The key therefore is to know the distribution of source-rock materials containing elevated levels of radionuclides and to understand the physical and geochemical processes that concentrate radionuclides. Dr. James K. Otton, U.S. Geological Survey Humans are exposed every day to radioactive elements that occur naturally in the environment. This radiation is implicated in cancers of the lung, bone, and of other organs. The health threat posed by uranium alone primarily as a heavy-metal chemical poison similar to arsenic. This is known as chemotoxicity and is implicated in kidney disease.
Radon is especially dangerous because it is a gas and can easily enter the lungs.
Although natural concentrations of these radioactive materials are usually less than established threshold health values, human activity often inadvertently exposes us to radionuclides at dangerous levels. An even greater percentage of private water supplies, unregulated by EPA, may contain elevated levels of radioactive materials. Radionuclides are present in all rocks in varying amounts, and they are easily mobilized in the environment. The high geochemical mobility of radionuclides in the environment allows them to move easily and to contaminate much of the environment with which humans come in contact. Uranium, in particular, is easily mobilized in ground water and surface water.