ZIP Codes with Highest Radon Risk — 2026 Rankings

Lebanon, Nebraska — ZIP 69036, population a few hundred, safety score 0 out of 100 — sits at the very top of this ranking. It is not there because of a single dramatic exposure event. It is there because of what lies underneath: uranium-bearing bedrock in the High Plains, a county the EPA placed in Zone 1, and a combination of compounding risk factors that no other ZIP in the dataset matches all at once. Radon does not smell, does not taste, and cannot be seen. It seeps through foundation cracks and slab joints, accumulates in basements and crawlspaces, and over years of exposure causes lung cancer. The EPA estimates radon kills about 21,000 Americans each year — making it the second-leading cause of lung cancer behind smoking, and the leading cause among non-smokers.

Welcome to the Highest Radon Risk Rankings. We analyzed 14,079 ZIP codes using EPA county-level radon zone classifications — every postal delivery area in our dataset that carries a Zone 1 designation, the EPA's highest-risk classification, indicating predicted average indoor radon levels above 4 pCi/L. That 4 pCi/L figure is the EPA's action level: the threshold at which the agency recommends mitigation regardless of how long you have lived in the home.

What the data reveals. The geography of high radon risk in the United States is not random — it follows the bedrock. Pennsylvania leads the national ranking with 1,596 Zone 1 ZIP codes, driven by uranium-bearing granitic and metamorphic formations across the Reading Prong corridor and the broader Appalachian terrain. New York follows with 1,161 ZIPs, anchored by the same Reading Prong geology that runs northeast through the Hudson Valley — accounting for the dense cluster of Albany ZIP codes (positions 15 through 54 in the top-100 table, plus several more in the 90s). Iowa ranks third with 1,056 Zone 1 ZIPs, reflecting the glacial till deposits of the Upper Midwest that trap radon-generating uranium decay products in the soil. That same glacial mechanism explains the strong representation of Minnesota (731 ZIPs), North Dakota (400), and South Dakota (282). Further west, Colorado (602 ZIPs), Montana (355), and Wyoming (185) carry elevated zone counts from Rocky Mountain uranium geology — the same formations that drove the mid-century uranium mining boom. Parker, PA (16049) and Olyphant, PA (18447 and 18448) in the top-15 reflect the Appalachian cluster; Flat Top, WV (25841) at position 67 adds the Appalachian southern extension.

The bottom of this list is just as revealing. The states with the fewest Zone 1 ZIP codes cluster predictably along the Gulf Coast, the southeastern coastal plain, and the Pacific rim. Florida, Louisiana, Mississippi, and Hawaii do not appear in this ranking at all — their sedimentary geology, high water tables, and coastal plain soils produce minimal radon generation. South Carolina contributes just 30 Zone 1 ZIPs; Nevada 38; Rhode Island 33. These are places where the underlying geology simply does not carry the uranium concentrations that feed radon production, and where shallow water tables limit the soil pathways that allow gas to migrate upward into structures.

How to read this ranking. Every ZIP code in this table carries the same EPA zone label — Zone 1 (High) — because the EPA's radon map is a county-level classification, not a property-level measurement. Zone 1 means the county's predicted average indoor radon exceeds 4 pCi/L; it does not mean every home in that county measures above the action level. Actual indoor concentrations vary significantly based on foundation type (basement vs. slab vs. crawlspace), construction age, ventilation design, and whether sub-slab depressurization has been installed. Within Zone 1, ZIP codes in this table are sub-ranked by overall Home Safety Score, so areas with more compounding risk factors appear higher on the list regardless of having the same zone designation.

What this ranking does not tell you. It does not tell you whether any specific home in these ZIP codes has been tested for radon, nor whether mitigation systems are already in place. It does not reflect local testing rates — some high-risk counties have active radon testing programs and well-documented mitigation rates, while others have almost no measurement data at all. It does not account for the difference between a 1960s basement-heavy suburb and a modern slab-on-grade development in the same ZIP code. And it does not replace a test. A short-term radon test kit costs $15–$40 at most hardware stores; a long-term test runs $25–$50. If results exceed 4 pCi/L, a certified sub-slab depressurization system typically costs $800–$2,500 and reduces indoor radon by up to 99 percent. The zone on this map is where to look first. The test in your basement tells you what is actually there.

14,079 ZIP codes analyzed · Data last refreshed 2026-04-13

100 Lowest-Ranked ZIP Codes

Rankings by State

Methodology

Radon rankings are based on EPA county-level radon zone classifications. Zone 1 (highest risk) has predicted average indoor radon levels above 4 pCi/L — the EPA action level. Zone 2 is moderate (2-4 pCi/L) and Zone 3 is low (below 2 pCi/L). Within Zone 1, ZIP codes are sub-ranked by Home Safety Score to prioritize areas with compounding risk factors.

Data sources: EPA Safe Drinking Water Information System (SDWIS), FEMA National Flood Insurance Program, EPA radon zone maps, EIA electricity rates, and Consumer Confidence Reports. Last updated: 2026-06-03.

Frequently Asked Questions

What is EPA Radon Zone 1?

Zone 1 is the EPA highest-risk classification, meaning the county has predicted average indoor radon levels above 4 pCi/L — the level at which the EPA recommends mitigation. Radon causes about 21,000 lung cancer deaths per year in the U.S.

Should I test for radon?

The EPA recommends testing all homes regardless of radon zone. A DIY test kit costs $15-40. Professional testing costs $150-250. If levels exceed 4 pCi/L, mitigation systems ($800-2,500) can reduce radon by up to 99%.

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