |
2020: 20.0%. Across these years the share ran from 0.0% to 20.0%. Each column counts radon tests reported to CDC that year, not homes.
What these figures count
Only 25 tests were reported to CDC for Whatcom County over 2020, and tests are often run on homes being sold or already suspected of a problem: so few describe neither the county nor this house.
Measured: CDC tracking data. Figure above: 2020. Measured data period: 2005 to 2020 (every CDC figure on file).
Whatcom County, Compared
Whatcom County radon figures, compared
Calculated by Radon411Whatcom County reports fewer high tests than Washington overall. 5.3% of its 113 tests over the 2007 to 2016 laboratory totals were at or above 4 pCi/L. That is 20.2 points below the 25.5% pooled from 38 Washington counties.
The newest figure, in 2020, counts only 25 tests (20.0% at or above 4 pCi/L), too few to compare, so this reading uses the 113-test figure.
Ordered from highest share down, it comes 14th of 19 Washington counties with 30 or more tests for the same period. Nationally, every county with a figure for the same period pools to 35.8%; Whatcom County sits 30.5 points below it.
Next door, the shares run from 2.7% in Skagit County to 35.6% in Okanogan County, with Skagit County below Whatcom County. Zone 3 on EPA's map (predicted average under 2 pCi/L) and a 5.3% share point the same way here.
Half the tests came in under 0.9 pCi/L and half over it; the single highest reached 16.3 pCi/L. The rest split 86.7% under 2 pCi/L and 8.0% from 2 to 4 (Washington: 56.6% and 17.9%). Year by year, 2014 opened at 1.2% and 2019 closed at 17.1% (up 15.9 points), with 2019 the high at 17.1%.
The busiest year on file was 2014, with 85 tests reported; the quietest, 2020, had 25.
Whatcom CountyWashington, pooled
| Year | Tests | Whatcom County, at or above 4 pCi/L | Washington, pooled |
|---|---|---|---|
| 2014 | 85 | 1.2% | 15.0% |
| 2016 | 39 | 2.6% | 16.6% |
| 2017 | 69 | 7.2% | 19.1% |
| 2019 | 35 | 17.1% | 20.9% |
Pooled shares: Radon411's sum of CDC's county counts for one period.
Whatcom County, Geology
The ground under Whatcom County
PredictedUSGS's geologic map puts all of Whatcom County's mapped land in one class: low radon potential. The map puts 84.0% of Whatcom County in the area it calls Cascade Mountains and 14.9% in Puget Lowlands. USGS gives both a radon index of 6, in the low band (5 to 8).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Cascade Mountains | Northern Cascade Mountains are Mesozoic metamorphic rocks intruded by Mesozoic and Tertiary granitic rocks. Southern Cascade Mountains are composed primarily of Tertiary and Holocene volcanic rocks. | Low | 6 | 84.0% |
| Puget Lowlands | Continental and marine sediments overlain by sandy and silty glacial deposits. | Low | 6 | 14.9% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Whatcom County beside the ground around it
Across Washington 13.7% of the land is rated high; none of Whatcom County's is. Of the 2 counties that border it, 1 has more high-potential ground, Okanogan County the most at 38.7%.
The map rates the ground, not the air in any home.
Local help
Whatcom County, Local resources
Radon testing and mitigation in Whatcom County
- Radon ProgramRadon Program, run by Washington State Department of Health, offers free or discounted test kits, and answers questions about testing and mitigation in Washington.Visit the program’s page(opens in a new tab)
- Free and low-cost kitsThe program says:
We have a limited supply of free radon test kits.
- Compare kits
- See the Washington directoryNo professionals are listed in Washington yet. The state program can point you to registered testers and mitigators.
What Washington's program says
- Phone
- 360-236-3200
- doh.radon@doh.wa.gov
What it means
Whatcom County, Questions
Questions about radon in Whatcom County
Are radon levels high in Whatcom County?
In 2020, 20.0% of the radon tests reported to CDC for Whatcom County, Washington were at or above 4 pCi/L, and the median reported pre-mitigation result was 0.7 pCi/L. Of 19 Washington counties with 30 or more tests for the same period, 13 reported a higher share; pooled, the state comes to 25.5%.
Which counties border Whatcom County?
Whatcom County borders 2 counties: Skagit County and Okanogan County.
Products
Whatcom County, Products
Testing a home in Whatcom County
In Whatcom County, 5.3% of 113 tests reported to CDC over the 2007 to 2016 laboratory totals reached 4 pCi/L, against 25.5% pooled across Washington. 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 Whatcom County.
Test kits and monitors3
See every kit and monitor
Long-term kit
RL416 long-term radon test kit, lab fee included
- Lab fee included
Method: Alpha track
In home: 90 days to 12 months
MonitorAEGTEST
HOUND-1085 palm-sized rechargeable radon detector
- C-NRPP 2024/25: Not included
- Battery
- Alarm
- Screen
Method: Semiconductor sensor
First reading: Within 6 hours
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Explore
Whatcom County, Bordering counties
Counties bordering Whatcom County
Calculated by Radon411- Radon levels in Okanogan CountyEPA zone 1
35.6%at or above 4 pCi/L
Median 2.4 pCi/L · 45 tests · 30.3 points above Whatcom County
- Radon levels in Skagit CountyEPA zone 3
2.7%at or above 4 pCi/L
Median 0.7 pCi/L · 37 tests · 2.6 points below Whatcom County
Whatcom County, Cities and towns
Cities and towns in Whatcom County
The Census Bureau estimates 236,392 residents in Whatcom County for July 1, 2025, 8,940 more than in 2020 (+3.9%). That works out to 112 people per square mile of land. Its largest town, Bellingham, has 96,395 residents, 40.8% of the total. Together its 7 incorporated places hold 60.9% of those residents; the other 39.1% live outside any of them. Reported testing is thin here: 113 tests over 2007 to 2016, or 0.5 for every 1,000 residents (2025 estimate), where Washington as a whole comes to 1.0.
From Bellingham to Sumas, CDC publishes no figure by town: each reads Whatcom County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Bellingham | 96,395 | +4.9% | 40.8% |
| Ferndale | 17,559 | +16.0% | 7.4% |
| Lynden | 16,881 | +6.7% | 7.1% |
| Blaine | 6,475 | +9.8% | 2.7% |
| Everson | 3,254 | +11.0% | 1.4% |
| Nooksack | 1,833 | +22.3% | 0.8% |
| Sumas | 1,672 | +3.8% | 0.7% |
7 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).
Whatcom County, Homes
Homes in Whatcom County
Of Whatcom County's 101,928 homes, 63% are detached houses, against 62% across Washington; 20% are in buildings of five or more homes. Half of its homes were built before 1988, close to Washington's 1984: 18% date from before 1960 and 31% from 2000 or later. 64% 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 | Whatcom County | Washington |
|---|---|---|
| Housing units | 101,928 | 3,262,667 |
| Detached houses | 63% | 62% |
| In buildings of 5 or more | 20% | 22% |
| Mobile homes | 6% | 6% |
| Built before 1960 | 18% | 21% |
| Built since 2000 | 31% | 28% |
| Middle year built | 1988 | 1984 |
| Owner-occupied | 64% | 64% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.