Assessment of Natural Radiation Levels and Associated Dose Rates from Surface Soils in Pontian District, Johor, Malaysia

The radiation survey of the ambient environment was conducted using two gamma detectors and the measurement results were used in the computation of the mean external radiation dose rate, mean weighted dose rate, annual effective dose and the collective effective dose, which are 69 nGy h, 0.447 mSv y, 237 μSv and 0.126 × 10 man Sv y, respectively. A hyper purity germanium (HPGe) detector was used to determine the activity concentrations of Th, Ra and K in soil samples. The results of the gamma spectrometry of the soil samples show a range from 2 ± 1 to 113 ± 9 Bq kg for Th, 3 ± 1 to 68 ± 6 Bq kg for Ra, and 26 ± 3 to 683 ± 29 Bq kg for K. Radium equivalent activity (Raeq) and external hazard index (Hex) were 136 Bq kg and 0.366 respectively; which were with recommended level for the population. The Mean lifetime dose and life time cancer risk for each person living in the area are 5.91 mSv, 3.44×10 Sv year, respectively. The results was compared with values giving in UNSCEAR 2000.