Radon Testing & Mitigation in Washington County, PA
34% of 38,685 basement radon tests reported to PA DEP in Washington County measured 4.0 pCi/L or higher, EPA's action level (median 2.9 pCi/L).
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Radon in Washington County: 34% of the 38,685 basement tests reported to PA DEP measured 4.0 pCi/L or higher, EPA's action level, 3 points below the 37% statewide share. The county ranks 54th highest of 67, and the median result is 2.9 pCi/L. Only a test shows one home's level.
Radon Test Results by ZIP Code in Washington County
52 ZIP codes in Washington County have at least 20 basement tests on record. Among those with 100 or more, the highest share at or above 4.0 pCi/L is in 15360 (Scenery Hill): 52% of 217 tests. The lowest is in 15055 (Lawrence): 18% of 455 tests.
| ZIP code | Post office | Basement tests | Median pCi/L | At or above 4.0 |
|---|---|---|---|---|
| 15317 | Canonsburg | 13,144 | 2.7 | 30% |
| 15301 | Washington | 7,365 | 2.9 | 35% |
| 15367 | Venetia | 3,545 | 2.8 | 33% |
| 15057 | Mc Donald | 2,771 | 3.1 | 40% |
| 15063 | Monongahela | 1,333 | 3.3 | 38% |
| 15332 | Finleyville | 1,176 | 3.1 | 38% |
| 15022 | Charleroi | 1,151 | 3.1 | 37% |
| 15330 | Eighty Four | 1,096 | 3.2 | 41% |
| 15342 | McGovern | 1,079 | 2.8 | 32% |
| 15021 | Burgettstown | 788 | 3.7 | 47% |
| 15055 | Lawrence | 455 | 2.3 | 18% |
| 15321 | Cecil-Bishop | 357 | 3.0 | 36% |
| 15314 | Bentleyville | 340 | 4.0 | 51% |
| 15323 | Claysville | 333 | 3.4 | 42% |
| 15312 | Avella | 271 | 3.7 | 48% |
Show all 52 ZIP codes
| 15419 | California | 238 | 2.7 | 21% |
| 15017 | Bridgeville (part) | 232 | 2.0 | 19% |
| 15033 | Donora | 230 | 2.6 | 30% |
| 15360 | Scenery Hill | 217 | 4.2 | 52% |
| 15067 | New Eagle | 198 | 3.0 | 30% |
| 15417 | Brownsville | 191 | 3.3 | 39% |
| 15423 | Coal Center | 168 | 3.1 | 39% |
| 15340 | Hickory | 165 | 3.5 | 41% |
| 15333 | Deemston | 146 | 3.5 | 39% |
| 15363 | Strabane | 143 | 3.3 | 41% |
| 15019 | Bulger | 137 | 3.6 | 44% |
| 15311 | Amity | 122 | 3.3 | 36% |
| 15376 | West Alexander | 105 | 4.3 | 51% |
| 15060 | Midway | 91 | 3.1 | 39% |
| 15345 | Marianna | 79 | 4.2 | 51% |
| 15012 | Belle Vernon (part) | 74 | 3.3 | 30% |
| 15329 | Prosperity | 70 | 2.9 | 43% |
| 15331 | Ellsworth | 68 | 4.1 | 50% |
| 15427 | Daisytown | 62 | 3.6 | 44% |
| 15313 | Beallsville | 50 | 4.0 | 52% |
| 15324 | Cokeburg | 49 | 3.1 | 45% |
| 15347 | Meadowlands | 48 | 3.1 | 40% |
| 15358 | Centerville | 39 | 4.5 | 51% |
| 15477 | Roscoe | 38 | 3.1 | 18% |
| 15241 | Pittsburgh (part) | 37 | 2.6 | 27% |
| 15322 | Clarksville (part) | 36 | 3.2 | 39% |
| 15377 | West Finley | 32 | 3.6 | 41% |
| 15038 | Elrama | 29 | 3.5 | 31% |
| 15350 | Muse | 29 | 2.6 | 28% |
| 15004 | Atlasburg | 27 | 2.6 | 22% |
| 15054 | Langeloth | 26 | 2.6 | 12% |
| 15078 | Slovan | 26 | 2.0 | 27% |
| 15432 | Dunlevy | 25 | 3.1 | 40% |
| 15483 | Stockdale | 25 | 2.5 | 24% |
| 15053 | Joffre | 24 | 3.4 | 29% |
| 15026 | Clinton (part) | 22 | 3.4 | 27% |
| 15412 | Allenport | 20 | 3.0 | 30% |
| Washington County | 38,685 | 2.9 | 34% | |
| Pennsylvania | 2,629,492 | 2.8 | 37% | |
See your ZIP in the table?
Get matched with a DEP-certified radon professionalFirst-floor tests in Washington County: 2,122 on record, median 1.8 pCi/L, 23% at or above 4.0 pCi/L.
EPA's Map of Radon Zones (1993) places Washington County in Zone 2, its middle category (predicted average between 2 and 4 pCi/L). The map is a county-wide prediction; the figures in this table are measurements.
Figures count tests, not homes. A home tested more than once is counted each time, and tests run after a mitigation system was installed are included because the dataset does not separate them. ZIP codes with fewer than 20 basement tests are not shown.
Housing Age in Washington County
66% of Washington County's 97,923 housing units were built before 1980, in line with the 67% statewide figure; 26% date from before 1940. Those homes predate EPA's 1994 model standards for radon-resistant construction. Age does not predict a test result: EPA's guidance is that any home, new or old, may have a radon problem.
Source: U.S. Census Bureau, American Community Survey 2020–2024 5-year estimates, table B25034. Counts all housing units, including vacant and seasonal ones. Retrieved September 29, 2026.
Bedrock Under Washington County
Monongahela Group (Pennsylvanian; limestone, shale and sandstone) underlies 30% of the county. Waynesburg Formation (Permian and Pennsylvanian; shale and sandstone) underlies 21% of the county.
Mapped bedrock describes an area. The USGS states that its radon assessment cannot be applied to individual homes. More on Pennsylvania radon and geology.
Sources: U.S. Geological Survey State Geologic Map Compilation, from Pennsylvania Geological Survey Map 1 (1980; digital edition 2001). Retrieved September 29, 2026. U.S. Geological Survey Open-File Report 93-292-C, Geologic Radon Potential of EPA Region 3 (1993).
Home Purchases in Washington County
Lenders reported 2,076 home-purchase mortgages originated in Washington County in 2024. The count covers financed purchases only; cash purchases are not in the data. See radon in a Pennsylvania home sale.
Source: FFIEC Home Mortgage Disclosure Act data, 2024. Retrieved September 29, 2026.
Municipalities in Washington County
Washington County has 66 municipalities: 2 cities, 32 boroughs and 32 townships.
Show all 66 municipalities
Allenport borough, Amwell township, Beallsville borough, Bentleyville borough, Blaine township, Buffalo township, Burgettstown borough, California borough, Canonsburg borough, Canton township, Carroll township, Cecil township, Centerville borough, Charleroi borough, Chartiers township, Claysville borough, Coal Center borough, Cokeburg borough, Cross Creek township, Deemston borough, Donegal township, Donora borough, Dunlevy borough, East Bethlehem township, East Finley township, East Washington borough, Elco borough, Ellsworth borough, Fallowfield township, Finleyville borough, Green Hills borough, Hanover township, Hopewell township, Houston borough, Independence township, Jefferson township, Long Branch borough, Marianna borough, McDonald borough, Midway borough, Monongahela city, Morris township, Mount Pleasant township, New Eagle borough, North Bethlehem township, North Charleroi borough, North Franklin township, North Strabane township, Nottingham township, Peters township, Robinson township, Roscoe borough, Smith township, Somerset township, South Franklin township, South Strabane township, Speers borough, Stockdale borough, Twilight borough, Union township, Washington city, West Bethlehem township, West Brownsville borough, West Finley township, West Middletown borough, West Pike Run township.
Source: U.S. Census Bureau, 2025 Gazetteer Files, county subdivisions. Retrieved September 29, 2026.
City Pages in Washington County
Neighboring Counties
- Radon in Allegheny County → 34% of 310,884 basement tests at or above 4.0 pCi/L
- Radon in Beaver County → 49% of 30,439 basement tests at or above 4.0 pCi/L
- Radon in Fayette County → 34% of 7,606 basement tests at or above 4.0 pCi/L
- Radon in Greene County → 34% of 1,559 basement tests at or above 4.0 pCi/L
- Radon in Westmoreland County → 40% of 66,661 basement tests at or above 4.0 pCi/L
- All 67 Pennsylvania county radon pages
DEP-Certified Mitigation Firms Based in County
3 DEP-certified mitigation firms are physically based in Washington County. Firms from adjacent counties routinely serve here as well.
Source: PA DEP Certified Mitigation Firms Directory, July 2026. This reflects business address only — firms based elsewhere may also serve Washington County.
Testing, Cost and Certification
Short-term tests run 48–96 hours; long-term tests run 90 days or more. At 4.0 pCi/L or higher, retest or mitigate. How radon testing works in a Pennsylvania real estate transaction.
Mitigation in Washington County typically costs $950–$2,300. Pennsylvania radon mitigation cost guide.
Anyone testing or mitigating for pay must hold DEP certification under 25 Pa. Code § 240. How to verify a contractor in the PA DEP Radon Services Directory.
Frequently Asked Questions
What share of radon tests in Washington County are at or above the EPA action level?
34% of the 38,685 basement tests reported to PA DEP from Washington County measured 4.0 pCi/L or higher, against 37% statewide. The median result is 2.9 pCi/L, and 3% of tests measured 20 pCi/L or higher.
Which Washington County ZIP code has the highest radon test results?
Among ZIP codes with at least 100 basement tests, 15360 (Scenery Hill) has the highest share at or above 4.0 pCi/L: 52% of 217 tests, with a median of 4.2 pCi/L. 15055 (Lawrence) has the lowest, at 18%.
How does Washington County compare with other Pennsylvania counties?
Washington County ranks 54th highest of 67 counties by share of basement tests at or above 4.0 pCi/L, at 34%. Among its neighbors, Beaver County has the highest share at 49% and Fayette County the lowest at 34%.
What bedrock is under Washington County?
The largest mapped units are Monongahela Group (30% of the county) and Waynesburg Formation (21% of the county), according to the USGS compilation of the Pennsylvania Geological Survey state map.