Determination of natural radiation levels and lifetime cancer risk in Kirikkale, Turkey

Abstract

The aim of this study is to determine the levels of background radiation in nine districts of Kirikkale, Turkey. The outdoor gamma dose rate in the air was measured using a portable digital environmental radiation detector at 170 locations. The mean outdoor gamma dose rate in the air was determined as 121 nGy h(-1) with a range between 23 and 320 nGy h(-1). The annual effective dose for districts was between 0.04 and 0.59 mSv year(-1) with a mean value of 0.23 mSv year(-1). Excess lifetime cancer risk values for districts ranged from 0.14 x 10(-3) to 2.07 x 10(-3) with a mean of 0.80 x 10(-3). The activity concentrations of Ra-226, Th-232, K-40 and Cs-137 in 84 soil samples were determined using HPGe detector. The mean activity values (ranges) of Ra-226, Th-232, K-40 and Cs-137 in soil samples were found to be 20.4 (4.9 +/- 3.0-53.0 +/- 0.8) Bq kg(-1), 38.8 (3.7 +/- 0.2-163.5 +/- 1.8) Bq kg(-1), 598.0 (108.5 +/- 70.2-1500.5 +/- 38.7) Bq kg(-1) and 3.9 (0.2 +/- 0.1-11.9 +/- 0.7) Bq kg(-1), respectively. The mean activity concentration of Th-232 and K-40 was higher than the world's mean value. The mean radium equivalent activity was 119.76 Bq kg(-1) which is lower than the recommended maximum value of 370 Bq kg(-1). The mean external terrestrial gamma dose rate was found to be 56.71 nGy h(-1). This mean value was lower than the world mean of 60 nGy h(-1). The calculated external hazard value was 0.32 and within the acceptable limit which is less than unity (H-ex <= 1). The indoor radon concentration in 150 houses for the summer and winter seasons was determined using solid state nuclear track detector (CR-39). The mean indoor concentration for the summer season was found to be 63.27 Bq m(-3) ranging from 14.0 +/- 1.5 to 288.0 +/- 21.9 Bq m(-3). On the other hand, the mean indoor concentration in the winter season was found to be 86.94 Bq m(-3) ranging from 17.0 +/- 4.5 to 484.0 +/- 26.9 Bq m(-3). The present results showed that the radon activity concentrations in winter were 42.3 % higher than in the summer. The mean annual effective dose equivalent and lifetime cancer risk were also calculated.