Radon is a radioactive colorless, odorless, tasteless noble gas released from the normal decay of the elements thorium, radium, and uranium in rocks and soil. It is an invisible gas that seeps up through the ground and diffuses into the air. Radon gas usually exists at very low levels outdoors. However, in areas without adequate ventilation, such as underground mines, radon can accumulate to levels that substantially increase the risk of lung cancer. Radon-222 decays into radioactive elements, two of which – polonium-218 and polonium-214 emit alpha particles, which are highly effective in damaging lung tissues.
These alpha-emitting radon decay products have been responsible for many cases of lung cancer in the United States and around the world.
Radon is estimated to cause approximately 21,000 of lung cancer deaths each year. In fact, the Surgeon General has warned that radon is the second leading cause of lung cancer in the United States. Only smoking causes more lung cancer deaths. If you smoke and your home has high radon levels, your risk of lung cancer is especially high.