Radon is a naturally occurring, radioactive gas found in soil and rock. It seeps into homes through cracks in the foundation, walls, and joints. Radon comes from the natural (radioactive) breakdown of uranium in soil, rock and water and gets into the air you breathe. It can get into any type of building--homes, offices, and schools--but you and your family are likely to get your greatest exposure at home, where you spend most of your time.
Among nonsmokers, radon is the leading cause of lung cancer in the United States. Based on U.S. Environmental Protection Agency estimates, lung cancer due to radon exposure claims about 21,000 US lives annually. In many cases lung cancer can be prevented; this is especially true for radon-related lung cancer.