Cancer Screening & PreventionJanuary 13, 2026·5 min read
By the CIRRUS Editorial Team — how we write and source this
Radon exposure and lung cancer risk at home
It's an odorless, invisible gas, and it's the second-leading cause of lung cancer in the US after smoking.
Radon is a naturally occurring radioactive gas produced by the decay of uranium in soil and rock, and it can seep into homes through foundation cracks, accumulating to concerning levels particularly in basements and lower floors with poor ventilation.
It's undetectable without testing — no smell, no visible sign — which is why radon exposure is often discovered only through a dedicated test kit or professional measurement, not through any symptom or environmental cue a homeowner would otherwise notice.
The EPA recommends mitigation action at or above 4 picocuries per liter of air, and testing is generally recommended for any home regardless of geographic region, since radon levels can vary significantly even between neighboring properties depending on local soil composition and home construction.
For smokers specifically, radon and tobacco exposure appear to interact synergistically rather than just additively in lung cancer risk research, meaning the combined risk is measurably higher than either exposure alone would suggest — an additional reason radon testing is particularly emphasized for smoking households.
This article is general health information, not medical advice, and doesn’t replace evaluation by your own physician. Talk to a doctor about anything specific to your own diagnosis or treatment.