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Radon Levels in Clearwater County, Idaho

EPA puts Clearwater County in Zone 1, its highest radon zone, and 30.3% of its 33 reported radon tests (2008 to 2017, laboratory totals) 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

    30.3%

    11.2 pts below ID

    Clearwater
    30.3%
    Idaho
    41.5%

    33 tests, 2008 to 2017

  • Median result

    1.8pCi/L

    Below action level

    Clearwater
    1.8 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    33

    34th of 37 by tests

    Clearwater
    33
    Ada
    3,030

    Reported to CDC before any fix, 2008 to 2017

  • EPA radon zone

    Zone 1

    Highest potential

    1. Zone 1
    2. 2
    3. 3

    1 highest, 3 lowest

    EPA predicts over 4 pCi/L indoors

  • Rank in Idaho

    21 of 37

    Middle half

    Clearwater
    30.3%
    Bear Lake
    78.1%

    By share, of 37 with 30+ tests

Read a result for Clearwater County

Starts at Clearwater County's median, 1.8 pCi/L

1.8pCi/L

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

EPA’s reading of 1.8 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. Clearwater County's median reported result, 2008 to 2017.

Interpret this reading

The data

Clearwater County, At a glance

Clearwater County at a glance

Predicted: EPA radon zone

EPA Zone 1: highest predicted potential

EPA puts all of Clearwater County in and predicts an average indoor of greater than 4 pCi/L (greater than 150 Bq/m³) across the county. That is one forecast for the whole county, not a reading of any address in it; homes above EPA's turn up in all three zones.

USGS geologic potential: High across 81% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

Radon tests reported for Clearwater County, 2008 to 2017, laboratory

Reported results by concentration band, Clearwater County, 2008 to 2017, laboratory
Under 2 pCi/L: 58%2 to 4 pCi/L: 12%4 pCi/L and above: 30%

Of 33 pre-mitigation tests reported to CDC, not homes in this area.

Reported results by concentration band, Clearwater County, 2008 to 2017, laboratory: data table
Result bandTests MeasuredShare Measured
Under 2 pCi/L1957.6%
2 to 4 pCi/L412.1%
4 pCi/L and above1030.3%
What these figures count

These are the 33 tests reported to CDC for Clearwater County over 2008 to 2017 (laboratory totals), 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: 2008 to 2017, laboratory. Measured data period: 2005 to 2017 (every CDC figure on file).

How to read these figures

Clearwater County, Compared

Clearwater County radon figures, compared

Calculated by Radon411

In Clearwater County, about 3 in 10 reported tests over the 2008 to 2017 laboratory totals (10 of 33) were at or above EPA's action level. Against the national pool of 35.7%, the gap is 5.4 points lower. Across 44 Idaho counties pooled together, 41.5% of tests reached that level, so Clearwater County runs 11.2 points below its state.

Of 6 neighbours with a figure, 4 reported a larger share at or above 4 pCi/L and 2 a smaller one; the spread is 22.1% (Nez Perce County) to 63.0% (Shoshone County). By share, Clearwater County is 21st of 37 Idaho counties with 30 or more tests for the same period.

Half the tests came in under 1.8 pCi/L and half over it; the single highest reached 9.2 pCi/L. Below the action level, 19 tests (57.6%) came in under 2 pCi/L, against 31.5% statewide, and 4 tests (12.1%) fell between 2 and 4, against 26.9% statewide.

Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 30.3% share point the same way here. USGS geology rates 81% of the county's land high radon potential.

CDC's ten-year totals for Clearwater County went from 36 tests (2005 to 2014) to 33 (2008 to 2017), the share going from 27.8% to 30.3%.

Clearwater County against Idaho, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Clearwater County
Clearwater County3330.3%1.8 pCi/LThis county
Idaho, pooled44 counties, pooled12,96141.5%Not pooled+11.2 points
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled+5.4 points
Bear Lake Countyhighest in the state3278.1%7.8 pCi/L+47.8 points
Payette Countylowest in the state614.9%1.5 pCi/L−25.4 points
Shoshone County, IDborders it8163.0%5.7 pCi/L+32.7 points
Mineral County, MTborders it3056.7%5.1 pCi/L+26.4 points
Lewis County, IDborders it650.0%3.8 pCi/L+19.7 points
Missoula County, MTborders it2,61344.6%3.4 pCi/L+14.3 points
Idaho County, IDborders it9040.0%2.9 pCi/L+9.7 points
Latah County, IDborders it15026.0%1.7 pCi/L−4.3 points
Nez Perce County, IDborders it14922.1%2.3 pCi/L−8.2 points
Where Clearwater County's reported results fell, 2008 to 2017, laboratory, beside Idaho and the United States
ResultClearwater County testsClearwater County shareIdaho shareU.S. shareAgainst Idaho
Under 2 pCi/L1957.6%31.5%39.6%+26.1 points
2 to 4 pCi/L412.1%26.9%24.7%−14.8 points
4 pCi/L and above1030.3%41.5%35.7%−11.2 points
Clearwater County ranked among the 37 Idaho counties with 30 or more tests, by share at or above 4 pCi/L, 2008 to 2017, laboratory
CountyRankTestsAt or above 4 pCi/LMedian
Bannock County16 of 3773241.9%3.2 pCi/L
Bonneville County17 of 371,11740.1%3.4 pCi/L
Idaho County18 of 379040.0%2.9 pCi/L
Franklin County19 of 377534.7%3.1 pCi/L
Bonner County20 of 3732133.0%2.3 pCi/L
Clearwater County21 of 373330.3%1.8 pCi/L
Gooding County22 of 376728.4%2.4 pCi/L
Valley County23 of 3712827.3%2.3 pCi/L
Power County24 of 374126.8%2.5 pCi/L
Latah County25 of 3715026.0%1.7 pCi/L
Ada County26 of 373,03025.2%2.4 pCi/L
Clearwater County ten-year laboratory totals, against Idaho's pooled share
PeriodTestsAt or above 4 pCi/LMedianHighestIdaho, pooledChange from the row before
2008 to 20173330.3%1.8 pCi/L9.2 pCi/L41.5%+5.9 points
2007 to 20164124.4%1.3 pCi/L9.2 pCi/L40.8%+1.9 points
2006 to 20154022.5%1.3 pCi/L8.3 pCi/L41.3%−5.3 points
2005 to 20143627.8%1.3 pCi/L22.2 pCi/L41.1%First on file

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

Clearwater County, Geology

The ground under Clearwater County

Predicted

Most of the ground under Clearwater County is one class on USGS's geologic map: 81.2% of its land is high radon potential, with 18.8% low. The map puts 81.1% of Clearwater County in the area it calls Northern Rocky Mountain Province and 18.8% in Seven Devils and Tri-State Uplands. USGS gives the first a radon index of 12, in the high band (12 to 17), and the second 8, in the low band (5 to 8).

USGS's geologic areas under Clearwater County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Northern Rocky Mountain ProvinceDiorite and granite of the Idaho batholith.High1281.1%
Seven Devils and Tri-State UplandsColumbia River basalt flows.Low818.8%

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

Clearwater County beside the ground around it

Clearwater County has more high-potential ground than Idaho as a whole: 81.2% of its land against 50.7%. Of the 7 counties that border it, 3 have more high-potential ground, Mineral County, MT the most at 100%.

Share of land by USGS radon potential: Clearwater County, the 7 counties bordering it and Idaho
AreaEPA zoneLow potentialModerate potentialHigh potential
Clearwater CountyZone 118.8%None81.2%
Lewis CountyZone 3100%NoneNone
Latah CountyZone 131.0%12.1%56.9%
Idaho CountyZone 120.7%0.1%79.3%
Nez Perce CountyZone 399.5%0.5%None
Mineral County, MTZone 1NoneNone100%
Shoshone CountyZone 1NoneNone100%
Missoula County, MTZone 1NoneNone100%
Idaho44 counties, pooled by land areaVaries8.0%41.3%50.7%

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

Local help

Clearwater County, Local resources

Radon testing and mitigation in Clearwater County

What Idaho's program says
Phone
800-445-8647
Email
radon@dhw.idaho.gov

What it means

Clearwater County, Questions

Questions about radon in Clearwater County

Are radon levels high in Clearwater County?

Over the 2008 to 2017 laboratory totals, 30.3% of the radon tests reported to CDC for Clearwater County, Idaho were at or above 4 pCi/L, and the median reported pre-mitigation result was 1.8 pCi/L. Of 37 Idaho counties with 30 or more tests for the same period, 20 reported a higher share; pooled, the state comes to 41.5%.

Which counties border Clearwater County?

Clearwater County borders 7 counties: Lewis County, ID, Latah County, ID, Idaho County, ID, Nez Perce County, ID, Mineral County, MT, Shoshone County, ID and Missoula County, MT.

Products

Clearwater County, Products

Testing a home in Clearwater County

In Clearwater County, 30.3% of 33 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 41.5% pooled across Idaho. In Zone 1 the year-round level in Clearwater County is the one to know: a long-term test (more than 90 days) or a monitor, with a short-term kit for a first answer.

Test kits and monitors3

See every kit and monitor

Clearwater County is in EPA Zone 1, the highest predicted radon potential. Best radon monitors for Zone 1 counties like Clearwater County

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Clearwater County, Bordering counties

Counties bordering Clearwater County

Calculated by Radon411

Clearwater County, Cities and towns

Cities and towns in Clearwater County

The Census Bureau estimates 9,118 residents in Clearwater County for July 1, 2025, 360 more than in 2020 (+4.1%). Spread over its land, that is 3.7 people to the square mile. Its largest town, Orofino, has 3,259 residents, 35.7% of the total. Together its 4 incorporated places hold 47.5% of those residents; the other 52.5% live outside any of them. Reported testing is thin here: 33 tests over 2008 to 2017, or 3.6 for every 1,000 residents (2025 estimate), where Idaho as a whole comes to 6.4.

From Orofino to Elk River, CDC publishes no figure by town: each reads Clearwater County's.

The cities and towns in Clearwater County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Orofino3,259+0.9%35.7%
Pierce516+10.5%5.7%
Weippe409−0.5%4.5%
Elk River144+2.1%1.6%

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).

Clearwater County, Homes

Homes in Clearwater County

Of Clearwater County's 4,603 homes, 73% are detached houses, against 74% across Idaho; 23% are mobile homes. The homes are older than Idaho's as a whole: half were built before 1975 (1990 for Idaho), and 23% date from before 1960. Owners live in 82% of the occupied homes (Idaho: 72%), so for most households a test and a fix are their own to order.

Homes in Clearwater County, Idaho, 2019 to 2023
HomesClearwater CountyIdaho
Housing units4,603776,683
Detached houses73%74%
In buildings of 5 or more2%9%
Mobile homes23%7%
Built before 196023%18%
Built since 200016%35%
Middle year built19751990
Owner-occupied82%72%

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