Pennsylvania · county radon data
Radon in Washington County, Pennsylvania
37.9% of the 2,504 home radon tests on record here reached the EPA action level — toward the lower end of the state's tested counties, ranked #53 of 67 tested Pennsylvania counties.
What the numbers say
Washington County sits 11.1 points below the Pennsylvania median (49% of tests over the limit across the state's counties). The median reading among its 2,504 reported tests was 3 pCi/L — and the single highest test on record reached 181.3 pCi/L, more than 45× the action level. EPA maps place the county in Radon Zone 2 — moderate predicted potential (2–4 pCi/L average screening levels), which still produces plenty of homes over the limit.
Why: the ground under Washington County
Sits on Pennsylvania's folded Appalachian sedimentary rock — sandstones, shales, and carbonates that carry enough uranium that every county in the state has produced homes above the EPA action level. PA DEP calls radon a statewide concern. (Regional attribution here is well supported; unit-level detail is coarser — see methodology.)
Geology sources: PA DEP Radon Division · USGS OFR 93-292-C.
The housing stock factor
The median Washington County home dates to 1966 — decades before radon-resistant new construction entered building codes. With 210,042 residents largely housed in that older stock, testing is the only way any individual household knows where it stands.
Radon by ZIP in Washington County
Pennsylvania is one of the few states publishing actual test results at ZIP level (PA DEP residential data, 1986–2026) — county averages hide a lot; this doesn't.
| ZIP | Place | Tests | % ≥ 4 pCi/L | Max |
|---|---|---|---|---|
| 15329 | Prosperity | 57 | 54.4% | 388.4 |
| 15345 | Marianna | 73 | 52.1% | 44.9 |
| 15358 | Richeyville | 33 | 51.5% | 40.1 |
| 15376 | West Alexander | 95 | 49.5% | 80.8 |
| 15021 | Burgettstown | 619 | 48.1% | 313.5 |
| 15312 | Avella | 226 | 47.8% | 61.8 |
| 15360 | Scenery Hill | 159 | 47.2% | 78.4 |
| 15363 | Strabane | 127 | 46.5% | 107.3 |
| 15313 | Beallsville | 53 | 45.3% | 35 |
| 15314 | Bentleyville | 338 | 45% | 122.5 |
| 15019 | Bulger | 104 | 44.2% | 23.8 |
| 15417 | Brownsville | 168 | 44% | 65.8 |
| 15347 | Meadow Lands | 48 | 43.8% | 22.1 |
| 15333 | Fredericktown | 140 | 43.6% | 46.9 |
| 15323 | Claysville | 301 | 41.5% | 101.3 |
| 15427 | Daisytown | 54 | 40.7% | 208 |
| 15330 | Eighty Four | 839 | 40.4% | 101.2 |
| 15332 | Finleyville | 40 | 40% | 32.5 |
| 15060 | Midway | 76 | 38.2% | 33 |
| 15423 | Coal Center | 131 | 38.2% | 316.1 |
| 15063 | Monongahela | 1,104 | 36.8% | 76 |
| 15022 | Charleroi | 918 | 36.2% | 114.7 |
| 15321 | Cecil | 307 | 36.2% | 31.8 |
| 15340 | Hickory | 131 | 35.9% | 80 |
| 15311 | Amity | 101 | 35.6% | 28.3 |
| 15301 | Washington | 6,390 | 35.5% | 505 |
| 15324 | Cokeburg | 43 | 34.9% | 13.8 |
| 15342 | Houston | 882 | 34.1% | 69.7 |
| 15367 | Venetia | 2,756 | 32.7% | 103.5 |
| 15331 | Ellsworth | 51 | 31.4% | 41.2 |
| 15057 | Mc Donald | 637 | 30.9% | 50.9 |
| 15067 | New Eagle | 179 | 30.2% | 64.3 |
| 15033 | Donora | 191 | 28.8% | 36.5 |
| 15477 | Roscoe | 30 | 26.7% | 5.7 |
| 15419 | California | 217 | 20.3% | 49 |
| 15317 | Canonsburg | 30 | 20% | 17.7 |
| 15055 | Lawrence | 444 | 17.1% | 16.4 |
Washington County in the Pennsylvania picture
| Washington County | 37.9% over the limit | 2,504 tests |
| Pennsylvania's highest: Fulton County | 69.7% | 90 tests |
| Pennsylvania county median | 49% | 67 counties ranked |
| Share of all Pennsylvania tests from this county | 1.4% | |
Ranked nearby in Pennsylvania
- Susquehanna County — #50, 40.1% of 173 tests over the limit
- Greene County — #51, 39% of 142 tests over the limit
- Sullivan County — #52, 38.8% of 43 tests over the limit
- Allegheny County — #54, 37.3% of 17,929 tests over the limit
- Mercer County — #55, 36.7% of 1,230 tests over the limit
- Lackawanna County — #56, 36.3% of 1,103 tests over the limit
(Ranking neighbors — counties adjacent in the Pennsylvania test ranking, not necessarily on the map.)
High test? Fixes and real pricing: the Pennsylvania mitigation cost guide. Every statistic here traces to the methodology (CDC EPHT (labs), 2008–2017; zones: EPA; year built & population: ACS 5-year; ZIP results: PA DEP).
Washington County radon FAQ
- Is radon high in Washington County?
- 37.9% of 2,504 home tests reported to the CDC came back at or above the EPA action level of 4 pCi/L — 11.1 points below the Pennsylvania county median of 49%, ranking #53 of 67 tested counties. EPA classifies the county as Zone 2.
- Does an older home in Washington County mean more radon risk?
- The county's median home was built in 1966 — before radon-resistant construction practices entered building codes in the 1990s, so most of the housing stock has no built-in radon protection. Construction age changes the odds, not the answer: only a test tells you about your house.
- Where do these Washington County numbers come from?
- 2,504 aggregated home tests in the CDC's Environmental Public Health Tracking dataset (CDC EPHT 2008-2017). Median reading: 3 pCi/L; the highest recorded test hit 181.3 pCi/L. How we handle the data, including its limits, is documented on our methodology page.
- Which ZIP codes in Washington County test highest?
- In PA DEP's residential results (1986–2026): 15329 (Prosperity) — 54.4% of 57 tests over the limit; 15345 (Marianna) — 52.1% of 73 tests over the limit; 15358 (Richeyville) — 51.5% of 33 tests over the limit. Full ZIP table below.