Indoor radon and its profile: a case study in Bangalore city, India

The natural radioactivity gives rise to internal and external indoor exposure. The external exposure is caused by gamma radiation originating from the members of the 238U, 232Th decay series and from 40K. The internal radiation exposure mainly affecting the respiratory tract is caused by the short-lived daughter products of radon, which are exhaled from the construction material into the room air. The area of present study is Bangalore City. The common rocks are pink, grey and porphyries gneisses with large feldspars and black dolerite. An attempt has been made to study the 222Rn and 220Rn levels in different volume rooms for the environment of Bangalore city, India. Solid State Nuclear Track Detector based dosimeters were used for the measurement of 222Rn and 220Rn. Rooms of the dwellings were carefully categorized on the basis of interior volume such as 30 - 200 m3 further they were classified into four groups as 30-40 m3, 64-75 m3, 80-100 m3 and 110- 200 m3. The measured arithmetic mean concentrations of 222Rn and 220Rn for a period of 5 years were 81.06 and 57.54, 54.09 and 31.00, 43.36 and 22.63, 30.68 and 15.74,16.67 and 11.08 respectively. The inhalation dose rate in higher volume rooms varied from 0.77 to 3.24 mSvy-1 with an AM as 1.35 ± 0.03 and in lower volume rooms they were ranged from 2.24 to 3.83 mSvy1 with an AM as 2.94 ± 0.14. Higher concentrations and dose rates were observed in smaller volume room and the lower concentration were observed in bigger volume rooms irrespective of the seasons. Results are discussed in detail. (author)