Seasonal variations in the occurrence of culturable airborne fungi in outdoor and indoor air in Craców

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Abstract

Sampling of air outdoors and indoors in a lecture hall in Craców for culturable fungi revealed seasonal variations both outdoors and indoors, with mean maximum counts occurring in summer, when members of the genus Cladosporium predominated at both test sites. In winter, the mean concentration of fungal propagules in the lecture theatre, although less than 40% of the summer mean, was more than 3 times that outdoors and was dominated by Penicillium and Aspergillus.

Introduction

As well as bacteria and their resting spores, the propagules of micro- and macrofungi are commonly present in the air. Their presence can be detected in both outdoor air and in enclosed environments, including dwelling houses, workplaces and public buildings such as lecture and gym halls (Medrela-Kuder 1991, Medrela-Kuder 1993a, Medrela-Kuder 1993b). Immediately upon putting an object into service it is likely to be contaminated by the wide range of airborne fungi that comprise the air spora and depend on the climatic and ecological conditions prevailing in that region.

In enclosed premises, the concentration of airborne fungal spores also depends on the conditions of general hygiene, on microclimate, on the occupancy and the use to which the premises are put, and on the concentration of fungi in outdoor air. The external environment is the chief source of the fungi found in indoor air, and seasonal variations in climatic conditions are therefore responsible not only for variations in the number and types of fungal spores in outdoor air but also the air indoors. The concentration of spores in indoor air is usually high during summer, when the numbers in the outdoor air are at their highest (Medrela-Kuder, 1991), but where there is indoor fungal growth that acts as a source of spores, numbers indoors may also be high during the other seasons. This paper reports on an investigation of the air spora at an indoor site and an adjacent outdoor site over a period of 1 year.

Section snippets

Materials and methods

Each month during one calendar year in Craców, Poland, six 1-min air samples were taken 2–3 times outside 15m above ground on the roof and inside 1m above floor level in a lecture hall, using a Chirana aeroscope (Chirana, Czechoslovakia; Dolezal et al., 1983; Medrela-Kuder, 1991) operating at a flow rate of 50lmin−1 and collecting onto a 9.0cm plate of Czapek's agar containing chloramphenicol to inhibit bacterial growth. After incubation for 7–10 days at 27°C, exposed plates were examined and

Results

The seasonal variations in the colony counts for both outdoor and indoor air are shown in Table 1. As expected, the maximum concentrations of airborne propagules were recorded in summer (July–August), when the outdoor mean count was 1211CFUm−3 air and in the lecture hall the mean was 939CFUm−3. In the other seasons (Table 1), the mean indoor and outdoor concentrations were all rather lower, especially in winter (January–March). Further, in contrast to summer (ratio of indoor:outdoor

Discussion

Since no irregularities in the usual manner of using the lecture hall were observed during this investigation, it confirms that the occurrence of Cladosporium was a major factor in the seasonal variation in the number of fungal propagules in indoor as well as outdoor air. In an earlier study of outdoor and indoor air in Craców (Medrela-Kuder, 1991), culturable Cladosporium was observed throughout the whole year, with maximum propagule counts in the summer months. However, in a more recent study

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