Radon levels in Michigan

About radon in Michigan

About one in four Michigan homes is expected to have radon above the EPA's 4 pCi/L action level, according to the state's Department of Environment, Great Lakes, and Energy, and in some counties the share may reach half (EGLE; EGLE, real estate).

Our Michigan figures agree closely. They come from EGLE's indoor radon map, which reports first-time short-term tests in homes without a mitigation system, from the test kits sold through the state program, over roughly the last ten years (EGLE map data). Across 56,518 of those tests, 23% were at or above 4 pCi/L.

Michigan publishes these results by ZIP code, not by county. To build county figures, we add up the ZIP codes that sit mostly inside each county, using Census counts of homes. ZIP codes near a county line can therefore include a few homes from the next county over. The county pages say so wherever it applies.

The differences across the state are striking. In our data, Lenawee County in the south has the highest share of high results (51%), while Muskegon County on Lake Michigan has the lowest (2%). The county map above shows how the rest of the state falls between them.

Michigan does not license or regulate radon testers or mitigators; EGLE describes it as a "buyer beware" situation and recommends professionals certified by the National Radon Proficiency Program or the National Radon Safety Board (EGLE). When a home is sold, Michigan's seller disclosure statement asks about known environmental hazards, including radon gas (MCL 565.957).

Pick your county below to see its results and how it compares with nearby counties.

Written and reviewed by Ray Roman · 2026-11-03