Annual Effective Dose of High Level Natural Radiation Areas of Ramsar

Abstract

The exposure of human beings to ionizing radiation from natural sources is a continuing and inescapable feature of life on earth. For most individuals, this exposure exceeds that from all man-made sources combined. In this study the annual effective dose in high level natural background radiation (HLNBR) areas of northern city of Ramsar in Iran was determined. For dosimetry a gamma radiation dosimeter was used. Measurements were performed in more than 90 point of 5 districts with HLNRAs (High Level Natural Radiation Areas) around and near hot springs. In some areas the annual effective dose from outdoor external gamma radiation in HLNR areas (30 mSv/y) exceeded the maximum permissible annual effective dose for radiation workers in Iran. Dosimetry in sea shore as normal background radiation areas showed that external radiation dose in HLNBR areas are 200 times higher than that in sea shore of Ramsar. For extracting the effective dose related to cosmic rays, measurement was performed within Caspian Sea 1km from the sea shore. These measured values were not considerable in comparison to those obtained in HLNR areas. The observed differences over location and measured doses between this study and the others revealed the dynamic nature of this phenomenon, and necessitate performing the periodic studies in these areas. Moreover, cytogenetic and immunologic researches for studying the long term effects of these high level natural radiations on the residents of these HLNRAs are necessary.