Their decay products are not gases and occur as unattached ions or atoms, condensation nuceli, or attached to particles. This decay product of uranium-238 is commonly found in uranium mines. Radon has been used in some spas for presumed medical effects. In addition, radon is used to initiate and influence chemical reactions and as a surface label in the study of surface reactions. It has been obtained by pumping the gases off of a solution of a radium salt, sparking the gas mixture to combine the hydrogen and oxygen, removing the water and carbon dioxide by adsorption, and freezing out the radon.
Most soils contain varying amounts of uranium.
It is usually found in igneous rock and soil, but in some cases, well water may also be a source of radon. The primary routes of potential human exposure to radon are inhalation and ingestion. Radon in the ground, groundwater, or building materials enters working and living spaces and disintegrates into its decay products. In comparison with levels in outdoor air, the concentrations of radon and its decay products to which humans are exposed in confined air spaces, particularly in underground work areas such as mines and buildings, are elevated. Although high concentrations of radon in groundwater may contribute to human exposure through ingestion, the radiation dose to the body due to inhalation of radon released from water is usually more important.