Radon breaks down into several radioactive elements called radon decay products, which are solid particles that become suspended in air. They are extremely small and easily inhaled, where they can attach to lung tissue. Not everyone exposed to radon will get lung cancer, but the greater the amount of radon and the longer the exposure, the greater the risk of developing lung cancer. Radon is classified as a Group A carcinogen, a substance known to cause cancer in humans. Next to smoking, scientists believe that radon is associated with more lung cancer deaths than any other carcinogen.