evaluation of high level environmental background radiation areas and its variation in ramsar

introduction 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. materials and methods in this study, the annual effective dose in high level environmental background radiation areas (hlebras) of northern city of ramsar in iran was determined. for dosimetry, a gamma radiation dosimeter was used. measurements were performed in more than 90 points in five districts with hlebr around and near hot springs. results in some areas, the annual effective dose from outdoor external gamma radiation in hlebras (30 msv/y) exceeded the annual effective dose limit for radiation workers. our results are evident that the population dose from normal background radiation in hlebras is 200 times higher than corresponding values in ramsar sea shore. to estimate the cosmic ray contribution, dose measurements were performed on the sea surface one km off the sea shore. conclusion the observed differences over locations 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 environmental radiations on the residents of these hlebras are necessary.