Evaluation of the natural gamma radiation level in residential zones and determination of annual effective exposure dose in the residents of Hamadan province, Iran, 2012

Human is always exposed to natural background ionizing radiation which may have harmful effects; therefore، measurement of the natural background radiation is important. In this study، was measured the dose of effective natural background gamma radiation in indoor residential zones of Hamadan Province. In this cross-sectional study، we selected four stations along the main geographic directions and one in the center of city for measurement of the indoor dose rate in each of the cities in Hamadan Province. Based on the household numbers، some houses were selected randomly in every station and natural background indoor dose was measured by using RDS-110 survey meter. Then، using the results of our previous study about measuring the level of outdoor natural gamma radiation in this province، we determined the level of annual effective exposure dose from natural gamma radiation in Hamadan residents. In Hamadan province cities، maximum and minimum indoor natural background radiation (gamma ray) belonged to Razan City (1. 41±0. 079 mSv) and Asadabad City (0. 955±0. 044 mSv)، respectively. Mean annual equivalent indoor dose in Hamadan Province was 1. 20±0. 070 mSv. Also the maximum indoor natural background radiation dose (gamma ray) in the buildings with the age of more and less than 25 years were 1. 42±0. 219 mSv and 1. 44±0. 149 mSv، respectively. According to the results of this study and our previous study about outdoor gamma natural background radiation، the annual effective dose in Hamadan Province residents was 0. 83 mSv. According to the results of this study، it seems that annual effective equivalent dose due to indoor gamma radiation in Hamadan Province exceeded the mean external exposure amount reported by UNSCEAR (0. 5 mSv). Also the annual effective dose due to gamma background radiation in Hamadan Province residents is 0. 83 mSv، which is higher than the global average (0. 48 mSv) reported by UNSCEAR – 2000. Therefore epidemiological studies to assess the prevalence of chronic diseases associated with natural radiation exposure among Hamadan Province residents are recommended.