Skip to content
RADON411

Locations and reports

Radon Levels in Washington County, Indiana

EPA puts Washington County in Zone 1, its highest radon zone, and high results are common there: 42.1% of the 38 radon tests reported to CDC (2008 to 2017, laboratory totals) came back 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

    42.1%

    3.2 pts above IN

    Washington
    42.1%
    Indiana
    38.9%

    38 tests, 2008 to 2017

  • Median result

    3.5pCi/L

    Below action level

    Washington
    3.5 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2008 to 2017

  • Tests reported

    38

    67th of 69 by tests

    Washington
    38
    St. Joseph
    7,346

    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 Indiana

    37 of 69

    Middle half

    Washington
    42.1%
    Miami
    63.3%

    By share, of 69 with 30+ tests

Read a result for Washington County

Starts at Washington County's median, 3.5 pCi/L

3.5pCi/L

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

EPA’s reading of 3.5 pCi/L

Between 2 and 4 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 between 2 and 4 pCi/L. EPA recommends considering a fix when the level is between 2 and 4 pCi/L. Washington County's median reported result, 2008 to 2017.

Interpret this readingWhat a fix costs

The data

Washington County, At a glance

Washington County at a glance

Predicted: EPA radon zone

EPA Zone 1: highest predicted potential

EPA puts all of Washington 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: Moderate across 100% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

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

Reported results by concentration band, Washington County, 2008 to 2017, laboratory
Under 2 pCi/L: 29%2 to 4 pCi/L: 29%4 pCi/L and above: 42%

Of 38 pre-mitigation tests reported to CDC, not homes in this area.

Reported results by concentration band, Washington County, 2008 to 2017, laboratory: data table
Result bandTests MeasuredShare Measured
Under 2 pCi/L1128.9%
2 to 4 pCi/L1128.9%
4 pCi/L and above1642.1%
What these figures count

These are the 38 tests reported to CDC for Washington 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

Washington County, Compared

Washington County radon figures, compared

Calculated by Radon411

In Washington County, about 4 in 10 reported tests over the 2008 to 2017 laboratory totals (16 of 38) were at or above EPA's action level. Against the national pool of 35.7%, the gap is 6.4 points higher. Across 92 Indiana counties pooled together, 38.9% of tests reached that level, so Washington County runs 3.2 points above its state.

Of 5 neighbours with a figure, 3 reported a larger share at or above 4 pCi/L and 2 a smaller one; the spread is 27.3% (Jackson County) to 62.4% (Harrison County). By share, Washington County is 37th of 69 Indiana counties with 30 or more tests for the same period.

Half the tests came in under 3.5 pCi/L and half over it; the single highest reached 21.5 pCi/L. Below the action level, 11 tests (28.9%) came in under 2 pCi/L, against 32.8% statewide, and 11 tests (28.9%) fell between 2 and 4, against 28.3% statewide.

Zone 1 on EPA's map (predicted average above 4 pCi/L) and a 42.1% share point the same way here. USGS geology rates 100% of the county's land moderate radon potential. CDC also counts 5 tests taken after mitigation in Washington County for the same period: tests in homes where a fix was already in.

CDC's ten-year totals for Washington County went from 41 tests (2005 to 2014) to 38 (2008 to 2017), the share going from 51.2% to 42.1%.

Washington County against Indiana, the United States and nearby counties, 2008 to 2017, laboratory
AreaTestsAt or above 4 pCi/LMedianDifference from Washington County
Washington County3842.1%3.5 pCi/LThis county
Indiana, pooled92 counties, pooled43,14838.9%Not pooled−3.2 points
United States, pooled2,661 counties, pooled2,013,54435.7%Not pooled−6.4 points
Miami Countyhighest in the state3063.3%5.3 pCi/L+21.2 points
Jasper Countylowest in the state7114.1%1.2 pCi/L−28.0 points
Harrison County, INborders it22162.4%5.5 pCi/L+20.3 points
Clark County, INborders it51247.7%3.6 pCi/L+5.6 points
Orange County, INborders it2343.5%2.9 pCi/L+1.4 points
Floyd County, INborders it31642.4%3.3 pCi/L+0.3 points
Lawrence County, INborders it26735.6%2.7 pCi/L−6.5 points
Scott County, INborders it1735.3%2.0 pCi/L−6.8 points
Crawford County, INborders it1030.0%2.7 pCi/L−12.1 points
Jackson County, INborders it8827.3%2.8 pCi/L−14.8 points
Where Washington County's reported results fell, 2008 to 2017, laboratory, beside Indiana and the United States
ResultWashington County testsWashington County shareIndiana shareU.S. shareAgainst Indiana
Under 2 pCi/L1128.9%32.8%39.6%−3.9 points
2 to 4 pCi/L1128.9%28.3%24.7%+0.6 points
4 pCi/L and above1642.1%38.9%35.7%+3.2 points
Washington County ranked among the 69 Indiana counties with 30 or more tests, by share at or above 4 pCi/L, 2008 to 2017, laboratory
CountyRankTestsAt or above 4 pCi/LMedian
Vigo County32 of 6945544.0%3.6 pCi/L
Huntington County33 of 6916943.8%3.5 pCi/L
Gibson County34 of 6912043.3%3.4 pCi/L
Knox County35 of 695843.1%3.4 pCi/L
Floyd County36 of 6931642.4%3.3 pCi/L
Washington County37 of 693842.1%3.5 pCi/L
Allen County38 of 693,99041.8%3.3 pCi/L
LaGrange County39 of 6912041.7%3.4 pCi/L
Hendricks County40 of 691,17041.5%3.2 pCi/L
Montgomery County41 of 6915241.4%2.9 pCi/L
Marion County42 of 693,66840.1%3.1 pCi/L
Washington County ten-year laboratory totals, against Indiana's pooled share
PeriodTestsAt or above 4 pCi/LMedianHighestIndiana, pooledChange from the row before
2008 to 20173842.1%3.5 pCi/L21.5 pCi/L38.9%−4.2 points
2007 to 20164146.3%3.6 pCi/L21.5 pCi/L39.2%Level
2006 to 20154146.3%3.6 pCi/L21.5 pCi/L39.6%−4.9 points
2005 to 20144151.2%4.0 pCi/L21.5 pCi/L39.3%First on file

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

Washington County, Geology

The ground under Washington County

Predicted

USGS's geologic map puts all of Washington County's mapped land in one class: moderate radon potential. All of it lies in the area the map calls Crawford Upland/Mitchell Plain/Norman Upland, to which USGS gives a radon index of 11, in the moderate band (9 to 11).

USGS's geologic areas under Washington County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Crawford Upland/Mitchell Plain/Norman UplandUnglaciated, underlain by karsted Mississippian carbonate rocks.Moderate11100%

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

Washington County beside the ground around it

Across Indiana 56.6% of the land is rated high; none of Washington County's is. Of the 8 counties that border it, 4 have more high-potential ground, Scott County the most at 61.6%.

Share of land by USGS radon potential: Washington County, the 8 counties bordering it and Indiana
AreaEPA zoneLow potentialModerate potentialHigh potential
Washington CountyZone 1None100%None
Jackson CountyZone 2None79.6%20.4%
Scott CountyZone 1None38.4%61.6%
Clark CountyZone 1None49.1%50.9%
Orange CountyZone 1None100%None
Floyd CountyZone 2None95.7%4.3%
Lawrence CountyZone 1None100%None
Harrison CountyZone 1None100%None
Crawford CountyZone 2None100%None
Indiana92 counties, pooled by land areaVariesNone43.4%56.6%

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

Local help

Washington County, Local resources

Radon testing and mitigation in Washington County

What Indiana's program says
Phone
1-800-272-9723
Licensing of radon professionals
According to the Indiana Radon Rule, 410 IAC 5.1, everyone who is serving Indiana by doing radon testing, analysis and mitigation (radon reduction) in residential structures must be certified by the Indiana State Department of Health.

What it means

Washington County, Questions

Questions about radon in Washington County

Are radon levels high in Washington County?

Over the 2008 to 2017 laboratory totals, 42.1% of the radon tests reported to CDC for Washington County, Indiana were at or above 4 pCi/L, and the median reported pre-mitigation result was 3.5 pCi/L. Of 69 Indiana counties with 30 or more tests for the same period, 36 reported a higher share; pooled, the state comes to 38.9%.

Which counties border Washington County?

Washington County borders 8 counties: Jackson County, Scott County, Clark County, Orange County, Floyd County, Lawrence County, Harrison County and Crawford County.

Products

Washington County, Products

Testing a home in Washington County

In Washington County, 42.1% of 38 tests reported to CDC over the 2008 to 2017 laboratory totals reached 4 pCi/L, against 38.9% pooled across Indiana. In Zone 1 the year-round level in Washington 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

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

Explore

Washington County, Bordering counties

Counties bordering Washington County

Calculated by Radon411

Washington County, Cities and towns

Cities and towns in Washington County

The Census Bureau estimates 28,383 residents in Washington County for July 1, 2025, 153 more than in 2020 (+0.5%). That works out to 55 people per square mile of land. Its largest town, Salem, has 6,427 residents, 22.6% of the total. Reported testing is thin here: 38 tests over 2008 to 2017, or 1.3 for every 1,000 residents (2025 estimate), where Indiana as a whole comes to 6.2.

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

The 6 largest cities and towns in Washington County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Salem6,427−1.7%22.6%
New Pekin1,378+1.2%4.9%
Campbellsburg539+0.9%1.9%
Little York198+2.1%0.7%
Livonia103+3.0%0.4%
Saltillo101+11.0%0.4%
  • Hardinsburg

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).

Washington County, Homes

Homes in Washington County

Washington County is a place of houses on their own lots: 76% of its 12,162 homes are detached single-family houses, against 73% across Indiana. Half of its homes were built before 1982, close to Indiana's 1976: 28% date from before 1960 and 22% from 2000 or later. Owners live in 82% of the occupied homes (Indiana: 70%), so for most households a test and a fix are their own to order.

Homes in Washington County, Indiana, 2019 to 2023
HomesWashington CountyIndiana
Housing units12,1622,953,344
Detached houses76%73%
In buildings of 5 or more2%13%
Mobile homes19%4%
Built before 196028%32%
Built since 200022%21%
Middle year built19821976
Owner-occupied82%70%

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