Radon Testing & Mitigation in Union County, PA
45% of 8,040 basement radon tests reported to PA DEP in Union County measured 4.0 pCi/L or higher, EPA's action level (median 3.5 pCi/L).
Connect with a DEP-Certified Radon Professional
or call(717) 461-2427
Radon in Union County: 45% of the 8,040 basement tests reported to PA DEP measured 4.0 pCi/L or higher, EPA's action level, 8 points above the 37% statewide share. The county ranks 39th highest of 67, and the median result is 3.5 pCi/L. Only a test shows one home's level.
Radon Test Results by ZIP Code in Union County
8 ZIP codes in Union 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 17844 (Mifflinburg): 55% of 1,327 tests. The lowest is in 17837 (Lewisburg): 42% of 5,271 tests.
| ZIP code | Post office | Basement tests | Median pCi/L | At or above 4.0 |
|---|---|---|---|---|
| 17837 | Lewisburg | 5,271 | 3.2 | 42% |
| 17844 | Mifflinburg | 1,327 | 4.7 | 55% |
| 17889 | Winfield (part) | 515 | 4.5 | 52% |
| 17856 | New Columbia | 430 | 4.0 | 51% |
| 17855 | New Berlin | 158 | 3.9 | 50% |
| 17886 | West Milton | 120 | 3.1 | 44% |
| 17845 | Millmont | 102 | 4.0 | 50% |
| 17810 | Allenwood (part) | 70 | 4.2 | 50% |
| Union County | 8,040 | 3.5 | 45% | |
| Pennsylvania | 2,629,492 | 2.8 | 37% | |
See your ZIP in the table?
Get matched with a DEP-certified radon professionalFirst-floor tests in Union County: 1,349 on record, median 1.6 pCi/L, 21% at or above 4.0 pCi/L.
EPA's Map of Radon Zones (1993) places Union County in Zone 1, its highest category (predicted average indoor screening level above 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 Union County
58% of Union County's 16,205 housing units were built before 1980, 9 points below the 67% statewide figure; 24% 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 Union County
Clinton Group (Silurian; sandstone and shale) underlies 21% of the county. Tuscarora Formation (Silurian; quartzite) underlies 18% of the county. Bloomsburg and Mifflintown Formations (Silurian; shale) underlies 16% 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).
Private Wells in Union County
An estimated 69% of Union County residents supplied their own household water in 2015, typically from a private well. Radon dissolves in groundwater and is released into indoor air when water is used for showering and other household purposes. EPA's guidance: if an air test finds a radon problem and your water comes from a well, have the water tested too. A water test is separate from an air test.
Sources: U.S. Geological Survey, Estimated Use of Water in the United States, county-level data for 2015. Retrieved September 29, 2026. U.S. EPA, A Citizen's Guide to Radon.
Home Purchases in Union County
Lenders reported 263 home-purchase mortgages originated in Union 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 Union County
Union County has 14 municipalities: 4 boroughs and 10 townships.
Show all 14 municipalities
Buffalo township, East Buffalo township, Gregg township, Hartleton borough, Hartley township, Kelly township, Lewis township, Lewisburg borough, Limestone township, Mifflinburg borough, New Berlin borough, Union township, West Buffalo township, White Deer township.
Source: U.S. Census Bureau, 2025 Gazetteer Files, county subdivisions. Retrieved September 29, 2026.
City Pages in Union County
Neighboring Counties
- Radon in Centre County → 56% of 39,672 basement tests at or above 4.0 pCi/L
- Radon in Clinton County → 46% of 4,689 basement tests at or above 4.0 pCi/L
- Radon in Lycoming County → 46% of 15,366 basement tests at or above 4.0 pCi/L
- Radon in Mifflin County → 60% of 3,746 basement tests at or above 4.0 pCi/L
- Radon in Northumberland County → 47% of 9,978 basement tests at or above 4.0 pCi/L
- Radon in Snyder County → 50% of 4,733 basement tests at or above 4.0 pCi/L
- All 67 Pennsylvania county radon pages
DEP-Certified Mitigation Firms Based in County
No DEP-certified mitigation firms are physically based in Union County. Certified professionals from adjacent counties travel here to perform testing and mitigation.
Source: PA DEP Certified Mitigation Firms Directory, July 2026. This reflects business address only — firms based elsewhere may also serve Union 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 Union County typically costs $895–$2,400. 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 Union County are at or above the EPA action level?
45% of the 8,040 basement tests reported to PA DEP from Union County measured 4.0 pCi/L or higher, against 37% statewide. The median result is 3.5 pCi/L, and 10% of tests measured 20 pCi/L or higher.
Which Union County ZIP code has the highest radon test results?
Among ZIP codes with at least 100 basement tests, 17844 (Mifflinburg) has the highest share at or above 4.0 pCi/L: 55% of 1,327 tests, with a median of 4.7 pCi/L. 17837 (Lewisburg) has the lowest, at 42%.
How does Union County compare with other Pennsylvania counties?
Union County ranks 39th highest of 67 counties by share of basement tests at or above 4.0 pCi/L, at 45%. Among its neighbors, Mifflin County has the highest share at 60% and Clinton County the lowest at 46%.
What bedrock is under Union County?
The largest mapped units are Clinton Group (21% of the county), Tuscarora Formation (18% of the county) and Bloomsburg and Mifflintown Formations (16% of the county), according to the USGS compilation of the Pennsylvania Geological Survey state map.
Should Union County well owners test their water for radon?
An estimated 69% of Union County residents supplied their own household water in 2015. EPA's guidance is to test the air first. If the air test finds a radon problem and the water comes from a well, have the water tested as well.