Yes. Hamilton County and most of Greater Cincinnati sit in EPA Radon Zone 1, the highest-risk classification. Radon is the second leading cause of lung cancer in the US, responsible for about 21,000 deaths annually.
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Cincinnati sits on Ordovician-period limestone and shale that releases radon as uranium-238 decays. Hamilton, Butler, Warren, Clermont, and Campbell counties are all designated EPA Radon Zone 1, meaning predicted indoor screening levels at or above 4.0 pCi/L. Roughly 1 in 3 homes tested in Hamilton County exceeds that action level per Ohio Department of Health data. Risk is dose-dependent: long-term exposure at 8.0 pCi/L roughly doubles non-smoker lung-cancer risk over a 70-year window per the EPA Citizen's Guide to Radon. For smokers, the multiplicative effect with tobacco is significantly larger. Children breathe more rapidly than adults and have developing lung tissue, so households with children sleeping on lower floors have a higher risk-weighted exposure profile. Cincinnati-specific consideration: lower-floor occupied spaces (basement bedrooms, walk-out family rooms in homes built into a slope, finished basement workshops) compound the household-weighted exposure picture. The same 8 pCi/L reading carries materially different risk for a household sleeping on the second floor versus a household with a teenager bedroom in the basement. Mitigation closes the gap regardless.