ESTIMATION OF ANNUAL EFFECTIVE RADON DOSES AND RISK OF LUNG CANCER IN THE RESIDENTS OF DISTRICT BHIMBER, AZAD KASHMIR, PAKISTAN

Results of indoor radon survey in the dwellings of district Bhimber are presented. Current study is continuation of our preceding studies aiming to setup baseline indoor radon data for the state of Azad Jammu & Kashmir, Pakistan. In this context, 60 representative houses were carefully selected and CN-85 based box type radon detectors were installed in bedrooms and living rooms of each house. The detectors were exposed to indoor radon for 90 days. After etching CN-85 detectors in 6M NaOH at 70 degrees C for 3 hours, the observed track densities were related to the indoor radon concentration using calibration factor of 0.0092 tracks cm(2)/h per Bq/m(3). The measured indoor radon concentration ranged from 29 +/- 11 to 58 +/- 8 Bq/m(3), 40 +/- 9 to 60 +/- 7 Bq/m(3), and 29 +/- 12 to 66 +/- 7 Bq/m(3) in the regions of Bhimber, Samani, and Barnala, respectively. Excess relative risk factors were calculated using measured indoor radon concentrations, by using the risk model reported in the Biological Effects of Ionizing Radiation (BEIR VI, 1999) report. Excess relative risk was calculated for age groups of 35 and 55 years. Using local occupancy factor, average excess lung cancer risk for the population group of 35 and 55 years of age was found to be 0.42 +/- 0.09 and 0.34 +/- 0.08. The mean annual effective dose for Bhimber, Samani, and Barnala regions were found to be 1.05 +/- 0.17 mSv, 1.09 +/- 0.17 mSv, and 1.16 +/- 0.17 mSv, respectively. These values are within in the safe limits recommended by the international organizations.