Assessment of radiological health implicat from ambient environment in the Muar district, Johor, Malaysia

•Activity concentration of 232Th are four times world average.•232Th is found to be the main contributor to gamma ray dose in the Muar district.•Gross alpha and beta activity concentrations were lower than the value of WHO.•A digital map plotted for isodose.

This study aims to obtain baseline data of environmental terrestrial radiation and to assess the corresponding health risk in the ambient environment in Muar District, Johor, Malaysia in view of the possible construction of nuclear power plant (NPP) in the future. The external gamma dose rate (GDR), measured using two portable survey meters, was 151 nGy h−1. The activity concentrations of 232Th, 226Ra, and 40K were determined using hyper pure germanium (HPGe) detector. The activity concentrations were varied from 11±1 to 583±18 Bq kg−1 for 232Th, 6±1 to 244±9 Bq kg−1 for 226Ra, and 13±6 to 830±13 Bq kg−1 for 40K. Various types of water samples were analyzed using a Low Background Alpha Beta Series 5 XLB instrument at Nuclear Malaysia (NM). Gross alpha activity concentrations in tap water varied from 3±1 mBq L−1 to 34±6 mBq L−1 and gross beta activity concentrations varied from 58±5 mBq L−1 to 709±39 mBq L−1 which were lower than the recommended value by Interim National Water Quality Standards for Malaysia (INWQS) and World Health Organization (WHO, 1993). The radiological health which are the annual effective dose equivalent, the collective effective dose, radium equivalent activity and external hazard index 0.220 mSv, 0.526×102 man Sv y−1, 359 Bq kg−1 and 0.969, respectively. The results were comparable to internationally recommended values and discussed accordingly.