Krakow is a city where, due to mostly so-called low-stack emissions and intensified traffic, air dustiness continues to increase and often, especially in winter, the threshold values of dustiness are exceeded. Air dustiness increases the number of airborne microorganisms, as they are associated with particles of dust to form bioaerosols. Actinomycetes are one of the most significant components of bioaerosol. Their presence in bioaerosol is dangerous to human health, since even very low

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... tions of these microorganisms can cause allergic reactions. The aim of this study was to verify the relationship between the concentration of actinomycetes in the air of Krakow depending on spatial variation of thermal conditions and the degree of air dustiness. The study was conducted using a cascade impactor for bioaerosol particle separation, including the respirable fraction. Moreover, the measurements of air dustiness were performed simultaneously, separating 4 dust fractions. The research was conducted over 12 months (full calendar year) and the measurements were performed once per month, within one day, at 16 research sites. The lowest average numbers of actinomycetes were recorded in places characterized by little urban green space (eg Main Square or crossroads). On the other hand, the highest numbers were found in green areas (eg Blonia Park meadows, green area at the Krakow University of Technology). Based on the normative classification of air quality (Polish Standard PN-89/Z-04111/02) the number of actinomycetes in 75 % measurements showed that the air was polluted, including heavily polluted air in 16 % measurements. The most common actinomycetes belonged to the genus Streptomyces (St. albus, St. badius, St. globisporus). Actinomycetes acquired the unique ability to colonize the so-called solid surfaces. They can survive on rocks, plants, animals, clothing, food and other bare surfaces. This is due to the properties of their spores, which are resistant to long periods of drying and capable of survival at low moisture content of the substrate on which they grow [1]. Abstrakt: Kraków jest miastem, w którym g³ównie na skutek tzw. niskiej emisji oraz wzmo¿onego ruchu ko³owego zapylenie powietrza wci¹¿ wzrasta i nierzadko szczególnie w okresie zimowym s¹ przekraczane progowe wartooeci zapylenia. Zapylenie powietrza wp³ywa na zwiêkszenie siê ilooeci drobnoustrojów