Indoor radon concentration, outdoor gamma dose rates and impact of geology in the Dhirkot area, Azad Jammu and Kashmir, sub-Himalayas, Pakistan

Abstract

The sedimentary sandstone and clay sequence of the Miocene Kamlial and Murree Formations is exposed in the sub-Himalayas of the Dhirkot area, State of Azad Jammu and Kashmir, Pakistan. The indoor radon and outdoor gamma dose rates were measured from dwellings and basement sandstone and clay rocks, respectively. The radon concentration in dwellings was 36 ± 14 Bq.m -3 to 195 ± 27 Bq.m -3 , with an average of 121 ± 26 Bq.m -3 . The average radon concentration in pucka, semi-kucha and kucha houses was 124 ± 25 Bq.m -3 , 143 ± 25 Bq.m -3 and 136 ± 26 Bq.m -3 , respectively. The outdoor gamma dose rates for the basement sandstones and clays of the Murree Formation and Kamlial Formation were 74.0 ± 1.4-113.1 ± 2.4 nGy/h and 69.6 ± 2.2-108.8 ± 1.4 nGy/h, respectively. The average gamma dose rates for the Murree and Kamlial Formations were 91.3 ± 14.3 nGy/h. The gamma dose rate is maximum (113.1 ± 2.4 nGy/h) and minimum (69.6 ± 2.2 nGy/h) at higher (5 539 feet) and lower (4 493 feet) altitudes, respectively. The overall causes for the increase in average radon concentration in dwellings of the Dhirkot area were poor ventilation, old houses, humidity and temperature, cracks in houses, geology, and aggregates. The gamma dose rate variation depends on sandstone and clay lithologies, altitude and radionuclide contributions. This study shows that the average radon (121 ± 26 Bq.m -3 ) concentration for the inhabitants of the Dhirkot area was within the accepted safe health limit (200 Bq.m -3 , ICRP, 1993; UNSCEAR, 1993).