Randon
Radon (Rn-222) is a rare, radioactive, colorless, and odorless gas resulting from the decay of radium (Ra-226), itself a byproduct of uranium (U-238) naturally found in the Earth's crust. Commonly present in granitic and volcanic regions (Vosges, Massif Central, Alps, Pyrenees...), radon migrates from underground to the surface, accumulating in poorly ventilated, enclosed spaces where it poses significant health risks.
Classified as a carcinogen, radon is the second leading cause of lung cancer after tobacco. To lower indoor radon levels, ventilate daily for at least 10 minutes. Monitoring devices are available to measure radon levels in indoor air.