Radon concentration in soil-gas and in the atmospheric air has been studied around Mysore city (12°N and 76°E) using Solid State Nuclear Track Detectors. The radon in soil-gas is found to be higher at a depth of 1 m than at a depth of 0.5 m from the ground surface. The higher radon concentration in soil was observed near Chamundi Hills and Karigatta village with average values of 5.94 kBq.m -3 and 5.32 kBq.m -3 at 1 m depth from the ground surface. Seasonal variations in radon in soil gas shows that, the concentration is lower in summer with an average value of 0.60 kBq.m -3 and higher in monsoon season with an average value of 4.70 kBq.m -3 . Estimation of 226 Ra in soil at these locations is also made using HPGe detector. The activity of 226 Ra, varies from 4.82 to 74.23 Bq.kg -1 with an average value of 32.11 Bq.kg -1 . Radon concentrations in soil-gas shows good correlation with the activity of 226 Ra in soil with a correlation coefficient of 0.76

It is well known that atmospheric electrical conductivity is mainly due to the presence of small ions. Near the surface of the earth, radon and its daughter products predominantly produce small ions. In the presence of aerosol particles, the small ion concentration is reduced due to attachment of small ions to aerosol particles which decreases mobility and conductivity in the atmosphere. The ion pair production rate is estimated from the measured radon and its progeny concentrations and correlated with electrical conductivity of the atmosphere. Measurement of concentrations of suspended particulate matter (SPM), SO 2 , and NO 2 of air was also carried out. Data showed that reduced electrical conductivity was related to concentration of airborne SPM.