Skip to content
RADON411

Locations and reports

Radon Levels in Washington County, Pennsylvania

EPA puts Washington County in Zone 2, its middle radon zone, and 33.6% of its 1,227 reported radon tests (2020) 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

How to test this homeFind a certified tester

  • Share at 4+ pCi/L

    33.6%

    3.3 pts above PA

    Washington
    33.6%
    PA
    30.3%

    1,227 tests, 2020

  • Median result

    2.8pCi/L

    Below action level

    Washington
    2.8 pCi/L
    EPA
    4.0 pCi/L

    Midpoint of the tests, 2020

  • Tests reported

    1,227

    17th of 63 by tests

    Washington
    1,227
    Montgomery
    10,508

    Reported to CDC before any fix, 2020

  • EPA radon zone

    Zone 2

    Moderate potential

    1. 1
    2. Zone 2
    3. 3

    1 highest, 3 lowest

    EPA predicts 2 to 4 pCi/L indoors

  • Rank in PA

    43 of 63

    Middle half

    Washington
    33.6%
    Perry
    57.7%

    By share, of 63 with 30+ tests

Read a result for Washington County

Starts at Washington County's median, 2.8 pCi/L

2.8pCi/L

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

EPA’s reading of 2.8 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, 2020.

Interpret this readingWhat a fix costs

The data

Washington County, At a glance

Washington County at a glance

Predicted: EPA radon zone

EPA Zone 2: moderate predicted potential

Washington County is a county: EPA's forecast for it as a whole is an average indoor of 2 to 4 pCi/L (75 to 150 Bq/m³). It describes no single address, and homes above EPA's are found in every zone, this one included.

USGS geologic potential: Moderate across 59% of the county's area

Predicted: EPA Map of Radon Zones

Measured: tests reported to CDC

Radon tests reported for Washington County, 2020

Share of reported tests at or above 4 pCi/L, by year, Washington County
Share of reported tests at or above 4 pCi/L, by year, Washington County
YearShare of reported tests at or above 4 pCi/L
201434.3%
201537.4%
201630.8%
201735.3%
201831.2%
201931.4%
202033.6%

2020: 33.6%. Across these years the share ran from 30.8% to 37.4%. Each column counts radon tests reported to CDC that year, not homes.

What these figures count

These are the 1,227 tests reported to CDC for Washington County over 2020, 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: 2020. Measured data period: 2005 to 2020 (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 3 in 10 reported tests in 2020 (412 of 1,227) were at or above EPA's action level. Against the national pool of 25.5%, the gap is 8.1 points higher. Across 67 Pennsylvania counties pooled together, 30.3% of tests reached that level, so Washington County runs 3.3 points above its state.

Of 5 neighbours with a figure, 2 reported a larger share at or above 4 pCi/L and 3 a smaller one; the spread is 17.4% (Fayette County) to 42.4% (Beaver County). By share, Washington County is 43rd of 63 Pennsylvania counties with 30 or more tests for the same period.

Year by year, 2014 opened at 34.3% and 2020 closed at 33.6% (about level), with 2015 the high at 37.4%. Half the tests came in under 2.8 pCi/L and half over it; the single highest reached 71.7 pCi/L. Below the action level, 395 tests (32.2%) came in under 2 pCi/L, against 44.3% statewide, and 420 tests (34.2%) fell between 2 and 4, against 25.4% statewide.

Zone 2 on EPA's map (predicted average between 2 and 4 pCi/L) and a 33.6% share point the same way here. USGS geology rates 59% of the county's land moderate radon potential.

The busiest year on file was 2019, with 1,607 tests reported; the quietest, 2014, had 764.

Share of reported tests at or above 4 pCi/L by year, Washington County against Pennsylvania2014 to 2020, years with 30 or more tests: Washington County 34.3% to 33.6%, the state's pooled share 30.3% in 2020.
Washington CountyPennsylvania, pooled
Share of reported tests at or above 4 pCi/L by year, Washington County against Pennsylvania: data table
YearTestsWashington County, at or above 4 pCi/LPennsylvania, pooled
201476434.3%36.1%
201599537.4%37.8%
20161,29830.8%34.4%
20171,02335.3%35.1%
20181,17931.2%30.5%
20191,60731.4%31.4%
20201,22733.6%30.3%
Washington County against Pennsylvania, the United States and nearby counties, 2020
AreaTestsAt or above 4 pCi/LMedianDifference from Washington County
Washington County1,22733.6%2.8 pCi/LThis county
Pennsylvania, pooled67 counties, pooled93,66930.3%Not pooled−3.3 points
United States, pooled915 counties, pooled405,35525.5%Not pooled−8.1 points
Perry Countyhighest in the state18957.7%4.9 pCi/L+24.1 points
Philadelphia Countylowest in the state8,44210.6%1.7 pCi/L−23.0 points
Beaver County, PAborders it86842.4%3.2 pCi/L+8.8 points
Westmoreland County, PAborders it1,58834.9%2.6 pCi/L+1.3 points
Allegheny County, PAborders it8,33730.5%2.5 pCi/L−3.1 points
Greene County, PAborders it4520.0%3.2 pCi/L−13.6 points
Fayette County, PAborders it28717.4%1.8 pCi/L−16.2 points
Where Washington County's reported results fell, 2020, beside Pennsylvania and the United States
ResultWashington County testsWashington County sharePennsylvania shareU.S. shareAgainst Pennsylvania
Under 2 pCi/L39532.2%44.3%51.6%−12.1 points
2 to 4 pCi/L42034.2%25.4%22.9%+8.8 points
4 pCi/L and above41233.6%30.3%25.5%+3.3 points
Washington County ranked among the 63 Pennsylvania counties with 30 or more tests, by share at or above 4 pCi/L, 2020
CountyRankTestsAt or above 4 pCi/LMedian
Dauphin County38 of 632,98636.9%2.0 pCi/L
Lawrence County39 of 6328636.0%2.7 pCi/L
Westmoreland County40 of 631,58834.9%2.6 pCi/L
Columbia County41 of 6340934.7%2.0 pCi/L
Venango County42 of 6317934.1%3.0 pCi/L
Washington County43 of 631,22733.6%2.8 pCi/L
Clarion County44 of 6310731.8%2.9 pCi/L
Mercer County45 of 6331831.4%2.5 pCi/L
Wyoming County46 of 6312330.9%2.0 pCi/L
Pike County47 of 631,15830.7%2.2 pCi/L
Monroe County48 of 631,64930.7%2.1 pCi/L
Washington County radon tests by year, against Pennsylvania's pooled share
YearTestsAt or above 4 pCi/LMedianHighestPennsylvania, pooledChange from the row before
20201,22733.6%2.8 pCi/L71.7 pCi/L30.3%+2.2 points
20191,60731.4%2.7 pCi/L125.3 pCi/L31.4%+0.2 points
20181,17931.2%2.7 pCi/L373.4 pCi/L30.5%−4.1 points
20171,02335.3%2.9 pCi/L91.8 pCi/L35.1%+4.5 points
20161,29830.8%2.8 pCi/L96.1 pCi/L34.4%−6.6 points
201599537.4%3.0 pCi/L316.1 pCi/L37.8%+3.1 points
201476434.3%2.7 pCi/L70.5 pCi/L36.1%First on file

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

Washington County, State data

Pennsylvania's own radon test data

Measured

What Pennsylvania's own agencies publish about radon tests in Washington County, with their period. These are not CDC's figures and are never added to them.

MeasuredState figures, not CDC's

What Pennsylvania DEP reports for the ZIP codes in Washington County

Pennsylvania DEP publishes its figures by ZIP code, not by county. These are the 65 ZIP codes that lie wholly or partly in Washington County, each with the state's own figures for it. Period: Period not stated by DEP.

ZIP codes in Washington County
ZIP codeWhat the state reports
15004Basement: figures not shown
15012Basement: average 4.6 pCi/L, 1,117 tests; First floor: average 3.7 pCi/L, 75 tests
15017Basement: average 3.8 pCi/L, 3,119 tests; First floor: average 2.0 pCi/L, 231 tests
15019Basement: average 5.2 pCi/L, 71 tests; First floor: figures not shown
15021Basement: average 6.4 pCi/L, 490 tests; First floor: average 3.4 pCi/L, 33 tests
15022Basement: average 6.6 pCi/L, 696 tests; First floor: average 5.2 pCi/L, 44 tests
15026Basement: average 9.9 pCi/L, 597 tests; First floor: average 6.8 pCi/L, 30 tests
15033Basement: average 4.4 pCi/L, 135 tests; First floor: figures not shown
15038Basement: figures not shown
15053Basement: figures not shown
15054Basement: figures not shown; First floor: figures not shown
15055Basement: average 2.7 pCi/L, 290 tests; First floor: figures not shown
15057Basement: average 5.6 pCi/L, 2,345 tests; First floor: average 4.2 pCi/L, 107 tests
15060Basement: average 4.4 pCi/L, 69 tests; First floor: figures not shown
15063Basement: average 4.6 pCi/L, 861 tests; First floor: average 4.4 pCi/L, 40 tests
15067Basement: average 4.0 pCi/L, 131 tests; First floor: figures not shown
15078Basement: figures not shown; First floor: figures not shown
15102Basement: average 4.0 pCi/L, 6,724 tests; First floor: average 2.4 pCi/L, 363 tests
15126Basement: average 4.5 pCi/L, 1,411 tests; First floor: average 3.3 pCi/L, 93 tests
15129Basement: average 4.1 pCi/L, 1,661 tests; First floor: average 2.8 pCi/L, 138 tests
15241Basement: average 4.0 pCi/L, 6,779 tests; First floor: average 3.0 pCi/L, 658 tests
15301Basement: average 5.4 pCi/L, 4,564 tests; First floor: average 4.1 pCi/L, 240 tests
15311Basement: average 3.9 pCi/L, 75 tests; First floor: figures not shown
15312Basement: average 5.3 pCi/L, 155 tests; First floor: figures not shown
15313Basement: figures not shown; First floor: figures not shown
15314Basement: average 8.0 pCi/L, 175 tests; First floor: average 4.2 pCi/L, 41 tests
15317Basement: average 4.0 pCi/L, 8,642 tests; First floor: average 3.2 pCi/L, 466 tests
15321Basement: average 4.9 pCi/L, 246 tests; First floor: figures not shown
15322Basement: average 6.1 pCi/L, 69 tests; First floor: figures not shown
15323Basement: average 8.7 pCi/L, 166 tests; First floor: figures not shown
15324Basement: figures not shown; First floor: figures not shown
15329Basement: average 13.7 pCi/L, 43 tests; First floor: figures not shown
15330Basement: average 5.8 pCi/L, 715 tests; First floor: average 9.6 pCi/L, 37 tests
15331Basement: average 8.5 pCi/L, 32 tests; First floor: figures not shown
15332Basement: average 4.7 pCi/L, 773 tests; First floor: average 2.9 pCi/L, 34 tests
15333Basement: average 6.4 pCi/L, 74 tests; First floor: figures not shown
15340Basement: average 7.4 pCi/L, 112 tests; First floor: figures not shown
15342Basement: average 4.2 pCi/L, 643 tests; First floor: average 2.5 pCi/L, 33 tests
15345Basement: average 10.7 pCi/L, 49 tests; First floor: figures not shown
15347Basement: figures not shown; First floor: figures not shown
15348Basement: figures not shown
15350Basement: figures not shown; First floor: figures not shown
15358Basement: figures not shown
15360Basement: average 13.5 pCi/L, 130 tests; First floor: figures not shown
15361Basement: figures not shown
15363Basement: average 5.9 pCi/L, 77 tests; First floor: figures not shown
15365Basement: figures not shown; First floor: figures not shown
15366Basement: figures not shown
15367Basement: average 4.5 pCi/L, 2,490 tests; First floor: average 3.1 pCi/L, 113 tests
15368Basement: figures not shown
15370Basement: average 6.9 pCi/L, 267 tests; First floor: figures not shown
15376Basement: average 6.9 pCi/L, 50 tests; First floor: figures not shown
15377Basement: figures not shown; First floor: figures not shown
15378First floor: figures not shown
15379Basement: figures not shown; First floor: figures not shown
15412Basement: figures not shown
15417Basement: average 5.8 pCi/L, 212 tests; First floor: figures not shown
15419Basement: average 3.6 pCi/L, 123 tests; First floor: figures not shown
15423Basement: average 5.6 pCi/L, 84 tests; First floor: figures not shown
15427Basement: figures not shown; First floor: figures not shown
15429Basement: figures not shown
15432Basement: figures not shown
15434Basement: figures not shown; First floor: figures not shown
15477Basement: figures not shown
15483Basement: figures not shown
  • DEP's report gives the number of tests, the highest result and the average result for each floor tested; it states no period.
  • DEP says the smartest thing to do is to test your home for radon, no matter where you live.
  • A ZIP code that crosses the county line is listed whole; its figures cover all of it.

Measured: Pennsylvania DEP data, Period not stated by DEP.

Washington County, Geology

The ground under Washington County

Predicted

USGS's geologic map splits Washington County: 58.8% of its land is moderate radon potential and 41.2% high. The map puts 58.8% of Washington County in the area it calls Permian Rocks of the Pittsburgh Low Plateau and 41.2% in Pennsylvanian Rocks of the Pittsburgh Low Plateau. USGS gives the first a radon index of 11, in the moderate band (9 to 11), and the second 14, in the high band (12 to 17).

USGS's geologic areas under Washington County
AreaThe rock, in USGS's wordsPotentialRadon indexShare of land
Permian Rocks of the Pittsburgh Low PlateauPermian sandstone, shale, limestone, and coal.Moderate1158.8%
Pennsylvanian Rocks of the Pittsburgh Low PlateauPennsylvanian marine shale, siltstone, sandstone, limestone, and coal.High1441.2%

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

Pennsylvania as a whole has more high-potential ground than Washington County: 70.4% of its land, against 41.2% here. Of the 9 counties that border it, 6 have more high-potential ground, Allegheny County the most at 100%.

Share of land by USGS radon potential: Washington County, the 9 counties bordering it and Pennsylvania
AreaEPA zoneLow potentialModerate potentialHigh potential
Washington CountyZone 2None58.8%41.2%
Brooke County, WVZone 1None10.2%89.8%
Allegheny CountyZone 1NoneNone100%
Ohio County, WVZone 1None69.7%30.3%
Greene CountyZone 2None92.3%7.7%
Hancock County, WVZone 1NoneNone100%
Beaver CountyZone 1None0.5%99.5%
Marshall County, WVZone 1None96.8%3.2%
Fayette CountyZone 2None55.8%44.2%
Westmoreland CountyZone 1None34.6%65.4%
Pennsylvania67 counties, pooled by land areaVaries0.7%28.9%70.4%

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

Local help

Washington County, Local resources

Radon testing and mitigation in Washington County

Listed radon businesses with an address in Washington County:

Listed radon professionals by town: Canonsburg, McDonald

What Pennsylvania's program says
Phone
800-237-2366
Licensing of radon professionals
The Radon Certification Act requires DEP to establish by regulation, a certification program for persons conducting radon gas and radon progeny testing, laboratory analysis and mitigation of radon contamination in buildings.

What it means

Washington County, Questions

Questions about radon in Washington County

Are radon levels high in Washington County?

In 2020, 33.6% of the radon tests reported to CDC for Washington County, Pennsylvania were at or above 4 pCi/L, and the median reported pre-mitigation result was 2.8 pCi/L. Of 63 Pennsylvania counties with 30 or more tests for the same period, 42 reported a higher share; pooled, the state comes to 30.3%.

Which counties border Washington County?

Washington County borders 9 counties: Brooke County, WV, Allegheny County, PA, Ohio County, WV, Greene County, PA, Hancock County, WV, Beaver County, PA, Marshall County, WV, Fayette County, PA and Westmoreland County, PA.

Products

Washington County, Products

Testing a home in Washington County

In Washington County, 33.6% of 1,227 tests reported to CDC in 2020 reached 4 pCi/L, against 30.3% pooled across Pennsylvania. In Zone 2 a short-term kit (2 to 90 days) is the quick first check in Washington County; a long-term test tells the year-round average.

Test kits and monitors3

See every kit and monitor

Best radon monitors for Washington County homes, compared

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 210,802 residents in Washington County for July 1, 2025, 1,389 more than in 2020 (+0.7%). That works out to 246 people per square mile of land. No town dominates: Washington, the largest, has 13,377 residents, 6.3% of the total. CDC's 1,227 reported tests for 2020 work out to 5.8 per 1,000 residents (2025 estimate), close to Pennsylvania's 7.2.

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

The 12 largest cities and towns in Washington County by residents, July 1, 2025
PlaceResidentsSince 2020Share of residents
Washington13,377+1.9%6.3%
Canonsburg9,529−1.9%4.5%
California4,615−14.0%2.2%
Donora4,462−2.2%2.1%
Charleroi4,112−2.4%2.0%
Monongahela4,041−2.3%1.9%
Centerville3,223−1.6%1.5%
Bentleyville2,326−1.9%1.1%
New Eagle2,018−1.7%1.0%
McDonaldextends beyond Washington County1,994−2.8%Counted whole
East Washington1,814−2.2%0.9%
Burgettstown1,390−1.5%0.7%
  • North Charleroi
  • Houston
  • Speers
  • West Brownsville
  • Midway
  • Ellsworth
  • Deemston
  • Claysville
  • Roscoe
  • Cokeburg
  • Allenport
  • Stockdale
  • Long Branch
  • Beallsville
  • Marianna
  • Dunlevy
  • Finleyville
  • Elco
  • Twilight
  • Coal Center
  • West Middletown
  • Green Hills

34 incorporated places, as listed in the U.S. Census Bureau’s 2020 place reference files. “(part)” marks a place that extends into another county. Residents: U.S. Census Bureau population estimates for July 1, 2025 (Vintage 2025). A place that extends beyond Washington County is counted whole, so it has no share.

Washington County, Homes

Homes in Washington County

Of Washington County's 97,476 homes, 74% are detached houses, against 57% across Pennsylvania; 8% are in buildings of five or more homes. Half of its homes were built before 1965, close to Pennsylvania's 1965: 45% date from before 1960 and 16% from 2000 or later. Owners live in 76% of the occupied homes (Pennsylvania: 69%), so for most households a test and a fix are their own to order.

Homes in Washington County, Pennsylvania, 2019 to 2023
HomesWashington CountyPennsylvania
Housing units97,4765,779,663
Detached houses74%57%
In buildings of 5 or more8%13%
Mobile homes5%4%
Built before 196045%45%
Built since 200016%14%
Middle year built19651965
Owner-occupied76%69%

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