Indoor radon concentration: impact of geology in the 2005 Kashmir earthquake-affected Bagh area, Azad Jammu and Kashmir, Pakistan

摘要

The early Miocene Murree Formation, late Miocene Nagri Formation and recent alluvium rock units are exposed in the sub-Himalayas of the Bagh area, State of Azad Jammu and Kashmir, Pakistan. The Bagh area was badly affected by the Kashmir earthquake of October 8th 2005 which, along the Muzaffarabad Fault, deformed both the hanging and footwall blocks. The cracks, joints, fissures and fractures in houses and bedrocks might have affected the emission of radon to the surface. Indoor radon concentration measurements were carried out in some dwellings of the Bagh area, Azad Kashmir, Pakistan. The measurements were based on passive integrative detection of radon using CN-85 plastic track detectors in box-type dosimeters. The radon concentration in dwellings was between 50 +/- 11.6 Bq.m(-3) and 167.1 +/- 21.4 Bq.m(-3) with an overall average of 95.1 +/- 15.8 Bq.m(-3) (geometric mean = 93.4 Bq.m(-3)). The average radon concentrations in pucka, semi-pucka and kucha houses were 97.6 +/- 15.4 Bq.m(-3), 89.7 +/- 15.2 Bq.m(-3) and 101.9 +/- 15.9 Bq.m(-3), respectively. The mean values of radon concentrations in the Nagri Formation, Murree Formation and recent alluvium lithology were 99.3 +/- 15.8, 90.1 and 96.2 +/- 15.5 Bq.m(-3), respectively. The annual effective dose to the Bagh population was calculated as 2.38 +/- 0.77 (1.33 +/- 0.2 to 4.7 +/- 0.5) mSv. The average radon (95.1 +/- 15.8 Bq.m(-3)) concentration in dwellings for the inhabitants of the Bagh area was safe from radon-related health hazards and was within the recommended action level (ICRP publication 65 (1993) Protection against radon at home and at work, International Commission on Radiological Protection, Ann. ICRP 23(2)). The indoor radon values obtained in the present study are more than the world average of 40 Bq.m(-3) (UNSCEAR (2000) United Nations Scientific Committee on the Effects of Atomic radiation, Report to the General Assembly, United Nations, New York).