Why can inhaled radon increase radiation damage in the lungs?

Inhaled radon gas itself is not the primary cause of radiation damage in the lungs; rather, the danger arises from the radioactive "daughter" products produced by its decay.12

When radon gas decays, it transforms into a series of short-lived, radioactive isotopes—such as polonium, bismuth, and lead—that exist in particulate form. These radioactive particles can attach to dust in the air and be inhaled into the respiratory tract, where they become deposited on lung tissue.12

Once these particles are trapped in the lungs, they emit alpha particles as they continue to decay. Because alpha particles have limited penetrability, they deposit their energy locally, intensely irradiating the surrounding lung tissue. This localized exposure to high-energy alpha radiation can cause significant cellular damage, which, over many years of exposure, greatly increases the risk of developing lung cancer.21