According to the CDC: “Radon is a colorless, tasteless, odorless, radioactive gas. It occurs naturally and is produced by the breakdown of uranium in soil, rock, and water.” and “Uranium is found in small amounts in most rocks and soil. It slowly breaks down to other products such as radium, which breaks down to radon.”
The EPA says “Radon is the number one cause of lung cancer among non-smokers” (overall, its second only to smoking).
The particles released seep up from the ground and can seep into the house and get trapped, causing a build up of radon in the air which people then breathe in.
The EPA says “(January 13 2005) U.S. Surgeon General, Richard H. Carmona, issues a Health Advisory warning Americans about the health risk from exposure to radon in indoor air. The Chief Physician urged Americans to test their homes to find out how much radon they might be breathing. Dr. Carmona also stressed the need to remedy the problem as soon as possible when the radon level is 4pCi/L or more”
If the average level is more than 4pCi/L, a radon mitigation system should be installed.