Assessment of chronic exposure effects and radioadaptive response of natural occurring radioactive materials (NORM)

A large amount of naturally occurring radioactive materials (NORM) is produced by the technological enhanced activities of gas and oil industries as by-products or waste. The present study aims to estimate the risk of chronic exposure to the Technological Enhanced Naturally Occurring Radioactive Materials (TE-NORM) and its radio-adaptive response before exposure to 2Gy single dose on male rats. The electrical properties of blood (conductivity and conductance) were measured. In addition to the Electron Para-magnetic Resonance (EPR) technique was used to estimate the free radical in blood, some hematological parameters and lipid peroxidation (MDA) were determined. Six groups of adult male rats were classified according to the period of TE-NORM exposure. All irradiated groups showed increase in Red blood cells Distribution Width (RDW), membrane conductivity, capacitance, EPR intensity and lipid peroxides. However, TE-NORM exposure for two months before 2 Gy exposure reduced the EPR intensity and lipid peroxidation when compared to 2Gy group. The results of this study demonstrated that chronic radiation exposure has some deleterious effects as it appeared in EPR and lipid peroxides elevation, while it showed radio-adaptive response as noticed in TE-NORM for two months before 2Gy group. It could be postulated that radio-adaptive response occurs especially for longer period of chronic exposure before irradiation with a single high dose.