It emits alpha particles which damages tissues.
Step-by-step explanation
The radon is the decay byproduct of radium which emits alpha rays to convert into the lead or polonium. The alpha particles have less penetration inside the cell than the beta particle or gamma rays and have the more dangerous effect than these other days. In the environment, the high presence of radon enters into the lungs through breathing and start to decay. In their decay, it emits alpha rays, which acts as the carcinogenic agent in the body.