Radon (Rn-222) is a colorless, odorless, naturally occurring radioactive gas produced by the breakdown of uranium in soil. It seeps into homes through cracks and gaps and accumulates indoors, where it becomes the second leading cause of lung cancer in the US.
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Radon-222 is part of the uranium-238 decay chain, and with a half-life of about 3.8 days it lasts long enough to move from soil into a house. Once inside, it breaks down into short-lived radioactive decay products (polonium-218, lead-214, bismuth-214, and polonium-214) that can lodge in lung tissue and release alpha radiation there. The risk builds with both the level and the years of exposure. EPA estimates that radon causes about 21,000 lung cancer deaths a year in the United States, about 2,900 of them among people who never smoked, and the Ohio Department of Health calls radon the number one cause of lung cancer among non-smokers. At EPA's 4.0 pCi/L action level, EPA's lifetime estimates are about 7 lung cancers per 1,000 people who never smoked and about 62 per 1,000 smokers. Locally, Ohio Department of Health data from licensed testers since 2010 shows about 22 percent of Hamilton County tests and roughly 36 to 37 percent of Butler, Warren, and Clermont County tests above that level, and our radon levels by ZIP code table breaks those results down further. Because radon has no color, smell, or taste, a test is the only way to know your own level; see radon testing for kits and professional options.