f Environmental Radiation Pattern of the Lagoa Real Uranium District, Bahia, Brazil

Natural or environmental radiation is the main source of radiation that affect man, comprising more than 70% of the total (natural plus man made). Man made radiation is originated from several sources, such as x-rays, nuclear weapons fallout, radioactive waste disposal, potassium in smokes of vegetal origin (cigarrettes, etc.), building materials, fertilizers with high U content, etc. Due to that it is important to know precisely the natural dose in order to monitor the man made sources. Natural radiation is composed of two parts, indoor and outdoor. Indoor radiation is mainly due to radon gas emanating from soil or rocks arid trapped inside houses. Outdoor radiation is manily due to gamma radiation, resulting from the decay of 40K, 238U and 2310, and high energy cosmic radiation. Radioactive isotopes (40K, 14C, 87Rb and 222Rn) within the body also contribute to the total dose.