A study of 222Rn/220Rn exhalation rate and indoor 222Rn/220Rn levels in higher Himalayan terrain

The noble radioactive gas radon and its isotope thoron dominate terrestrial radiation in the indoor environment. These gases eventually disintegrate generating radioactive ions that readily adhere to aerosol particles. This study was conducted in a tectonically active location with significant radon concentrations. The obtained average values of radon mass exhalation and thoron surface exhalation rate from this study are higher than the global average values of 56 mBq kg(-1) h(-1) and 1000 mBq m(-2) s(-1), respectively. As the exhalation rates are higher, naturally the average radon and thoron concentrations are also greater than the worldwide average values of 40 and 10 Bq m(-3), respectively. No significant correlation was observed between Rn-222 and Rn-220 exhalation rate and indoor Rn-222/Rn-220 concentration. The exposure dose due to Rn-222, Rn-220 and their progenies shows no significant health risk.