Outdoor radioactivity and health risks in Balikesir, Northwestern Turkey

External irradiation from radionuclides naturally present in the environment or released from man-made practices or events is usually an important component of the exposure of human populations. These exposures derive primarily from gamma radiation arising from the decay of these radionuclides at locations outside the human body. The main objective of this study is to evaluate the radioactivity levels and health risks due to terrestrial radionuclides in the soil of Balikesir, one of the largest cities of the country, northwestern Turkey. For this purpose, activity concentrations of radionuclides in soil and outdoor gamma dose rates (terrestrial and cosmic) have been investigated in the city of Balikesir. In addition, maps for the radionuclide activity concentrations of soil and the outdoor gamma dose rate distributions have been plotted for the region. The average activities of radionuclides, 238U, 232Th, 40K, 235U and 137Cs in the soil were determined to be 37.6±10.8, 54.7±15.1, 674.5±203.2, 3.6±1.6, 3.4±2.2 Bq kg-1, respectively, in the region. The average outdoor gamma dose rates due to terrestrial and cosmic radiations were found to be 78.5±12.4 and 48.9±5.8 nGy h-1 with the total of 127.4±18.9 nGy h-1 in the region. Annual effective dose due to environmental outdoor gamma radiation exposures was determined to be 156.3 nSv. The mean estimated cancer risk values were found to be 0.063x10-2 for the region using risk factors of ICRP 103. The results of the study were discussed with the studies done in other cities of Turkey and the worldwide averages. (authors)