Radon by Zip / County

Alabama Radon Levels by Zip Code & County.

The short version: radon levels by zip code in Alabama really come down to which county your zip sits in — and even inside the same county, the house next door can read very differently. This page shows what has actually been measured near your Birmingham-area address in plain numbers, plus the honest limits of the public data. A pCi/L (picocuries per liter) is just a measure of how much radon is in the air.

Metro Spotlight

Jefferson, Shelby, and St. Clair — the measured picture.

All three metro counties sit in EPA Radon Zone 2 (the middle rating on the EPA's three-zone map of radon potential). ADPH also names Jefferson and Shelby among Alabama's 15 highest-potential radon counties. Here's what the CDC's actual test data shows.

Roughly 1 in 9 reported tests in Jefferson and Shelby — and about1 in 7 in St. Clair — came back at or above the EPA action level. ADPH names Jefferson and Shelby among Alabama's 15 highest-potential radon counties. Neither one is EPA Zone 1; both are Zone 2 (moderate potential), matching every Zone 2 label you'll see on the metro rows above.

Why Here

Why the Birmingham area tests high.

The Birmingham metro sits in the Valley and Ridge physiographic province, a folded and faulted belt of limestone, dolomite, sandstone, and shale running southwest to northeast through central Alabama. The Geological Survey of Alabama (GSA) ranks this province as moderate-to-high in geologic radon potential, and its stakeholders' briefing calls out three specific mechanisms.

• Faulting creates conduits. The province is heavily faulted, and faults give radon a direct migration path from bedrock into overlying soils — and, from there, up into basements, crawl spaces, and slab-on-grade homes.
• Limestone and carbonaceous shale carry uranium. GSA's statewide radon inventory identifies specific limestone, carbonaceous shale, and granitic units as the state's higher-uranium rock types. All three occur in the Birmingham metro's stratigraphy.
• Thin soils, fractured rock, hillside siting. GSA lists nine radon-potential factors; thin soils over bedrock, fractured rock, and hillside/slope construction — all common "over the mountain" in Vestavia Hills and Mountain Brook — raise radon transport into occupied space.

This is the honest geologic reason Jefferson and Shelby show up on the state's highest-potential list even though the EPA's 1993 map assigns them Zone 2 rather than Zone 1. Local rocks carry uranium, faulting moves radon up, and the metro's terrain means many homes are built on or over exposed bedrock. TheGSA 2025 briefing is the primary source for this section.

Data Gaps

Where the public data honestly stops.

Three limits are worth naming plainly before anyone reads too much into a county number:

• ADPH's ZIP tool is the only official ZIP-level source, and it isn't bulk-scrapable. Public per-ZIP averages for Alabama don't exist in downloadable form. Anyone publishing a full ZIP-by-ZIP Alabama radon table is either querying ADPH one ZIP at a time, or estimating.
• Some sites publish very small samples as "regional averages." One widely-linked page cites a "Birmingham metro regional average of 6.4 pCi/L" — that figure is drawn from five user-submitted tests, and it labels the metro EPA Zone 1. Jefferson, Shelby, and St. Clair are all EPA Zone 2. We do not use that figure anywhere on this page.
• House-to-house variation swamps county averages. ADPH says this directly: "radon levels can vary greatly from home to home — even levels next door can be very different." A county average is a useful prior, not a prediction for any one address. The only way to know your home's number is to test it.

FAQ

Frequently Asked Questions.