Radon is a radioactive gas that forms naturally when uranium, thorium, or radium, which are radioactive metals break down in rocks, soil and groundwater. People can be exposed to radon primarily from breathing radon in air that comes through cracks and gaps in buildings and homes. Because radon comes naturally from the earth, people are always exposed to it.
- Radiation Protection Division: Radon - https://www.epa.gov/radiation/radionuclide-basics-radon
- EPA's Integrated Risk Information System profile on Radon 222 [CASRN 14859-67-7] is located at: https://cfpub.epa.gov/ncea/iris/iris_documents/documents/subst/0275_summary.pdf
- Radioactive Decay
Read more about Radon at www.epa.gov/radon