Risk assessment due to inhalation of radon in Coorg district, Karnataka

Evaluation of indoor 222Rn and 220Rn concentrations in Dakshina Kannada, Karnataka, India

Naturally occurring radioactive gases which tend to build up (radon and thoron) in indoor environs can cause deleterious health effects including the development of lung cancer. The present study aims to measure ²²²Rn and ²²⁰Rn levels in dwellings in different seasons in the environs of Dakshina Kannada region of India. The ²²²Rn and ²²⁰Rn concentrations were measured in the monsoon, autumn, winter, and summer seasons using Solid State Nuclear Track Detector (SSNTD, LR-115 type II) films fixed in single-entry pinhole cylindrical twin-cup dosimeters. The higher ²²²Rn levels in indoors were observed during winter with an average concentration of 38.8 Bq m^-3 and lower during summer with an average of 14.1 Bq m^-3. The average indoor thoron concentration was also highest in winter with an average value of 25.5 Bq m^-3 and lowest in summer with 8.8 Bq m^-3. The annual inhalation dose ranged from 0.44 to 1.06 mSv year^-1 with a mean value of 0.66 mSv year^-1. The annual effective dose varied from 1.03 to 2.57 mSv year^-1 with an average value of 1.59 mSv year^-1. The assessed values have been contrasted with the limit suggested by the UNSCEAR and the ICRP and were found to be within the permissible level. The normality of frequency distribution curves of ²²²Rn and ²²⁰Rn concentrations was assessed by the Kolmogorov-Smirnov test.

Seasonal variation of indoor radon, thoron and their progeny in Belagavi district of Karnataka, India

Systematic investigations on the seasonal variation of indoor radon, thoron and their progeny levels have been carried out in Belagavi district of Karnataka, India. The radon and thoron levels were measured using LR-115 type II dosimeter in cups with single-entry pinhole. The measurements were carried out in all the four season, viz, monsoon, autumn, winter and summer, in selected houses of the region. The higher indoor radon levels were observed during autumn with an average concentration of 56.45 Bq m^-3. The minimum in radon levels was observed in summer with an average concentration of 21.8 Bq m^-3. The indoor thoron concentration was also maximum during autumn with an average value of 36.44 Bq m^-3 and minimum in summer with an average value of 15.9 Bq m^-3. The radon and thoron levels were also found to depend on the nature of walls and floorings of dwellings. The lung dose rate to the population due to radon ranged from 1.195 to 9.557 mSv year^-1, with an average of 4.572 mSv year^-1. Risk levels were found to be significant during autumn and winter due to the inhalation of indoor radon and thoron. The study forms the first comprehensive report on the indoor radon and thoron levels and the resulting population dose in the Belagavi region. The studies reveal that the major contributor to the population is radon and its progeny. However, a sizable dose also comes from indoor thoron and its progeny. The study emphasises the need to provide better ventilation system to future dwellings to reduce the risk from indoor radon and thoron.