Study of grain size effect on radon exhalation rate using different detection methods and associated health risk assessment

The effects of radon released from phosphate ore samples of different grain sizes on radon emanation and exhalation rates, annual effective dose and excess lifetime cancer risk and the associated health risk assessment were investigated. The activity concentrations of 226Ra and 222Rn were evaluated using a high purity germanium gamma-ray spectrometer, an AlphaGUARD ionisation chamber and nuclear track detector (NTD). Specific activities for different phosphate grain sizes ranging from 100 µm to 500 µm were obtained using the NTD. The 226Ra activity concentrations were found to be 500 ± 35 Bq kg−1. The annual effective dose rate and excess lifetime cancer risk were calculated to be 0.032 mSv y−1 and 0.12×10−3, respectively. The results were compared with those reported elsewhere and with UNSCEAR safety limits.