Radon Levels in Lehigh County: Allentown and the Reading Prong's Uranium Core
Lehigh County is EPA Zone 1. Allentown sits at the heart of Reading Prong crystalline bedrock with among the highest residential radon exposure rates in Pennsylvania. Pre-1960 housing stock with basement construction is particularly high-risk. PA DEP requires all mitigation work be performed by a DEP-certified contractor under PA Code § 240.
Why Lehigh County Has Elevated Radon Risk
Lehigh County is designated EPA Zone 1 — the highest radon potential classification — by the United States Environmental Protection Agency. Lehigh County sits directly on the Reading Prong's highest-uranium crystalline bedrock, where gneiss and granite with elevated uranium-238 concentrations underlie Allentown's entire residential footprint. The decay chain — uranium-238 to radium-226 to radon-222 — operates continuously, producing a constant upward flux of radon gas through soil and into structures.
Allentown's pre-1960 housing density is among the highest in the Lehigh Valley. Older construction in this era predates radon awareness and was built with stone block, poured concrete, or brick foundations that develop cracks and gaps over time, creating multiple radon entry pathways. Even well-maintained older homes in Lehigh County test above the EPA action level at rates that significantly exceed the Pennsylvania average.
Homeowners, school administrators, and real estate professionals in Lehigh County should treat radon testing as mandatory, not optional. Pennsylvania's statewide testing data consistently shows Lehigh County exceeding the EPA's 4.0 pCi/L action level in a significant percentage of tested homes.
Lehigh County Municipalities with Elevated Radon Risk
The following cities and boroughs in Lehigh County are covered by PA Radon Hub with city-level radon data, DEP-certified contractor listings, and local geological analysis:
PA Radon Hub currently covers Allentown as Lehigh County's primary municipality. The Allentown city page includes detailed radon risk data, local geological analysis, cost estimates, and DEP-certified contractor listings. The Lehigh County page covers the full county service area. Adjacent Northampton County — home to Bethlehem and Easton — shares identical Reading Prong geology.
Reading Prong Geology and the Lehigh County Risk Profile
The Reading Prong runs directly beneath Allentown and the surrounding Lehigh County residential corridor. Pennsylvania DEP's radon division has tracked Lehigh County data since the 1980s, consistently placing it among the state's top-tier risk counties. The Prong's uranium concentrations in this area are not a surface phenomenon — bedrock in many parts of Allentown sits within a few feet of residential foundation slabs, eliminating the soil buffer that partially attenuates radon in lower-risk regions. Across the Lehigh River, Northampton County records comparable or higher averages in Bethlehem and Easton.
Under Pennsylvania radon regulations (PA Code § 240), all radon mitigation work must be performed by a DEP-certified contractor. The standard mitigation approach for Lehigh County foundations is active sub-slab depressurization (ASD), typically using a system such as the RadonAway RP145 fan unit. Installation creates a negative pressure zone beneath the foundation slab, preventing radon from migrating upward into living spaces.
SB 760 and Lehigh County School Districts
Pennsylvania Senate Bill 760, if enacted as drafted, would mandate radon testing in all public school buildings by the 2026–2027 academic year. As of 2026, the bill remains in committee. Lehigh County school districts would be subject to this requirement if SB 760 is enacted. Elevated radon in school buildings follows the same geological patterns as residential exposure — districts in Lehigh County should prioritize testing in older buildings with basement or slab-on-grade construction.
DEP-certified contractors serving Lehigh County school districts retained for mitigation would be required to follow the same PA Code § 240 protocols required for residential mitigation. PA Radon Hub connects school administrators with verified DEP-certified professionals for both testing and mitigation scopes.
Get Connected with a DEP-Certified Contractor in Lehigh County
PA Radon Hub is an independent informational resource. We are not a mitigation company, not a government agency, and not affiliated with PA DEP. We connect Pennsylvania property owners and school administrators with independent, DEP-certified radon professionals.
To find a DEP-certified radon contractor serving Lehigh County, visit the Lehigh County contractor page or browse city-level listings below:
- Allentown — Lehigh County radon data and DEP contractor listings
- Lehigh County — full county contractor directory
- Northampton County — adjacent Reading Prong county
- Bethlehem — Reading Prong city data
- Easton — Reading Prong city data
Verify any contractor's DEP certification independently at dep.pa.gov before hiring. Retain all documentation including the DEP certification number, installation records, and post-mitigation test results.
PA Radon Hub is an independent resource and not the direct service provider. All listed contractors are independent DEP-certified professionals.