Pennsylvania · county radon data
Radon in Philadelphia County, Pennsylvania
12.4% of the 8,973 home radon tests on record here reached the EPA action level — toward the lower end of the state's tested counties, ranked #67 of 67 tested Pennsylvania counties.
What the numbers say
Philadelphia County sits 36.6 points below the Pennsylvania median (49% of tests over the limit across the state's counties). The median reading among its 8,973 reported tests was 1.5 pCi/L — and the single highest test on record reached 404.2 pCi/L, more than 101× the action level. EPA maps place the county in Radon Zone 3 — lower predicted potential, though individual homes here still test high; zone maps predict averages, not addresses.
Why: the ground under Philadelphia 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 Philadelphia County home dates to 1949 — decades before radon-resistant new construction entered building codes. With 1,579,706 residents largely housed in that older stock, testing is the only way any individual household knows where it stands.
Radon by ZIP in Philadelphia 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 |
|---|---|---|---|---|
| 19118 | Philadelphia | 4,409 | 30.3% | 104 |
| 19124 | Philadelphia | 2,539 | 23.3% | 99.8 |
| 19115 | Philadelphia | 2,959 | 21% | 89.7 |
| 19128 | Philadelphia | 12,157 | 19.2% | 68.6 |
| 19119 | Philadelphia | 7,226 | 19% | 65.8 |
| 19137 | Philadelphia | 664 | 17.5% | 27.5 |
| 19127 | Philadelphia | 2,818 | 17.2% | 47 |
| 19126 | Philadelphia | 125 | 16.8% | 9.9 |
| 19133 | Philadelphia | 452 | 16.2% | 16.6 |
| 19129 | Philadelphia | 2,918 | 14.8% | 137.2 |
| 19111 | Philadelphia | 5,450 | 14.6% | 41.7 |
| 19104 | Philadelphia | 2,216 | 14.4% | 9999.9 |
| 19116 | Philadelphia | 2,776 | 14% | 98 |
| 19144 | Philadelphia | 3,873 | 13.9% | 155 |
| 19151 | Philadelphia | 3,898 | 13.5% | 54.2 |
| 19132 | Philadelphia | 900 | 12.2% | 15.3 |
| 19121 | Philadelphia | 3,064 | 12% | 22.3 |
| 19123 | Philadelphia | 2,506 | 10.6% | 17.6 |
| 19125 | Philadelphia | 7,297 | 9.9% | 243 |
| 19134 | Philadelphia | 3,153 | 9.8% | 112.4 |
| 19131 | Philadelphia | 3,034 | 9.1% | 30.4 |
| 19130 | Philadelphia | 6,464 | 9% | 204 |
| 19102 | Philadelphia | 190 | 8.4% | 13.6 |
| 19122 | Philadelphia | 2,162 | 7.7% | 26.8 |
| 19150 | Philadelphia | 2,481 | 7.5% | 49.2 |
| 19146 | Philadelphia | 11,446 | 7.4% | 65.2 |
| 19139 | Philadelphia | 2,327 | 7.2% | 71 |
| 19140 | Philadelphia | 1,105 | 6.8% | 103.2 |
| 19135 | Philadelphia | 1,948 | 6.5% | 17.3 |
| 19143 | Philadelphia | 5,128 | 6.4% | 78.8 |
| 19152 | Philadelphia | 1,949 | 6.2% | 104.73 |
| 19136 | Philadelphia | 2,129 | 6% | 104 |
| 19141 | Philadelphia | 1,427 | 6% | 17 |
| 19147 | Philadelphia | 10,634 | 5.4% | 847.6 |
| 19149 | Philadelphia | 1,738 | 5.4% | 37 |
| 19106 | Philadelphia | 1,812 | 5.2% | 104 |
| 19107 | Philadelphia | 939 | 5% | 85.9 |
| 19114 | Philadelphia | 2,629 | 4.8% | 43 |
| 19120 | Philadelphia | 2,985 | 4.8% | 31 |
| 19145 | Philadelphia | 5,851 | 4% | 101 |
| 19148 | Philadelphia | 7,579 | 3.9% | 801 |
| 19138 | Philadelphia | 2,187 | 3.5% | 22.6 |
| 19103 | Philadelphia | 2,567 | 3.3% | 86.3 |
| 19154 | Philadelphia | 2,912 | 3.1% | 39.7 |
| 19142 | Philadelphia | 1,176 | 1.6% | 23 |
| 19153 | Philadelphia | 667 | 0.6% | 6.3 |
Philadelphia County in the Pennsylvania picture
| Philadelphia County | 12.4% over the limit | 8,973 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 | 5.2% | |
Ranked nearby in Pennsylvania
- Montgomery County — #64, 27.2% of 14,749 tests over the limit
- McKean County — #65, 26.4% of 144 tests over the limit
- Delaware County — #66, 21% of 8,601 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).
Philadelphia County radon FAQ
- Is radon high in Philadelphia County?
- 12.4% of 8,973 home tests reported to the CDC came back at or above the EPA action level of 4 pCi/L — 36.6 points below the Pennsylvania county median of 49%, ranking #67 of 67 tested counties. EPA classifies the county as Zone 3.
- Does an older home in Philadelphia County mean more radon risk?
- The county's median home was built in 1949 — 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 Philadelphia County numbers come from?
- 8,973 aggregated home tests in the CDC's Environmental Public Health Tracking dataset (CDC EPHT 2008-2017). Median reading: 1.5 pCi/L; the highest recorded test hit 404.2 pCi/L. How we handle the data, including its limits, is documented on our methodology page.
- Which ZIP codes in Philadelphia County test highest?
- In PA DEP's residential results (1986–2026): 19118 (Philadelphia) — 30.3% of 4,409 tests over the limit; 19124 (Philadelphia) — 23.3% of 2,539 tests over the limit; 19115 (Philadelphia) — 21% of 2,959 tests over the limit. Full ZIP table below.