Radon is a naturally occurring, odorless, colorless and radioactive inert gas produced by the breakdown of uranium in soil, rock, and water. Because radon is a gas, it can enter buildings through openings or cracks in the foundation. The radioactive radon gas itself decays into radioactive solids, called radon daughters. The radon daughters attach to dust particles in the air, and can be inhaled. The inhalation of radon daughters has been linked to lung cancer. As a result of this, radon has been identified as the second leading cause of lung cancer next to smoking in the United States and other parts of the world. "WHO now suggests that homeowners take action when radon levels exceed 2.7 pCi/l" in order to safe themselves from lung cancer that can be caused by radon and its daughters. This is a much more conservative safe limit than "the Environmental Protection Agency (EPA's) action level of 4.0 pCi/l", which has been the U.S. standard for over 20-years. I hope that this review literature/project work/ contributes in filling the gap of knowledge of the health risks of radon and can be used as a bench mark for other future studies.