Inhalation of indoor radon has been recognized as thelargest contributor to the total effective dose received by humanbeings. Indoor radon data were collected from the dwellings lyingon the sedimentary rocks (sandstones, siltstones and clays) ofthe Murree Formation, Nagri Formation, Dhok Pathan Formation, Mirpurconglomerate and surficial deposits of the Kotli area in Azad Jammuand Kashmir, Pakistan. Radon measurements were made using the passivetime-integrated method using Kodak CN-85 Solid-State Nuclear Track Detectors.The radon concentration in dwellings varied from 13 ± 6 Bq.m-3 to185 ± 23 B. qm-3, with an average of 73 ± 15 Bq.m-3.Theradon concentration in the Murree Formation, Nagri Formation, riverterrace and Dhok Pathan Formation were 89.7 ± 16.5, 72 ± 15, 68.5and 69 Bq.m-3, respectively. The average value of allthe measured concentrations (73 ± 15 Bq.m-3) within theframework of this study is more than the world average value of40 Bq.m-3 given by UNSCEAR (United Nations ScientificCommittee on the Effects of Atomic Radiation, report to the GeneralAssembly, United Nations, New York, 2000) and is within the actionlevel of 200-600 Bq.m-3 fixed by the ICRP(InternationalCommission on Radiological Protection, ICRP publication65, Protectionagainst radon at home and at work, 1993). The ambient gamma doserates both indoors and outdoors in different parts of Kotli werealso measured. The average value of gamma absorbed dose rates prevailingin the indoor environment was 131.2 ± 16.6 nGy/h. The gamma exposurerates recorded outdoors were 35% lower than in the indoor environment.The measured gamma dose rates have a weak positive correlation withindoor radon concentration. The annual effective dose for inhabitantsin Kotli due to radon ranged from 0.32 to 4.7 mSv.y-1,with an average value of 1.8 mSv.y-1. This dose is relativelyhigher than the world mean dose of 1.15 mSv/y. That is explainedby the particular geology of the state of Azad Jammu and Kashmir,and the method of construction of the dwellings.

Public exposure to radioactive gas radon and its progeny present in the air results in the largest contribution to total effective dose received by human beings. It is therefore of great concern to monitor radon concentration in energy conserved air tight buildings. Measurements of radon in the Fatima Jinnah Women University (FJWU) have been carried out for investigation and comparison of radon concentration in the new and old buildings of the campus at Rawalpindi, Pakistan. The study was done because according to the international guidelines concerning environmental problems, it is necessary to evaluate and know the radon levels, especially since most of the natural radiation dose to human beings comes from radon gas and its progeny. Solid State Nuclear Track Detectors (SSNTDs) being efficient, therefore, the measurements were carried out by passive, time integrated method, using CR-39 detector in polythene bags. The detectors were exposed for more than six month in various loctations indoors and outdoors. The detectorswere etched using NaOH, the tracks were counted manually, and the track density was converted to radon concentration. Radon concentration varied from 31 to213 Bq.m–3 in old building and from 27 to 143 Bq.m–3 in new buildings, showing slight elevated values in the old buildings. Radon concentration values were found to be less than the values quoted by radiation protection agencies. Radiation dose due to radon varied in the university campus depending on occupancy factor.