Yes. The EPA identifies radon as the leading cause of lung cancer among people who have never smoked, and the second leading cause overall after smoking. Risk accumulates over years of exposure, not days.
More detail
Radon is a radioactive gas produced by uranium decaying in soil and rock. It has no smell, no color, and no taste, which is why the only way to know a home has it is to measure. When inhaled, its decay products lodge in lung tissue and emit alpha radiation, which damages the cells lining the airway. The EPA estimates radon causes roughly 21,000 lung cancer deaths in the United States each year, and about 2,900 of those occur among people who have never smoked. It is the leading cause of lung cancer in non-smokers by that measure. Risk also multiplies for smokers: the combination is substantially worse than either exposure alone. The honest framing on timeline is that this is a long-exposure risk. There is no acute radon poisoning, no set of symptoms that indicates radon exposure specifically, and nothing a homeowner would feel at any residential concentration. Anyone searching for symptoms of exposure will not find a useful list, because there are none. That absence is exactly why testing is the only reasonable response, and why a result above the action level warrants action within weeks rather than panic within hours. The practical takeaway: exposure that has already happened cannot be undone, and exposure going forward is entirely controllable. A mitigation system reduces the concentration for every year the household lives there afterward, which is where the whole benefit sits. Regional context worth having. Central Ohio sits on flat-lying glacial till with dense clay subsoils that drain slowly and perch water above the till rather than letting it through. That geology is why much of Greater Columbus and Central Ohio falls in EPA Zone 1, the highest of the three predicted-average zones, and why testing here is not a precaution against an unlikely event.