Bioaerosols as carriers of radon progeny

Bioaerosols, such as bacteria, pollen and spores, constitute a major fraction of the ambient aerosols, thereby acting as potential carriers for radon decay products. Activity size distributions of the short-lived radon progeny attached to environmental aerosols were measured at four selected sites in urban and rural regions of the Province of Salzburg, Austria, varying in bioaerosol and radon progeny concentrations. Bacteria and spores were sampled with the aid of an Andersen impactor by using selective media, while pollen was collected with a custom-made filter system. Activities of size-fractionated radon progeny attached to environmental aerosols were determined by in situ gamma spectrometry. Additional measurements comprised mass and particle number size distributions and total number of ambient aerosols. Measured size distributions indicated that a considerable fraction of radon progeny were attached to larger particles, say above 1 pm. At particle sizes above about 5 Pm, practically all particles were of biological origin. However, the relative fractions of bioaerosols varied significantly with sampling site and local environmental conditions. Based on computed dose-exposure conversion factors, it was estimated that about 20% of the annual effective dose incurred in Badgastein may be attributed to the inhalation of large environmental aerosols, about one third being caused by biological aerosols.