Seasonal variation of indoor radon levels in coastal Karnataka on the south-west coast of India

Indoor radon levels were measured in different seasons throughout 1995 in selected dwellings of coastal Karnataka using LR-115 type II peelable films. Seasonal variations were studied. The arithmetic mean value of radon levels during winter was found to be about 35% higher than the annual average value. The annual average radon levels were found to vary from 45.4 to 65.0 Bq m-3 with an arithmetic mean value of 56.3 Bq m-3. The annual effective dose equivalent to the population of the region due to inhalation of radon was found to be in the range 0.78-1.12 mSv y-1 with a mean value of 0.97 mSv y-1. A moderate positive correlation was observed between indoor radon levels and radium content in the underlying soil, while a weak negative correlation was found to exist between indoor radon levels and indoor gamma dose rates in air. These results are discussed and possible inferences are drawn