Size distribution of radon daughters in the atmosphere

Radon daughter aerosols in the atmosphere are generally classified into two categories attached and unattached. It is however difficult to develop their size distribution model because of the uncertainty about the sticking coefficient. Recently inferred values of this coefficient are in the range of 5 x 10-2 to 8 x 10-2 for radon daughters and even smaller for elemental iodine aerosols. Estimated size of radon daughters in Trombay (Bombay) is in the range of 0.002 μm to 0.004 μm which agrees with the median size of aerosols in the nuclei mode. The growth of radon daughter aerosols is thus similar to other nuclei formed through gas-to-particle conversion reactions in the atmosphere. It is suggested that observed size distribution of radon daughters (median size and geometric standard deviation) is a more useful parameter in calculating their health effects than classifying them as attached and unattached