Short-term kitFirst Alert
RD1 short-term charcoal radon test kit
- Lab fee included
Method: Charcoal
In home: 2 to 4 days
Locations and reports
Radon Levels in Asotin County, Washington
EPA puts Asotin County in Zone 2, its middle radon zone, and only 1 radon test from it is on file with CDC (2020). Homes with elevated levels occur in all three zones, so only a test measures yours.
Data checked By Radon411Methodology
Highest bordering
22.4%
Whitman County
- Whitman
- 22.4%
- Nez Perce
- 22.1%
2 of 4 neighbours have 30+ tests, 2008 to 2017
Nearest county
22.4%
Whitman County, 51 miles
- Whitman
- 22.4%
- Washington
- 25.5%
Share at 4+ pCi/L, 58 tests, 2008 to 2017
Ground above low
100.0%
47.2 pts above Washington
- Asotin
- 100.0%
- Washington
- 52.7%
Share of land USGS rates moderate or high potential
Tests reported
15
Too few for a share
- Asotin
- 15
- Needed
- 30
2005 to 2014, laboratory
EPA radon zone
Zone 2
Moderate potential
- 1
- Zone 2
- 3
1 highest, 3 lowest
EPA predicts 2 to 4 pCi/L indoors
Read a result for Asotin County
Starts at EPA's action level
EPA’s own thresholds; the figures are the area’s, never this home’s.
EPA’s reading of 4.0 pCi/L
At or above 4 pCi/L
- Under 20 to 1.9 pCi/L
- 2 to 4consider a fix
- 4 and aboveEPA says fix it
This result is at or above 4 pCi/L. EPA recommends fixing a home when the radon level is 4 pCi/L or higher.
The data
Asotin County, At a glance
Asotin County at a glance
Predicted: EPA radon zone
EPA Zone 2: moderate predicted potential
Asotin County is a
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 Asotin County, 2020
| Year | Share of reported tests at or above 4 pCi/L |
|---|---|
| 2015 | 0.0% |
| 2016 | 100.0% |
| 2017 | 0.0% |
| 2019 | 25.0% |
| 2020 | 0.0% |
2020: 0.0%. Across these years the share ran from 0.0% to 100.0%. Each column counts radon tests reported to CDC that year, not homes.
What these figures count
Only 1 test was reported to CDC for Asotin 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).
Asotin County, Compared
Asotin County radon figures, compared
Calculated by Radon411CDC's largest figure for Asotin County rests on 15 tests over the 2005 to 2014 laboratory totals, 0 of them at or above 4 pCi/L, so each test moves its share by 6.7 points and no rank or comparison is drawn from it. Results reached as high as 3.5 pCi/L, with a middle value of 1.2 pCi/L.
Of the counties bordering it, 2 have a figure over the 2008 to 2017 laboratory totals: Whitman County reported the largest share at or above 4 pCi/L, 22.4%, and Nez Perce County, ID the smallest, 22.1%. Farther out, Walla Walla County (61 miles away) at 16.4%, Spokane County (99 miles away) at 41.4% and Benton County (111 miles away) at 19.5% have figures too. Pooled across 39 Washington counties, 25.5% of reported tests reached that level; across every county in the country with a figure, 35.7%.
Statewide for the same period, Pend Oreille County reported the highest share (63.2%) and Snohomish County the lowest (2.3%). EPA's 1993 map puts Asotin County in Zone 2, its middle label: a predicted county average between 2 and 4 pCi/L. USGS geology rates 100% of the county's land moderate radon potential.
Pooled shares: Radon411's sum of CDC's county counts for one period.
Asotin County, Geology
The ground under Asotin County
PredictedUSGS's geologic map puts all of Asotin County's mapped land in one class: moderate radon potential. The map puts 77.2% of Asotin County in the area it calls Blue Mountains and 21.3% in Columbia Basin, with one smaller area beside them. USGS gives the first a radon index of 9 and the second 10, both in the moderate band (9 to 11).
| Area | The rock, in USGS's words | Potential | Radon index | Share of land |
|---|---|---|---|---|
| Blue Mountains | Tertiary basalt, andesite, tuffaceous sedimentary rocks, and tuff. | Moderate | 9 | 77.2% |
| Columbia Basin | Basaltic rocks low in uranium content. Uranium content of soils is moderately elevated. | Moderate | 10 | 21.3% |
| Snake River Canyon | Cenozoic basalt and andesite flows and minor continental sedimentary rocks. | Moderate | 9 | 1.4% |
Names, descriptions and indexes: U.S. Geological Survey, Geologic Radon Potential Map (2025). Shares: Radon411, from the map cut to the boundary.
Asotin County beside the ground around it
Across Washington 13.7% of the land is rated high; none of Asotin County's is. Of the 4 counties that border it, 1 has more high-potential ground, Whitman County the most at 0.9%.
The map rates the ground, not the air in any home.
Local help
Asotin County, Local resources
Radon testing and mitigation in Asotin 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
Asotin County, Questions
Questions about radon in Asotin County
Are radon levels high in Asotin County?
In 2020, 0.0% of the radon tests reported to CDC for Asotin County, Washington were at or above 4 pCi/L, and the median reported pre-mitigation result was 0.9 pCi/L. Of the counties bordering it, 2 have a figure over the 2008 to 2017 laboratory totals: Whitman County reported the largest share at or above 4 pCi/L, 22.4%, and Nez Perce County, ID the smallest, 22.1%.
Which counties border Asotin County?
Asotin County borders 4 counties: Nez Perce County, ID, Garfield County, WA, Whitman County, WA and Wallowa County, OR.
Products
Asotin County, Products
Testing a home in Asotin County
No CDC figure names Asotin County; the nearest county with one, Whitman County (51 miles away), reported 22.4% of its tests at or above 4 pCi/L over the 2008 to 2017 laboratory totals, the only reading nearby until a test of this home. In Zone 2 a short-term kit (2 to 90 days) is the quick first check in Asotin County; a long-term test tells the year-round average.
Test kits and monitors3
See every kit and monitor
Long-term kit
RL116 long-term radon test kit
- Lab fee extra
Method: Alpha track
In home: 90 days to 12 months
MonitorAEGTEST
HOUND-1011S rechargeable radon detector with a screen
- C-NRPP 2024/25: Not included
- Battery
- Alarm
- Screen
Method: Semiconductor sensor
First reading: Within 12 hours
- See every kit and monitor Test kits and monitors
Test kits and monitors: 1 of 3
Explore
Asotin County, Bordering counties
Counties bordering Asotin County
Calculated by Radon411- Radon levels in Garfield County, WAEPA zone 2
50.0%at or above 4 pCi/L
Median 3.8 pCi/L · 2 tests
- Radon levels in Wallowa County, OREPA zone 3
26.7%at or above 4 pCi/L
Median 1.1 pCi/L · 15 tests
- Radon levels in Whitman County, WAEPA zone 2
22.4%at or above 4 pCi/L
Median 1.5 pCi/L · 58 tests
- Radon levels in Nez Perce County, IDEPA zone 3
22.1%at or above 4 pCi/L
Median 2.3 pCi/L · 149 tests
Asotin County, Cities and towns
Cities and towns in Asotin County
The Census Bureau estimates 22,545 residents in Asotin County for July 1, 2025, 218 more than in 2020 (+1.0%). That works out to 35 people per square mile of land. Its largest town, Clarkston, has 7,189 residents, 31.9% of the total. Together its 2 incorporated places hold 37.2% of those residents; the other 62.8% live outside any of them. CDC's 15 reported tests for 2005 to 2014 work out to 0.7 per 1,000 residents (2025 estimate), close to Washington's 0.8.
From Clarkston to Asotin, CDC publishes no figure by town: each reads Asotin County's.
| Place | Residents | Since 2020 | Share of residents |
|---|---|---|---|
| Clarkston | 7,189 | −0.6% | 31.9% |
| Asotin | 1,187 | +0.8% | 5.3% |
2 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).
Asotin County, Homes
Homes in Asotin County
Of Asotin County's 10,165 homes, 74% are detached houses, against 62% across Washington; 13% are mobile homes. Half of its homes were built before 1977, close to Washington's 1984: 30% date from before 1960 and 19% from 2000 or later. 74% 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 | Asotin County | Washington |
|---|---|---|
| Housing units | 10,165 | 3,262,667 |
| Detached houses | 74% | 62% |
| In buildings of 5 or more | 5% | 22% |
| Mobile homes | 13% | 6% |
| Built before 1960 | 30% | 21% |
| Built since 2000 | 19% | 28% |
| Middle year built | 1977 | 1984 |
| Owner-occupied | 74% | 64% |
Census Bureau, American Community Survey, 2019 to 2023: estimates from a sample of homes, looser for a small place. Shares by Radon411.